Effect of Siam weed extract and its bioactive component scutellarein tetramethyl ether on anti-inflammatory activity through NF-κB pathway

Siam weed (Chromolaena odorata (L.) King and Robinson) is a medicinal herb used for wound healing and inflammation-related diseases.In this study, we evaluated the molecular mechanism by which Siam weed extract (SWE) and its bioactive components, scutellarein tetramethyl ether (scu), stigmasterol, and isosakuranetin affect anti-inflammatory activity.The expression of several inflammatory proteins in RAW 264.7 (murine) macrophages was assessed by Western blot and reverse transcription-polymerase chain reaction (RT-PCR). Biochemical assays including prostaglandin E2 (PGE2) and nitric-oxide (NO) quantification were performed. Luciferase promoter activity and immunocytochemistry of Nuclear factor-κB (NF-κB) were investigated.Cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) are critical pro-inflammatory proteins. The level of protein and mRNA expression of these enzymes induced by lipopolysaccharide (LPS) was dramatically suppressed by treatment with SWE, scu, or stigmasterol compounds in a dose-dependent manner. They also reduced PGE2 and NO release. We further analyzed the NF-κB pathway and found that the scu compound suppressed IκB kinase complex alpha/beta (IKKα/β) and Inhibitory-kappa-B-alpha (IκBα), thereby suppressing COX-2 and iNOS expression.This is the first report of the anti-inflammatory molecular mechanism in SWE and/or its bioactive component scu, indicating alteration NF-κB pathway and further providing potential uses in the treatment of inflammatory-related diseases.