Anti-hyperglycaemic Activity of Tribulus terrestris L Aerial Part Extract in Glucose-loaded Normal Rabbits

Purpose: To investigate the anti-hyperglycaemic activity of methanol extract of Tribulus terrestris L. Zygophyllaceae in glucose-loaded normal rabbits. Methods: The animals were randomly assigned to 4 groups (n = 5) and treated with a single oral dose. Group 1 served as normal control group and received distilled water; group 2 served as hyperglycaemic control; group 3 was treated with glibenclamide (5 mg/kg, aqueous suspension) and served as reference standard; group 4 received methanol extract of Tribulus terrestris L. (250 mg/kg). Groups 3 and 4 were orally treated with glucose (5 g/kg) after 1 h of drug and extract administration, respectively. Fasting blood glucose (FBG) was determined prior to (0 h) and at 30 min, 1, 2 and 3 h after dosing for acute toxicity study. Results: On comparing within groups, a single dose of the methanol extract of Tribulus terrestris L. lowered FBG to levels comparable to that of glibenclamide (36 vs. 55 %), and reaching the initial level (0 h) at 2 h. FBG were significantly (p < 0.05) lowered at 2 and 3 h in both glibenclamide (45.5 and 56.9 %) and extract (45.7 and 52.7 %) groups as compared with their respective glucose levels at 0.5 h. On the other hand, on comparing between groups, both glibenclamide and methanol extract significantly (p < 0.05, p < 0.001) lowered the rise in blood glucose at 1 h (33.9 and 22.5 %), 2 h (62.8 and 59.16 %), and 3 h (64.6 and 57.1 %) with respect to the hyperglycaemic control group. Conclusion: The methanol extract of the aerial parts of Tribulus terrestris L. possesses potential antihyperglycaemic activity in glucose-loaded normal rabbits. Further studies on various organic solvents fractions and isolated compounds from this plant are required.