Shedding light on the composition and fading mechanisms of dye molecules in Phellodendron amurense Rupr. Dyed silk

The dye extracted from the Phellodendron amurense Rupr. (PA) is highly susceptible to fading under various environmental factors, which poses a considerable challenge for the preservation task of PA-dyed artworks. In this study, colorimetry and UV–Vis absorption spectroscopy were employed to investigate the fading behaviors of PA-dyed silks under LED illumination, as well as UV and thermal radiation. A total of 16 dye molecules, predominantly alkaloids, were identified in PA-dyed silk by LC-MS/MS. It was discovered that coptisine, jatrorrhizine, columbamine, berberrubine, berberine, and palmatine were the most light-sensitive constituents in PA-dyed silk. Additionally, the degradation mechanisms of dye molecules in PA-dyed silk under LED illumination through O2-mediated oxidation were investigated using quantum chemical calculation (QCC) including frontier orbitals analysis, electronic structure analysis, and reaction site prediction. Collectively, these results can provide a new insight into the photofading and degradation mechanisms of PA dyes, which help to provide the basis for the identification of PA dyes in historical artworks.