Triterpene and steroid saponins isolated from two Melilotus species

Abstract

Four new triterpene saponins of the oleanan series - melilotosides I, II, III, IV and nonglycosylated soyasapogenol B have been isolated from roots of Melilotus albus Medik. (Leguminosae) and four steroid saponins were isolated from M. tauricus (Bieb.) ser. seeds. The chemical structure of the saponins and of their aglycone was proved based on chemical transformations and spectral data. Melilotoside I has the structure of 3-O-[a-L- arabinopyranosyl] soyasapogenol B, melilotoside II that of 3-O-[β-D- galactopyranosyl (1→2)-O-α-L-arabinopyranosyl]soyasapogenol B, melilotoside III that of 3-O-[α-L-rhamnopyranosyl-(1→2)-O-β-D-galactopyranosyl-(1→2)- O-α-L-arabinopyranosyl]soyasapogenol B, and melilotoside IV that of 3-O- [α-L-rhamnopyranosyl-(1→2)-[α-L-arabinopyranosyl-(1→3)]-O-β-D- galactopyranosyl-(1→2)-O-α-L-arabinopyranosyl soyasapogenol B. The steroid saponins have been identified as 3-O-β-D-glucopyranoside-diosgenin (V); 3- O-α-L-rhamnopyranosyl (1→2)-[α-L-rhamnopyranosyl(1→3)-O-β-D- glucopyranoside-diosgenin (VI), 26-O-β-D-glucopyranoside (25R)-furost-5-ene 3β,22α,26-triol (VII), and 3-O-α-L-rhamnopyranosyl(1→4)-α-O-β-D- glucopyranoside (25R)-furost-5-ene 3β,22α,26-triol-26-O-β-D- glucopyranoside (VIII).