Four New Dihydrostilbene Glycosides And Their Alpha-Glucosidase Inhibitory Effect From Camellia Sinensis Var. Assamica

Four new dihydrostilbene glycosides, assastilbosides A-D (1-4), along with seven known compounds, 5,4'-dihydroxydihydrostilbene 3-O-beta-D-glucopyranoside (5), 3,5 dihydroxydihydrostilbene 4'-O-beta-D-glucopyranoside (6), 3,5-dihydroxydihydrostilbene 4'-O-(6 ''-O-4'''-methoxy)galloyl]-beta-D-glucopyranoside (7), 3,5-dimethoxydihydrostilbene 4'-O-alpha-L-rhamnopyranosyl-(1 -> 6)-beta-D-glucopyranoside (8), (-)-epicatechin (9), (-)-epicatechin 3-O-gallate (10), and (-)-epigallocatechin 3-O-gallate (11) were isolated from methanol extract of the leaves of Camellia sinensis var. assamica (J.W.Mast.) Kitam. Their structures were elucidated by HR-ESI-MS, 1D- and 2D-NMR spectra and compared with NMR data in the literature. In addition, all isolated compounds were screened by alpha-glucosidase assay. Compounds 10 and 11 showed significant inhibitory alpha-glucosidase with IC50 values of 18.3 +/- 1.1 and 21.9 +/- 0.8 mu M, respectively.