Triterpenoid glycosides from the leaves of Medicago arborea L

Eighteen triterpene saponins (1-18) from Medicago arborea leaves have been isolated and their structures elucidated by spectroscopic, spectrometric (1D and 2D NMR, FAB-MS, ESI-MS/MS), and chemical methods. They have been identified as glycosides of medicagenic, zanhic, and 2 beta-hydroxyoleanolic acids, soyasapogenol B, bayogenin, and 2 beta, 3 beta-dihydroxyolean-12-en-23-al-28-oic acid. Twelve of them, identified as 3-O-beta-D-glucopyranosyl-28-O-[alpha-L-arabinopyranosyl(1 -> 3)-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranoside] zanhic acid (3), 3-O-beta-D-glucopyranosyl-28-O-{beta-D-xylopyranosyl(1 -> 4)-[alpha-L-arabinopyranosyl-(1 -> 3)]-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyrano- side} zanhic acid (4), 3-O-[alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranosyl(1 -> 2)-beta-D-glucopyranosyl]-2 beta-hydroxyoleanolic acid (5), 3-O-beta-D-glucuronopyranosyl-28-O-[alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranoside] medicagenic acid (6), 3-O-beta-D-glucuronopyranosyl-28-O-[beta-D-xylopyranosyl(1 -> 4)alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranoside]bayogenin (9), 3-O-beta-D-glucuronopyranosyl-28-O-[beta-D-xylopyranosyl(1 -> 4)-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranoside]-2 beta,3 beta-dihydroxyolean-12-en-23-al-28-oic acid (10), 3-O-beta-D-glucuronopyranosyl-28-O-{beta-D-xylopyranosyl(1 -> 4)-[beta-D-apiofuranosyl(1 -> 3)]-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranosidelzanhic acid (12), 3-O-beta-D-glucuronopyranosyl-28-O-{beta-D-xylopyranosyl(1 -> 4)-[alpha-L-arabinopyranoside(1 -> 3)]-alpha-L-rhamnopyrano- syl(1 -> 2)-alpha-L-arabinopyranosidelzanhic acid (13), 3-O-beta-D-glucuronopyranosyl-28-O-[beta-D-xylopyranosyl(1 -> 4)-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranoside]zanhic acid (14), 3-O-[alpha-L-arabinopyranosyl(1 -> 2)-D-glucopyranosyl(1 -> 2)-beta-D-glucopyranosyl]-2 beta-O-{beta-D-xylopyranosyl(1 -> 4)-[beta-D-apiofuranosyl(1 -> 3)]-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyranosidelzanhic acid (16), 3-O-[beta-D-glucopyranosyl (1 -> 2)-(beta-D-glucopyranosyl]-28-O{beta-D-xylopyranosyl (1 -> 4)-[alpha-L-arabi nopyranosyl(1 -> 3)]-alpha-L-rhamnopyranosyl (1 -> 2)-alpha-L-arabinopyranosidelzanhic acid (17), and 3-O-beta-D-glucuronopyranosyl-28-O-1pD-xylopyranosyl(1 -> 4)-beta-D-apiofuranosyl(1 -> 3)]-alpha-L-rhamnopyranosyl(1 -> 2)-alpha-L-arabinopyrano-sideImedicagenic acid (18), are reported as new natural compounds. The presence of the aldehydic group on the sapogenin moiety of saponin 10 is discussed in the framework of a possible elucidation of the biosynthesis of these metabolites.