Comparative total phenolic content, anti-lipase and antioxidant activities of two Nigerian Aframomum species
The anti-obesity drug development is presently not a bright story. So far, drugs reported to be effective have stimulated controversies due to side effects they elicit. Obesity and its co-morbidities continue however to constitute major problems in both developed and developing countries. This has resulted in a continuous search for novel, cost-effective, safe and potent alternatives. This study investigated the ethanolic extracts of two Nigerian Aframomum species for their anti-lipase and anti-oxidant activities as well as estimates of their polyphenol contents. Lipase activity was determined using glyceryltrioleate emulsion as a substrate and measuring the release rate of oleic acid from it. Percentage inhibition of lipase by the methanolic extracts of plants was determined spectrophotometrically at T0 and T30 (30 minutes after incubation at 37oC). DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity of the extracts and that of gallic acid as control was measured using the stable radical DPPH method and absorbance at 515 nm using a spectrophotometer. The IC50 (half-maximal inhibitory concentration) value was calculated by linear regression analysis and the total phenolic content was determined by the Folin-Ciocalteau method at 765 nm. The standard curve was prepared by solutions of Gallic acid in methanol: water (50:50, v/v). Total phenol values are expressed in terms of Gallic acid equivalent (w/w of dry mass). Aframomum melegueta exhibited the highest phenolic content of 60.4 ± 2.36 mgGAE/g, a percentage antioxidant activity of 86.6 % at 200μg/ml and percentage lipase inhibition of 89% at 1mg/ml while Aframomum danielli revealed a total phenolic content of33.3 ± 2.71mgGAE/g, a percentage antioxidant activity of 77.3% at 200μg/ml and percentage lipase inhibition of 73% at 1 mg/ml. The result provides some justifications for the use of these plants in ethno-medicine for the management of obesity. The species exhibited properties that are beneficial to health and therefore could find use as an alternative and/or complementary strategy in managing associated co-morbidities of obesity, and also as possible template for future anti-obesity drug development.
Keywords: Pancreatic lipase, Aframomum, Orlistat®, Obesity