Triterpene saponins from aerial parts of Medicago arabica L.

Eight major triterpene saponins have been isolated from the aerial parts of Medicago arabica and their structures elucidated by FAB-MS and NMR analysis. Three of them are new compounds and are identified as 3-O-(alpha-L-arabinopyranoside) bayogenin, 3-O-(alpha-L-arabinopyranosyl), 28-O-(beta-D-glucopyranoside) bayogenin, and 3-O-[alpha-L-arabinopyranosyl(1-->2)-beta-D-glucuronopyranosyl], 28-O-beta-D-glucopyranoside 2-beta-hydroxyoleanolic acid. Two saponins, identified as 3-O-(alpha-L-arabinopyranoside) hederagenin and 3-O-(alpha-L-arabinopyranosyl), 28-O-(beta-D-glucopyranoside) hederagenin are known compounds but not previously reported as saponin constituents of Medicago species, while three other saponins, being mono- and bidesmosides of hederagenin, have been previously isolated from roots of M. sativa.