Abstract
Five flavonoid glycosides were isolated from the n-butanol soluble fraction of the ethanolic extract of Rapistrum rugosum and their structures were assigned from H-1- and C-13-NMR spectra (DEPT) with 2D NMR as quercetin-3-O-alpha-L-rhamnopyranoside (1), quercetin-3-O-beta-D-xyloside (2), quercetin, 3-O-alpha-L-arabinopyranoside, 7-O-alpha-L-rhamnopyranoside (3), kaempferol 3-O-alpha-L-arabinopyranoside, 7-O-alpha-L-rhamnopyranoside (4) and rutin (5). The SRB cytotoxic assay was used to investigate the antitumor activities of n-butanol extract, compound 3 and its hexaacetate 3a, for the first time. Compounds 3 and 3a showed cytotoxic activity against the human cancer cell line, namely, HepG2 (hepatocellular carcinoma cell line) with IC50 (concentration of compound required to reduce cell survival by 50%) 0.86 mu g/mL and 3.50 mu g/mL, respectively. These results proved that compound 3, the major flavonoid of the n-butanol soluble fraction, has significant cytotoxic activity compared with the standard antitumor drug doxorubicin (0.60 mu g/mL).