New steroidal glycosides from the fruits of Tribulus terrestris.

Three new steroidal saponins (1-3) were isolated from the fruits of Tribulus terrestris. Their structures were assigned by spectroscopic methods (IR, HRESIMS, 1D- and 2D-NMR) as 26-O-beta-D-glucopyranosyl-(25S)-5beta-furost-20(22)-en-3bet a, 26-diol-3-O-alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl- (1-->4)]-beta-D-glucopyranoside (1), 26-O-beta-D-glucopyranosyl-(25S)-5beta-furost-20(22)-en-3bet a, 26-diol-3-O-alpha-L-rhamnopyranosyl-(1-->2)-[beta-D-glucopyranosyl-(1 -->4)]-beta-D-galactopyranoside (2), and 25(S)-5beta-spirostan-3beta-ol-3-O-alpha-L-rhamnopyranosyl-( 1-->2)-[b eta-D-glucopyranosyl-(1-->4)]-beta-D-galactopyranoside (3). Compound 3 showed cytotoxicity against a human malignant melanoma cell line (SK-MEL).