Characterization of the pigment in naturally yellow-colored domestic silk

Abstract Naturally colored silks are not durable and apt to fade during fabric processing and home laundering due to the unstable pigment composition and the accumulation of pigment in the surface sericin layer. In this study, the pigment of naturally yellow-colored silk was isolated, characterized and quantified. A dominant pigment composition identified by NMR analysis was all-trans -lutein and other five components were identified as all- trans -neoxanthin, all- trans -violaxanthin, all- trans - α -carotene, all- trans - β -carotene and 9- cis - β -carotene, according to their characteristic UV–Vis spectra and EI-MS data. All six carotenoids were accumulated in sericin layer and exhibited a remarkable decrease in total content in the outer layer (220 μg/g), middle layer (117 μg/g) and inner layer (50 μg/g) of the cocoon shell as determined by analyzing the reeled fiber from one end to the other.