[[alternative]]Investigation of bitter gourd Fractions with inhibitory effect on Prostaglandin E2 Production in Macrophage Cell Line

[[abstract]]Researches on the anti-inflammation have attached great attention in recent years, since inflammation was recognized as a major cause of tissue damage through the progression of many diseases. Activation of macrophages and the induced expression of COX-2 that increases PGE2 production play an important role in the inflammatory process. PGE2 is the major prostaglandin produced by macrophages and is a well-known pro-inflammatory mediator. Inhibition of the production of PGE2 is regarded as a major approach to ameliorate the inflammatory symptoms. It was reported that bitter gourd extract could inhibit the PGE2 production of the LPS activated murine macrophage cell line. This study is therefore aimed at identifying fractions and compounds isolated from bitter gourd extract, which have inhibitory effect on PGE2 production in the LPS activated RAW264.7 cell line. The whole bitter gourd (Momordica charantia L.) was extracted with water and the water-insoluble residue was further extracted with ethyl acetate (EA). Both of water and EA extracts had inhibitory activity, and the ethyl acetate extract (EAE) had higher activity than water extract. The whole bitter gourd was freeze-dried and directly extracted by EA. The EAE was partitioned by n-hexane and 90%MOH+10%H2O. The n-hexane fraction had inhibitory activity and was further separated by silica gel column chromatography, successively eluted with solvents of increasing polarity (100% n-hexane to 100% EA and then with 90% EA+10%MeOH finally). The fraction 190 eluted by 90% EA+10%MeOH showed the highest inhibitory activity. The fraction 190 was further separated by silica gel column chromatography, eluted with chloroform/MeOH (6/1) and the fraction F1-6 obtained showed higher inhibitory activity. The F1-6 fraction was further separated by silica gel column chromatography twice to obtain the active fraction. And the active fraction was further separated by RP-18 column chromatography to obtain the RP-10 which had the best inhibitory activity (IC50=2.31µg/mL). The RP-10 was identified as triacylglycerol (TG) constituted of short and medium chain fatty acids identified by NMR, IR and H-H Cosy. To verify the components identified from the n-hexane fraction of the whole bitter gourd were TG containing short and medium chain fatty acids, the F1-6 was further hydrolyzed and extracted with EA, and the fatty acid compositions were determined by GC-mass. Octanedioic acid, nonanedioic acid and decanedioic acid were found. On the other hand, the fatty acids standards with 3-20 carbons were tested for the inhibitoryactivity and capric acid (C10:0) was found to possess the highest inhibitory activity. 50µM of it almost completely inhibited PGE2 production in this cell system (IC50=6.46µM or 1.216µg/mL). The octanedioic acid and nonanedioic acid also had inhibitory activity but were inferior to capric acid. In addition, the MCT oil containing mainly C8 and C10 fatty acids also showed partial inhibitory activity. In conclusion, the ester forms of short and medium chain saturated fatty acids or dicarboxylic acids in the n-hexane fraction of the whole bitter gourd were identified as components with activity of inhibiting the PGE2 production in the LPS activated RAW264.7 cell line. Other components from the EA partitioned fraction may also have activity and need further investigation.