Fractionation and identification of 9c, 11t, 13t-conjugated linolenic acid as an activator of PPARα in bitter gourd (Momordica charantia L.)

Bitter gourd (Momordica charantia L.) is a common vegetable in Asia that has been used in traditional medicine for the treatment of Diabetes. PPARs are ligand-dependent transcription factors that belong to the steroid hormone nuclear receptor family and control lipid and glucose homeostasis in the body. We previously reported that the ethyl acetate (EA) extract of bitter gourd activated peroxisome proliferator receptors (PPARs) alpha and gamma. To identify the active compound that activated PPAR alpha, wild bitter gourd EA extract was partitioned between n-hexane and 90% methanol/10% H2O, and the n-hexane soluble fraction was further separated by silica gel column chromatography and finally by preparative HPLC. A transactivation assay employing a clone of CHOK1 cells stably transfected with a (UAS)(4)-tk-alkaline phosphatase reporter and a chimeric receptor of GAL4-rPPAR alpha LBD was used to track the active component. Based on Mass, NMR, and IR spectroscopy, 9cis, 11trans, 13trans-conjugated linolenic acid (9c, 11t, 13t-CLN) was identified as a PPAR alpha activator in wild bitter gourd. The isolated 9c, 11t, 13t-CLN rich fraction also significantly induced acyl CoA oxidase (ACO) activity in a peroxisome proliferator-responsive murine hepatoma cell line, H4IIEC3, implying that 9c, 11t, 13t-CLN was able to act on a natural PPAR alpha signaling pathway as well. The content of 9c, 11t, 13t-CLN was estimated to be about 7.1 g/kg of our dried wild bitter gourd sample. The concentration of 9c, 11t, 13t-CLN and activation activity in the hydrolyzed EA extract of the seeds was higher than that of the flesh. The potential health benefits of 9c, 11t, 13t-CLN through the PPAR alpha regulated mechanism are worthy to be further characterized in in vivo studies.