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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.

This paper aimed to elucidate the anti-inflammatory effects of EtOAc fraction prepared from Melilotus suaveolens Ledeb ethanol extract with a cellular model of LPS-stimulated RAW 264.7 cell.Some key pro-inflammatory cytokines and mediators including IL-1 beta, IL-6, NO, iNOS, COX-2 and TNF-alpha, two important anti-inflammatory cytokines and mediators IL-10 and HO-1, I-kappaB and NF-kappaB were studied by sandwich ELISA, real-time PCR, western blot analysis and immunocytochemistry. At last a HPLC fingerprint was taken to evaluate the fraction.The EtOAc fraction could significantly inhibit the production of IL-1 beta, IL-6, NO, TNF-alpha, COX-2 in LPS-stimulated cell than that of single LPS-stimulated cell (p0.01 or p0.05), and the extract could increase the production of IL-10 and HO-1 than that of single LPS intervention cell (p0.01 or p0.05). Meanwhile, the extract also could inhibit the production of NF-kappaB compared to single LPS-stimulated cell. All the results showed that the extract had a good anti-inflammatory effect on LPS-stimulated RAW264.7 cell.Taken together, the anti-inflammatory actions of M. suaveolens Ledeb EtOAc fraction might be due to the down-regulation of IL-1 beta, IL-6, NO, TNF-alpha and COX-2 via the suppression of NF-kappaB activation, and another pathway was up regulating the production of IL-10 and HO-1. Meanwhile, the EtOAc fraction might be further studied to isolate the active anti-inflammatory ingredients besides coumarin.