Coumaroyl and feruloyl flavonoid glycosides from the male flowers of Ginkgo biloba L. and their inhibitory activity against α-glucosidase.

Four flavonoid glycosides containing coumaroyl or feruloyl groups were isolated from the male flowers of Ginkgo biloba L., and compounds 3 and 4 were identified as novel compounds. The inhibitory activities against α-glucosidase were investigated by docking studies, in vitro assays and kinetic studies. The docking results showed that all compounds mainly formed hydrogen-bond and π-π-stacking interactions with α-glucosidase. Compound 4 had the lowest binding energy and maximum number of hydrogen bonds. Subsequently, the in vitro assays showed that compound 4 exhibited the strongest inhibitory potency. Finally, the kinetic studies indicated the inhibitory mode of compounds 1 - 4 against α-glucosidase were mixed types of competitive and non-competitive. Together, these findings suggested that the isolated flavonoid glycosides in this study, especially compound 4 , have potential as α-glucosidase inhibitors.