Inhibitory Potential and Antidiabetic Activity of Leaf Extracts of Justicia carnea

The aim of this study was to evaluate the in-vitro inhibitory potential of various leaf extracts of Justicia carnea on alpha-amylase and alpha-glucosidase activities and the anti-diabetic activity of the ethanol leaf extract using albino wistar rats. The analyses were carried out using standard biochemical methods. The oral acute toxicity test (LD50) in rats of the ethanol leaf extract was determined using Lorke’s method. Diabetes was induced in the rats by a single intraperitoneal dose of 120 mg/kg. b.w of alloxan. Six (6) experimental groups of rats (n=6) were used for the study. Three groups of diabetic rats received oral daily doses of 200 mg/kg, 400 mg/kg and 600 mg/kg ethanol leaf extract of Justicia carnea respectively while gilbenclamide (5 mg/ml); a standard diabetic drug was administered to a specific group. Treatment lasted for 14 days. From the results of the in-vitro inhibitory activity, the different extracts of Justicia carnea demonstrated dose dependent strong inhibitory activity against α-amylase but moderate inhibitory activity against α-glucosidase. The ethanol leaf extract was the most potent inhibitor of both α-amylase and α-glucosidase in comparison with other extracts and acarbose; the standard. The ethanol leaf extract exhibited maximum of 82.18% inhibition with IC50 of 2.99 ± 1.14 mg/ml for α-amylase and 41.66% with IC50 of 9.66 mg/ml ± 0.32 mg/ml for α-glucosidase. From the analysis of the Lineweaver-Burk plot, the ethanol leaf extract exhibited mixed noncompetitive inhibition of α-amylase and competitive inhibition of α-glucosidase activities. The acute toxicity study showed that the extract had an LD50 > 5000 mg/kg. From the result of the anti-diabetic study, the fasting blood glucose levels significantly (p<0.05) decreased in the animals treated with the ethanol leaf extract of Justicia carnea when compared to the untreated rats. It can be concluded from the results that the leaf extracts of Justicia carnea can be used in the management of diabetes.