Acute hypoglycemic and antihyperglycemic effects of ten Sri Lankan medicinal plant extracts in healthy and streptozotocin induced diabetic rats

The efficacy and dose response of oral hypoglycemic and antihyperglycemic effects of ten Sri Lankan plant extracts on glucose tolerance were evaluated in healthy and streptozotocin induced diabetic rats. A single dose of 0.25, 0.50, 0.75, 1.00, 1.25 and 2.00 g/kg of plant extracts was administered orally to healthy and streptozotocin induced (65 mg/kg, ip) diabetic Wistar rats (N = 6). Glibenclamide (0.50 mg/kg) was used as the standard drug. The optimum effective dose of each extract and the percentage of improvement at the optimum effective dose were evaluated over a four hour period using area under the oral glucose tolerance curve. The percentage improvement on glucose tolerance at the optimum effective dose was in the decreasing order of Momordica charantia (9.00 %), Coccinia grandis (8.50 %), Spondias pinnata (8.14 %), Gmelina arborea (7.69 %), Scoparia dulcis (7.43 %) in healthy rats. All ten plant extracts showed dose dependent improvement on glucose tolerance in streptozotocin induced diabetic rats (P < 0.05). The optimum effective dose on glucose tolerance for eight extracts was found to be 1.00 g/kg in diabetic rats with the exception of Coccinia grandis : 0.75 g/kg and Momordica charantia : 0.50 g/kg. The plant extracts studied showed dose dependent improvement on glucose tolerance at and above the optimum effective dose in streptozotocin induced diabetic rats. The optimum effective dose was found to be approximately equal to the therapeutic dose of each extract.