Triterpene saponins from the roots of Medicago hybrida

Fourteen triterpene saponins (1−14) have been isolated from the roots of Medicago hybrida and their structures elucidated by FAB-MS and NMR analysis. Two of them are new compounds and were identified as hederagenin 3-O-[α-l-rhamnopyranosyl(1→2)-β-D-glucopyranosyl(1→2)-β-D-glucopyranosyl]-28-O-β-D-glucopyranoside (7) and oleanolic acid 3-O-[β-D-galactopyranosyl(1→2)-β-D-glucuronopyranosyl]-28-O-[α-l-rhamnopyranosyl(1→4)-β-D-glucopyranoside] (14). Seven saponins being mono- and bidesmosides of hederagenin (1, 5, 6, 9), one bidesmoside of bayogenin (2), and two bidesmosides of 2β,3β-dihydroxyolean-12-en-23-al-28-oic acid (11) and oleanolic acid (13) are known compounds but not previously reported as saponin constituents of Medicago, whereas five other saponins, being mono- and bidesmosides of medicagenic acid (3, 4, 8, 10, 12), and one monodesmoside of hederagenin (8) have been previously isolated from other Medicago species. The presence of 2β,3β-dihydroxyolean-12-en-23-al-28-oic acid might represent an interesting intermediate in the biosynthesis of these substances. Keywords: Medicago hybrida L.; triterpene saponins; chemical structure; FAB-MS; NMR