INHIBITORY POTENTIAL OF AN AFRICAN VERNONIA AMYGDALINA DEL. (ASTERACEAE) LEAVES ON A GLUCOSIDASE ENZYME

Extracts of medicinal plants origin have been reported in several studies to regulate postprandial hyperglycemia by impeding the rate of carbohydrate digestion in the small intestine thereby hampering the diet associated acute glucose excursion. This study describes the inhibitory activity of an African Vernonia amygdalina leaves on a glucosidase enzyme. Powdered sample (100g) was extracted by cool maceration with acetone. Acetone crude extract was fractionated by column chromatography. In vitro α-glucosidase activity was evaluated at varying concentrations using standard method. One way analysis of variance was used to compare the data. Qualitative phytochemical analysis was carried out to identify bioactive constituents present in the fractions. Column chromatographic separation resulted in eight fractions that were pooled together to give three fractions (PF1 - PF3). In vitro α-glucosidase inhibitory studies showed potent inhibitory activity with PF3 exhibiting a strong inhibitory activity having an IC50 = 70 ± 0.03 μg/ml. PF1 had the highest percentage inhibition (75.95%) at 20 μg/ml. The least inhibitory activity (6.33%) at 120 μg/ml was observed in PF3. The fractions showed a concentration dependent inhibitory activity except for the CE. Inhibitory activity varied significantly (p<0.05) between the crude extract and fractions tested. Qualitative phytochemical analysis of the fractions showed the presence of triterpenes, phenolics, sugars and sugar phenylhydrazones in varying quantities. The results of this study showed that the leaf of Vernonia amygdalina possessed potent inhibitory activity on α-glucosidase and can serve as a source of lead compounds for isolation and optimization as an antidiabetic agent.