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Dyes derived from brazilwood (Caesalpiniaspp.) are known to have been used in a diverse range of objects, from Medieval European textiles to North American First Nations objects, while pigments made from brazilwood feature in the palette of a number of painters, including Rembrandt and Van Gogh. For almost two decades, an unknown marker has been used to detect brazilwood colourants in historical objects. Limited sampling opportunities mean that the identification of the chemical structure of this marker has eluded scientists to date. Using a combination of synthesis, UPLC-ESI-MS/MS, HPLC, NMR and GC-MS, the identity of this unknown marker was confirmed as the benzochromenone, urolithin C. Structural identification provides a reliable reference compound for use across a range of analytical techniques employed in the cultural heritage sector and will enable the future development of non-destructive techniques for its identification on high-status objects.

Polyphenolic components from Genistaspecies have been well characterised because of their potential as antioxidants and as therapeutic leads; however, the identification of dyer's greenweed (Genista tinctoriaL.) in historical textiles has been the subject of only limited studies. This paper presents a comprehensive UPLC-PDA MS/MS study of reference and historical yarns dyed with this species. Several so far unreported dye components that could assist with the identification of this dye source, were characterised by MS/MS. Furthermore, the effect of photo-degradation and textile preparation techniques (such as over-dyeing) on the dye fingerprint was investigated and the results correlated with those obtained from historical samples from the Burrell and Bodleian collections, UK.