Bibliography of Tyrian purple

Originally published in Dyes in History and Archaeology 1994, 12, 57-66

last modified ...
Aceto M, Idone A, Agostino A, Fenoglio G, Gulmini M, Baraldi PP, Crivello F, Non-invasive investigation on a VI century purple codex from Brescia, Italy, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2014, 117, 34-41
doi : 10.1016/j.saa.2013.07.092
The VI century purple codex, Codex Brixianus, held in the Biblioteca Civica Queriniana at Brescia (Italy) was investigated with XRF spectrometry, UV–visible diffuse reflectance spectrophotometry, molecular spectrofluorimetry and optical microscopy. The results suggest that Tyrian purple had been used as a minor component mixed with other less precious dyes such as folium or orchil.

Aceto M, Agostino A, Fenoglio G, Baraldi P, Zannini P, Hofmann C, Gamillscheg E, First analytical evidences of precious colourants on Mediterranean illuminated manuscripts, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2012, 95, 235-245
doi : 10.1016/j.saa.2012.04.103
Two Byzantine 6th century manuscripts, Vienna Dioskurides and Vienna Genesis, held in the Austrian National Library at Vienna, were analysed using Raman spectroscopy, UV–Vis diffuse reflectance spectrophotometry with optic fibres (FORS) and X-ray fluorescence spectrometry (XRF). Tyrian purple may have been used to dye the parchment of Vienna Genesis since a weak peak for bromine (XRF) was observed, but the FORS spectrum did not confirm this and the Raman spectrum could not be observed.

Ajiki H, Pozzi F, Huang L, Massa L, Leona M and Lombardi JR, Raman spectrum of monobromoindigo, Journal of Raman Spectroscopy, 2011; doi: 10.1002/jrs.3066
6-Bromoindigo was synthesised and a complete Raman spectral characterization performed, including experimental spectra recorded at 488 and 785nm. Theoretical calculations using density functional theory were used to give a complete assignment

Allan J K, Tyrian Purple: An Ancient Industry, Australian Museum Magazine, 1934, 5(5), 147-151
A brief historical survey with drawings of Murex brandaris, Purpura lapillus, Tethys norfolkensis, Violet snails and ladder shells (Epitonium australe). No refs

Aloupi E, Karydas AG and Paradellis T, Pigment Analysis of Wall Paintings and Ceramics from Greece and Cyprus. The Optimum Use of X-Ray Spectrometry on Specific Archaeological Issues, X-Ray Spectrometry, 2000, 29, 18-24
A single sample of a purple material found in 1969 in Akrotiri, Thera, was shown (XRF) to have a high (5300 ppm) bromine content, consistent with it being of shellfish origin

Aloupi E, Maniatis Y, Paradellis T, Karali-Yannacopoulou, L, Analysis of a Purple Material Found at Akrotiri, in Hardy, D.A, Thera and the Aegean World III, Vol. I: Archaeology, Proceedings of the Third International Congress, Santorini, September 03-09, 1989, London, 1990
Purple dye was found on powdered material at Akrotiri. It was probably used for cosmetics

Andreotti A, Bonaduce I, Colombini M P, Ribechini, E, Characterisation of natural indigo and shellfish purple by mass spectrometric techniques, Rapid Communications in Mass Spectrometry, 2004, 18(11), 1213-1220
doi: 10.1002/rcm.1464
Online pyrolysis GC in the presence of hexamethyldisilazane followed by MS analysis (Py-silylation/GC/MS), and direct exposure MS (DE-MS), were used for indigo (from Indigofera tinctoria) and shellfish purple (from Murex trunculus). The following molecular markers were found to useful: 1,2-dihydro-3H-indol-3-one for indigoid dyes, 1,3-dihydro-2H-indol-2-one for indirubine, and 6-bromo-1,2-dihydro-3H-indol-3-one for shellfish purple. DBI, MBI and IND were found in shellfish purple and the presence of tyriverdin indicated.

Anon, Tyrian purple research, International Dyer, 2006, 191(4), 6
The researches of Papanastasiou (2005) are sumarised and illustrated

Anon, On the Tyrian, or Purple Dye, The Belfast Monthly Magazine, 1810, 5(25), 93-95
An account of recent experiments published in Montague's Testacea Britannica

Anon, Tyrian purple, The Ladies' repository, 1876, 4(5), 424-427
History, myths and legends reproduced from Chambers's Journal

Augusti S, Sui Colori degli Antichi: Il Purpurissum, Rendiconti della Accademia di Archeologia, Lettere e Belle Arti, nouv. ser., 1961, 36, 123-130

Baker J T, Studies on Tyrian Purple and Its Precursors from Australian Molluscs, Ph.D. Thesis, 1967, University of Queensland, Brisbane, Australia

Baker J T, Tyrian purple. Ancient dye, a modern problem, Endeavour, 1974, 33(118), 11-17
A review with 23 references

Baker J T, Duke C C, Chemistry of the indoleninones. II. Isolation from the hypobranchial glands of marine molluscs of 6-bromo-2,2-dimethylthioindolin-3-one and 6-bromo-2-methylthioindoleninone as alternative precursors to Tyrian Purple, Australian Journal of Chemistry, 1973, 26, 2153-2157
abstract; doi:10.1071/CH9732153
The title compounds were isolated from ether extracts of Dicathais orbita. Both compounds are derived from sodium tyrindoxyl sulfate.

Baker J T, Duke C C, Precursors of Tyrian Purple, Food-Drugs Sea, Proc. [Conf.], 4th, Meeting Date 1974, 1976, 345-353
A review and discussion of the formation of Tyrian Purple from mollusks with 25 references

Baker J T, Duke C C, Isolation of Choline and Choline ester salts of Tyrindoxyl Sulphate from the Marine Mollusks Dicathais Orbita and Mancinella Keineri, Tetrahedron Letters, 1976, 1233-1234

Baker J T, Sutherland M D, Pigments of marine animals VIII. Precursors of 6,6'-Dibromoindigotin (Tyrian Purple) from the mollusc Dicathais Orbita Gmelin, Tetrahedron Letters, 1968, (1), 43-46
Chromatography and reactions of tyrindoxyl sulfate and the photolysis of tyriverdin

Bancroft E, Experimental Researches concerning the Philosophy of Permanent Colours; and the best means of producing them, by Dyeing, Calico Printing, &c, Philadelphia: published by Thomas Dobson, at the Stone House, No. 41, South Second Street, 1814, vol. 1 Chap IV, Of substantive animal colours, and principally of the Tyrian purple. pp. 89-121
"This, during many ages, was the most celebrated, and venerated of all the colours given by dyeing; and among the rich and beautiful, ..." The author gives a critical survey of the literature, including Pliny, Fabius Columna (1616), William Cole (1684), Jussieu (1709), Reaumur (1710), Duhamel (1736) and then describes his own observations (1803, 1812), concluding that sunlight is essential to the production of the colour and that (incorrectly) the associated smell was due to phosphine. "Some of my readers may indeed think that I have been too minute in my statements concerning it. But to me, the colouring matter under consideration, has appeared to deserve my utmost attention, because, (independently of the veneration with which it was contemplated by the ancients) its properties are more extraordinary, more interesting, and more instructive, than those of any other."

Becker C, Did the people in Ayios Mamas produce purple-dye during the Middle Bronze Age? Considerations on the prehistoric production of purple-dye in the Mediterranean, Animals and Man in the Past: ARC-Publicatie, Groningen, the Netherlands, 2001, 122-134
Archaeological investigations with 77 refs

Begbie P, On the purple Dye of the ancient Tyrians, Transactions of the Society of Antiquaries of Scotland, 1822, 2, 168-180
The author reviews existing literature and describes his encounter with Helix Ianthina

Benkendorff K, Natural Product Research in the Australian Marine Invertebrate Dicathais orbita, Marine Drugs, 2013, 11(4), 1370-1398
doi: 10.3390/md11041370
A review of the chemistry and biochemistry associated with Dicathais orbita with 119 references

Benkendorff K, McIver CM, and Abbott CA, Bioactivity of the Murex Homeopathic Remedy and of Extracts from an Australian Muricid Mollusc against Human Cancer Cells, Evidence-Based Complementary and Alternative Medicine, 2011, Article ID 879585, 12 pages, 2011
doi: 10.3390/60100070
The aim of this study was to evaluate the in vitro bioactivity of egg mass extracts of the Australian muricid Dicathais orbita, in comparison to the Murex remedy, against human carcinoma and lymphoma cells. Liquid chromatography coupled with mass spectrometry (LC-MS) was used to characterize the chemical composition of the extracts and homeopathic remedy, focusing on biologically active brominated indoles. 42 refs

Benkendorff K, Bioactive molluscan resources and their conservation: Biological and chemical studies on the egg masses of marine molluscs, Thesis, University of Wollongong, 1999
Abstract and index

Benkendorff K, Bremner J B, Davis A R, Tyrian purple precursors in the egg masses of the Australian muricid, Dicathais orbita: A possible defensive role, Journal of Chemical Ecology, 2000, 26(4), 1037-1050
The fresh egg masses of Dicathais orbita contain a high proportion of tyrindoleninone, which reacts to form tyriverdin and subsequently Tyrian purple and 6-bromoisatin as the eggs develop and the larvae hatch. Tyrindoleninone and especially tyriverdin have antimicrobial activity.

Benkendorff K, Bremner J B, Davis A R, Indole derivatives from the egg masses of Muricid molluscs, Molecules, 2001, 6(2), 70-78 ; link here , pdf, doi:10.3390/60100070
A range of brominated indole derivatives were found in the egg masses of six species of muricid molluscs. Several non-brominated indoles were also present in the eggs of two Mediterranean Muricidae, although these were not found in the Australian species

Benkendorf K, Westley C B and Gallardo C S, Observations on the production of purple pigments in the egg capsules, hypobranchial and reproductive glands from seven species of Muricidae (Gastropoda: Mollusca), Invertebrate reproduction and development, 2004, 46(2-3), 93-102; link ; doi: 10.1080/07924259.2004.9652612
Tyrian purple is a well-known colourant that can be obtained from the hypobranchial glands of muricids. Here we investigate the presence of purple and related pigments in the hypobranchial glands, reproductive glands and egg capsules of three Rapaninae, three Ocenebrinae and one Muricinae species. Observations on the dissected specimens revealed the presence of purple pigmentation in the hypobranchial glands of all species. All of the Rapaninae and the Muricinae, but only some species of Ocenebrinae, appear to transfer the pigment precursors to their egg capsules. This provides evidence that the precursors of Tyrian purple are not produced for the sole purpose of protecting the egg masses as has been previously suggested. In all the subfamilies, the hypobranchial and reproductive (capsule and prostate) glands lie adjacent to one another. Colour changes in the reproductive glands, indicating the presence of dye precursors, were observed in two species of Rapaninae. In Dicathais orbita, colour changes could be seen in both the capsule glands of females and prostrate glands of males. The final colour was more red in the reproductive glands than the purple observed in the hypobranchial glands. Preliminary observations of detached hypobranchial gland sections in both D. orbita and Pterynotus triformis indicate a different suite of colour reactions occur when compared to sections that are intact and attached to the reproductive glands. This demonstrates that the reproductive glands can influence the chemical conversions of dye precursors synthesized by these species. Further studies on the secondary metabolism occurring within the hypobranchial glands and reproductive organs of Muricidae are ongoing, including histological sectioning and confirmation of the chemistry behind the colours observed and functional analysis of Tyrian purple precursors.

Biggam CP, Whelks and purple dye in Anglo-Saxon England, THE ARCHAEO+MALACOLOGY GROUP NEWSLETTER, (9), 2006; pdf ; another pdf
A brief summary of written records which are being investigated to provide evidence for the importation of Mediterranean shellfish purple fabrics and whether Britain produced its own purple cloth and parchment

Biggam CP, Knowledge of whelk dyes and pigments in Anglo-Saxon England, Anglo-Saxon England, 2007, 35 23-55 ; doi: 10.1017/S0263675106000032
Anglo-Saxon texts in Latin, as well as glosses and glossaries, are peppered with words such as purpura, purpureus, murex, ostrum and others, which are usually found to have dictionary definitions involving the word 'purple'. In addition, some of the surviving manuscripts from the period have purple pages, and the 'vast textile wealth' of Anglo-Saxon churches and monasteries, is known to have included fabrics called purpurae. It has often been assumed, therefore, that religious communities, and the wealthier strata of secular society, would have been familiar with the extremely expensive and prestigious pigment and dye suggested by these words. The purpose of this paper is to attempt to assess the likelihood and extent of this presumed familiarity with whelk-derived colouring in Anglo-Saxon England. Two possibilities will be explored: that whelk-dyed fabrics and garments were imported into England from the Mediterranean region, and, secondly, that whelk dyeing was carried out in Britain. The first step is to acquire some background information which will enable such assessments to be made. 135 refs.

Bizio B, Scoperta del principio purpureo nei due Murex brandaris e trunculus Lina., e studio delle sue proprietà, Annali delle Scienze del regno Lombardo-Veneto, 1833, 346-364

Boekschoten G J, Note on Roman Purple Winning at Chersonnissos, Basteria, Tijdschrift van de Nederlandse Malacologische Vereenigung, 1962, 26, 59-60
Report on a find of shells of Hexaplex trunculus from the Roman period at Chersonissos, Crete

Born W, Purpura Shell-Fish, Ciba Review, 1937, 1(4), 106-110
A brief description of the researches of Lacaze-Duthiers and others, and historic drawings of molluscs

Born W, Purple in Classical Antiquity, Ciba Review, 1937, 1(4), 111-118
A survey of the surviving relics from the Mediterranean industry

Born W, Purple in the Middle Ages, Ciba Review, 1937, 1(4), 119-123
A survey of the use of shell-fish purple from 200 AD to 1453 AD

Born W, The Use of Purple among the Indians of Central America, Ciba Review, 1937, 1(4), 124-127
The use of shellfish purple for dyeing and body painting, derived from Purpura pansa / patula

Bouchilloux S and Roche J, Contribution a l'etude biochimique de la pourpre des Murex, Bull. Inst. Oceanographique, 1955, 52(1054), 1-23

Bouchilloux S and Roche J, Sur la pourpre des Murex trunculus et ses précurseurs, Comptes rendus des seances de la Societe de Biologie: Societe de Biologie de Lyon, 1954, 148, 1583-1587
Glands were extracted with ethanol (+2 degrees C, 2 d). After evaporation at 35 degrees C, paper chromatography (butanol - acetic acid - water, 78:5:17) showed Rf 0.29, 0.46 for Murex trunculus and Rf 0.50 for Murex brandaris. Column chromatography (Amberlite IRC50) gave the trunculus products as pale green and pale yellow crystals resp. which with purpurase gave blue and purple pigments

Bouchilloux S and Roche J, Sur les prochromogenes et les pigments purpuriques de Murex trunculus Linné, Comptes rendus des seances de la Societe de Biologie: Societe de Biologie de Lyon, 1954, 148, 1732-1734
The two prochromogens from Murex trunculus are indoxyl sulfates which on hydrolysis give indigo and dibromoindigo

Briend J, Humbert, J B, Tell Keisan (1971-1976), une cité phenicienne en Galilee, Fribourg-Göttingen-Paris, 1980, 1980
Report on the excavations at Tell Keisan, suggesting the existence of a purple dyeing workshop about 1100 B. C.

Bruin F, Royal Purple and the dye industries of the Mycenaeans and Phoenicians, Sociétés et Compagnies de Commerce en Orient et dans l'Océan Indien (Acts du huitième colloque international d'histoire maritime, Beyrouth - 5-10 Septembre 1966), 1966, 73-90
Historical review of early use, molluscs used, technique of dyeing, chemistry and with details of electron spin resonance experiments. 156 references.

Bruin F, Heineken F W and Bruin M, Electron spin resonance spectra of the basic indigoid dye radicals, Journal of Organic Chemistry, 1963, 28, 562-564
The dibromoindigo radical anion was generated using sodium hydroxide and acetone and observed by electron spin resonance spectroscopy. The esr spectrum of the product from Murex trunculus, processed according to the instructions of Aristotle and Pliny, was identical to that of synthetic dibromoindigo

Bruneau P, Documents sur l'industrie Délienne de la Pourpre, Bulletin de Correspondance Hellénique, 1969, 93, 759-761
Report on Purple Dyeing at Delos in Antiquity

Bruni S, Guglielmi V, Pozzi F, Surface-enhanced Raman spectroscopy (SERS) on silver colloids for the identification of ancient textile dyes: Tyrian purple and madder, Journal of Raman Spectroscopy, 2010, 41(2), 175-180 ; abstract ; doi: 10.1002/jrs.2456
Surface-enhanced Raman spectroscopy (SERS) was used for the identification of natural organic dyes belonging to indigoid and anthraquinone classes in archeological samples. A purplish bone fragment found in the tomb of the martyrs Gervase and Protase in the Basilica of Sant’Ambrogio, Milano (4th century A.D.) was shown to contain mainly monobromoindigo

Cardon D, Natural Dyes : Sources, Tradition, Technology and Science, Archetype Publications, 2007, 551-606
A translation of Le monde des teintures naturelles (2003) updated with more than 201 references

Cardon D, Le monde des teintures naturelles, Belin, Paris, 2003, 421-467
Detailed descriptions in Chapter 11, with illustrations and 81 refs

Cardon D, Teinture Precieuses de la Mediterranee - Pourpre - Kermes - Pastel, Carcassonne et Terrassa, 1999/2000, Exhibition catalogue,
179 page exhibition catalogue with examples of purple dyeing and a description of purple dyeing in antiquity.

Cardon D, du Chatenet G, Guide des Teintures Naturelles, Delachaux et Niestlé, Lausanne, 1990, 338-354
A history and description of 7 species of molluscs with 23 references.

Chávez F J L, Chávez P R and Oyama K, Brominated precursors of Tyrian purple (C.I. Natural Violet 1) from Plicopurpura pansa, Plicopurpura columellaris and Plicopurpura patula, Dyes and Pigments, 2009, 88(1), 7-13 ; sciencedirect ; doi: 10.1016/j.dyepig.2009.03.019
6,6'-Dibromoindigo was identified using the tfa derivative in P. pansa derived from tyrindolinone (1H and 13C NMR). Tyrindoleninone was found (GC/MS) was found in the milk and hypobranchial gland of P. pansa and 6-bromoindalin-2-one in the hypobranchial glands of P. patula and P. columellaris.

Cheek G T, Barthel, R V, Electrochemical studies of indigoid systems, Proc. - Electrochem. Soc., 93-11(Proceedings of the Fifth International Symposium on Redox Mechanisms and Interfacial Properties of Molecules of Biological Importance, 1993), 1993, 165-74
Redox potentials for the dibromoindigotin system were determined in order to determine the most likely reducing agent in the ancient process. Results suggest tin rather than lead or iron was the reagent.

Christophersen C, Waetjen F, Buchardt O, Anthoni U, On the formation of indigotins, Tetrahedron Letters, 1977, (20), 1747-1748
A dimethylthio compound derived from the addition of methanethiol to dehydroindigo, gave on heating or exposure to light indigo and a similar precursor is postulated in the mollusks which give dibromoindigotin

Christophersen C, Watjen F, [Organic marine chemistry of] purple, (Den.). Naturen Verden, 1978, (10), 326-334
A review in Danish of the history, biology, chemistry and dye use of Tyrian purple with 4 references

Christophersen C, Watjen F, Buchardt O, Anthoni U, A revised structure of tyriverdin. The precursor of Tyrian purple, Tetrahedron, 1978, 34(18), 2779-2781 ; sciencedirect ; doi: 10.1016/0040-4020(78)88419-1
The spectral data for natural and synthetic tyriverdin are compared; synthetic tyriverdin was prepared from dibromoindigotin by acetylation, elimination of acetic acid and the addition of methanethiol, and the photochemical transformation to dibromoindigotin is shown to be a radical process

Clark R J H, Cooksey C J, Bromoindirubins: the synthesis and properties of minor components of Tyrian purple and the composition of the colorant from Nucella lapillus, Journal of the Society of Dyers and Colourists, 1997, 113(11), 316-321 ; abstract ; doi: 10.1111/j.1478-4408.1997.tb01852.x
The identification of 6,6'-dibromoindirubin as a component of Tyrian purple has been confirmed by a practical synthesis; the first investigation of the composition of Tyrian purple from Nucella lapillus is reported

Clark R J H, Cooksey C J, Monobromoindigos: a new general synthesis, the characterization of all four isomers and an investigation into the purple colour of 6,6'-dibromoindigo, New Journal of Chemistry, 1999, 323-328; abstract ; doi: 10.1039/A808562E ; Synthetic details
6-Bromoindigo is synthesised and characterised. The purple colour of wool dyed with 6,6'-dibromoindigo is thought to be due to the interaction of the π-system of two parallel molecules

Clark R J H, Cooksey C J, Daniels M A M, Withnall R, Indigo - red, white and blue, Education in Chemistry, 1996, 33(1), 16-19
A review with 24 references and details of UV/VIS, IR and mass spectra of indigo, dibromoindigo and indirubin, and a preparation of the latter

Clark R J H, Cooksey C J, Daniels M A M, Withnall R, Indigo, woad, and Tyrian Purple: important vat dyes from antiquity to the present, Endeavour, 1993, 17(4), 191-199 ; doi: 10.1016/0160-9327(93)90062-8 ; abstract
A review with 35 references and illustrations of molluscs and the mosaic in San Vitale, Ravenna. The emphasis is on the chemistry of the production and syntheses of the dyes, together with some reference to the use of their spectroscopic properties as an aid to their identification in artefacts.

Cocaign J Y, Le pourpre (Nucella lapillus) et son utilisation comme teinture en Armorique, Annales de Bretagne et des Pays De L'Ouest, 1997, 104(4), 7-22; pdf
In 1992, the study of a large midden of dog-whelk shells (Nucella lapillus) at "La Grandville" (Hillion, 22, Brittany), had shown the production of colouring matter during the Gallo-Roman period. In the absence of regional references, the possibily of a delocalization of a typically mediterranean tinctorial industry was considered. Now, owing to the literature, the records and the discovery of sites in the Finistère, this study becomes more than anecdotical. These new informations allow a better definition of this colouring matter, and to chronogically insert it in the periods from Protohistory to the Middle Ages.

Cockburn J, A Journey over Land, from the Gulf of Honduras to the great South-Sea, performed by John Cockburn, and five other Englishmen, London: C Rivington, 1735
... the Method used to die the Thread is only this, they take the Shell off the Rock where it sticks very fast, and rub it gently on the Thread, and then lay it down again where they found it, with great Care, for they are very cautious of killing the Fish.

Eds: Coldstream J N, Huxley G L, Kythera - Excavations and Studies, London: Faber, 1972
Report on the excavations of Kythera with reference to the early purple dyeing industry there

Cole W, Purple Fish, Philosophical Transactions of the Royal Society of London, 1685, 15, 1278-1286 ; pdf (2.7 Mb)
In a letter to the Philosophical Society of Oxford, William Cole describes the colouring of linen with hypobrachial extracts of purpura species (with line drawings) from Minehead, the colour changes and odours on exposure to light and refers to ancient literature on Tyrian purple

Cooksey C J, Making Tyrian purple, Dyes in History and Archaeology, 1994, 13, 7-13
A convenient synthesis of 6,6'-dibromoindigo via a nitrone

Cooksey C J, TLC of the Indigoid Colorants in Shellfish Purple, Dyes in History and Archaeology, 1995, 14, 70-77
N-trifluoroacetylation provides solubility and TLV mobility to distinguish indigo and bromoindigos

Cooksey C J and Sinclair R S, Colour Variations in Tyrian Purple Dyeing, Dyes in History and Archaeology, 2005, 20, 127-135
Theoretical calculations on the intermediate tyriverdin molecule formed during the formation of Tyrian purple from molluscs suggest that tyriverdin absorbs light maximally below 450nm and therefore has a yellow colour, rather than the green normally attributed to it. However, experiments on the colour pathway during oxidation of the leuco dye from chemically synthesised 6,6'-dibromoindigotin (DBI), the main constituent of Tyrian purple dyeings, shows that a green colour is produced when, some of the yellow leuco dye is oxidised to form a small amount of the blue-purple final product DBI. Overexposure of the leuco dye solution to UV radiation causes debromination and a change of colour from the red-purple hue of dyed DBI on cotton cellulose to the pure blue of indigotin itself. Variations in the colour of Tyrian purple dyeings reported over the years can be attributed to variations in the chemical compositions of the mollusc prochromogens, as recent studies have shown the presence of brominated and unsubstituted indigotins and indirubins. However the variations in colour shown by chemically synthesised DBI on different textile substrates are attributed here to the varying strengths of the intermolecular forces between the dye molecules and the substrate molecules and also possibly on the extent of self-aggregation or crystallinity of the DBI species in the final dyed product. The colour variations are quite significant, have been measured spectrophotometrically, and are specified quantitatively in international (CIE, CIELAB and Munsell) colour coordinates.

Cooksey C J, Marine indirubins, in Indirubin, the red shade of indigo, editors Meijer L, Guyard N, Skaltsounis LA and Eisenbrand G, France: Life in Progress Editions, ISBN 2-9518029-0-0, 2006, 23-30
This chapter covers analytical techniques which have been applied to the purple pigment from shellfish to disclose the presence of indirubins (indirubin and three brominated indirubins), published analytical data on indirubins in shellfish, the chemical synthesis of bromoindirubins for use as analytical standards and some suggestions about the chemistry of the generation of indirubins in shellfish.

Cooksey C, The Synthesis and Properties of 6-Bromoindigo: Indigo Blue or Tyrian Purple? The Effect of Physical State on the Colours of Indigo and Bromoindigos, Dyes in History and Archaeology, 2001, 16/17, 97-104
The first synthesis of 6-bromoindigo is reported and the properties are described. The purple colour of Tyrian purple probably arises from the closer stacking of the molecules compared to those of indigo, the situation being caused by van der Waals interaction between the bromine atoms

Cooksey C and Withnall R, Chemical studies on Nucella lapillus, Dyes in History and Archaeology, 2001, 16/17, 91-96
The first investigations into the chemical nature of the initial precursors of the purple dye in Nucella lapillus and the composition of the resulting dye suggest that it is very similar to those of the dyestuff from Dicathais orbita and Thais clavigera

Cooksey C J, The Synthesis of minor Components of Shellfish Purple: Bromoisatin, Bromoindigotin and Bromoindirubins, from Dibromoindigotin, Beiträge zur Waidtagung, 1998, 7, 71-74
Chemical oxidation of dibromoindigo gives 6-bromoisatin which can serve as a precursor to other mollusc pigments

Cooksey C J, Tyrian purple: 6,6'-Dibromoindigo and Related Compounds, Molecules, 2001, 6, 736-769
A review with 133 references; available from here

Cooksey C, Tyrian purple: The first four thousand years, Science Progress, 2013, 96(2), 171-186
DOI ; request copy
Some of the long history of shellfish purple is recounted. Understanding how the dye is produced from molluscs, the composition of the pigment and the chemistry involved has only been achieved as a result of the advances in analytical chemistry in the 20th century, but some mysteries remain. Other diverse aspects such as the taste of the molluscs, the actual colour of the dye, the smell associated with the production and even the application in photography contribute to the fascination of the subject. 58 references

Cooksey C J, Dronsfield A T and Edmonds J, First, catch your fish, Education in Chemistry, 2005, 24(1), 16-19
The synthesis of dibromoindigo based on the Pinkney and Chambers route is described with examples of dyeing of wool and cotton

Daniels V, The light-fastness of textiles dyed with 6,6'-dibromoindigotin (Tyrian purple), Journal of Photochemistry and Photobiology A: Chemistry, 2006, 184(1-2), 73-77; doi: 10.1016/j.jphotochem.2006.03.034 ; abstract
Samples of cotton, linen, silk, wool, Nylon 6 and Nylon 66 were dyed with dibromoindigo, reflectance spectra were measured, showing wavelength maxima between 522 (wool) and 540, 594 nm (Nylon 66) and fading under daylight simulation illumination measured. Of the various textile types, dyed wool was most light-fast followed by silk, linen, nylons 6 and 66 and finally cotton.

Daniels V, Further work on the dye analysis of textile fragments from Enkomi, Dyes in History and Archaeology, 1987, 6, 3-7
Purpurin is identified (by TLC) in addition to dibromoindigotin. Extraction with 1:1 aqueous dimethylformamide differentiated between indigotin (soluble) and dibromoindigotin (insoluble)

Daniels V, Dye analysis of two fragments from Enkomi, Dyes in History and Archaeology, 1985, 4, 15-18
Dibromoindigotin and indigotin on its own were identified in two textiles from Enkomi. Analysis was by extraction with hot pyridine followed by spectroscopy when indigo showed maximum absorption at 611.5 nm (20 deg) and 606 nm (60 deg) and dibromoindigotin at 601 nm (20 deg and 60 deg) [Note: this textile later proved to be from Kertch, E. Crimea - ed]

Darvekar M, Ghorpadeand B, Vankar VS, Microwave Assisted Improved Syntheses of Indigoid and Anthraquinoid Dyes, Asian Journal of Chemistry, 2004, 16(2), 965-970
The authors describe a microwave-assisted bromination of indigo to give 5,5'-dibromoindigo which they call Tyrian blue, but which has no connection with Tyrian purple.

Degano I, Ribechini E, Modugno F, Colombinia MP, Analytical Methods for the Characterization of Organic Dyes in Artworks and in Historical Textiles, Applied Spectroscopy Reviews, 2009, 44(5), 363-410
DOI: 10.1080/05704920902937876
This review focuses on several analytical methods based on spectrometric and chromatographic techniques that have contributed to the study of organic dyes, including dibromoindigo, in works of art and archaeological findings.

Desjacques J P, Koeberlé P, Mogador et les Iles Purpuraires, Hespéris, 1955, 42, 193-202
Investigation into the origin of Gaetulian Purple. The authors demonstrate the existence of purple dyeing on Mogador and the origin of Gaetulian purple from this island

Desrosiers S, Textiles decouverts dans deux tombes du Bas-Empire à Naintré (Vienne), in Cardon, D. u. Feugere, M., Archéologie des Origines au Ve Siècle, Montagnac, 2000
Find of purple dyestuff on textile material from a children's grave dated 4 - 5 century AD

Devièse T, Ribechini E, Baraldi P, Farago-Szekeres B, Duday H, Regert M and Colombini MP, First chemical evidence of royal purple as a material used for funeral treatment discovered in a Gallo–Roman burial (Naintré, France, third century AD), Analytical and Bioanalytical Chemistry, 2011, 401(6), 1739-1748; DOI: 10.1007/s00216-011-5217-7
Violet–purple residues collected from a Gallo–Roman burial dated back to the second half of the third century A.D. and excavated at Naintré (France) were chemically investigated by multi-analytical methodology involving the use of Raman spectroscopy, direct exposure-mass spectrometry (DE-MS) and high-performance liquid chromatography (HPLC–UV–visible), finding dibromoindigo. These results are the earliest chemical evidence of purple colorant used during funeral rituals (not as textile dye) and enabled us to highlight new aspects of funeral practices in Roman times

Diadick Casselman K, Takako T, The Politics of Purple: Dyes from Shellfish and Lichens, Textile Society of America Symposium Proceedings. Paper 666., 2012

Doumet J, Étude sur la couleur pourpre ancienne et tentative de reproduction du procédé de teinture de la ville de Tyr décrit par Pline l'Ancien, Imprimerie Catholique, Beirut, 1980

Doumet J, De la Teinture en Pourpre des Anciens par l'Extraction du Produit Colorant des Murex Tronculus, Brandaris et des Purpura Haemastoma, National Museum News, 1999, 9, 10-18
The recipe of Pliny is detailed with emphasis on the use of tin metal as a reductant. With pictures of the relevant mollusks.

Doumet J, De la Teinture en Pourpre des Anciens, Teintures précieuses de la Méditerranée: Musée des Beaux-Arts, Carcassonne, 1999-2000, 1999, 46-57
The recipe of Pliny is detailed with emphasis on the use of tin metal as a reductant. With pictures of the relevant mollusks.

Driessen L A, Über eine charakteristische Reaktion des antiken Purpurs auf der Faser, Melliand Textilberichte, 1944, 25, 66
Photodebromination of leuco-dibromoindigo by UV or sunlight is described

Dubois R, Sur la formation de la pourpre de Purpura lapillus, Comptes rendus de l'academie des sciences, 1903, 136, 117-118 ; BNF
A note which refutes the assertion of Letellier that the mechanism of formation of the purple is different in Purpura lapillus and Murex brandaris: the precursor, purpurine, is acted on by an enzyme, purpurase

Duhamel du Monceau H L, Quelques experiences sur la liqueur colorante que fournit la Pourpre, Mémoires de l'Académie Royale des Sciences, Paris, 1736, 49-63
Working with a Murex on the coast of Provence, he showed that light is necessary for the development of colour from purple producing mollusks

Duke CC, A Study of Precursors to Purple Dyes from Australian Gastropod Molluscs and of Analogous Synthetic Compounds, Ph.D. Thesis, 1973, James Cook University, Townsville, Qld, Australia

Dupont C, The Dog Whelk Nucella lapillus and Dye Extraction Activities From the Iron Age to the Middle Ages Along the Atlantic Coast of France, The Journal of Island and Coastal Archaeology, 2011, 6(1), 3 - 23; doi: 10.1080/15564894.2011.542070
This article summarizes the archaeological data for dyeing activities using the dog whelk Nucella lapillus and the oyster drill Ocenebra erinaceus at 27 sites along the Channel and Atlantic coasts of France with 46 references.

Edmonds J, Tyrian or Imperial purple dye, Historic Dye Series No 7, ISBN 0 9534133 65, 2000, 41pp
Historic Dye Series No 7; Ancient vat dyeing was performed using biochemical reduction analogous to that used in woad dyeing. 18 refs

Elsner O, Solution of the enigmas of dyeing Tyrian purple and the biblical tekhlet, Dyes in History and Archaeology, 1991, 10, 11-16
The ratio of indigotin to dibromoindigotin in the purple dye derived from Phyllonotus (Murex) trunculus alters as this mollusc changes its sex. The dye must be vatted, although other shellfish such as Thais (Purpura) haemostoma may be used as direct dyes. A range of shades can be obtained, one of which may be the biblical 'tekhelet'

Elsner O, Spanier E, Dyeing with Murex extracts, an unusual dyeing method of wool to the Biblical sky blue, Proceedings of the 7th International Wool Textile Research Conference, Tokyo, 1985, 1985, 5, 118-130
The dyeing of wool with Tyrian purple to give tekhlet by a mollusk sex segregation method and by the photochemical debromination method are discussed

Elsner O, Spanier E, The dyeing with Purpura haemostoma, 7th International Symposium on Fiber Science & Technology, September 1985, Hakone, Japan, 1985
Experiments in dyeing with P. haemastoma, which gives a reddish purple and was considered in antiquity to be a poorer dye

Esmaeelian B, Benkendorff K, Johnston MR, Abbott CA, Purified Brominated Indole Derivatives from Dicathais orbita Induce Apoptosis and Cell Cycle Arrest in Colorectal Cancer Cell Lines, Marine Drugs, 2013, 11, 3802-3822; 10.3390/md11103802
Flash chromatography was used to separate the components of Dicathais orbita egg capsules which were identified as 6-bromoisatin, tyrindoxylsulphate, tyrindolinone, tyrindoleninone and tyriverdin using MS and NMR. 67 refs.

Fabius Columna, De Purpurea, Rome, 1616
Woodcuts of molluscs used for purple

Forbes R J, , Studies in Ancient Technology E. J. Brill: Leiden, 1964, 4, 98-142
Purple dyeing is described in the context of the dyeing methods of Antiquity . The reports of Plinius and other authors of Antiquity on purple dyeing are rendered

Fouquet H, Bielig H J, Biological Precursors and Genesis of Tyrian Purple, Angewandte Chemie (Int Edit), 1971, 10, 816-817 ; doi: 10.1002/anie.197108161
Four chromogens in Murex trunculus are identified; the major chromogen of Murex brandaris, M. erinaceus and Purpura haemastoma is 6-bromo-2-methylsulfonyl-indoxyl sulfate

Fouquet H, Bielig H J, Biologische Vorstufen und Genese von antikem Purpur, Angewandte Chemie, 1971, 83, 856-857 ; doi: 10.1002/ange.19710832114
Four chromogens in Murex trunculus are identified; the major chromogen of Murex brandaris, M. erinaceus and Purpura haemastoma is 6-bromo-2-methylsulfonyl-indoxyl sulfate

Fouquet H, Bau und Reaktionen natürlicher Chromogene indigoider Farbstoffe bei Purpurschnecken., Ph.D. Thesis. University of Saarbrücken, Saarbrücken, 1970
A major study of the chromogens of Mediterranean molluscs and their subsequent reactions giving Tyrian purple

Fox M R, Pierce J H, Indigo: Past and Present, Textile Chemist and Colorist, 1990, 22(4), 13-15
A brief history with no references

Friedlander P, Uber die Farbstoffe aus Purpura aperta und Purpura lapillus, Berichte der Deutschen Chemische Gesellschaft, 1922, 55, 1656-1658
Extraction of Tyrian purple from Purpura aperta and Purpura lapillus is described and photographs of these molluscs as well as Murex brandaris and Murex trunculus shown

Friedlander P, Uber den Farbstoff des antiken Purpurs aus murex brandaris, Berichte der Deutschen Chemische Gesellschaft, 1909, 42, 765-770
The first identification of 6,6'-dibromoindigo from Murex brandaris, when 1.4g of dye was isolated from 12,000 mollusks, determined the empirical formula, synthesised it by two different routes and the products shown to have identical light absorption

Friedlander P, Bruckner, S and Deutsch G, Uber Brom- und Methoxyderivate des Indigos, Annalen, 1912, 388, 23-49
The syntheses of dibromo- and dimethoxy-indigos is described; 6,6'-dibromoindigo has an absorption maximum of 585 nm in tetrachloroethane

Fujii H, Sakamoto K and Ichihashi M, Textiles from at-Tar Caves - Part II-(3): Cave 16, Hill C, al-Rafidan, 1993, 14, 109-133
Details of textiles dyed with Tyrian purple, kermes, indigo and an unidentified yellow dye

Fujise Y, Chemistry of the Production of Tyrian Purple and Related Natural Products, Kagakushi, 1999, 26(1), 34-44
A summary of chemical investigations since 1909 with 24 references

Fujise Y, Miwa K and Ito S, Structure of tyriverdin, the intermediate precursor of Tyrian purple, Chemistry Letters, 1980, (6), 631-632
Stereoisomeric tyriverdins were isolated from Thais clavigera and characterised by UV, NMR (1H and 13C) and IR spectroscopy

Gage T, The English-American. A new survey of the West-Indies, George Routledge & Sons Ltd: London, 1928, 359
An edited reprint of the 1648 1st edition. At Chira, Golfo de Salinas and Nicoya, shellfish are used to dye pita (a thread)

Gage T, A new survey of the West-India's: or, The English American his travail by sea and land; ..., J. Sweeting: London, 1655, 192-193
2nd edition. Dyeing of thread (Pita) and Segovia cloth with shellfish at Nicoja

Garay L, Le coquillage a Pourpre, Archimède, l'école des loisirs. Paris. ISBN 2 211 03684 8, 1996
Text and pictures of purple dyeing with Purpura pansa

Gerhard P, Emperors' Dye of the Mixtecs, Natural History, 1964, 73(1), 26-31
History of the use of Purpura patula in Mexico and the current use at Pinotepa de Don Luis for making the posahuanco

Gerlach, H J, Verfahren zur Herstellung von 2-Nitrobrombenzaldehyden sowie von 6,6'-Dibromindigo, Ger. Offen. DE 3910648 A1 901004 (BASF AG), 1990
4-Bromo-2-nitrobenzaldehyde is prepared in 92% yield by selective lithiation of 1,4-dibromo-2-nitrobenzene followed by reaction with dimethylformamide, and converted into 6,6'-dibromoindigotin by reaction with nitromethane followed by reduction.

Ghiretti F, Bizio, Bartolomeo and the rediscovery of Tyrian purple, Cellular and Molecular Life Sciences, 1994, 50(9), 802-807 ; abstract ; doi: 10.1007/BF01956459
A review with 33 references, claiming that the origin and chemical properties of Tyrian purple were first described by Bartelmeo Bizio, a Venetian chemist, whose description of the nature and properties of the dye was not only accurate, but predate what were claimed as original discoveries by later authors

Gibaja Oviedo S, Salazar de Cavero L, Production of Tyrian purple from the Concholepas mollusk "Chanque", Boletin de la Sociedad Quimica del Peru, 1977, 43(3), 139-40
A light green extract of the hypobranchial gland of the mollusk gave a single greenish-yellow band on paper chromatography which turned to purple when exposed to sunlight

Gleba M and Vanden Berghe I, Shellfish purple in pre-Roman Italy: new evidence from Strozzacapponi (Perugia/Corciano), DHA30, Derby, 2011 (abstract)
The paper presents dye test results of mineralised textiles from the necropolis of Strozzacapponi near Perugia, Italy dated to the 2nd-1st centuries BCE. Textiles from several burials represent the first and earliest direct evidence for the use of shellfish purple for dyeing textiles in Italy.

Glover B, Are natural colorants good for your health - are synthetic ones better, Textile Chemist and Colorist, 1995, 27(4), 17-20
The feasibility and/or desirability of using natural dyes is compared to the alternative use of synthetic products including Tyrian purple and cochineal

Glover B, Pierce J H, Are natural colorants good for your health ?, Journal of the Society of Dyers and Colourists, 1993, 109(1), 5-7
The impractibility of using mollusc dyeing in the modern world is discussed

Głowacki ED, Voss G, Sariciftci NS, 25th Anniversary Article: Progress in Chemistry and Applications of Functional Indigos for Organic Electronics Advanced materials, 2013, DOI
A brief description of the origin and chemistry of indigo and Tyrian purple production, and of solid state structures and photophysics.

Głowacki ED, Voss G, Demirak K, Havlicek M, Sunger N, Okur AC, Monkowius U, Gasiorowski J, Leonat L, Sariciftci NS, A facile protection-deprotection route for obtaining indigo pigments as thin films and their applications in organic bulk heterojunctions Chemical Communications, 2013, 49(54), 6063-6065; DOI
Halo-indigos including 6,6'-dibromoindigo can be protected using tert-butoxy carbonyl groups to give solvent soluble and chromatographically separable bis-derivatives. X-ray crystallography shows the derivatives to be non-panar. Cis-trans isomerism is observed. The parent indigos are readily recovered by heating to 190-200 °C.

Głowacki ED, Leonat L, Voss G, Bodea M-A, Bozkurt Z, Ramil AM, Irimia-Vladu M, Bauer S, and Sariciftci NS, Ambipolar organic field effect transistors and inverters with the natural material Tyrian Purple, AIP Advances 1, 2011, 042132 (6 pages); link
The natural pigment Tyrian Purple (6,6’-dibromoindigo) shows promising electron and hole transport properties. X-ray diffraction of Tyrian Purple films reveals a highly-ordered structure with a single preferential orientation, attributed to intermolecular hydrogen bonding. This material, with a band gap of ca. 1.8 eV, demonstrates high hole and electron mobilities of 0.22 cm2/V·s and 0.03 cm2/V·s in transistors, respectively; and air-stable operation. Inverters with gains of 250 in the first and third quadrant show the large potential of Tyrian Purple for the development of integrated organic electronic circuits.

Głowacki ED, Voss G, Leonat L, Irimia-Vladu M, Bauer S and Sariciftci NS, Indigo and Tyrian Purple – From Ancient Natural Dyes to Modern Organic Semiconductors, Israel Journal of Chemistry, 2012
doi: 10.1002/ijch.201100130 ; abstract ; pdf
Due to hydrogen bonding and π-stacking, indigo and Tyrian purple form highly-ordered crystalline thin films. Such films have been used to fabricate high-performance organic field-effect transistors with ambipolar charge transport, as well as complementary-like circuits. Mobility values were found to be in the range of 10-2 – 0.4 cm2/Vs. With performance on par with the best available organic semiconductors, indigoids demonstrate the potential of sustainable electronics based on biodegradable and biocompatible materials.

Golding B T, Pierpoint C, Indigo Blue, Education in Chemistry, 1986, (3), 71-73
A brief history with biosynthetic details

Grandmougin E, Seyder P, Uber Indigo. V:Uber halogenierte Indigo und Derivate, Berichte der Deutschen Chemische Gesellschaft, 1914, 47, 2365-2373
The synthesis of dibromoindigotin is described from 6,6'-diaminoindigo by diazotization and reaction with copper(I) bromide and absorption maxima in xylene (591.6, 536.5 nm) and methyl benzoate (593.3, 554.0 nm) determined

Greenberg H S, An Improved synthesis of Tyrian purple, M.A. Thesis (Temple University), 1964, 49
A synthesis via a nitrone intermediate is described, see Cooksey (1994); 49 pages

Greenspan A, Bromine, Chemical & Engineering News, 2003, 81(36), 96
A short article introducing the element bromine is presented. The use of bromine as a dye in ancient Rome times, the Talmud, and the bible is discussed. The author describes his interaction with the Murex trunculus snail that has the ability to take bromine from the sea and bind it to indigo, forming dibromoindigo - Tyrian purple

Grosjean D, Sensharma, D K & Cass G R, Fading of colorants by atmospheric pollutants: mass spectrometry studies., The Science of the Total Environment, 1994, 152(2), 125-134
Chemical ionization mass spectra are reported for curcumin, indigos, alizarin derivatives and isatins, the products of ozone-induced fading of indigo pigments.

Grosjean D, Whitmore P M, Cass G R, Druzik J R, Ozone fading of natural organic colorants: mechanisms and products of the reaction of ozone with indigos, Environ. Sci. Technol., 1988, 22(3), 292-298
Samples of dibromoindigotin exposed to 10 ppm of ozone for 4 days were entirely decomposed to bromoisatin and bromoisatoic anhydride, as revealed by MS

Haubrichs R, L'étude de la pourpre: histoire d'une couleur, chimie et expérimentations, Preistoria Alpina, 2005, Suppl. 1, v.40, 133-160
An illustrated bibliography of the ancient use of purple, the molluscs from which it is obtained, its archaeology, literature, chemistry and different dyeing techniques. About 224 refs

Haubrichs R, Natural history and iconography of purple shells, in Indirubin, the red shade of indigo, editors Meijer L, Guyard N, Skaltsounis LA and Eisenbrand G, France: Life in Progress Editions, ISBN 2-9518029-0-0, 2006, 55-70
The descriptions of molluscs in ancient literature, both in text and in illustrations, are accurate enough from the sixteenth century on to enable identification of the species used to obtain the Tyrian purple so prized in the Mediterranean region. This study is completed by an overview of some descriptions of other purple molluscs from various parts of the world, dating from the seventeenth to the nineteenth centuries. A brief account of the many illustrations which adorn the works reviewed is also given. 18 illustrations, 65 refs.

Herzog I, The dyeing of purple in anciant Israel, Proceedings of the Belfast Natural History and Philosophical Society, 1919-1920, 2, 21-33
A history of argaman and tekhelet

Hidaka S, Chemistry of the purple coloring matter from shellfish, Sen'i Kako, 1984, 36(6), 279-283, 300
A review with 10 references

Higa T, Scheuer P J, Bisindoxyl-derived blue marine pigments, Heterocycles, 1976, 4(2), 227-230
The marine invertebrate Ptychodera flava laysanica contained 3 blue pigments, 6,6'-dibromoindigotin, 5,5',7,7'-tetrabromo-6,6'-dimethoxyindigotin, and 5,6',7-tribromo-6-methoxyindigotin, in addition to a colorless companion, 5,7-dibromo-6-methoxyindole

Hiyoshi Y, Nakatsuji S, Japanese Translation of William Cole's Paper on Tyrian Purple in the Philosophical Transactions (1685), Kagakushi Kenkyu (History of Chemistry), 2006, 33, 28-39

Hiyoshi Y, Chemical education with familiar material in our hometown -- Dyeing with Tyrian purple from Thais bronni, Kagaku to Kyoiku, 1989, 37, 654-655

Hiyoshi Y, Fujise Y, Synthesis of Tyrian Purple as a Project for High School Students, Chemical education, 1996, 44(11), 731-732
The synthesis of Wahl (1935) from p-toluidine is followed, with experimental details, via nitro-p-toluidine and bromonitrotoluene, which is oxidised using ceric ammonium nitrate and perchloric acid to give bromonitrobenzaldehyde. Reaction with aqueous NaOH completes the synthesis of dibromoindigo.

Hiyoshi Y, Fujise Y, Tyrian purple. As a learning tool for natural product chemistry, Kagaku to Kyoiku, 1992, 40(6), 390-393
The isolation of Tyrian Purple from Thais clavigera and T. bronii, conversion of it to indigotin and dyeing of cotton or silk is described.

Hoffman RC, Zilber RC, Hoffman RE, NMR spectroscopic study of the Murex trunculus dyeing process, Magnetic Resonance in Chemistry, 2010, 48(11), 892-895 ; 10.1002/mrc.2685
The debromination of natural leucoindigos and their binding to wool is studied using NMR spectroscopy. Debromination is observed prior to reaction with the wool and prior to oxidation. Binding to the wool is shown to occur prior to oxidation. NMR allows the dyeing process to be followed.

Hoffmann R, Marginalia - Pigments from a Snail - Biblical Blue and the Royal Purple, American Scientist, 1990, 78(4), 308-309
An historical review with 5 references on the production and identification of dibromoindigotin and tekhelet

Hoffmann R, The Royal Purple and the Biblical Blue - Argaman and Tekhelet - The Study of Chief Rabbi Herzog,Isaac on the Dye Industries in Ancient-Israel and recent Scientific Contributions - Spanier,E, TLS-the Times Literary Supplement, 1989, (4524),
Book review

Hoffmann R, The royal purple and the biblical blue, Abstracts of papers of the American Chemical Society, 1999, 217(2), 1

Horn P, Textilien in biblischer Zeit - Die Färberei, Ciba-Rundschau, 1968, (2), 17-23
Review on dyeing methods of the Jews with some remarks on purple dyeing particularly on old workshops

Huxtable R J, The Mutability of Blue, Molecular Interventions, 2001, 1(3), 141-144
A brief summary with 10 references of the origin and history of indigo (dye, pigment, in urine) and Tyrian purple (tekhelet)

Imming P, Zentgraf M and Imhof I, An improved synthetic procedure for 6,6'-dibromoindigo (Tyrian purple), Synthetic Communications, 2001, 31(23), 3721-3727 ; doi: 10.1081/SCC-100107023
A simple synthetic procedure is described that yields 6,6'-dibromoindigo in considerably improved overall yield (10%), of analytical purity and also being amenable to scale-up

Imming P, Zentgraf M and Imhof I, Welche Farbe hatte der antike Purpur?, Textilveredlung, 2000, 35(9 to 10), 22-24; references
A review

Imming P, Purpur, die Farbe der Kaiser, Pharmazeutische Zeitung, 2000, 145(16), 1263-1266
History and chemistry with 13 references

Jackson J W, The Geographical Distribution of the Shell-Purple Industry, London: Longmans, Green and Co, 1917, 1-29
A chapter in 'Shells as Evidence of the migrations of early culture' with 92 references

James M A, Reifarth N, Mukherjee A J, Crump M P, Gates P J, Sandor P, Robertson F, Pfälzner P, Evershed R P, High prestige Royal Purple dyed textiles from the Bronze Age royal tomb at Qatna, Syria, Antiquity, 2009, 83, 1109-1118
During the ongoing excavations in the palace of the famous Qatna complex, the excavators noted patches of brown staining on the floor of a high status tomb. Chemical extraction revealed the presence of seven zero-, mono- and di-brominated derivatives of indigo and indirubin, and more detailed characterisation showed that it likely came from Hexaplex trunculus

James M A, Anna J. Mukherjee A J, Robertson F, Crump M P, Pfälzner P, Evershed R P, Recovery of Tyrian Purple from anthropogenic sediments from a bronze age Syrian royal tomb, Poster 23rd International Meeting on Organic Geochemistry September 2007 (Torquay, Devon, United Kingdom)., 2007, pdf
DMF extracts of sediment showed the presence of Tyrian purple containing mainly indigo, monobromoindigo and dibromoindigo as detected by HPLC. A 2D ZQ filtered TOCSY NMR spectrum of 6-monobromoindigo is shown.

Jannun R and Coe E L, Bromoperoxidase from the marine snail, Murex-trunculus, Comparative Biochemistry and Physiology B-Comparative Biochemistry, 1987, 88B(3), 917-922

Jensen L B, Royal Purple of Tyre, Journal of Near Eastern Studies, 1963, 22, 104-118
A review of purple dyeing in Antiquity with remarks on finds of shells of purple snails, on purple dyeing and on the importance of purple

Jodin A, Les établissements du roi Juba II aux îles Purpuraires (Mogador), fouilles du Service des antiquités du Maroc, Tanger, 1967
Based on the report of Plinius on Gaetulian purple its nature is discussed. According to the conclusion of the author it was dyed by using purple snails on the island Mogador

Juan, Don Jorge and de Ulloa, Don Antonio, Relacion Historica del viage a la America Meridional, Madrid, 1748, (book 4), 242-244
Observations in 1744 of the dyeing methods used in Guayaquil (Ecuador) and Nicoya (Costa Rica) where cotton thread is drawn through the shellfish secretion, when after drying it becomes green then purple.

Kanbur Y, Irimia-Vladu M, Głowacki ED, Voss G, Baumgartner M, Schwabegger G, Leonat L, Ullah M, Sarica H, Erten-Ela S, Schwödiauer R, Sitter H, Küçükyavuz Z, Bauer S, Sariciftci NS, Vacuum-processed polyethylene as a dielectric for low operating voltage organic field effect transistors, Organic Electronics, 2012, 13(12), 919–924
doi: 10.1016/j.orgel.2012.02.006
Tyrian purple (6,6'-dibromoindigo) was synthesised using the procedure of G. Voss, H. Gerlach (1989) and purified by sublimation. Devices using Tyrian purple as a semiconductor show low-voltage ambipolar operation with equal electron and hole mobilities of ~0.3 cm2/Vs.

Kanold I B, The Purple Fermentation Vat: Dyeing or Painting Parchment with Murex trunculus, Dyes in History and Archaeology, 2005, 20, 150-154
In January 2001, Inge Boesken Kanold succeeded in reconstructing a fermentation vat using fresh Murex trunculus with the help of John Edmonds' book. This was done at the Conservatoire des Ocres et Pigments Appliqués in Roussillon, Provence, during a private workshop where several ancient purple specialists were present. The escargot de mer, as the French call it, is available at the local markets. It was then suggested that we should demonstrate the operation of a working vat of shellfish purple that was described by Pliny in ancient times, but has not been used since 1453, at the 20th DHA meeting in Amsterdam in November 2001. During the following months, while preparing for travelling with fresh molluscs, the idea came up to preserve cut-out murex glands in salt in order to be independent of markets and seasons. Experiments were carried out to prove the feasibility. In August 2001, the first fermentation vat using dried murex glands produced dark purple coloured wool. This led to more research on a purple related subject: the parchment. Besides using the method of dyeing parchment in a cold murex vat, she also managed to paint the surface with the coloured liquid. Finally she invented a recipe of staining parchment in an artistic way by dipping the material in cut-out fresh glands for several hours, even days.

Kanold I B and Haubrichs R, Tyrian Purple Dyeing: an Experimental approach with fresh Murex trunculus, in Purpureae Vestes I. Textiles y tintes del Mediterráneo en época romana, Ed: Carmen Alfaro Giner, Universitat de València, 2011, 253-256
Detailed instructions are given on how to prepare a purple dye vat.

Karapanagiotis I, Mantzouris D, Cooksey C, Mubarak MS, Tsiamyrtzis P, An improved HPLC method coupled to PCA for the identification of Tyrian purple in archaeological and historical samples, Microchemical Journal, 2013, 110, 70-80; sciencedirect ;
DOI: 10.1016/j.microc.2013.02.008
The efficiencies of DMSO, DMF and pyridine to solubilise Tyrian purple samples are compared using HPLC. The optimum parameters were determined to be DMSO at 80 °C for 15 min. The quantitative composition of purple samples from Hexaplex trunculus, Bolinus brandaris and Stramonita haemastoma was determined and data on historic samples collected from the literature. PCA found that it was not possible to distinguish between brandaris and haemastoma samples but there was a slight separation of these species from trunculus samples, which showed a wide variation.

Karapanagiotis I, de Villemereuil V, Magiatis P, Polychronopoulos P, Vougogiannopoulou K, and Skaltsounis A-L, Identification of the Coloring Constituents of Four Natural Indigoid Dyes, Journal of Liquid Chromatography & Related Technologies, 2006, 29, 1491-1502 ; abstract
A high performance liquid chromatography (HPLC) method combined with spectrophotometric UV-Vis detection is developed for the separation and identification of seven indigoid coloring compounds: indigotin, which is commercially available, and indirubin, 6-bromoindigotin, 6'-bromoindirubin, 6-bromoindirubin, 6,6'-dibromoindigotin, and 6,6'-dibromoindirubin, which are synthesized to be used as reference compounds in the HPLC analysis. The chromatographic method is employed for the identification of the blue/purple coloring compounds in samples extracted from four mollusks, which have been used for the production of Tyrian Purple since antiquity: Hexaplex trunculus, Murex brandaris, Nucella lapillus, and Thais haemastoma. The composition of the analyzed samples, with respect to the reference materials, is compared and discussed. All seven indigoids are identified in Hexaplex trunculus and some of them are identified in the other three purple extracts.

Karapanagiotis I, Identification of Indigoid Natural Dyestuffs Used in Art Objects by HPLC Coupled to APCI-MS, American Laboratory, 2006, 38(3), 36-39
HPLC with spectrophotometric detection (UV-VIS) and coupled with mass spectrometry (MS-APCI) was utilized for the separation and detection of six indigoids, which allowed unequivocal identification of Tyrian Purple in an extract originating from a historic painting from the Late Bronze Age (17th century B.C., Greece).

Karapanagiotis I, Sotiropoulou S and Valianou L, Identification of Tyrian Purple in Aegean Bronze Age pigments, DHA30, Derby, 2011 (abstract)
We report the HPLC identification of Tyrian purple in four pigment samples from the Bronze Age at Thera and Trianda. The following compounds were detected using HPLC-DAD in the extracts of the historical samples: indigo, 6-bromoindigo, 6,6'-dibromoindigo, and 6,6'-dibromoindirubin. All four historical samples contained these four indigoid compounds.

Karapanagiotis I, Mantzouris D and Cooksey C, An improved method for the analysis of Tyrian purple samples and the application to historical and archaeological samples., DHA31, Antwerp, 2012 (abstract)
DMSO, DMF and pyridine have been used in the past to treat and solubilise Tyrian purple, prior to HPLC analysis. Our goal is to investigate (i) the efficiencies of these solvents to treat true purple and (ii) the effects that they have on the results for the relative composition of the dye. To achieve our objective, samples of Tyrian purple are treated with the aforementioned solvents at various temperatures and time periods. Solutions are then analysed with HPLC. The following compounds are monitored at 288nm to compare the three solvents: IND, INR, 6'MBIR, 6MBIR, 6MBI, DBI and DBIR. The comparison leads to the conclusion that DMSO gives, overall, the best results. The improved treatment method is then applied to archaeological and historical samples which have been analysed - and presented in DHA meetings - in the past. The new method provides better results with respect to the number of extracted compounds, as detected by HPLC.

Karman N, Spanier E, Remains of a Purple Dye Industry Found at Tel Shiqmona, Israel Exploration Journal, 1988, 38, 184-186
Report on a dyeing workshop from the 9th century B. C. found in Tel Shiqmona in Israel. Fragments of dyeing vessels and shells of purple snails were found there

Karmous T, Alatrache A, Ayed N, Chemistry as a tool for differentiation between natural and synthetic dyes, Bulletin - Union des Physiciens Paris, 2000, 94(820), 13-23
The authors identified a dye sample represented as the natural dye Royal purple as actually being basic fuchsin, using solubility, redox behaviour, the effect of pH on colour, TLC, IR spectra, and direct dyeing behaviour

Karmous T, Ayed, N, Fantar M H, Wouters J, Analysis of Punic Natural Dyes: Purple Earth from Zembra and Cosmetic Make-up from Carthage, Dyes in History and Archaeology, 1996, 14,
Dibromoindigo was found in an earth specimen from Punic time on the isle of Zembra

Kazumi U, Ikue H, Kiyoko I, Tousaku K, Teruko A, Color analysis by means of a color computer system - an examination into the color-changing process of the Tyrian purple and its dyeing effects, Kenkyu Kiyo - Tokyo Kasei Daigaku, 2: Shizen Kagaku, 2003, 43, 77-85

Kelley WP, Wolters AM, Sack JT, Jockusch RA, Jurchen JC, Williams ER, Sweedler JV, Gilly WF, Characterization of a novel gastropod toxin (6-Bromo-2-mercaptotryptamine) that inhibits shaker K channel activity, Journal of Biological Chemistry, 2003, 278(37), 34934 - 34942 A novel potassium channel antagonist has been purified from the defensive mucus secreted by Calliostoma canaliculatum, a marine snail found in the temperate coastal waters of the western Pacific. The toxin is expelled from the hypobranchial gland as part of a defensive response and is contained within a viscous matrix that minimizes dilution and degradation. The active compound was isolated by multistage microbore HPLC separations followed by bioactivity assays. Nuclear magnetic resonance, combined with electrospray ionization Fourier transform ion cyclotron resonance and electrospray ionization ion trap mass spectrometry indicate that the active component is a heretofore unknown indole-derivative, a disulfide-linked dimer of 6-bromo-2-mercaptotryptamine (BrMT). Exudates from the hypobranchial glands of various marine mollusks have been sources for dye compounds such as 6-6 dibromoindigo, the ancient dye Tyrian purple. BrMT represents the first correlation of a hypobranchial gland exudate with a molecular response. Voltage clamp experiments with a number of K channel subtypes indicate that BrMT inhibits certain voltage-gated K channels of the Kv1 sub-family.

Kimura M, Sakamoto K, Fujii H, Studies on identification of the natural dyes on the textiles from at-Tar caves, al-Rafidan, 1993, 14, 141-148
2000 year old samples of kermes and Tyrian purple / indigo dyes on wool are distinguished by UV/VIS spectra following extraction with dimethylformamide and DMF-NaOH solutions giving wavelength maxima at 550-600 nm (two peaks) and 600-620 nm respectively

Koren Z C, HPLC analysis of the natural scale insect, madder and indigoid dyes, Journal of the Society of Dyers and Colourists, 1994, 110, 273-277
A linear gradient elution method applied to dyes which are found on ancient textiles, including indigotin, its mono- and di-brominated compounds, and indirubin and a previously undetected component from Murex trunculus, tentatively identified as a dibromoindirubin

Koren Z C, High-performance Liquid Chromatographic Analysis of an Ancient Tyrian Purple Dyeing Vat from Israel, Israel Journal of Chemistry, 1995, (35), 117-124
HPLC analysis of Tyrian purple from modern Murex trunculus and from a basin shard from Tel Kabri, dated to the 7th century BCE, showed similar compositions, mainly dibromoindigo with smaller amounts of monobromoindigo, indigo and dibromoindirubin

Koren Z C, The Unprecedented Discovery of the Royal Purple Dye on the Two Thousand Year-Old Royal Masada Textile., The Textile Specialty Group Postprints., 1997, 7, 23 – 34
HPLC analysis showed mainly DBI, less MBI and a little IND, similar to modern Murex trunculus pigments from northern Israel

Koren Z C, The First Optimal All-Murex Completely Natural Purple Dyeing in the Eastern Mediterranean in a Millennium and a Half and its Colorimetric Characterization, Dyes in History and Archaeology, 2005, 20, 136-149
Experiments with Hexaplex trunculus are described in which a dye vat is prepared at pH 9 and 50 degrees C and the solution used to dye wool. The colors obtained, purples and blues, were analysed.

Koren Z C, HPLC-PDA analysis of brominated indirubinoid, indigoid, and isatinoid dyes, in Indirubin, the red shade of indigo, editors Meijer L, Guyard N, Skaltsounis LA and Eisenbrand G, France: Life in Progress Editions, ISBN 2-9518029-0-0, 2006, 45-53
A reverse-phase HPLC-PDA method has been formulated for the identification of isatinoid, indigoid and indirubinoid dyes, and applied to their detection in Tyrian Purple pigments from Murex trunculus sea snails. These pigments are spontaneously produced from indoxyl precursors in excised hypobranchial glands of various mollusca. The linear gradient elution method consists of an aqueous acidic methanolic system and separates ten brominated and unbrominated indole and biindole dione colorants in under thirty minutes. This is the first time that all of these components were analyzed by a single elution method, which would allow for the multicomponental chemical fingerprinting of modern and archaeological molluskan pigments. 40 refs.

Koren Z C, Color My World : A Personal Scientific Odyssey into The Art of Ancient Dyes, For the Sake of Humanity: Essays in Honour of Clemens Nathan., 2006, 155-189
Recollections of Tyrian purple analyses by the author. publisher Martinus Nijhoff - Brill Academic Publishers, Leiden, Netherlands, ISBN 90-04-14125-1

Koren Z C, Archaeo-chemical analysis of Royal Purple on a Darius I stone jar, Microchimica Acta, 2008,162, 381-392 ; 10.1007/s00604-007-0862-4; pdf
High-performance liquid chromatography (HPLC) coupled with photodiode array (PDA) detection was used for the microchemical analysis of a purple residue on the surface of a 2500-year old stone jar. This 30 × 37cm pear-shaped marble vessel contains carved inscriptions praising the Persian king Darius I and is unique due to the use of quadrilingual writings on a vessel of that king. The major colorants identified in the purple pigment are 6,6'-dibromoindigo, 6-monobromoindigo, and 6,6'-dibromoindirubin, with negligible contributions by indigo and 6-bromoisatin. This analysis establishes that a marine mollusk was the source of the purple pigment, which is the famous Royal Purple or Tyrian Purple of the ancients. A comparison with the relative dye compositions of various Muricidae species (Hexaplex trunculus, Bolinus brandaris, and Stramonita haemastoma), and with their newly formulated Di-Mono Index values, suggests that the biological provenance of this ancient pigment was probably an indigo-deficient Hexaplex trunculus sea snail. The entire exterior of the vessel - including its base - was originally painted purple by using a fresco-type technique. This is only the second chromatographic finding of a molluskan purple colorant in use as an ancient paint pigment and not as a textile dye, and the only example yet discovered where it is the sole paint pigment on such a large royal art object

Koren Z C, A New HPLC-PDA Method for the Analysis of Tyrian Purple Components, Dyes in History and Archaeology, 2008, 21 26-35
An HPLC method is used to identify isatins, indigos and indirubins in shellfish purple pigments

Koren Z C, Non-Destructive vs. Microchemical Analyses: The Case of Dyes and Pigments., Proceedings of ART2008, 9th International Conference, Non-destructive investigations and microanalysis for the diagnostics and conservation of cultural and environmental heritage, May 25-30, Jerusalem, Israel, 2008, 37.1-37.10
The HPLC method is described for the identification of shellfish purple pigments. pdf

Koren Z C, Chromatographic and colorimetric characterizations of brominated indigoid dyeings., Dyes and Pigments, 2012, 95(3), 491-501
doi: 10.1016/j.dyepig.2012.06.016 ; sciencedirect
Indigo, 6-bromoindigo, and 6,6'-dibromoindigo samples were analysed by HPLC and then were applied to multifiber fabric swatches, each consisting of 13 different synthetic and natural fibrous materials. The results show that filament triacetate and nylon-66 possess the most remarkable color strengths of all the fiber materials investigated in all the dyeings, and of the natural fibers studied, wool possessed the highest color strength and cotton the poorest with all three dyes.

Koren Z C, Chromatographic Investigations of Purple Archaeological Bio-Material Pigments Used as Biblical Dyes., In Sil J.L.R., Trujeque J.R., Castro A.V., Pesqueira M.E. (Editors), Cultural Heritage and Archaeological Issues in Materials Science. Materials Research Society Symposium Proceedings, 2012, Volume 1374, Cambridge University Press (NY), 29-48.
doi: 10.1557/opl.2012.1376
This article discusses recent scientific research performed by the author in understanding the composition of archaeological purple pigments and dyes from molluskan sources, which were primarily used for the dyeing of royal and priestly textiles, as also cited in the Bible. Application of the HPLC analytical method to purple pigments and dyes on archaeological artifacts from the ancient Near and Middle East has lead to a number of breakthroughs and discoveries made by this laboratory.

Koren Z C and Verhecken-Lammens C, An Integrated Microscopic and Chromatographic Analysis of the Molluskan Purple Yarns in the Katoen Natie KTN 1475 Coptic Textile.,DHA31, Antwerp, 2012 (abstract)
The red-purple and blue-purple yarns excised from a 1,500-year old Coptic textile in the collection of Katoen Natie were analysed by means of an integrated physical and chemical approach. The yarns were first examined under a stereo microscope in order to determine their physical construct. It was observed that the red-purple yarn was produced from homogeneously dyed fibres. The blue-purple yarn was dissected and found to consist of fibres possessing three different colours: undyed, red-purple, and blue-purple. Subsequently, HPLC analyses were individually performed on the whole red-purple and blue-purple yarns as well as on the fibres dissected from another sample of the blue-purple yarn. The dye component present in significant quantities in all of the samples was MBI. The dissected red-purple fibres would have been produced solely from a DBI-rich trunculus snail, whereas the blue-purple fibres originated from an IND-rich trunculus snail.

Kosugi Y & Matsumoto K, A convenient and rapid detection method of Kaimurasaki coloring matter by MS., Bunseki Kagaku(Japan analyst, 1994, 43(12), 1133-1136 ; abstract
Mass spectrometry has been applied to the analysis of Kaimurasaki (Tyrian purple), a coloring material of archaeological importance. Kaimurasaki coloring matter was obtained from the hypobrachial glands of Akanishi-gai (Rapana venosa Valencinnes) and mixed with 5% salt water at 5 ºC. The salt water-based sample was directly introduced to the electron ionization source and was heated rapidly. The resulting total ionization current was monitored while adjusting the ionization current from 70 eV to 15 eV. Mass spectra thus obtained at ca. 250 ºC gave parent peaks of dibromoindigotin (m/z 418,420,422), fragment ions of the precursor, 6-bromo-2-methylthioindoleninone and another dibromo compound of ions m/z 404,406,408. The solid coloring matter after removal from salt water and washing with pure water was analyzed well, too. This method was found to be applicable to the detection of the coloring matter in dyed cloth

Krafts KP, Hempelmann E, Oleksyn BJ, The color purple: from royalty to laboratory, with apologies to Malachowski., Biotechnic & Histochemistry, 2011, 86(1), 7-35;
doi: 10.3109/10520295.2010.515490
A detailed history of Tyrian purple up to 1453 AD is followed by a survey of the development of a stain for blood cells, starting 80 years ago with methylene blue and eosin which gave blue and red colors, which was modified to produce a purple which revealed previously unseen structures in, for example, the malarial parasite, Plasmodium.

Krishnaswamy NR and Sundaresan CN, Fascinating organic molecules from nature: 2. The blue of blue jeans and Royal purple, Resonance, 2012, 17(11), 1022-1033; pdf
An introduction to the production and chemistry of indigo and Tyrian purple with 7 references.

Larsen S, Watjen F, The crystal and molecular structures of tyrian purple (6,6'-dibromoindigotin) and 2,2'-dimethoxyindigotin, Acta Chemica Scandanavica, Ser. A, 1980, A34(3), 171-176 ; pdf
Crystals of dibromoindigotin are monoclinic, space group P21/c, a=12.609, b=4.842, c=11.611, beta=104.42 and Z=2; the final R was 0.037

Lavinda O, Mironova I, Karimi S, Pozzi F, Samson J, Ajiki H, Massa L, Ramig K, Singular thermochromic effects in dyeings with Indigo, 6-Bromoindigo, and 6,6’-Dibromoindigo, Dyes and Pigments, 2013, 96(2), 581-589
The dyeing properties of IND, MBI and DBI on 13 fabrics were determined. Many of the dyed fabrics change color markedly with application of gentle heat. For indigo and MBI, the color changes are predominantly towards absorption of longer wavelengths (giving a bluer fabric color), while for DBI, the color changes are towards absorption at shorter wavelengths (giving a redder fabric color). Transmission electron microscopy analysis of MBI-dyed carbon nanotubes suggests that the basis of the thermochromic effect is a change in the size distribution of dye aggregates.

Leshchenko P, Royal purple, Khimiia i Zhizn, 1982, 51-54
The history of discovery of the title dye in mollusks is presented, including methods of isolation, availability, and chemical structure.

Letellier A, Recherches sur la pourpre produite par le Purpura lapillus, Archives de Zoologie Expérimentale et Générale, deuxième série, 1890, 8, 361-403
A detailed examination of the hypobranchial gland of Purpura lapillus and the intermediates which eventually lead to the purple colour

Letellier A, Recherches sur la pourpre produite par le Purpura lapillus, Comptes rendus de l'academie des sciences, 1889, 109, 82-85
A summary of Letellier (1890)

Lacaze-Duthiers H, Mémoire sur le Pourpre, Annales des Sciences Naturelles comprenant la Zoologie, la Botanique, 1859, 4th series, 12, 5-84
A historical and zoological survey with drawings of the hypobranchial glands of M brandaris, P lapillus, M trunculus, M erinaceus

Lacaze-Duthiers H, Mémoire sur le Pourpre, Mémoires de la Sociéte Imperiale des Sciences de l'Agriculture et des Arts de Lille, 1859, 2éme Serie, 6, 303-380
A multi-part review and research summary

Lech L, Jarosz M , High-performance liquid chromatography coupled with spectrophotometric and electrospray mass spectrometric detection (HPLC–UV–Vis–ESI MS) was used for characterization of natural dyes present in historical art works, Analytical and Bioanalytical Chemistry, 2011, 399(9), 3241–3251; doi
A procedure was developed using high-performance liquid chromatography coupled with spectrophotometric and electrospray mass spectrometric detection (HPLC-UV-Vis-ESI MS) for the characterization of natural dyes, including indigo, indirubin and bromoindigos, present in historical art works, and was used to identify dyes taken from three selected historical chasubles which belong to the collection of the Wawel Cathedral treasury (Cracow, Poland). 6-Bromoisatin was obtained from a 30-day exposure of a Tyrian purple solution to sunlight

Lincke G, Molecular stacks as a common characteristic in the crystal lattice of organic pigment dyes. A contribution to the "soluble-insoluble" dichotomy of dyes and pigments from the technological point of view, Dyes and Pigments, 2003, 59, 1-24
Dichloroindigo and dibromoindigo have a different stack spacing from the parent indigo

Magiatis P and Skaltsounis L, From Hexaplex trunculus to new kinase inhibitory indirubins, in Indirubin, the red shade of indigo, editors Meijer L, Guyard N, Skaltsounis LA and Eisenbrand G, France: Life in Progress Editions, ISBN 2-9518029-0-0, 2006, 147-156
Gastropod mollusks of the Muricidae family have been used since the antiquity to produce the "Tyrian purple" dye. In an effort to identify kinase inhibitors, we investigated the natural indirubins produced by the Mediterranean mollusk Hexaplex trunculus. Bio-guided fractionation of the extracts of that mollusk, led to the isolation of a new natural product, 6-bromoindirubin. See Meijer 2003. This product showed very strong inhibitory activity against glycogen synthase kinase (GSK-3) and was used as a lead compound for the synthesis of several derivatives, with various substituents at positions 1,4,5,6,3',6'. The product 6-bromo-indirubin 3'-oxime (BIO) showed the most powerful activity (IC50 = 5 uM), combined with very good selectivity for GSK-3. Using the co-crystal structures of various indirubins with GSK-3beta, CDK2 and CDK5/p25, we have modelled the binding of indirubins within the ATP-binding pocket of these kinases. This modelling approach provided some insight into the molecular basis of indirubins' action and selectivity and allowed us to forecast some improvements of this family of bis-indoles as kinase inhibitors.

Malaszkiewicz J, Chromogene und Farbstoff-Komponenten der Purpurschnicke Murex trunculus, Thesis, Saarbrucken, 1967
The chemistry of the prochromogens of Murex trunculus are investigated

Mantzouris D and Karapanagiotis I, Identification of indirubin and monobromoindirubins in Murex brandaris, Dyes and Pigments, 2014, 104, 194-196
doi: 10.1016/j.dyepig.2014.01.011
For the first time, indirubin, 6-bromoindirubin and 6'-bromoindirubin are detected in hypobranchial glands, removed from Murex brandaris molluscs collected from the coastline of Thera island, Greece.

Maravelaki-Kalaitzaki P and Kallithrakas-Kontos, Pigment and terracotta analyses of Hellenistic figurines in Crete, Analytica Chimica Acta, 2003, 497, 209-225 ; sciencedirect ; pdf
The purple colour was identified from IR measurements as dibromoindigo and bromine detected by EDXRF

Margariti C, Protopapas S, Allen N, Vishnyakov V, Identification of purple dye from molluscs on an excavated textile by non-destructive analytical techniques, Dyes and Pigments, 2013, 96, 774-780;
doi: 10.1016/j.dyepig.2012.11.003
This paper presents the results of dye analysis performed on the excavated textile find HTR-73 from the Kerameikos cemetery, dated from the 5th century BC, in Athens. The techniques applied were Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) analysis, Cathodoluminescence and micro Raman, finding dibromoindigo originating from Murex trunculus.

March RE, Papanastasiou M, McMahon AW, Allen NS, An investigation of paint from a mural in the church of Sainte Madeleine, Manas, France, Journal of Mass Spectrometry, 2011, 46(8), 816-820 ; doi: 10.1002/jms.1950
The pigment in brown paint samples was shown to contain 6-bromoindigo and 6,6'-dibromoindigo (98:2) using atmospheric pressure photoionization combined with liquid chromatography and tandem mass spectrometry. The authors conclude that the origin is Murex brandaris.

Mcgovern P E, The Royal Purple and the Biblical Blue (Argaman and Tekhelet) - The Study of Chief Rabbi Herzog,Isaac on the Dye Industries in Ancient-Israel and recent Scientific Contributions - Spanier,E, ISIS, 1990, 81(308), 563-565
Book review

McGovern P E, Lazar J, Michel R H, Caveats on the analysis of indigoid dyes by mass spectrometry, Journal of the Society of Dyers and Colourists, 1991, 107(n7-8), 280-281 ; 10.1111/j.1478-4408.1991.tb01354.x
Dibromoindigotin on fibres subjected to MS gives some monobromoindigo and the amount formed is reduced by extraction of the dye with DMSO.

McGovern P E, Lazar J, Michel R H, The analysis of indigoid dyes by mass spectrometry, Journal of the Society of Dyers and Colourists, 1990, 106(1), 22-25 ;doi: 10.1111/j.1478-4408.1990.tb01225.x
MS was used to identify indigo and dibromoindigo in archaeological fibres and the significance of the monobromo derivative is discussed, viz. that it can be used to distinguish between the natural pigment and the pigment which is an intentional mixture of indigo and dibromoindigo

McGovern P E, Michel R H, Royal Purple dye: its identification by complementary physicochemical techniques, Chemtracts: Inorg. Chem., 1991, 3(1), 69-76
Purple deposits on pottery at Sarepta were examined by PIXE, ESCA, FT-IR and chemical reduction - oxidation and photodebromination showed them to be dibromoindigotin.

McGovern P E, Michel R H, The Photochemistry of Royal Purple, The Spectrum, 1991, 4, 6-9
The photochemical processes associated with purple production and dyeing with leuco-indigos are discussed

McGovern P E, Michel R H, Royal purple dye: its identification by complementary physicochemical techniques., MASCA Res. Pap. Sci.Archaeol., 1990, 7, 69-76
Purple deposits on pottery at Sarepta were examined by PIXE, ESCA, FT-IR and chemical reduction - oxidation and photodebromination showed them to be dibromoindigotin.

McGovern P E, Michel R H, Royal Purple dye: the chemical reconstruction of the ancient Mediterranean industry, Accounts of Chemical Research, 1990, 23(5), 152-158 ; doi: 10.1021/ar00173a006 ; pdf
The historical production, social and religious significance of dibromoindigotin in the Mediterranean region is discussed

McGovern P E, Michel R H, Royal Purple dye: tracing the chemical origins of the industry, Analytical Chemistry, 1985, 57(14), 1514A-1522A ; doi: 10.1021/ac00291a002
13th century BC pottery sherd analysis by PIXE, ESCA and FT-IR showed that a purple deposit was dibromoindigotin

McGovern P E, Michel R H, Royal purple and the pre-Phoenician dye industry of Lebanon, MASCA J., 1984, 3(3), 67-70
13th century BC pottery sherd analysis by PIXE, ESCA and FT-IR showed that a purple deposit was dibromoindigotin

K McLaren, a letter, COLOR research and application, 1983, 8(3), 164
A letter arguing that Tyrian purple, as produced by photochemical reactions from molluscs, is not a vat dye

Meijer L, Skaltsounis A-K, Magiatis P, Polychronopoulos P, Knockaert M, Leost M, Ryan X P, Vonica C A, Brivanlou A, Dajani R, Crovace C, Tarricone C, Musacchio A, Roe S M, Pearl L, and Greengard P, GSK-3-Selective Inhibitors Derived from Tyrian Purple Indirubins, Chemistry & Biology, 2003, 10(12), 1255-1266 ; doi: 10.1016/j.chembiol.2003.11.010 ; link ; pdf
Gastropod mollusks have been used for over 2500 years to produce the "Tyrian purple" dye made famous by the Phoenicians. This dye is constituted of mixed bromine-substituted indigo and indirubin isomers. Hexaplus trunculus (60 kg) were processed to give indirubin (3.5 mg), 6'-bromoindirubin (5.5 mg), 6-bromoindirubin (2.8 mg) and 6,6'-dibromoindirubin (3 mg)

Melzer R R, Brandhuber P, Zimmermann T, Smola U, Der Purpur: Farben aus dem Meer, Biologie in unserer Zeit, 2001, 31(1), 30-39
In ancient times the colour of gods and kings, Tyrian purple, was made by extracting the leucobase from myriads of purple snails (Muricidae) and light-induced oxidation. A survey of its history, production. and cultural and social relevance is given. The biology of purple snails is described in the light of old as well as of modern sources. In addition, studies on the purple stain's chemistry as well as biochemistry are reviewed, and a procedure for the making of purple is presented to be used in marine biology courses. Tyrian purple was a treasured substance, and a myth. The colour and its uncommon producers stand for the way in which humans look at the sea - and how this view changes.

Michel R H, Lazar J, McGovern P E, The chemical composition of the indigoid dyes derived from the hypobranchial glandular secretions of Murex molluscs, Journal of the Society of Dyers and Colourists, 1992, 108(3), 145-150
Mass spectrometry of pigments from Murex brandaris and M. trunculus reveals indigo and mono- and di-bromo derivatives.

Michel R H, Lazar J, McGovern P E, Indigoid Dyes in Peruvian and Coptic Textiles, Archeomaterials, 1992, 6, 69-83
Dibromoindigo was found on Coptic and Peruvian textiles

Michel R H, McGovern P E, The chemical processing of Royal Purple dye: ancient descriptions as elucidated by modern science, part II, Archeomaterials, 1990, 4(1), 97-104
The chemistry of Tyrian Purple production is discussed with reference to ancient descriptions from Rome and Egypt, with some supporting evidence from experiments

Michel R H, McGovern P E, The chemical processing of Royal Purple dye: ancient descriptions as elucidated by modern science, Archeomaterials, 1987, 1(2), 135-143
Ancient Tyrian Purple production is suggested to be via a leuco-form with tin as reductant

Michel-Morfin J E, Chavez E A, Effect of repetitive dye extraction over yield and survival rate of the purple snail Plicopurpura pansa (Gould, 1853), Journal of Shellfish Research, 2000, 19(2), 913-917
The purple snail is an important economic species because of the dye obtained from it in western Mexico. This dye has been used since ancient times to color ceremonial dresses purple. Other. snails produce dye, but Plicopurpura pansa dye extraction was done without killing the snail. Repetitive dye extraction is possible. The repeat time between each milking, dye yield versus milking frequency, and effect on survival was determined by repetitive milking snail groups several times (7, 14, 21, and 28 days). Mortality in the most frequently milked groups and dye yield reduction occurred (every 7 and 14 days). When milking frequency occurred every 21 days, the best dye yield and 100% survival rate was observed. These results suggest wild populations can be exploited using optimum extraction schedules, leaving at least 21 days between each dye extraction.

Michel-Morfin J E, Chavez E A, Landa V, Population parameters and dye yield of the purple snail Plicopurpura pansa (Gould, 1853) of west central Mexico, Journal of Shellfish Research, 2000, 19(2), 919-925
The purple snail (Plicopurpura pansa) is a conspicuous rocky shore species of the intertidal zone of tropical western America. It is considered a potential resource due to the dye it produces. Estimates of population density, sex ratio, growth parameters, mortality, and recruitment were obtained from bimonthly samplings from 1993 through 1995 on a rocky shore of west central Mexico. A different growth rate between sexes was observed. Mortality coefficients for the population are estimated for the first time. Recruitment to rocky shores occurs principally from September through March. The life span (longevity) was estimated as 11 y. Dye production related to size and sex was determined and is described by an exponential relation.

Naegel L C A and Murillo Alvarez J I, Biological and chemical properties of the secretion from the hypobranchial gland of the purple snail Plicopurpura pansa, Journal of Shellfish Research, 2005, 24(2), 421-428
The hypobranchial gland of the muricid Plicopurpura pansa (Gould, 1853) is so active that the snails can be stimulated periodically without harming them to expulse the secretion. This property is a great advantage in the study about its biologic and chemical characteristics. No statistical difference could be determined between the incidence of expulsion and the sex of the animals. Also the test on whether the size of the animals had an influence on the frequency of expulsion showed no relation. The incidence of expulsions is the same between the different size classes. From between September 2003 and February 2005 collected snails (total number 3,577) 1,724 (48.2%) expulsed secretion. The proportion of snails that expulsed or not varied from month to month, however no clear seasonal trend could be observed. We determined in the laboratory the amount of the total organic compounds in the "milk" and found great variations (from 34.2 mg/100 animals to 337.8 mg/100 animals). We determined from 11 samples collected during different months an average of 148.9 mg organic compounds/100 animals. The "milk" expulsed from the hypobranchial gland of P. pansa contains 6.15% ([+ or -] 1.07 SD n = 3) total solids, 21.3 mg/ml ([+ or -] 17.8 SD n = 38) soluble proteins, and 6.01 mg/ml ([+ or -] 3;2 SD n = 38) carbohydrates. In organic extracts from the secretion of the hypobranchial gland we determined in a microwell assay a 50% lethal dose ([LD.sub.50]) of 81.72 µg/mL (SD 35.78 n = 5) against Anemia nanplii. In assays to determine possible antibacterial activities in organic extracts we found two inhibition zones against Staphylococcus aureus. To quantify the microbial activity we determined a lowest inhibitory concentration of 125 µg/disk. By thin layer- and column chromatography, as well as by IR spectroscopy, we could preliminary identify some of the organic compounds in the "milk" and in organic extracts. By comparing previously reported front reference values (Rf-values) we could identify the dye precursor tyrindolinone, tyriverdin and bromoisatin. By column chromatography the extract was separated with different mixtures of organic solvents. In a first step gradient fractionation we obtained three fractions, which were unstable in light and turned immediately purple, and one yellow, light stable fraction. Two light stable brownish-colored fractions turned purple after acid hydrolysis. They were united and subjected to further fractionation, where four fractions and the green insoluble tyriverdin were obtained. By IR spectrophotometry and comparison with reported spectra it could be shown that one fractionated compound was a salt of probably 6-bromo-2-methylsulfonylindoxylsulfate and the other 6-bromoisatin. In organic extracts of the secretion free radical scavenging activities were determined by the 2,2-dipbenyl-l-picrylhydrazyl radical method (DPPH). We observed two yellow patches above a purple background. By IR spectroscopy of the organic extract used we could determine the chromogen IV, probably 6-bromo-2 methylsulfonylindoxylsulfate, as a substance responsible for the free radical scavenging activity.

Naegel, L and Cooksey C J, Tyrian purple from marine muricids, especially from Plicopurpura pansa (Gould, 1853), Journal of Shellfish Research, 2002, 21(1), 193-200
Most marine snails of the family Muricidae produce in the hypobranchial gland a viscous secretion containing, besides mucus and biologically-active compounds, minute amounts of chromogens. These chromogens develop enzymatically and under the influence of light and oxygen into a purple pigment known variously as "Tyrian Purple", "Royal Purple" or shellfish purple. In the hypobranchial gland the enzyme purpurase is kept apart from the chromogens, so that no pigments are formed under normal conditions. The chromogens together with the enzyme can be obtained from Plicopurpura pansa (Gould, 1853) by "milking" without harming the animals. Different species of muricids produce different pigments, depending on the number and concentration of different chromogens and on the varying light intensity and oxygen availability during pigment formation. The main pigment obtained from the hypobranchial gland from muricids contains indigoids. The "ink" of P. pansa is mainly 6,6´-dibromindigo with smaller amounts of 6-bromoindigo and 6,6'-dibromoindirubin, similar to that of Murex brandaris.

Napier J, Manufacturing Arts in Ancient Times with special reference to bible history, Paisley: Alexander Gardner, 1879, 254-264
The ancient literature is briefly surveyed and the author relates that the colour is readily obtained from Purpura lapillus found in Arran.

de Negri G and A F, Della Porpora degli Antichi e Relazione di altri lavori eseguiti nel Laboratorio di Chimice Generale della R. Università di Genova, Atti della Reale Accademia del Lincei, 2nd series, 1875-1876, 3, 394-442

de Negri G and A F, Dell' indigotina negli animali ovvero della porpora degli antichi (On Indigotin in Animals, or the Purple of the Ancients), Gazzetta Chimia Italiana, 1875, 5, 437-438

Nowik W, Marcinowska R, Kusyk K, Cardon D, Trojanowicz M, High Performance Liquid Chromatography of Slightly Soluble Brominated Indigoids from Tyrian Purple, Journal of Chromatography A, 2010, doi:10.1016/j.chroma.2011.01.004
This HPLC study of various stationary phase characteristics, mobile phase composition, elution gradient parameters and temperature on the peak shape of the main components of Tyrian purple reveals new analogues of brominated and unbrominated cis-indirubins which were found in the shellfish purple from Hexaplex trunculus. 43 refs.

Nuttall Z, A Curious survival in Mexico of the use of the Purpura Shell-fish for dyeing, Putnam Anniversary Volume, The Torch Press, Cedar Rapids, Iowa, 1909, 366-384
Details are given of the dyeing industry using Purpura pansa

Olivier J P, Treuil R, Vandenabeele F, Malia - Nécropole de l'Ilot du Christ, Bulletin de Correspondance Hellénique, 1970, 94, 871-879
Find of shells of Hexaplex trunculus from Middle Minoan time on Christ Island at Malia/Crete

Papanastasiou M, McMahon AW, The Use of Atmospheric Pressure Photoionization Mass Spectrometry for the Analysis of Indigoid Compounds in Natural Dyes, Proceedings of the 53rd ASMS Conference on Mass Spectrometry and Allied Topics, San Antonio, Texas, June 5-9, 2005, 2005
MS was used to detect and quantify indigo and bromoindigos in Mediterranean molluscs

Papanastasiou M, Allen NS, Adam McMahon A, Naegel LCA, Edge M and Protopappas S, Analysis of Indigo-type Compounds in Natural Dyes by Negative Ion Atmospheric Pressure Photoionization Mass Spectrometry, Dyes and Pigments, 2011, 92(3), 1192–1198 ; doi: 10.1016/j.dyepig.2011.08.007
Atmospheric Pressure Photoionization (APPI) in Mass Spectrometry (MS) has been used to detect indigo and bromoindigos in shellfish pigments and natural indigo in historic samples following HPLC

Pfister R, Textiles de Palmyre découverts par le Service des antiquités du Hautcommissariat de la Républic française dans la nécropole de Palmyre., Paris: Éditions d’Art et d’Histoire., 1934-1940, 1-3,
Proof of purple dyestuff on textiles found in Palmyra

Pfister R, Teinture et Alchimie dans l’Orient Hellènestique.., Seminarium Kondakovianum. Prague, 1935, 7, pp 1-59
Chemical tests (p32) for identifying genuine purple in textiles (60 Mb)

Pietra F, Total Synthesis of Marine Natural-Products - A powerful contribution to the understanding and development of marine organic-chemistry, Gazzetta Chimica Italiana, 1985, 115(9), 443-485

Pinkney J M, Chalmers J A, Synthesizing Tyrian purple, Education in Chemistry, 1979, 16(5), 144-145
p-Toluidine is nitrated and the product converted by the Sandmeyer reaction to 4-bromo-2-nitrotoluene which is oxidised to the corresponding aldehyde then converted into dibromoindigotin with acetone in low overall yield; the vat dyeing of cotton is described

Pliny the Elder, The Natural History, chapter 62: How wools are dyed with the juices of the purple, 79
An edited translation by John Bostock, M.D., F.R.S., H.T. Riley, Esq., B.A. in 1855. This chapter describes the preparation of a dye bath from molluscs. The full text can be found at

Polychronopoulos P, Magiatis P, Skaltsounis A-L, Myrianthopoulos V, Mikros E, Tarricone A, Musacchio A, Roe M, Pearl L, Leost M, Greengard P,and Meijer L, Structural Basis for the Synthesis of Indirubins as Potent and Selective Inhibitors of Glycogen Synthase Kinase-3 and Cyclin-Dependent Kinases, Journal of Medicinal Chemistry, 2004, 47(4), 935-946
Syntheses of 6-bromo-, 6'-bromo- and 6,6'-dibromo-indirubin are given with 1H and 13C NMR and MS data

Pouliquen J, Kossanyi J, Du Manteau de pourpre de Cesar aux blue jeans en passant par le Pays de Cocagne, New Journal of Chemistry, 1992, 16, 331-335
A review in French of the history, production and chemistry of dibromoindigotin and indigo, including historic line drawings of mollusks

Pozzi F, Development of innovative analytical procedures for the identification of organic colorants of interest in art and archaeology, PhD thesis (Milan), 2011
In Chapter 8, Raman and DFT study of monobromoindigo, the Raman spectrum measurements were made at 488 and 785 nm

Puchalska M, Poe-Pawlak K, Zadrona I, Hryszko H, Jarosz M, Identification of indigoid dyes in natural organic pigments used in historical art objects by high-performance liquid chromatography coupled to electrospray ionization mass spectrometry, Journal of Mass Spectrometry, 2004, 39(12), 1441-1449
Reversed-phase liquid chromatography with electrospray ionization mass spectrometry (ESI-MS) offers detection limits in the range 0.03-5.00 µg ml-1 for the color compounds examined. The method developed made it possible to identify indigo and its isomers in genuine Indian indigo, indigo from woad and Tyrian Purple.

Quiring H, Vorphönizischer Königspurpur und uquu-Stein, Forschungen und Fortschritte, 1947, 21/23, 98-99
The author tries to demonstrate that purple is not mentioned on tablets found in Ugarit. He means that realgar is mentioned in these documents

Réaumur R A F de, Decouverte d'une nouvelle Teinture de Poupre, Mém de l'Acad Royale des Sciences Amsterdam, 1711, 216-258
Working with Purpura capillus on the coast of Poitou, showed that air is necessary for the purple colour to develop from hypobranchial gland extracts

Réaumur R A F de, Quelques experiences sur la liqueur colorante qui fournait la pourpre, Mém Acad Roy Sci Amsterdam, 1736
Observations on the coast of Poitou

Reese D S, Shells from Sarepta (Lebanon) and east Mediterranean purple-dye production, Mediterranean Archaeology and Archaeometry, 2010, 10(1), 113-141
This paper concerns the shells from the 1969-74 excavations at Sarepta (Lebanon) under the direction of the late J.B. Pritchard (University of Pennsylvania). Most of the 500 marine shells, ranging in date from the LB I to Roman/Byzantine, are typical Mediterranean forms. Of special interest are three large accumulations of crushed Murex trunculus of LB II, LB III to Iron I, and LB III or Iron I date. The Sarepta shell purple-dye evidence is described in detail and is compared with the other evidence from the Eastern Mediterranean. Over 150 references.

Reese D S, Marine Shells, In Tristan J. Barako, Tel Mor - The Moshe Dothan Excavations, 1959-1960. IAA Reports 32. Jerusalem: Israel Antiquities Authority, 2007, ch. 12, 233-238
A description of murex shells found at Tel Mor and a referenced summary of shells found at other sites on the Levantine coast in Israel (Yavne-Yam, Apollonia-Arsuf, Tel Mevorakh, Tel Dor, Tel Megadim, Capernaum, Tel 'Akko, Tel Kabri), Lebanon (Tyre, Sarepta, Sidon) and Syria (Tell Rifa'at, Palmyra)

Reese D S, Whale bones and shell purple-dye at Motya (Western Sicily, Italy, Oxford Journal of Archaeology, 2005, 24(2), 107-114
Excavations 30 years ago at 5th-6th century BC Motya produced a unique assemblage of four Sperm whale vertebrae, crushed purple-dye shells, and stone tools.

Reese D S, Palaikastro Shells and Bronze Age Purple-dye production in the Mediterranean Basin, The Annual of the British School of Archaeology at Athens, 1987, 82, 201-206
Details of shells and fragments of purple-producing mollusks found at a variety of sites

Reese D S, The Mediterranean Shell Purple-dye Industry, American Journal of Archaeology, 1986, 90(2), 183
Abstract of a meeting in which the author presents information on shell purple-dye collections from Greece, Turkey, Cyprus, Lebanon and Israel

Reese D S, Industrial Exploitation of Murex Shells; Purple-dye and Lime Production at Sidi Khrebish, Benghazi (Berenice), Libyan Studies. The Society for Libyan Studies 11th Annual Report (1979-80), 1980, 79-93
Ancient and modern sources of mollusks and purple-dye production with 32 references

Reese D S, Iron Age Shell Purple-Dye Production in the Aegean, Kommos IV, The Greek Sanctuary, Part 1. Eds: J W and M C Shaw, Princetown University Press, 2000, 643-645
A summary of recent archaeological data on shell-fish purple sources

Reinhold M, The history of purple as a status symbol in antiquity, Collection Latomus, 1970, 116, 1-73
A major survey of classical references to the purple dye

Reimann M, Synthese von Antiken Purpur, report, 2008, 18 pages
The synthesis of dibromoindigo as described by Chambers and Pinkney in 1979 was examined and some alternatives suggested. Reaction mechanisms are discussed and IR spectra presented. The cost of dibromoindigo was estimated at 2000 euros/gram

Reinking K, Über den Schnecken-Purpur, Melliand Textilberichte, 1929, 10, 634-636
Review on the knowledge of purple dyeing in the time of about 1930

Ribechini E, Pérez-Arantegui J, Colombini MP, Positive and negative-mode laser desorption/ionization-mass spectrometry (LDI-MS) for the detection of indigoids in archaeological purple, Journal of Mass Spectrometry , 2013, 48(3), 384–391
Positive and negative-mode laser desorption/ionization mass spectrometry (LDI-MS) was used for the first time to detect indigoids in shellfish purple.
doi: 10.1002/jms.3169

Rios-Jara E, León H G, Lizárraga-Chávez L and Michel-Morfín J E, Produccíon y tiempo de recuperacíon del tinte de Plicopurpura patula pansa (Neogastropoda: Muricidae) en Jalisco, México, Revista de Biologia Tropical, 1994, 42(3), 537-545
In this study, it is shown that more dye is produced by larger snails; females produce more dye than males of the same size; individuals larger tham 5 cm recover from milking in 7 days and smaller ones in 15-21 days

Robertson A and Waters R B, IX.-Syntheses of Glucosides. Part VII. The Synthesis of 6-Bromoindican., Journal of the Chemical Society, 1931, 72-76
6-Bromoindican warmed with 2% HCl and FeCl3 immediately gave 6,6'-dibromoindigo. Hydrolysis of 6-bromoindican by warm 3% HCl in the presence of isatin gave a quantitative yield of 6-bromoindirubin, which crystallised from hot aniline in purple prisms with a green metallic sheen. m.p. >340 °C.

Roller R A, Rickett J D, Stickle W B, The hypobranchial gland of the estuarine snail Stramonita haemastoma canaliculata (Gray) (Prosobranchia, Muricidae) - A light and electron microscope study, American Malacological Bulletin, 1995, 11(2), 177-190
One of the secretory products of the hypobranchial gland possesses the staining characteristics of the "Tyrian Purple'' dye

Ron M, Difference between tyrian purple and hyacinthine purple, Yalkut Le-sivim, Le-tekhnol. U-le-minhal Shel Tekst., 1985, 104, 38-39
Hyacinthine purple, derived from Murex trunculus, is a mixture of dibromoindigotin and indigo, and the colourant from M. brandaris and Thais hemastoma is mainly dibromoindigotin

Ronci M, Rudd D, Guinan T, Benkendorff K, Voelcker NH, Mass spectrometry imaging on porous silicon: investigating the distribution of bioactives in marine mollusc tissues., Analytical chemistry, 2012, 84(21), 8996-9001
doi: 10.1021/ac3027433
Desorption/ionization on porous silicon-mass spectrometry (DIOS-MS)was used to investigate the distribution of biologically active brominated precursors to Tyrian purple in the hypobranchial gland of the marine mollusc, Dicathais orbita

Rottig W, Uber eine einfache Synthese des antiken Purpurs, J Prakt Chem, 1935, 142, 35-36
See Wahl A

Ruscillo D, Reconstructing murex Royal Purple and Biblical Blue in the Aegean, 2005, in Archaeomalacology: Molluscs in former environments of human behaviour (ed. Daniella E. Bar-Yosef Mayer), ISBN 1 84217 120 8 pp. 99–106
Catching and processing Murex trunculus in Crete in 2001

Sachs F, Kempf R, Uber p-Halogen-o-nitrobenzaldehyde, Berichte der Deutschen Chemische Gesellschaft, 1903, 36, 3299-3303
Synthesis of 6,6'-dibromoindigotin from 4-bromo-2-nitrobenzaldehyde and acetone with sodium hydroxide solution. The product is soluble in warm sulfuric acid, giving a deep green solution and in warm aniline to give a blue solution

Sachs F, Sichel E, Ueber p-substituirte o-Nitrobenzaldehyde, Berichte der Deutschen Chemische Gesellschaft, 1904, 37, 1861-1874
Synthesis of 6,6'-dibromoindigotin from 4-bromo-2-nitrophenyllactic acid methyl ketone and aqueous sodium hydroxide or carbonate solution. Bromination of indigotin gives a product of different colour (blue)

Saltzman M, Analysis of Dyes in Museum Textiles or, You Can't Tell a Dye by Its Color, Textile Conservation Symposium in Honor of Pat Reeves, The Conservation Center, Los Angeles County Museum of Art, 1986, 27-39
The use of reflectance and solution (in chloroform and sulfuric acid) spectra to determine the presence of shellfish purple

Saltzman M, Identifying Dyes in Textiles, American Scientist, 1992, 80, 474-481
Shellfish purple and indigo dyed textiles can be distinguished by light absorption reflectance maxima of 520 nm and 640 nm respectively

Saltzman M, Keay A M and Christensen, J, The Identification of Colorants in Ancient Textiles, Dyestuffs, 1963, 44(8), 241-251
Use of solution absorption spectroscopy in chloroform or sulfuric acid solution to identify dibromoindigo in pre-Columbian Peruvian textiles

Sasaki K, Chemical structure of ancient purple dye. Tyrian purple., Senryo To Yakuhin, 1975, 20(2), 36-45
Dibromoindigotin was found in products of Rapana thomasiana by IR and X-RAY spectroscopy

Sato M and Sasaki Y, Blue and Purple Dyestuffs Used for Ancient Textiles, Dyes in History and Archaeology, 2003, 19, 100-105
XRF and visible absorption spectra of an extract of a purple dyed wool textile from Al-Tar in Iraq suggest dibromoindigo as the colorant

Schaeffer A, Neuere Ansichten über den antiken Purpur, Chemiker-Zeitung, 1941, 65, 273-275
Review on the knowledge of purple dyeing in the time of about 1940

Schaeffer C F A, Une Industrie d'Ugarit - la Pourpre, Annales Archéologiques de Syrie, 1951, 1, 188-192
Report on Purple on the tablets found in Ugarit

Schatz P F, Indigo and Tyrian purple - In nature and in the lab, Journal of Chemical Education, 2001, 78(11), 1442-1443
The use and synthesis of the dyes indigo and Tyrian purple are discussed.

Schechter E, The Thin Blue Line, The Jerusalem Report, 1999, 10(1), 23
The origin and identity of tekhelet are described and a brief history of P'til Tekhelet given

Schmidt-Colinet A, Stauffer A, AI-Ascad K., Textilien aus Palmyra - Neue und alte Funde, P. von Zabern: Mainz, 2000
New investigations of the textiles from Palmyra with information on purple dyes

Schunck E, Notes on the Purple of the Ancients. 1. The Chromogen of Purpura Capillus. 2. Properties of the Colouring Matter formed by Insolation from the Chromogen of Purpura Capillus., Journal of the Chemical Society, 1879, 35, 589-596
Following a summary of literature from 1616, experiments are described in which 400 Purpura capillus collected from Hastings yielded 7 mg of purple dye, for which the name punicin is suggested, and demonstrated solubility and sublimation properties

Schunck E, Notes on the Purple of the Ancients. 3. Purple dyeing in modern times, Journal of the Chemical Society, 1880, 37, 613-617
Dyeing in South America is described and the analysis of a sample from Nicaragua

Schweppe H, Handbuch der Naturfarbstoffe. Vorkommen, Verwendung, Nachweis, ecomed: Landsberg/Lech., 1993, 304-318
A summary of the use of purple natural shell-fish dyes

Schweppe H, Untersuchung alter Textilfärbungen, Die BASF, 1976, 26, 29-36
Description of an analysis method for the proof of purple dyeing and a report on a find of purple in a Roman grave of Wehringen near Augsburg

Schweppe H, Nachweis von Farbstoffen auf alten Textilien, Fresenius' Zeitschrift fur Analytische Chemie, 1975, 276, 291-296
Use of ammonia - dithionite followed by exposure to sunlight for 30 min giving a blue colour to detect dibromoindigo in textiles

Shiomi K, Sasaki K, Yamanaka H, and Kikuchi T, Volatile Sulfur Compounds Responsible for a Fetid Odor of the Hypobranchial Gland of Muricid Gastropods Reishia (Thais) clavigera and R. (T.) bronni, Bulletin of the Japanese Society of Scientific Fisheries, 1982, 48(9), 1353-1356
GC was used to identify the odors from two species. In both, the highest concentration was found in the hypobranchial glands: methanethiol, 74-192 µg/g, and dimethyl disulfide, 15-49 µg/g

Shimoyama S, Studies on the non-destructive determination of dyestuffs used in ancient colored cloths and ukiyo-e prints by the three-dimensional display of fluorescence spectra, Bunseki Kagaku, 1999, 48(10), 951-952
For the purpose of the title, the fluorescence spectra of dyestuffs were measured with a Hitachi F-4500 spectrophotometer equipped with a personal computer for data transaction and a double-bundle-type fiber-optic cable. Three-dimensional (3-D) spectra were drawn as contour plot diagrams of the fluorescence intensity upon the coordinate of excitation vs emission wavelength. The 3-D spectra of standard natural dyestuffs (fifteen botanical and one mollusc origins) dyed on silk and/or cotton (for cloths) and Japanese paper (for Ukiyo-e) could be distinguished from the position of the top ring of contour lines and their fingerprint patterns, even though it contains two or three main components. From a comparison of the 3-D spectrum with standards, the origin of the colored textile remnant attached on a shell bracelet found at Yoshinogari ruin (B.C. 100) was identified to be deteriorated Tyrian purple, and blue, green, red yarns interwoven into Chinese Brocade (A.D. 1600?1700) to be indigo, Amur cork and indigo, Amur cork and safflower, respectively. Concerning Ukiyo-e, red and yellow colors on "Yokkaichi" from fifty-three-stages of Tokaido (A.D. 1823) by Katsushika Hokusai, and blue color on "Evening Snow" from eight views of Edo (A.D. 1821) by Gototei Kunisada were determined to be safflower, turmeric and indigo, respectively

Shimoyama S, Noda Y, Non-destructive three-dimensional fluorescence technique, Dyes in History and Archaeology, 1994, 12, 50-61
Identification of shellfish purple, probably from Rapana thomasiana, using a non-destructive technique. The dye was on a small fragment of silk textile dated to the 1st century BC, excavated in Japan

Shimoyama S, Noda Y, Nondestructive determination of Natural Dyestuffs used for ancient coloring cloth by the 3-dimensional fluorescence-spectrum, Bunseki Kagaku, 1992, 41(6), 243-250

Sidebotham S E, Wendrich W Z, Preliminary Report of the 1995 Excavations at Berenike (Egyptian Red Sea Coast) and the Survey of the Eastern Desert, Leiden : Research School CNWS, 1996
Proof of purple dyestuff on textiles of Roman time from Berenike

Sinclair R S and Thomson M, Light induced colour changes during tyrian purple dyeing, Dyes in History and Archaeology, 1994
A poster showing the different colour variations on substrates and the effect of sunlight induced photodebromination which results in a blue colour

Skaltsounis L A, Indigoids: From natural dyeing agents to selective kinase inhibitors, Planta Med, 2012; 78 - IL6
DOI: 10.1055/s-0032-1320193
Investigations into components of shellfish purple led to pharmacologically active bromoindirubins

Smith AM, From Murex shells to purple cloth, Journal for Semitics, 2010, 19(2), 599-611.
The Phoenicians produced, procured, transported and sold many different articles, but their most famous and most expensive product no doubt was purple dyed cloth, also called Tyrian or royal purple. In this article an overview will be given of the production methods of this precious commodity, various types of purple cloth, purple thread for embroidery and blue-purple cords in tassels on clothing as well as other uses for Murex shells. Also, attention will be given to the ecological impact of the use of Murex molluscs on the water quality of the Mediterranean Sea.

Soldt, W H van, Fabrics and Dyes at Ugarit, Ugarit-Forschungen, 1990, 321-357
Investigation of trading tablets from Ugarit, some containing mention of purple dye

Soleim O, Purple - an ancient dye and a modern problem, Naturen, 1975, 99(1), 3-9
The history and mythology of Tyrian purple are discussed with no references

Sotiropoulou S, La pourpre dans l’art cycladique: identification du pigment dans les peintures murales d’Akrotiri (Théra, Grèce), Preistoria Alpina, 2005, Suppl. 1, v.40, 167-176
Recent physico-chemical research on pigments of wall paintings of Akrotiri demonstrates the use of purple in the Egean Late Bronze Age.

Sotiropoulou S and Karapanagiotis I, Conchylian purple investigations in prehistoric wall paintings of the Aegean area, in Indirubin, the red shade of indigo, editors Meijer L, Guyard N, Skaltsounis LA and Eisenbrand G, France: Life in Progress Editions, ISBN 2-9518029-0-0, 2006, 71-78
According to the archaeological deductions, the origin of true purple dyeing technology is proven native of the Aegean world, dating at least from the 1700 - 1600 B.C., including indications of earlier developments belonging to Neolithic levels. Although the continuing fame of purple is always related to the prestigious garments of royalty or to high ranks of society and religion, archaeological evidence of any early dyed textile preserved is extremely unlikely to come to light, because of the fragility of the fibre substrate. The identification of the conchylian purple dyestuff in the form of a pigment, found applied on the wall paintings at Akrotiri of Thera, is shown to be of equal importance as being the earliest tangible evidence in the Aegean for the development of the vat dyeing technology in the early Late Bronze Age. 33 refs.

Spanier E, Rediscovering Royal Purple and Biblical Blue, Oceanus, 1990, 33(1), 75
A brief history with details of the preparation of tekhelet, Biblical Blue, from Murex trunculus

Spanier E (Ed), The Royal Blue and The Biblical Purple; Argaman and Tekhelet, Keter Publishing House Jerusalem Ltd, 1987
A major review of the Jewish connection

Spanier E, Karmon N and Linder E, Bibliography concerning various aspects of the purple dye, Levantina, 1982, (37), 437-447
A bibliography with 157 references, divided into general (30), biology - chemistry (82) and history and archaeology (45)

Steigerwald G, Die antike Purpurfarberi nach dem Berichte Plinius des Alteren in seiner Naturalis Historia, Traditio (Studies in ancient and medieval history, thought and religeon), 1986, 42, 1-58
Tyrian purple as it appears in Pliny's Natural History and other Roman documents

Steigerwald G, Herstellungsmethode des antiken Purpurs, Naturwissenschaftliche Rundschau, 1989, 42, 417-418
Summary of Traditio (Studies in in ancient and medieval history, thought and religion), 1986, 42, pp1-58

Steigerwald G, Der kaiserliche Purpur - eine schwarz-rote Doppelfärbung, Frankfurter Allgemeine Zeitung, 1991
30.01.1991, Nr. 25. Beilage: Natur und Wissenschaft N2; Der kaiserliche Purpur der römisch-byzantinischen Zeit war der tyrische Purpur, auch "Blatta" genannt. Er war kein Pigment, sondern das Ergebnis einer Doppelfärbung

Steigerwald G, Die Purpursorten im Preisedikt Diokletians vom Jahre 301, Byzantinische Forschungen (Internationale Zeitschrift für Byzantinistik), 1990, 15, 219-277
Höchstpreise für 12 verschiedene Purpurseiden und Purpurwollen- Sie unterscheiden sich nicht nur im Farbton, sondern auch durch die Farbstoffe . Ausser Schneckenpurpur sind dies Kermes und Fucus,der Farbstoff einer Rotalgenart (Rytiphloea tinctoria C. Ag)

Steigerwald G, Das kaiserliche Purpurprivileg in spätrömischer und frühbyzantinischer Zeit, Jahrbuch für Antike und Christentum, 1990, 33, 209-239
Nicht alle mit Schneckenpurpur gefärbten Kleidungsstücke waren dem Kaiser und seinem Haus vorbehalten, sondern nur bestimmte blattapurpurne (=tyrischpurpurne) Kleider

Steigerwald G, Purpur Spätantike und Byzantinisches Reich, Lexikon des Mittelalters, 1995, 7, 330-331
Zusammenfassung der Ergebnisse meines Aufsatzes im Jahrbuch für Antike und Christentum

Steigerwald G, Purpurgewänder biblischer und kirchlicher Personen als Bedeutungsträger in der frühchristlichen Kunst, HEREDITAS (Studien zur Alten Kirchengeschichte ), 1999, 16, XXXII
Diese Arbeit, konzentriert sich auf die Purpurkleider, soweit sie in Blattafarbe, so hiess der tyrische Purpur seit spätrömischer Zeit, und- wegen der besseren Farberhaltung in Mosaik dargestellt sind.. Erstmals in der Forschung werden hier die Purpurgewänder in der Kunst untersucht

Steinhart C E, Biology of the blues: The snails behind the ancient dyes, Journal of Chemical Education, 2001, 78(11), 1444
Three species of marine snails were used in the ancient Mediterranean dye industry. Colorless dye precursors, sulfur-containing indole derivatives, are secreted by the hypobranchial gland of these animals. The several functions of this gland and other aspects of the lives of the snails that are interesting and relevant to the dye industry are described and the chemistry of dye production is summarized

Stieglitz R H, The Minoan Origin of Tyrian Purple, Biblical Archaeologist, 1994, 57(1), 46-54
The industry existed in the Middle Minoan period, 1750 BCE; illustrations of sites at Palaikastro (East Crete), Thera and Kouphonisi (Middle Minoan), with 18 references

Stulz H, Die Farbe Purpur im frühen Griechentum, Stuttgart : B.G. Teubner; Beiträge zur Altertumskunde, vol 6, 1990
Investigation of the importance of purple at the Greeks, especially in the works of Homer

Surowiec I, Nowik W, Moritz T, Mass spectrometric identification of new minor indigoids in shellfish purple dye from Hexaplex trunculus, Dyes and Pigments, 2012, 94(2), 363–369; doi: 10.1016/j.dyepig.2012.01.023
The identification of minor indigoids found in extracts of the pigment obtained from Hexaplex trunculus was achieved using isotopic patterns and accurate mass measurements of protonated molecular ions and their high collision energy fragments obtained in LC–MS/MS experiments. The unknown compounds appeared to be analogues of indirubin and its mono- and dibrominated derivatives with one C=O group in the indirubin backbone substituted by a C=NH group, namely indirubin-3’-monoimines.

Süsse P, Krampe C, 6,6'-Dibromo-indigo, a main component of Tyrian purple. Its crystal structure and light absorption, Naturwissenschaften, 1979, 66(2), 110
Crystals of dibromoindigotin are monoclinic, space group P21/a, a=11.50, b=4.85, c=12.60, beta=104.0 and Z=2; the final R was 0.047;crystals are strongly pleochroic with light absorption maxima at 640 or 540 nm depending on the direction in the crystal

Süsse P, Polarisierte Lichtabsorptionsspektren des tyrischen Purpurs (6,6’- Dibromindigo), Zeitschrift fur Kristallographie, 1983, 162, 216-217
Crystals of dibromoindigotin are monoclinic, space group P21/a, a=11.61, b=4.842, c=12.61, beta=104.4 and Z=2; light absorption maxima are at 580 and 640 nm depending on the direction in the crystal

Szalda DJ, Ramig K, Lavinda O, Koren ZC, Massa L, 6-Bromoindigo dye, Acta crystallographica, 2012, C68, 160-163
doi: 10.1107/S0108270112006440
6-Bromoindigo crystallizes with one disordered molecule in the asymmetric unit about a pseudo-inversion center. Stacking interactions and hydrogen bonds are similar to those found in the structures of indigo and DBI. The interactions in MBI were calculated quantum mechanically using density functional theory and the quantum theory of atoms in molecules.

Szkudlarek C, Synthesis and Characterization of Tyrian Purple and 6-bromoindigo, 8TH ANNUAL ELMHURST COLLEGE Research and Performance Showcase May 6, 2010
6,6'-dibromoindigo and 6-bromoindigo were synthesised and characterised by IR, NMR and UV/vis absorption.
Performance Showcase p.25

Szostek B, Orska-Gawrys J, Surowiec I and Trojanowicz M, Investigation of natural dyes occurring in historical Coptic textiles by high-performance liquid chromatography with UV–Vis and mass spectrometric detection, Journal of Chromatography A, 2003, 1012(2), 179–192
doi: ; pdf
Among many other dyes, IND, INR, MBI and DBI were detected by HPLC-DAD and HPLC-MS

Terada Takako, Dyeing properties of shellfish purple obtained from Ocenebra inornata, Kwassui bulletin, 2011, 54, 35-42
Ocenebra inornata Ouu-youraku-gai in Japanese, was collected from Hokkaido Japan and used to dye a variety of fabrics. The major component of the colour is 6,6'-dibromoindigo with a smaller amount of monobromoindigo, very similar to Rapana venosa

Terada Takako, Validity of historical references to combined dyes of shellfish and lichen, Kwassui bulletin, 2009, 52, 9-15
The combination of lichen purple and shellfish purple is investigated

Terada Takako, Sea Snail Purple in Contemporary Japanese Embroidery, Textile Society of America 11th Biennial Symposium: Textiles as Cultural Expressions, September 4-7, 2008, Honolulu, Hawai'i paper 138, 9 pages
Techniques for dyeing using Japanese molluscs are described; the analyses of 14 species of Japanese mollusc pigments are given.

Terada Takako, Shellfish purple : field trips to Costa Rica and El Salvador, Kwassui bulletin, 2007, 50, 9-17
Shellfish purple is a pigment obtained from the secretion of certain species of marine mollusks, and has been highly prized since ancient times. In this report, my fifteen years of research on shellfish purple is summarized as a background to this investigation, along with some observations and experiences of traditional dyeing work using shellfish purple by indigenous dyers in Costa Rica and El Salvador

Terada Takako, Fieldwork on Shellfish Purple, Kwassui bulletin, 2005, 48, 51-62
The purple dye from shellfish, also variously known as Tyrian purple, purple of the Ancient, and Royal purple, was produced from the mucus of the hypobranchial gland of various species of marine mollusks. It is the oldest known pigment, the longest lasting, the subject of the first chemical industry, the most expensive and the best known since pre-Roman times in the Mediterranean region. In 1991, for the first time in Japan, shellfish purple was detected on fragments of ancient silk excavated from the Yoshinogari site, a village in Saga prefecture which dates to the Yayoi period (300 B.C.E.-A.D. 300). Since that time 1 have researched the dyeing properties and the history of shellfish purple, both in Japan and abroad. In this paper, the background to this study, the number of species that can be used for producing shellfish purple, the use of shellfish dye and archaeological evidence of shellfish purple are described. (Japanese)

Tanoue Y, Ikoma Y, Kai N, Nagai T, Synthesis of halogenoindirubins, Journal of Heterocyclic Chemistry, 2009, 46(5), 1016-1018
6'-Bromoindirubin was prepared in 81% yield and 6-bromoindirubin in 85% yield. IR, NMR (1H and 13C) and MS data is given.

Tanoue Y, Hara A, Kai N, Sakata K, Hashimoto M, Nagai T, A Revised Synthetic Scheme of 6,6'-Dibromoindirubin, Journal of Heterocyclic Chemistry, 2007, 39(4), 1135-1138
The synthetic scheme of 6,6'-dibromoindirubin was investigated in detail. The reaction of 6-fluoro-3-acetoxyindole with isatin in methanol with Na2CO3 produced 6'-fluoroindirubin in moderate yields, Its structure determination was mainly undertaken using IH NMR spectroscopy. On the basis of this result, the synthetic scheme of 2 reported by Cooksey was revised [but only by rotating the drawing of the reactant molecules !].

Tanoue Y, Sakata K, Hashimoto M, Kai N, Nagai T, Attempts to Isolate the Precursors of Tyrian Purple from Rapana thomasiana, ITE LETTERS ON BATTERIES NEW TECHNOLOGIES AND MEDICINE, 2006, 7(5), C17-C19
Extraction of a hypobranchial gland of Rapana thomasiana with chloroform followed by TLC (silica gel, chloroform-acetonitrile, 100:5) gave (a) a pale yellow-green powder, Rf 0.65, and (b) a yellow powder Rf 0.21. (a) could not be identified because it was photolabile. (b) was identified as 6-bromoisatin by mp, IR, NMR and MS.

Tanoue Y, Terada A, Sakata K, Hashimoto M, Morishita S I, Hamada M, Kai N, Nagai T, A facile synthesis of Tyrian purple based on a biosynthetic pathway, Fisheries Science, 2001, 67(4), 726-729
A facile synthesis of Tyrian purple, a valuable purple dye derived from gastropod mollusks in ancient times, has been accomplished. Tyrian purple, 6,6'-dibromoindigo, was easily obtained by three steps of reactions from the commercially available 6-bromoindole, on the basis of a biosynthetic pathway of indigo and biological precursors of the purple. Iodination of 6-bromoindole, followed by acetoxylation with silver acetate in acetic acid, afforded 6-bromo-3-acetoxyindole, whose alkaline hydrolysis accompanying air oxidation produced Tyrian purple.

Tanoue Y, Sakata K, Hashimoto M, Hamada M, Kai N, Nagai T, A facile synthesis of 6,6'- and 5,5' dihalogenoindigos, Dyes and Pigments, 2004, 62(2), 101-105
The dihaloindigos are prepared from commercially available haloindoles by acetylation (iodination; silver acetate in acetic acid), followed by alkaline hydrolysis and aerial oxidation.

Taylor G W, Detection of shellfish purples on textiles, Dyes on Historical and Archaeological Textiles, 1983, 2, 20-21
Purple pigment was extracted with pyridine, diluted with water and extracted into ether. The ether evaporated and the residue taken up in methanol for spectroscopy. Wavelength maxima in pyridine: indigo, 615 nm, dibromoindigo 605nm; in methanol, 610 and 600 nm respectively.

Terada A, Yahiro T, Ohanti T and Tanoue Y, Synthetic Tyrian purple and shikonin -- Dyeing with ancient purple, Baiko Jogakuin Daigaku Chiiki Bunka Kenkyusho Kiyou, 1996, 11, 14-22

Thompson J, Shellfish Purple: The Use of Purpura patula pansa on the Pacific Coast of Mexico, Dyes in History and Archaeology, 1995, 13, 3-6
A first-hand description of the use of the mollusc to dye posahuancos with comments on its cultural significance

Thorpe J F, Ingold C K, Synthetic Colouring Matters. Vat Colours, London: Longmans, Green and Co, 1923, 7-20
In a chapter, the literature and chemistry from pre-Roman times to the identification by Friedlander are covered; about 15 references

Thureau-Dangin F, Un Comptoir de Laine Pourpre à Ugarit d'après une Tablette de Ras-Shamra, Syrie, 1934, 15, 137-146
Investigation of trading tablets from Ugarit. Wool dyed with purple dyestuff is mentioned several times there

Timmermann I, Seide, Purpur und Gold: Untersuchungen zu den Gewebefragmenten aus dem Schrein der Heiligen Drei Könige im Dom zu Köln, Köln, 1982
Proof of purple dyestuff on the silk fabrics from the so-called Dreikönigsschrein at the cathedral of Cologne

Torimoto N, Morimoto S, Shingaki T, Synthesis of Tyrian Purple as a teaching material, Kagaku to Kyoiku, 1991, 39(2), 198-201
Dibromoindigotin was prepared from 2-nitrotoluene via 4-bromo-2-nitrotoluene, 4-bromo-2-nitrobenzylidene diacetate and 4-bromo-2-nitrobenzaldehyde (by reaction with acetone) and the visible spectra of the product compared to that obtained from shellfish and silk cloth was dyed with it.

Travis A S, The Royal Purple and the Biblical Blue - Argaman and Tekhelet - Spanier,E, Technology and Culture, 1989, 30(3), 667-668
Book review

Uerpmann M, Auswertung der Meeresmollusken aus der westphönizischen Faktorei von Toscanos, Madrider Mitteilungen, 1972, 13, 165-171
Report on investigations of shells of purple snails found at the Phoenician settlement of Toscanos in Spain

Van Alphen J, Remarks on the Action of Light on several substances, most of them containing halogen, in particular several Indigo Dyes, in a Reducing Medium, Recueil des travaux chimiques des Pays-Bas, 1944, 63, 95-96
Photodebromination of leuco-dibromoindigo by UV or sunlight is described. After 10 minutes (June or July), only leuco-indigo remained in solution, and after several days had completely decomposed to give indigo

Van Elslande E, Lecomte S, Le Ho AS, Micro-Raman spectroscopy (MRS) and surface-enhanced Raman scattering (SERS) on organic colourants in archaeological pigments, Journal of Raman Spectroscopy, 2008, 39(8), 1001-1006
A Raman procedure showed that a tiny lump of purple pigment discovered during excavations in the ancient Minoan city of Akrotiri, on the Santorini Island in Greece (1650 B.C.) was dibromoindigo

Verhecken A, Experiments with the dyes from European purple-producing shellfish, Dyes in History and Archaeology, 1994, 12, 32-35
Description of collecting and dyeing with three purple-producing shellfish of Spain

Verhecken A, Experiences with mollusc purple, La Conchiglia, 1990, 22, 250-252
The preparation of purple stains and dyes from three species of shellfish

Verhecken A, The Indole Pigments of Mollusca, Annales de la Societe Royale Zoologique de Belgique, 1989, 119(2), 181-197

Verhecken A, Lets over de Chemie van Molluskenpurpur, Gloria Maris, 1984, 22, 163-174
Description of the dyestuff formation during purple dyeing and a discussion of this process

Vogler H, The Craft of Dyeing in Ancient Egypt, Textile History, 1982, 13, 159-163
Often purple dyeing in Pharaonic Egypt is asserted and a purple dyer supposedly mentioned in old Egyptian literature is presented as a proof It was demonstrated that this is not true

Vogler H, Die Spuren früher Färberei im Minoerreich auf Kreta, Deutscher Färber­kalender, 1984, 88, 193-206
A discussion of purple dyeing in the scope of the description of the dyeing methods of ancient Minoans

Vogler H, Die Färberei der Antike, in Müller, W., Handbuch der Farbenchemie, Landsberg, 2000
Description of ancient purple dyeing in the context of a report on dyeing of antiquity

Voss G, Gerlach H, Regioselektiver Brom/Lithium-Austausch bei 2,5-Dibrom-1-nitrobenzol. Eine einfache Synthese von 4-Brom-2-nitrobenzaldehyde und 6,6'-Dibromindigo, Chemische Berichte, 1989, 122(6), 1199-1201
4-Bromo-2-nitrobenzaldehyde is prepared in 92% yield by selective lithiation of 1,4-dibromo-2-nitrobenzene followed by reaction with DMF, and converted into dibromoindigotin in 66% yield by reaction with nitromethane followed by reduction.

Voss G, The analysis of indigoid dyes as leuco forms by NMR spectroscopy, Journal of the Society of Dyers and Colourists, 2000, 116, 80-90
Reduction of indigos with sodium dithionite in D2O gives the leuco products and the proton and carbon NMR spectra can be obtained. 18 examples including 6,6'-dibromoindigo

Voss, G, Schramm W, Selectively C-deuterated indigotins, Helvetica Chimica Acta, 2000, 83(11), 2884-2892
Selectively C-deuterated indigotins were synthesized from halogenated indigotins as precursors. The described reactions - used already by the ancient purple dyers - allowed the introduction of D-atoms at defined positions of the indigo molecule. The exchange of halogen atoms by D-atoms was induced by UV irradiation. of the leuco compounds in D2O. The resulting leuco forms were oxidized to the deuterated indigotins. Some conclusions were drawn as to the kinetics of the reaction. The physical properties of the new compounds were determined

Wahl A, Sur une facile synthese de la pourpre antique, Revue Generale des Matieres Colorantes, 1935, 39, 121-122
Attention is drawn to a published synthesis (Rottig W, J. prakt. Chem., 1935, 142, 35) in which p-toluidine is nitrated then the amino group converted to Br to give 4-bromo-2-nitrotoluene; nitrosation with ethyl nitrite gives the aldoxime which is hydrolysed to the aldehyde. 50 g of p-toluidine yields 5.4 g of dibromoindigo

Walton P, Shellfish purple in a Coptic textile, Dyes in History and Archaeology, 1985, 4, 33-34
A yarn (5th century AD) extracted with pyridine for 1 hour at 60 deg showed maximum absorption at 610 nm showing the presence of dibromoindigotin rather than indigo (620 nm)

Westley CB, The distribution, biosynthetic origin and functional significance of Tyrian purple precursors in the Australian muricid Dicathais orbita (Neogastropoda: Muricidae), PhD thesis, 2008
abstract and links to chapters
Submitted in fulfillment of the requirements for the degree of Doctor of Philosophy. School of Biological Sciences, Faculty of Science and Engineering, Flinders University, Adelaide, South Australia. April, 2008.

Westley CB, Vine KL and Benkendorff K, A proposed functional role for indole derivatives in reproduction and defence of the Muricidae (Neogastropoda : Mollusca), in Indirubin, the red shade of indigo, editors Meijer L, Guyard N, Skaltsounis LA and Eisenbrand G, France: Life in Progress Editions, ISBN 2-9518029-0-0, 2006, 31-44
The Muricidae, also known as Murex or purple snails, are remarkable both as a source of the ancient indigoid dye, Tyrian purple and the homeopathic remedy "Murex", prescribed for the relief of women's problems. This purple secretion contains brominated indoles and indirubins with established antibiotic and anticancer properties, as well as choline esters with muscle relaxing activity. These properties have prompted considerable speculation, but little directed research, into the selective benefits of these bioactive compounds for the Muricidae. Consequently, this paper reviews the current literature on indole derivatives, their biosynthesis and associated bioactivities, with the aim of amassing evidence for a naturally selected function in the Muricidae. 82 refs.

Westley C and Benkendorff K, Sex-Specific Tyrian Purple Genesis: Precursor and Pigment Distribution in the Reproductive System of the Marine Mollusc, Dicathais orbita, Journal of Chemical Ecology, 2008, 34(1), 44-56
Exploitation of Tyrian purple from muricid molluscs, since antiquity, has prompted much interest in its chemical composition. Nevertheless, there remains a paucity of information on the biosynthetic routes leading to observed sexual differences in pigmentation. A liquid chromatography-mass spectrometry (LQ-MS) method was developed to simultaneously quantify dye pigments and precursors in male and female Dicathais orbita. The prochromogen, tyrindoxyl sulfate, was detected for the first time, by using this method in hypobranchial gland extracts of both sexes. Intermediates tyrindoxyl, tyrindoleninone, and tyriverdin were detected in female hypobranchial glands, along with 6,6'-dibromoindigo, while males contained 6-bromoisatin and 6,6'-dibromoindirubin. Multivariate analysis revealed statistically significant differences in the dye composition of male and female hypobranchial glands (ANOSIM, P=0.002), thus providing evidence for sex-specific genesis of Tyrian purple in the Muricida.

Westley C and Benkendorff K, The distribution of precursors and biosynthetic enzymes required for Tyrian purple genesis in the hypobranchial gland, gonoduct, and egg masses of Dicathais orbita (Gmelin, 1791) (Neogastropoda: Muricidae), The Nautilus, 2009, 123(3), 148-153 ; abstract

Westley CB, Lewis MC and Benkendorff K, Histomorphology of the Hypobranchial Gland in Dicathais Orbita (Gmelin, 1791) (Neogastropoda: Muricidae), Journal of Molluscan Studies, 2009, 76(2), 186-195, doi:10.1093/mollus/eyp056 ; details
Tyrian purple is a dye used in antiquity and is a natural product of marine molluscs of the family Muricidae. Bioactive precursors of Tyrian purple occur in the hypobranchial gland, reproductive glands and egg masses of muricids, such as Dicathais orbita. Histomorphological examination of the hypobranchial-gonoduct complex (rectum and hypobranchial, capsule, albumen and rectal glands) was conducted to provide the first description of the hypobranchial gland in Dicathais Orbita and to determine a mechanism for the transfer of Tyrian purple precursors to the gonoduct and ultimately to the egg masses. Seven secretory cell types were identified in the hypobranchial epithelium of Dicathais Orbita, which can be broadly classified into cells containing mucoproteins and acidic sulphated mucopolysaccharides. Three secretory cells new to the Muricidae were identified, along with two cell types that appear to be associated with synthesis of Tyrian purple. A subepithelial vascular sinus surrounding the rectum and rectal gland occurs between the hypobranchial gland and gonoduct. Examination of this region failed to reveal a direct anatomical mechanism for the transfer of precursors to the gonoduct. However, biochemical similarities in secretions from the hypobranchial, capsule and albumen glands suggest that the synthesis of precursors within the gonoduct may be possible.

White G, Purpurschnecken aus dem römischen Grenzach, Archäologische Nachrichten aus Baden, 1986, 37, 35-37
Discovery of shells of purple snails during the excavations of a Roman villa in Grenzach/Baden

Withnall R, Clark R J H, Cooksey C J and Daniels M A M, Non-destructive, in situ identification of indigo/woad and shellfish purple by Raman microscopy and visible reflectance spectroscopy, Dyes in History and Archaeology, 1992, 11, 19-24
Raman microscopy and visible reflectance spectroscopy of indigo and dibromoindigo

Withnall R, Patel D, Cooksey C and Naegel L, Chemical studies of the Purple Dye of Purpura pansa, Dyes in History and Archaeology, 2003, 19, 109-117
Visible absorption and reflectance spectra of the dye from Purpura pansa were consistent with the major colorant being dibromoindigo; HPLC showed that the monobromoindigo content was higher than for others in the brandaris group of mollusks; MS of the ethanol extract of the mollusk showed the presence of tyrindoleninone

Wolk JL, Frimer AA, A Simple, Safe and Efficient Synthesis of Tyrian Purple (6,6'-Dibromoindigo), Molecules, 2010, 15, 5561-5580; doi:10.3390/molecules15085561
Starting from 1,4-dibromobenzene, 6,6'-dibromoindigo is synthesised, via 2,4-dibromobenzoic acid, 4-bromo-2[(N-carboxymethyl)amino]benzoic acid and 6-bromo-N,O-diacetylindoxyl in five steps in about 25% yield

Wolk JL, Frimer AA, Preparation of Tyrian Purple (6,6'-Dibromoindigo): Past and Present, Molecules, 2010, 15, 5473-5508; doi:10.3390/molecules15085473
A comprehensive review of synthetic routes to dibromoindigo since 1903 with 275 references

Wouters J, A new method for the analysis of blue and purple dyes in textiles, Dyes in History and Archaeology, 1991, 10, 17-21
Examination by HPLC of stains and vatted dyes obtained from three different species of shellfish. It is possible to distinguish Ph. trunculus dyes from those from the group that includes Ph. brandaris and T. haemostoma, by the presence or absence of indigotin and a detectable component which may be brominated indirubin

Wouters J, Verhecken A, Composition of Murex dyes, Journal of the Society of Dyers and Colourists, 1992, 108(9), 404
Monobromoindigo can be formed from dibromoindigotin under vatting conditions and by some analytical procedures, and vatting of Murex trunculus hypobranchial glands increases the indirubin content from 1% to 14%

Wouters J, Verhecken A, High-performance liquid chromatography of blue and purple indigoid natural dyes., Journal of the Society of Dyers and Colourists, 1991, 107(7-8), 266-269
HPLC and visible spectra are used to characterise dyes from Murex trunculus, identifying indigo, mono- and dibromo-indigos and indirubin.

Wouters J and Verhecken-Lammens C, Royal purple in historical, analytical and technical context., DHA31, Antwerp, 2012 (abstract)
The detection of royal or real or murex purple in samples taken from objects of cultural and artistic value remains rare and exciting. An on-going study has revealed possible relationships between weaving technological features and a biased use of animal dyes on tapestry woven ornaments of 1st through 9th centuries CE Egyptian linen and woollen fabrics belonging to the textile collection of Katoen Natie, Antwerp, Belgium. Out of 33 samples of Z-spun weft woollen yarns, 4 were dyed with murex purple, whereas only 1 out of 61 S-spun weft woollen samples was dyed with murex purple.

Ye X, Karimi S, Irigoyen P, Synthesis and behavior of 6-Bromoindigo, Columbia University Spring Undergraduate Research Symposium, Columbia Undergraduate Research Symposium- Spring 2011 ; abstract
6-bromoindigo was synthesised with the intention of determining the X-ray structure and to dye various fibers

Yoshioka T and Ueno T, Chemistry of natural dyes -- Ancient purple, Kagaku to Kyoiku, 1985, 33, 488-491
Japanese language review

Ziderman I, Ancient Purple Dyes - reply, Chemistry in Britain, 1985, 21(5), 447
Reference is made to the process used to prepare the purple dye and the current use of the term tekhelet

Ziderman I, Tyrian Purple or Hyacinthine Purple?, Chemical & Engineering News, 1983, 61(24), 88
A letter pointing out that Hyacinthine purple from Murex trunculus is a mixture of indigo and dibromoindigotin

Ziderman I I, Purple dyes made from shellfish in antiquity, Review of progress in coloration and related topics, 1986, 16, 46-52
The identity of the colourants of argaman and tekhelet is reviewed, concluding that the former is dibromoindigotin and the latter a mixture of dibromoindigotin and indigo

Ziderman I I, The 3600 years of purple-shell dyeing: characterization of hyacinthine purple (tekhelet), Advances in chemistry series. 0065-2393. 212 (Historic textile and paper materials, conservation and characterization), 1986, 187-198
Chemical, archaeological,biological and talmidic studies suggest that tekhlet was prepared from Trunculariopsis trunculus and the colourant is an equal mixture of indigo and dibromoindigotin; 24 references

Ziderman I I, Biblical Dyes of Animal Origin, Chemistry in Britain, 1986, 22(5), 419-421;454;638
A review of insect and shellfish dyes with 26 refs

Ziderman I I, Blue Thread of the Tzitzit - was the ancient dye a Prussian Blue or Tyrian Purple, Journal of the Society of Dyers and Colourists, 1981, 97(8), 362-364
The identity of the dyes used for tekhelet and argaman is reviewed. 35 refs

Ziderman I I, a letter, COLOR research and application, 1985, 10(4), 258
Arguments against (and the author's reply) McLaren's suggestion (1983) that Tyrian purple is not a vat dye

Ziderman I I, Seashells and Ancient Purple Dyeing, Biblical Archaeologist, 1990, 53(2), 98-101
A brief summary of the dye-forming process, the mollusks and the importance of chemical analysis to confirm the presence of bromoindigotin; 29 refs

Ziderman I I, Molluscan source of Biblical "Blue" dyestuff, Proceedings of the ninth Malacological Congress, 1992, 407-414
A review with 31 references of evidence for Hyacinthine Purple from Murex trunculus being a mixture of indigotin and 6,6'-dibromoindigotin

Ziderman I I, The Biblical Dye Tekhelet and its Use in Jewish Textiles, Dyes in History and Archaeology, 2008, 21, 36-44
A review with 33 references

Zollinger H, Welche Farbe hat der antike Purpur?, Textilveredlung, 1989, 24(6), 207-12
The changed perception of the hue of Tyrian Purple over the last two millenia is discussed and related to biochemistry, technology, historical and linguistic investigations. 26 refs

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