Antiinflammatory and antibacterial activities of C-methylflavonols from Piliostigma thonningii

Newly described C-methylflavonols, 6,8-di-C-methylquercetin 3-methyl ether, 6-C-methylquercetin 3,7-dimethyl ether, 6,8-di-C-methylquercetin 3,7-dimethyl ether together with the known compounds quercetin, quercitrin, 6-C-methylquercetin 3-methyl ether, 6-C-methylquercetin 3,7,3′-trimethyl ether, 6,8-di-C-methyl- kaempferol 3-methyl ether and 6,8-di-C-methylkaempferol 3,7-dimethyl ether isolated from the leaves of Piliostigma thonningii, were tested for their ability to inhibit prostaglandin synthesis in vitro and antibacterial activity against Staph. aureus. The influence of the B ring 3′,4′ diol group on the activity of C-methylflavonols in the inhibition of prostaglandin synthesis differ from that observed for a series of flavonoids without C-methyl groups. The antibacterial activity in the series mirror those of methylated antimicrobial flavonoids. The traditional uses of the plant in infections and inflammatory conditions were rationalized on the basis of the activities of these compounds. © 1997 John Wiley & Sons, Ltd.