Characterization of saponin biotransformation driven by intrinsic proteins in Aralia elata leaves.

Aralia elata (Miq.) Seem. a nutrient-rich wild vegetable widely consumed in Northeast Asia, is abundant in triterpenoid saponins. Methanol and water are commonly used for phytochemical extraction and food processing, respectively. Although solvent-dependent alterations in saponin composition have been reported in Panax leaves, whether similar effects occur in A. elata leaves (AEL), another member of the Araliaceae family, remain unclear. In this study, a UPLC-Q-TOF MS method was established to comprehensively profile saponins in methanolic and aqueous extracts of AEL. A total of 78 saponins were identified and 22 quantified, including one previously unreported compound. The major saponins detected in methanolic extracts were transformed in aqueous extracts into their corresponding deglucosylated forms through selective hydrolysis at the C-28 position. This conversion was mediated by intrinsic proteins during the aqueous extraction process. One of transformed product was isolated and structurally elucidated by NMR spectroscopy as a new saponin. These findings demonstrate protein-mediated, solvent-dependent saponin biotransformation during AEL processing, and provide new insights into the chemical changes occurring in edible and medicinal plant materials.