Brazilin (7,11b-dihydrobenz[b]indeno[1,2-d]
pyran-3,6a,9,10 (6H)-tetrol) isolated from Caesalpinia sappan has been known as a natural red pigment. Many studies suggest that inducible
isoform of
nitric oxide synthase (NOS) plays an important role in
inflammation and
carcinogenesis. On this line, we evaluated the inhibitory effect of
brazilin on
nitric oxide (NO) production and investigated its mechanism of action. As a result,
brazilin exhibited the inhibitory effect on
lipopolysaccharide (LPS)-stimulated NO production in a dose-dependent manner (IC50=24.3 microM). In addition,
brazilin suppressed LPS-induced iNOS
protein and
mRNA expression in RAW 264.7 macrophage cells, indicating that the inhibitory activity of
brazilin possibly involved in the regulation of iNOS expression. To further investigate the mechanism responsible for the suppression of iNOS gene expression by
brazilin, the effect of
brazilin on LPS-induced
transcription factors nuclear factor-kappaB (
NF-kappaB) and
activator protein-1 (AP-1) activation was examined. The
DNA binding activity of
NF-kappaB and
AP-1 stimulated LPS was inhibited by treatment of
brazilin in a dose-dependent manner, suggesting that
brazilin-mediated inhibition of NO production might be associated with the regulation of
transcription factors NF-kappaB and
AP-1. Taken together, these findings suggest that the suppressive effect of iNOS gene expression by
brazilin might provide one possible mechanism for its anti-inflammatory and
cancer chemopreventive activity.