Fresh Dendrobium officinale juice (FDOJ) changes color from green to purple after processing; however, the mechanism behind this is unknown. In this study, untargeted and targeted metabolomics were used to analyze pigment-related metabolites. The results showed that the content of delphinidin-type anthocyanin more than doubled in FDOJ after processing. Correlation analysis revealed that major substances in the anthocyanin biosynthesis pathway, including phenylalanine, cinnamic acid, and naringenin chalcone, changed with processing. We speculate that accumulation of anthocyanins during processing occurs through de novo anthocyanin biosynthesis starting from phenylalanine, and the addition of phenylalanine traced that the enhancement of enzyme activity promoted the accumulation of anthocyanins. This potential mechanism for development of the purple color in FDOJ provides theoretical guidance for quality control of FDOJ during processing.
Ni et al. (Mon,) studied this question.