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. Keywords: Tribulus terrestris L., Zygophyllaceae, Anti-hyperglycaemic activity, Fasting blood glucose, Acute toxicity