In vitro studies on the inhibition of α-amylase and α-glucosidase by leaf extracts of Picralima nitida (Stapf)

Abstract

Purpose: To investigate the anti-diabetic potential of Picralima nitida leaf extracts in vitro. Methods: The current study evaluated the anti-diabetic potential of Picralima nitida leaf via in vitro inhibition of α-amylase and α-glucosidase using the acetone, water and ethanol extracts. Preliminary phytochemical analysis was performed on the acetone, aqueous and ethanol extracts of Picralima nitida leaf. The α-amylase inhibitory potentials of the extracts were investigated by reacting different concentrations of the extracts with α-amylase and starch solution while α-glucosidase inhibition was determined by pre-incubating α-glucosidase with different concentrations of the extracts followed by the addition of p-nitrophenylglucopyranoside (pNPG). The mode(s) of inhibition of both enzymes was determined using Lineweaver-Burke plot. Results: The acetone extract of Picralima nitida displayed the most effective inhibition of both α-amylase and α-glucosidase activities with half-maximal inhibitory concentration (IC50) of 6.50 and 3.00 mg/ml, respectively. The results also showed that the extracts contain both non-competitive and competitive inhibitors of α-amylase and α-glucosidase respectively. The results of phytochemical analysis of the extract revealed the presence of saponins, flavonoids, tannins, terpenoids and reducing sugars. Conclusion: The observed inhibitions of α-amylase and α-glucosidase suggest that the leaf extracts of P. nitida may be useful in the management of diabetes mellitus. This buttresses the traditional use of P. nitida for the management of sugar-related disorders in some parts of Nigeria. © Pharmacotherapy Group, Faculty of Pharmacy, University of Benin, Benin City, 300001 Nigeria. All rights reserved.