This research was undertaken to find the in vitro inflammatory action of 5,7-dimethyloxy-4-p-methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin produced by Streptomyces aureofaciens CMUAc130. We investigated the effects of 5,7-dimethyloxy-4-p-methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin not only on the formation of NO, prostaglandin E2 (PGE2), and tumor necrosis factor-α (TNF-α) but also on inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-induced murine macrophage RAW 264.7 cells. The data obtained were consistent with the modulation of iNOS enzyme expression. A similar fashion was also observed when LPS-induced PGE2 release and COX-2 expression were tested. The significant inhibitory effects were shown in concentration-dependent manners. In addition, 5,7-dimethyloxy-4-p-methoxylphenylcoumarin and 5,7-dimethoxy-4- phenylcoumarin also mildly but significantly reduced the formation of TNF-α. These findings support the application of 5,7-dimethyloxy-4-p- methoxylphenylcoumarin and 5,7-dimethoxy-4-phenylcoumarin as anti-inflammatory agents. © 2006 Informa Healthcare.