Inhibition of cyclooxygenase and lipoxygenase activities of momordica charantia

Abstract

Momordica charantia (MC) or bitter gourd is a climber belongs to the family of cucurbitaceae. There are numbers of evidences showing anti-diabetic, anti-oxidant, anti-inflammatory and anti-cancer activities of MC, however the effects of fractionation and processing of MC on its anti-inflammatory activity have not been fully elucidated. Therefore, the objectives of this study are to investigate the antiinflammatory effects of MC raw juice and fractions and to evaluate the effect of processing methods on its anti-inflammatory activity. First, MC juice was obtained using a conventional juicer and fractionated into five fractions, namely strong acid, weak acid, neutral, weak base, and strong base fractions using solid phase extraction method. The raw juice and its fractions were then tested for their anti-inflammatory activities which included cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), 5- lipoxygenase (5-LOX), and 15-lipoxygenase (15-LOX) inhibition assays. The current results showed that the COX-1 inhibition activity of MC can be attributed to the neutral fraction metabolites (52.60% inhibition), and no significant difference in COX-1 inhibition activity was found between the neutral fraction and the raw juice. In contrast, the anti-COX-2 activity of MC was found exerted collectively by metabolites in multiple fractions (including strong base, neutral, and strong acid fractions). On the other hands, all five fractions contributed to the inhibition activities of MC juice on 5- LOX (55.51% inhibition for raw juice) and 15-LOX (55.3% inhibition for raw juice). In addition, the current findings showed that the juice processing method using conventional juicer or slow juicer influenced the bioactivity of the plant, where fruit juice obtained from a slow juicer showed consistently higher anti-inflammatory activities than juice from a conventional juicer. The MC juice has a bitter taste and may be unfavorable to some people. Results from a descriptive sensory analysis showed that a mixture of 50% MC + 50% green apple juice able to improve palatability of MC juice. The mixture also gave better inhibition effects on COX-1, COX-2 and 15-LOX activities, even when compared with the 100% MC raw juice. This study reported on the anti-inflammatory activities of MC and its fractions, which may contribute towards an effective processing and fractionation strategy for MC.