In vitro Studies on the Inhibition of α-Amylase and α- Glucosidase by Leaf Extracts of &lt;i&gt;Picralima nitida&lt;/i&gt; (Stapf)

Jv Ogunbiyi,Ao Ashafa,Mi Kazeem

doi:10.4314/tjpr.v12i5.9

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 αamylase and α-glucosidase activities with half-maximal inhibitory concentration (IC 50 ) 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.

Highlights

Diabetes mellitus is a complex disease characterized by gross derangement in carbohydrate, fat and protein metabolism due to deficiency in insulin secretion and/or action [1]
Mammalian α-amylase is a prominent enzyme in the pancreatic juice which breaks down large and insoluble starch molecules into absorbable molecules maltose [2]. α-glucosidase, on the other hand, anchored in the mucosal brush border of the small intestine catalyzes the end step of digestion of starch and disaccharides that are abundant in human diet [3]
The inhibitory potentials of different extracts of P. nitida on α-amylase activity are presented on Figure 1

Summary

Introduction

Diabetes mellitus is a complex disease characterized by gross derangement in carbohydrate, fat and protein metabolism due to deficiency in insulin secretion and/or action [1]. Inhibitors of α-amylase and α-glucosidase delay the breakdown of carbohydrate in the small intestine and decrease the postprandial blood glucose excursion levels in diabetic patients [4]. The inhibition of these two prominent enzymes has been found as a useful and effective strategy to lower the levels of postprandial hyperglycemia [6]. Picralima nitida (Staph) (Apocynaceae) otherwise known as Akuama or ‘Abeere’ among the Yoruba speaking people of South-Western Nigeria, is a medicinal plant with diverse uses [7] It is used in traditional medicines in the treatment of inflammation, otitis, pulmonary bronchitis, venereal diseases, various fevers, hypertension, jaundice, gastrointestinal disorders and malaria [8, 9]. Previous studies have shown that the extracts from its seeds, fruit rind and stem bark possess antimicrobial, anti-inflammatory, antipyretic, anti-trypanosomal, anti-plasmodial [10], anti-leishmanial, larvicidal [11] and hypoglycaemic potentials [12]

Results

Discussion

Conclusion