Prenylated Flavanone Enantiomers with α-Glucosidase Inhibitory Activity from the Root Bark of Morus alba.

ABSTRACT

A focused chemical investigation into the polar fractions of a well-known traditional Chinese medicine called Sang-Bai-Pi (the root bark of Morus alba) yielded a panel of prenylated flavanones. The new compounds were identified as four pairs of enantiomers (1a/1b-4a/4b) featuring the same constitution structure, on the basis of HRMS, NMR and ECD analyses. Several previously reported known racemic co-metabolites were also analyzed and separated by HPLC on chiral columns, and the absolute configurations of pure enantiomers were established via ECD technique for the first time. The inhibition of these isolates against the antidiabetic target a-glycosidase was further tested, with most of them showing decent inhibitory activity compared with the positive control acarbose. The interaction mechanism of two selected compounds (3a & 4b) was explored by kinetics experiment, which revealed a mixed type of inhibition pattern toward the enzyme.