Abstract
This study was performed to investigate potential bioactive secondary metabolites from the leaves of Acacia mearnsii, a forest waste product in China. The polyphenol constituents and bioactivity of crude extract (L) and semi purified fractions (L1-L4) were examined. The L and L1-L4 showed qualitative and quantitative differences in their phenolic content, antioxidant activities and the activities against inflammation-related genes such as the inducible forms of COX-2, iNOS, and the pro-inflammatory IL in lipopolysaccharide (LPS)-stimulated mouse macrophage cell line RAW 264.7. All the fractions depressed reactive oxygen species (ROS) in LPS-stimulated RAW 264.7 macrophage cells, and (except L2) inhibited the release of nitric oxide (NO). Fractions L3 and L4 significantly inhibited the mRNA expression levels of the anti-inflammatory cytokine IL-1β, COX-2, iNOS, and IL-6. In addition, L4 (1.8 g obtained from 5 g crude leaves extract) which contained 646.6 mg/g gallic acid equivalent total phenolic content and consisted of primarily proanthocyanidins (12.6 mg/g as procyanidin B2 equivalent by the DMAC assay) showed the best activity in all the assays. Results indicate that A. mearnsii leaves, a forest waste product, could be a valuable natural source of anti-inflammatory and functional components related to human health.