In vitro anti-inflammatory effects of different solution fractions of ethanol extract from Melilotus suaveolens Ledeb

BACKGROUND Melilotus suaveolens Ledeb (M. suaveolens Ledeb) has long been used as a folk medicine in inflammation-related therapy. This study was undertaken to determine the anti-inflammatory effect of the plant. METHODS Petroleum ether fraction, ethyl acetate fraction, n-butanol fraction, aqueous fraction were obtained from ethanol extract of M. suaveolens Ledeb and evaluated by high performance liquid chromatography (HPLC). While dexamethasone (DM) was used as a positive control, the effects of different solution fractions of ethanol extract on tumor necrosis factor alpha (TNF-alpha) mRNA, cyclooxygenase 2 (COX-2) mRNA, COX-2 and nuclear factor kappaB (NF-kappaB) of LPS-stimulated RAW 264.7 cells were studied by real-time PCR, Western blot analysis and immunocytochemical assay, respectively. RESULTS Coumarin was one of the main ingredients in different solution fractions of ethanol extract except the aqueous fraction with no inflammatory effect. The petroleum ether fraction, ethyl acetate fraction and n-butanol fraction of ethanol extract could inhibit the production of TNF-alpha mRNA, COX-2 mRNA and NF-kappaB to some extent. CONCLUSIONS Different solution fractions of ethanol extract from M. suaveolens Ledeb had similar anti-inflammatory effect as did dexamethasone except the aqueous fraction. Coumarin was likely to be essential to the anti-inflammatory effect, and other ingredients might attribute to their different anti-inflammatory effects from the HPLC fingerprint.