Paeonol (2-hydroxy-5-methoxyacetophenone) obtained by silica gel column chromatography of the essential oil extracted from Paeonia moutan (Paeoniaceae) was methylated by dimethylsulfate to yield methylpaeonol (2,5-di-O-methylacetophenone). Both compounds inhibited nitric oxide (NO) foundation in lipopolysaccharide-induced macrophage RAW 264.7 cells in nitrite assay. In the western blotting assay, it was shown that both compounds also decreased inducible nitric oxide synthase (iNOS)-and cyclooxygenase-2(COX-2) formation. Methylpaeonol produced more potently inhibited NO-, iNOS and COX-2 formation in the assays than paeonol. These results suggest that paeonol is in part responsible for anti-inflammatory activity of Paeonia moutan, and that synthesis of paeonol derivatives may produce a promising candidate for andtiifnalmmatory agent.