Anti-hyperglycemic Effects of Vaccinium arctostaphylos L. Fruit and Leaf Extracts in Alloxan-Induced Diabetic Rats

Background: Vaccinium arctostaphylos L. (Caucasian whortleberry) fruit is used as an anti-hyperglycemic agent for treatment of diabetes mellitus. Objective: The effects of whortleberry fruit and leaf extracts on the blood levels of fasting glucose, HbA1c (glycosylated hemoglobin), insulin, creatinine and liver enzymes SGOT and SGPT in alloxan-diabetic rats as well as LD50s of the extracts in rats were studied. Methods: The effects of 2 months daily gavage of each extract at the doses of 250 mg/kg, 500 mg/kg and 1000 mg/kg on the parameters after single alloxan intraperitoneal injection at a dose of 125 mg/kg in the rats were evaluated. To calculate LD50 (median lethal dose), each extract was gavaged to groups of 30 healthy male and female Wistar rats at various doses once and the number of dead animals in each group within 72 hours was determined. Results: Alloxan injection resulted in significant increase of fasting glucose and HbA1c levels but decreased insulin levels significantly. Oral administration of whortleberry fruit and leaf extracts (each at the doses of 250, 500 and 1000 mg/kg) significantly reduced the fasting glucose and HbA1c levels but significantly increased the insulin levels without any significant effects on the SGOT, SGPT and creatinine levels in the diabetic rats compared with the control diabetic rats. The LD50s of the extracts were more than 15 g/kg. Conclusion: Whortleberry fruits and leaves may have anti-hyperglycemic and blood insulin level elevating effects without hepatic and renal toxicities in the alloxan-diabetic rats and are relatively nontoxic in rats.