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.