Photosensitivity in South Africa. IX. Structure elucidation of a beta-glucosidase-treated saponin from Tribulus terrestris and the identification of saponin chemotypes of South African T. terrestris

Abstract

Saponin C, a β-glucosidase-treated saponin isolated from ethanol-water extracts of a South African collection of Tribulus terrestris, was shown by one- and two-dimensional NMR spectroscopy to be ruscogenin 1-O-α-L- rhamnopyranosyl-(1→2)-β-D-6-O-acetylglucopyranoside.GC-MS analysis of the hydrolysed ethanol-water (4:1) extracts of T. terrestris specimens from two of four sites, revealed high levels of ruscogenin and potentially lithogenic diosgenin saponins. Specimens from two other sites contained non-lithogenic saponins derived predominantly from tigogenin, neotigogenin, gitogenin and neogitogenin.