When true colors still shine through: LC-MS-based metabolomics study of fabrics dyed with European buckthorn (Rhamnus cathartica) berries after accelerated light ageing

Since prehistoric times, humans have used dye-producing plants to color textiles, artworks, and ritual objects. Yellow-yielding species have been especially important due to their availability and the chemical stability of many of their flavonoid-based colorants. Among them, Rhamnus species (buckthorns) are notable for producing yellow to greenish hues from their flavonoid-rich berries. These long-standing practices inform modern research on natural colorants, phytochemistry, and sustainable textile science.In this context, this study investigates the chemical and chromatic evolution of cotton fabrics dyed with Rhamnus cathartica (European buckthorn) berries when subjected to accelerated light ageing. Fabrics were exposed to xenon-lamp irradiation equivalent to 3, 30, and 300 years of museum-type light. Color fading was assessed by CIELAB colorimetry, and dye degradation was analyzed using LC-DAD and untargeted LC-MS-based metabolomics. Colorimetric data showed rapid fading, fabrics appearing even whiter than undyed samples after the 300-year equivalent exposure. LC-DAD analysis revealed a drastic decline of most coloring compounds, including flavonoids and anthraquinones, which became undetectable in the most aged samples, highlighting the limited sensitivity of LC-DAD for heavily degraded textiles. In contrast, LC-MS metabolomics enabled the detection and putative annotation of 25 dye molecules, mainly flavonoid glycosides and anthraquinones. Molecular networking highlighted distinct structural families, and many dye-related compounds remained detectable even in fully bleached fabrics.These results demonstrated that LC-MS-based metabolomics is a powerful tool for identifying residual chemical markers in faded historical textiles, supporting conservation and the reconstruction of ancient dyeing practices.