Anti‐inflammatory Activities of an Active Fraction Isolated from the root of Astragalus membranaceus in RAW 264.7 Macrophages

The root of Astragalus membranaceus (AR), which has been widely used in Traditional Chinese herbal formulae for treating foot ulcer, was found to exhibit anti‐inflammatory property, but its molecular mechanism still remains unknown. We previously identified the anti‐inflammatory sub‐fraction using bioassay‐guided fractionation. The objective of the present study was to investigate the anti‐inflammatory mechanism of the major active fraction (MAF) (0.039 to 0.156 mg/mL) using lipopolysaccharide (LPS)‐stimulated mouse macrophage RAW 264.7 cells. MAF was shown to inhibit LPS‐induced mRNA and protein expression of inducible nitric oxide synthase by 54.7% and 65.1%, respectively. Additionally, MAF down‐regulated the protein expression of cyclooxygenase‐2 and MAPK regulator by 45.0% to 74.6%, as well as the reduction of DNA binding activity of nuclear factor kappa B (NFκB) by 66.5%. It also attenuated the production of prostaglandin E₂, interleukin‐1 beta (IL‐1β), IL‐6 and tumor necrosis factor alpha by 21.2% to 86.2%. Furthermore, the chemical constituents of MAF were identified. A total of 13 known chemical compounds were found in MAF, including five isoflavonoids and eight saponins. In conclusion, a bioactive fraction of AR was identified which possessed anti‐inflammatory property by reducing the release of inflammatory mediators and inactivation of NFκB through MAPK signalling pathway. Copyright © 2013 John Wiley & Sons, Ltd.