Abstract

Melilotus suaveolens Ledeb is an annual or biennial plant of Melilotus genus in the Leguminosae family, which was used for treatment of inflammation-related diseases. The paper aims to investigate the anti-inflammatory mechanisms of ethanol extracts from M. suaveolens Ledeb. RAW 264.7 cells were stimulated with 10 ng/ml lipopolysaccharide (LPS) and intervened with 1 to 10 μg/ml ethanol extracts of M. suaveolens Ledeb. Several pro-inflammatory cytokines and mediators including inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin (IL)-1β and tumour necrosis factor-α (TNF-α) were studied by the method of enzyme-linked immunosorbent assay (ELISA) analysis, real time – polymerase chain reaction (RT-PCR) and western blot, respectively. The anti-inflammatory cytokines and mediators, such as IL-10 and heme oxygenase-1 (HO-1), were also investigated by the same method. The activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) was studied using immunocytochemistry assay. Meanwhile, high performance liquid chromatography (HPLC) fingerprint was used to elucidate the active compounds in the extracts. The results showed that the extracts of M. suaveolens Ledeb have an anti-inflammatory effect by down-regulation of pro-inflammatory cytokines and mediators, such as iNOS, COX-2, IL-1β and TNF-α gene expression through the suppression of NF-κB activation. At the same time, the extracts increased anti-inflammatory cytokines and mediators IL-10 and HO-1. HPLC fingerprint chromatography of the M. suaveolens Ledeb extracts showed that coumarin is one of the main anti-inflammation compounds present in the plant, which is likely to be the basis of its anti-inflammation effect. The findings demonstrated that ethanol extracts from M. suaveolens Ledeb have great anti-inflammatory activities, which may be due to its dual effects on antagonizing pro-inflammatory and augmenting anti-inflammatory mediators.

Key words: Melilotus suaveolens Ledeb, ethanol extract, anti-inflammatory effects, pro-inflammatory cytokines and mediators, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), anti-inflammatory cytokines and mediators.