In vitro inducible nitric oxide synthesis inhibitors from Alismatis Rhizoma

Bioassay-guided fractionation of an aqueous extract of Alismatis Rhizoma ha s furnished two inducible nitric oxide synthase (iNOS) inhibitory compounds , alismol (1) and alisol B monoacetate (2), together with an inactive trite rpene, alisol C monoacetate (3). Compounds 1 and 2 inhibited nitric oxide ( NO) synthesis in a dose-dependent manner in murine macrophage-like RAW 264. 7 cells stimulated with interferon-gamma (IFN-gamma) plus lipopolysaccharid e (LPS), The inhibitory effects of 1 and 2 on NO synthesis were partly due to suppression of iNOS mRNA expression as determined by Northern blotting.