Anti‐inflammatory effect of isopimarane diterpenoids from Kaempferia galanga

Two new isopimarane diterpenes, 1alpha-hydroxy-14alpha-methoxyisopimara-8(9),15-diene (7) and 1alpha,14alpha-dihydroxyisopimara-8(9),15-diene (9) and eight known isopimarane diterpenes including (-)-sandaracopimaradiene (1), 6beta-acetoxysandaracopimaradiene-9alpha-ol (2), sandaracopimaradiene-7beta,9alpha-diol (3), sandaracopimaradiene-1alpha,9alpha-diol (4), 6beta-acetoxysandaracopimaradiene-9alpha-ol-1-one (5), 6beta-acetoxysandaracopimaradiene-1alpha,9alpha-diol (6), 6beta,14alpha-dihydroxyisopimara-8(9),15-diene (8), and 6beta,14beta-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 muM, 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.