Osteosaponins 1 and 2: two new saponin glycosides from Osteospermum vaillantii.

Osteospermum vaillantii (Decne) T. Norl., collected from southern Saudi Arabia, yielded two new saponins characterised as 3-O-beta-D-glucopyranosyl-(2' --> 1'')-beta-D-glucopyranosyl-(3' --> 1''')-O-beta-D-galactopyranosyl-oleanolic acid, designated as osteosaponin, and 3-O-beta-D-glucopyranosyl-(2' --> 1'')-beta-D-glucopyranosyl-(2''-1''''')-beta-D-glucopyranosyl-(3' --> 1''')-O-beta-(-D-galactopyranosyl-oleanolic-acid-28-C(O)-O-beta-D-(1'''')-glucopyranosyl ester, designated as osteosaponin. The sugar attachments and configurations were confirmed by spectroscopic methods, that is, 1H, 13C-NMR, COSY, HSQC and HMBC-NMR experiments.