In the course of our screening, we found that the methanolic extract of Sappan Lignum showed strong activity against lipopolysaccharide (LPS)-induced nitric oxide (NO) production by macrophages in vitro. As it was reported that Brazilin inhibited inducible NO gene, we conducted to similar tests for six known compounds isolated from Sappan Lignum, namely, brazilein, sappanchalcone, protosappanin A, protosappanin B, protosappanin C besides brazilin. And six compounds were also subjected to six tests to speculate their properties: (1) inhibition of NO production by cultured J774.1 (macrophage-like) cell line, (2) suppression of inducible NO synthase (iNOS) gene expression, (3) inhibition of NO production by murine peritoneal macrophages, (4) DPPH radical scavenging activity, (5) reduction of ferric ion and (6) antioxidant activity. Brazilein and sappanchalcone showed significant inhibition of lipopolysaccharide (LPS)-induced NO production by J774.1 cell line like Brazilin; 100% inhibition at 30 μM in test (1) and at 10 μM in test (3). The mechanisms underlying the inhibition of NO production by the compounds were investigated in test (2). As a result, brazilin was found to almost completely suppress iNOS gene expression at 100 μM as reported, and brazilein and sappanchalcone also suppressed iNOS gene expression. But strong activities were not observed for protosappanins A, B and C. So, we conducted tests (4), (5) and (6) to investigate other properties about six compounds. Protosappanin A and Brazilin demonstrated high antioxidant activity compared with Vitamin E in tests (4) and (5). Protosappanin A and B inhibited the oxidation of linoleic acid in test (6). Among the dibenzoxocin derivatives, only protosappanin C did not show significant activity in all the tests. We found that sappanchalcone showed same activity as brazilin, and six compounds isolated from Sappan Lignum showed various properties.