Cycloartane triterpene glycosides from the roots of Astragalus brachypterus and Astragalus microcephalus

Three new cycloartane-type triterpene glycosides, brachyosides A (1), B (3), and C (2), from the roots of Astragalus brachypterus and one new glycoside, cyclocephaloside II (4), from the roots of Astragalus microcephalus have been isolated together with five known saponins, astragalosides I, II, and IV, cyclocanthoside E, and cycloastragenol. The structures of the new compounds were established as 3-O-[beta-D-xylopyranosyl(1-->3)-beta-D-xylopyranosyl-3 beta,6 alpha,24(S),25-pentahydroxycycloartane (1), 3-O-beta-D-xylopyranosyl-6-O-beta-D-glucopyran pentahydroxycycloartane (2), 20(R),24(S)-epoxy-6-O-beta-glucopyranosyl-3 (3), and 20(R),24(S)-epoxy-3-O-(4'-O-acetyl)-beta-D-16 beta,25-tetrahydroxycycloartane (4). For the structure elucidations, 1D- and 2D-NMR experiments and FABMS were used.