Activity of triterpenoid glycosides from the root bark of Mussaenda macrophylla against two oral pathogens

Four new triterpenoid glycosides were isolated from the root bark of Mussaenda macrophylla. Their structures were determined as 3-O-beta-D-glucopyranosyl-28-O-alpha-L-rhamnopyranosyl- protobassic acid (1), 28-O-beta-D-glucopyranosyl-16 alpha-hydroxy-23-deoxyprotobassic acid (2), 3-O-beta-D-glucopyranosyl-28-O-alpha-L-rhamnopyranosyl- 16 alpha-hydroxyprotobassic acid (3), and 3-O-([beta-D-glucopyranosyl- (1-->6)1-O-alpha-L-rhamnopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->2))-O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-cycloarta-22,24-dien-27-oic acid (mussaendoside W, 4). Four known triterpenoids [3-O-acetyloleanolic acid (5), 3-O-acetyldaturadiol (6), rotundic acid (7), and 16 alpha-hydroxyprotobassic acid (8)] were also isolated. The structures of 1-4 were determined by several spectroscopic techniques including 2D NMR methods. Compounds 1-6 showed inhibitory activity against a periodontopathic bacterium, Porphyromonas gingivalis, but were inactive against the cariogenic organism, Streptococcus mutans.