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RESEARCH PROFILES Yellow dyes in pre-Columbian Andean textiles
RAN BOYTNER
sisted of flavonol 3-O -sulfates, which Laursen and his graduate student, In many early cultures, textiles were hadn’t been previously reported in dyes, Xian Zhang, developed a milder extracmore than just clothes. They played a and 3-O- glycosides. tion method based on formic acid and role in rituals and often indicated a perLaursen recalls the discovery of the methanol that pulled the yellow dyes son’s social status. In the February 15 flavonol 3-O-sulfates. “My student ran out of the textile fibers without removissue of Analytical Chemistry (pp the mass spectrum on these things and ing the sugars (Anal. Chem. 2005, 77, 1575–1582), Richard Laursen and colsaid, ‘Looks like a flavonol with leagues at Boston University, the a sulfate attached.’ I said, ‘That’s University of California Los Annonsense. No one has ever regeles (UCLA), and Universidad ported flavonol sulfates.’ I had Nacional de Córdoba (Argentinever heard of them at all, parna) analyzed yellow dyes in preticularly in the dye field.” Columbian Andean textiles (ca. Zhang turned to the Inter1050–1200 AD) to see whether net and in less than a day, they could identify the dyes and Laursen says, “she came up trace them back to their original with a guy in Argentina who plant sources. had described flavonol-sulfateIdentifying dyes in historical producing plants.” The plant textiles helps conservators rewas Flaveria haumanii. Laursen store artifacts and sniff out contacted José Luis Cabrera at fakes. The dyes and their origins Universidad Nacional de Córalso provide clues about the redoba to ask him for plant samsources and technologies availples. “Cabrera said, ‘The [inable to the people who created digenous people] down here the textiles. have been using this stuff for Laursen and colleagues fodyes.’ It all tied together,” says cused on the yellow dyes beLaursen. “It turns out this plant cause they can be derived from grows in many places, including hundreds of plant sources. where these archeological samWorldwide, only one natural Laursen and colleagues analyzed yellow dyes from samples ples came from.” The flavonol blue dye, indigo, can be isolated much like the pre-Colombian textile fragment from northern 3-O-sulfates and 3-O-glycosides from several plants; reds have Peru shown above. identified by Laursen and about a dozen plant and insect 2022–2025). They analyzed the dyes by Zhang came from either F. haumanii or sources. Yellows, therefore, are the best a close relative. way to trace the dye to the plant and re- LC with diode array and mass spectroLaursen and Zhang are now creating metric detection (LC/DAD-MS). Previlate the culture that produced the texan online compilation of analytical data ous dye analyses were carried out with tile to its environment. on dyestuffs. In collaboration with Irene HPLC/DAD, but with this approach, But there is a problem. Most yellow Good of Harvard University, they are reference samples are needed to identify dyes are synthesized in plants as glycotrying to identify dyes in 3000-year-old, the peaks, says Laursen. “But if you sides or other derivatives, which are inbrightly colored textiles from mummies have a mass spectrometer also, you can corporated more or less intact into the discovered in the Xinjiang province of fibers of the textile. “In the past, people get the mass and that gives you a lot China. The mummies and their belongmore information.” would cook up these fiber samples with ings are in exceptionally good condiLaursen and Zhang discovered two HCl and extract the dye out,” explains tion. “Apparently one of the main forms major types of dyes in the textile samLaursen. “Most of the dyes, particularly of wealth in those days was textiles beples collected by archaeologist Ran the yellow ones, are glycosides so they cause they didn’t have much else,” says Boytner from UCLA. One type had have sugars attached to the dye moleLaursen. “They put a lot of textiles in both chalcones, which hadn’t been recule. The sugar gets hydrolyzed, so all with the bodies. They are very well preported in pre-Columbian textiles, and you see is what gets left over after served. Some of them look like they luteolin glycosides; the investigators, you’ve stripped off the sugars. You lose were woven last week.” a however, were unable to identify a spemost of the distinctive information —Rajendrani Mukhopadhyay cific plant source. The second type conabout the dyestuff.” M A R C H 1 , 2 0 0 7 / A N A LY T I C A L C H E M I S T R Y
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