Abstract
The chemical identification of indigoid dyes in archeological textiles remains a significant analytical challenge due to the diversity of indigoid components, their susceptibility to post-deposition degradation, and the risk of further transformation during sample preparation. Seventeen samples of early medieval textiles from the ancient city of Deraheib (Sudan) were studied. Tryptanthrin—an indoloquinazoline alkaloid previously documented only in model solutions—was identified in archeological textiles for the first time, providing a new qualitative marker of indigo-type dyeing that may persist when the original dye has undergone substantial degradation. Two variants of the methanolic hydrochloric acid treatment step—ultrasonication without heating versus boiling in a water bath at 100 °C—and the replacement of dimethylformamide with acetonitrile in the third extraction stage were systematically compared.