Saponins and sapogenins from Brachiaria decumbens Stapf

Abstract

Four steroidal saponins and three sapogenins were identified from aerial parts of Brachiaria decumbens. Their structures were established by chemical and spectroscopic means (1H and 13C NMR, HMBC, HMQC) as 3β-methoxy-lanost-9(11)-ene (1), diosgenin (2a), yamogenin (2b), 3-O-β-D-glucopyranosyl-24(S)-ethyl-22E-dihydrocholesterol (3a), 3-O-β-D-glucopyranosyl-24(R)-ethyl-22E-dihydrocholesterol (3b), dioscin (4a) and 3-O-{α-L-rhamnopyranosyl-(1→4)-[α-L-rhamnopyranosyl- (1→2)]-β-D-glucopyranosyl}-25(S)-spirost-5-en-3β-ol (4b). All these compounds were isolated for the first time from B. decumbens and compound 4b is described for the first time as far as we know.