In vitro antioxidant activities of African birch (Anogeissus leiocarpus) leaf and its effect on the α-amylase and α-glucosidase inhibitory properties of acarbose

Abstract

Objective This study sought to determine the antioxidant activities of African birch leaf, to assess its interaction with key enzymes relevant to type 2 diabetes (α-amylase and α-glucosidase) and to evaluate its effect on acarbose in vitro.

Methods One milligram per milliliter of aqueous extract of African birch and acarbose were separately prepared. At the same time, both the African extract and acarbose solution (50:50 v/v) were thoroughly mixed until homogeneity was attained. The phenolic phytoconstituents and antioxidant properties of African birch leaf were subsequently determined. Finally, the effects of African birch extract, acarbose solution and a mixture of acarbose and African birch extract on α-amylase and α-glucosidase activities were assessed in vitro.

Results The results showed that African birch extract demonstrated a remarkable antioxidant effect, as exemplified by its radical scavenging abilities, Fe2+ chelating ability and prevention of lipid peroxidation. Acarbose had significantly (p < 0.05) higher α-amylase (IC50 = 11.77 μg/ml) and α-glucosidase (IC50 = 9.05 μg/ml) activities compared to African birch extract [α-amylase (IC50 = 242.17 μg/ml); α-glucosidase (IC50 = 196.35 μg/ml)]. However, the combination of acarbose and African birch extract showed an additive effect on α-amylase inhibition, while a resultant synergistic action was observed against α-glucosidase inhibition.

Conclusion The additive and synergistic actions of the combination of African birch extract and acarbose solution suggest effective, complementary and alternative strategies towards the management/treatment of hyperglycaemia associated with type 2 diabetes.