Isolation of neolignan and phenolic glycosides from the branches of Viburnum macrocephalum f. keteleeri and their α-glucosidase inhibitory activity

Abstract

Abstract Viburnum macrocephalum f. keteleeri, not well explored in the pharmaceutical field, is a tall deciduous shrub and commonly used as folk medicines for the treatment of type 2 diabetes (T2D). In this study, the dried branches of V. macrocephalum f. keteleeri were extracted with 95% ethanol and the extract was fractionated on the basis of polarity with ethyl acetate and n-butanol. Among the different fractions, the ethyl acetate fraction exhibited the highest α-glucosidase inhibitory activity, and its bioassay-guided fractionation led to the isolation and identification of six compounds including a new 8-O-4′-neolignan glycoside (1), categorized as a rare 7-deoxy skeleton, three previously undescribed phenolic glycosides (2–4), together with two known secondary metabolites (5, 6), which were found for the first time in Viburnum. Noticeably, compound 1 had almost the same intestinal α-glucosidase inhibitory activity as the positive control acarbose.