[Studies on two new furostanol glycosides from Allium macrostemon Bunge]

Further studies on the active constituents in the bulbs of Allium macrostemon Bunge led to the isolation and structural determination of two new furostanol saponin macrostemonoside E and F. On the basis of chemical evidences and spectral analysis (UV, IR, 1H-NMR, 13C-NMR and FAB-MS), the structure of macrostemonoside E(I) was elucidated as (25R)-26-O-beta-D-glucopyranosyl-5 alpha-furost-20(22)-ene-3 beta,26-diol-3-O- beta-D-glucopyranosyl (1-->2) [beta-D-glucopyranosyl (1-->3)]-beta-D-glucopyranosyl (1-->4)-beta-D-galactopyranoside; macrostemonoside F(II) was established to be (25R)-26-O-beta-D-glucopyranosyl-5 beta-furost-20(22)-ene-3 beta,26-diol-3-O- beta-D-glucopyranosyl (1-->2)-beta-D-galactoside. Preliminary pharmacological tests showed that both macrostemonoside E and F could strongly inhibit ADP-induced human platelet aggregation in vitro. The IC50 of the former was 0.417 mM and that of the latter was 0.020 mM.