Inhibitory effects of new varieties of bitter melon on lipopolysaccharide-stimulated inflammatory response in RAW 264.7 cells

Bitter melon is widely used as a food and a traditional herbal medicine for the treatment of diabetes; it also possesses antioxidant, anti-tumour, anti-bacterial, anti-obesity, and anti-hypertension activities. The aim of this work was to study the in vitro anti-inflammatory effects of different solvent extracts of the seeds and fruits of new varieties of bitter melon. Of the 30 bitter melon extracts tested, the ethyl acetate extract of the fruit of Momordica charantia MDS72 (EAEF-MCMDS72) exhibited the strongest anti-inflammatory activity. EAEF-MCMDS72 significantly inhibited the production of NO, IL-6, PGE2, TNF-α, and MCP-1 in lipopolysaccharide (LPS)-treated RAW 264.7 cells. The expression levels of the iNOS and COX-2 proteins in LPS-stimulated RAW 264.7 cells were inhibited by EAEF-MCMDS72. Real-time RT-PCR analysis indicated that the mRNA expression levels of iNOS, COX-2, IL-6, and TNF-α were suppressed by EAEF-MCMDS72. Moreover, four known triterpene compounds including (23E)-cucurbita-5,23,25-triene-3β,7β-diol (1), (23E)-25-methoxycucurbit-23-ene-3β,7β-diol (2), (23E)-5β,19-epoxycucurbita-6,23-diene-3β,25-diol (3), and 3,7-dioxo-23,24,25,26,27-pentanorcucurbit-5-en-22-oic acid (4) were isolated from the fruit of M. charantia MDS72. Compounds 2, 3, 4 suppressed the LPS-induced NO production in RAW 264.7 cells. Furthermore, the present study may contribute to our understanding of the anti-inflammatory effects of EAEF-MCMDS72 and its triterpene compounds.