Effects of sesquiterpenes and triterpenes from the rhizome of Alisma orientale on nitric oxide production in lipopolysaccharide-activated macrophages: Absolute stereostructures of alismaketones-B 23-acetate and -C 23-acetate

The methanolic extract from a Chinese herbal medicine, the rhizome of Alism a orientale, was found to exhibit inhibitory activity of nitric oxide (NO) production in lipopolysaccharide (LPS)-activated macrophages. Novel triterp enes, alismaketones-B 23-acetate and -C 23-acetate, were isolated from the active extract together with eight sesquiterpenes and eighteen protostane-t ype triterpenes. The absolute stereostructures of new triterpenes were char acterized on the basis of chemical and physicochemical evidence, which incl uded the chemical correlations with known triterpenes. The guaiane-type ses quiterpenes (alismol, orientalols A and C) and protostane- and seco-protost ane-types triterpenes (alisols C monoacetate, E-23-acetate, F, H, I, L-23-a cetate, and M-23-acetate, alismaketones-B 23-acetate and -C 23-acetate, ali smalactone 23-acetate, and 3-methylalismalactone 23-acetate) inhibited LPS- induced NO production (IC50 8.4-68 mu M). Other triterpenes (alisols A, A m onoacetate, B, B monoacetate, E, G, K-23-acetate, and N-23-acetate and 11-d eoxyalisol B) also showed the potent inhibitory activity, but they showed c ytotoxic effects more than 30 mu M (MTT assay). In addition, alismol and al isol F were found to suppress iNOS induction. (C) 1999 Elsevier Science Ltd . All rights reserved.