Dihydrostilbene glycosides from Camellia sinensis var. assamica and their cytotoxic activity

Three undescribed dihydrostilbene glycosides, 3,5-dihydroxyldihydrostilbene 4′-O-[6′′-O-(4′′′-hydroxylbenzoyl)]-β-D-glucopyranoside (1), 3,5-dihydroxyldihydrostilbene 4′-O-(6′′-O-galloyl)-β-D-glucopyranoside (2), and 3,5-dihydroxyldihydrostilbene 4′-O-[6′′-O-(3′′′,4′′′-dimethoxyl)galloyl]-β-D-glucopyranoside (3), and seven known compounds, kaempferol 3-O-β-D-glucopyranoside (4), isoquercitrin (5), kaempferol 3-O-α-L-rhamnoside (6), quercitrin (7), (6S,9R)-roseoside (8), (-)-epicatechin 3-O-gallate (9), and (-)-epigallocatechin 3-O-gallate (10) have been isolated from the methanol extract of the leaves of Camellia sinensis var. assamica (J.W.Mast.) Kitam. (synnonym of Camellia assamica (Mast.) H.T.Chang) (Theaceae). Their structures were elucidated by spectroscopic methods (1 D-, 2 D-NMR) and mass spectra. All compounds were evaluated for cytotoxic activity against human oral cancer (CAL27) and human breast cancer (MDAMB231) cell lines. Compound 10 showed significant cytotoxic activity against CAL27 and MDAMB231 cell lines with IC₅₀ values of 9.78 ± 0.25 and 3.27 ± 0.18 μM, respectively, compared to those of positive control, capecitabine (IC₅₀ values of 8.20 ± 0.75 and 5.20 ± 0.89 μM).