Anti-inflammatory effect of isopimarane diterpenoids from Kaempferia galanga

Two new isopimarane diterpenes, 1 alpha-hydroxy-14 alpha-methoxyisopimara-8(9),15-diene (7) and 1 alpha,14 alpha-dihydroxyisopimara-8(9),15-diene (9) and eight known isopimarane diterpenes including (-)-sandaracopimaradiene (1), 6 beta-acetoxysandaracopimaradiene-9 alpha-ol (2), sandaracopimaradiene-7 beta,9 alpha-diol (3), sandaracopimaradiene-1 alpha,9 alpha-diol (4), 6 beta-acetoxysandaracopimaradiene-9 alpha-ol-1-one (5), 6 beta-acetoxysandaracopimaradiene-1 alpha,9 alpha-diol (6), 6 beta,14 alpha-dihydroxyisopimara-8(9),15-diene (8), and 6 beta,14 beta-dihydroxyisopimara-8(9),15-diene (10) were isolated from hexane fraction of Kaempferia galanga ethanol extract. Compounds 5, 6, 8, and 9 exerted the good anti-inflammatory effect on lipopolysaccharide-stimulated nitric oxide production from RAW264.7 cells with IC50 of 11.2, 7.7, 14.3, and 12.1 mu M, respectively. These four compounds inhibited nitric oxide synthase (iNOS) mRNA expression. Compounds 5 and 6 also suppressed cyclooxygenase 2 (COX-2) mRNA expression; in addition, compound 6 had mild inhibitory effect on TNF-alpha mRNA. Among these compounds, 5 dramatically inhibited iNOS and COX-2 mRNA expression. The influential structures were proposed to be oxygen substitute at C-1, C-6, and alpha-OH at C-14.