Effect of phytocompounds from the heartwood of Acacia confusa on inflammatory mediator production

Acacia confusa Merr. (Leguminosae) is traditionally used as a medicinal plant in Taiwan. In the present study, anti-inflammatory activity of extracts from the heartwood of A. confusa were investigated for the first time. Results demonstrated that ethanolic extracts of A. confusa heartwood strongly suppressed NO production in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. Among all fractions derived from ethanolic extracts, the EtOAc fraction exhibited the best inhibitory activity. Following column chromatography and reverse-phase high-performance liquid chromatography, 13 specific phytocompounds including 5 new flavonoids (i.e., 7,8,3′,4′-tetrahydroxy-4- methoxyflavan-3-ol, 7,8,3′,4′-tetrahydroxyflavone, 7,8,3′-trihydroxy-3,4′-dimethoxyflavone, 7,3′,4′- trihydroxyflavone, and 7,3′,4′-trihydroxy-3-methoxyflavone) were isolated and identified from the EtOAc fraction. In addition, melanoxetin (3,7,8,3′,4′-pentahydroxyflavone), a major compound in the EtOAc fraction, markedly suppressed LPS-induced NO and prostaglandin E ₂ (PGE ₂) production. Moreover, melanoxetin completely suppressed gene expression of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) at 50 and 100 μM, respectively. This is the first report to identify the inhibitory bioactivities of melanoxetin on iNOS and COX-2.