Five furostanol saponins from fruits of Tribulus terrestris and their cytotoxic activities.

Two new furostanol saponins, terrestroside A, 3-O-{beta-D-xylopyranosyl-(1-->3)-[beta-D-xylopyranosyl(1-->2)]-beta-D-glucopyranosyl(1-->4)-[alpha-L-rhamnopyranosyl(1-->2)]-beta-D-galactopyranosy}-26-O-beta-D-glucopyranosyl-L-5a-furost-20(22)-en-(25R)-3beta,26-diol (1) and terrestroside B, 3-O-{beta-D-xylopyran-osyl(1-->3)-[beta-D-xylopyranosyl(1-->2)]-beta-D-glucopyranosyl(1-->4)-[alpha-L-rhamnopyranosyl-(1-->2)]-beta-D-galactopyranosy}-26-O-beta-D-glucopyranosyl-5a-furostan-12-one-(25R)-22-methoxy-3beta,26-diol (2), together with three known compounds, chloromaloside E (3), terrestrinin B (4) and terrestroneoside A (5) were isolated from the dry fruits of Tribulus terrestris. Furthermore, the inhibitory effects of the compounds on tumour cells were evaluated, and compounds 1-5 showed potential anti-tumour activity.