Mass Spectrometry for Investigation of Natural Dyes in Historical Textiles: Unveiling the Mystery behind Safflower-Dyed Fibers

[Image: see text] Safflower (Carthamus tinctorius L.) petals, depending on the nature of a dyeing bath, dye fibers yellow or red. This is due to the presence of two kinds of components, water-soluble yellow colorants and alkali-soluble red compounds. In this study, safflower-yellow- and safflower-red-dyed silk, cotton, and wool fibers were investigated using high- or ultrahigh-performance liquid chromatography hyphenated with spectrophotometry and tandem mass spectrometry (HPLC–UV–vis–ESI-MS/MS) and high-resolution Orbitrap mass spectrometry (HPLC–HESI-HRMS) in order to identify the natural dye in historical textiles. This way, several quinochalcone C-glycosides were separated and characterized. Their low- and high-resolution MS/MS spectra expanded the database of natural colorants in cultural heritage objects. Moreover, the colorless ct-markers (with a hitherto unknown structure) present in all safflower-dyed fabrics, regardless of the color or preservation conditions, were revealed to be E/Z stereoisomers of N(1),N(5),N(10)-tri-p-coumaroylspermidine. Since most of the standards was not available, discussion on possible molecular structures was provided. As a consequence, the analytical investigation of the reference fibers dyed with safflower demonstrated that the dye composition varies, depending on the dyeing conditions and type of fiber. Moreover, it was proven that carthamin, although alkali soluble, can be successfully released with a mild extraction method, without its hydrolysis under these conditions. The results helped us to characterize threads sampled from 16th to 18thcentury textiles of European and Near Eastern origin. It has completed the picture of natural dyes used in the most valuable textiles availed in liturgical vestments from the collections of Krakow churches.