Identification of yellow dye types in pre-Columbian Andean textiles

A number of pre-Columbian textiles, most discovered in northern Peru and dating to the Late Intermediate Period (ca. 1050-1200 AD), were analyzed by high-performance liquid chromatography with diode array and mass spectrometric detection (LC-DAD-MS), after extraction of the dyes with formic acid and methanol. The focus of this work was yellow dyes, most of which are present as glycosides of flavonoids and related compounds, with the objective of identifying the plants originally used for dyeing. Two major types of dyes were found in this set of specimens. The first type is characterized by the presence of flavonol 3-O-sulfates (never before reported as being present in dyes) and 3-O-glycosides; this type was probably derived from the plant Flaveria haumanii or a close relative. The second type is characterized by the presence of both chalcone (heretofore not reported in pre-Columbian textiles) and luteolin glycosides, though a specific plant source could not be identified. Two other yellow dye types appeared to be present, but there were not enough examples to allow conclusions to be drawn. Also present in some extracts were various hydroxybenzoic acids, which appear to be oxidation products of the respective unsubstituted flavonol (3-hydroxyflavone) dyes. Most yellow dyes are synthesized in plants as glycosides (or other derivatives), which are incorporated more or less intact into textile fibers during dyeing. Extraction of these derivatives and analysis by LC-DAD-MS yields distinctive profiles that, with appropriate plant reference materials, can aid in the identification of the original plant dyestuffs.