Antidiabetic effect of d-limonene, a monoterpene in streptozotocin-induced diabetic rats

d-limonene (p-Menthal-1, 8-diene) is a monocyclic monoterpene obtained from orange, grape fruit and lemon. It exhibits a wide variety of pharmacological properties, including antioxidant, anti-inflammatory and anticarcinogenic activities. The present study evaluates the antidiabetic effect of d-limonene in streptozotocin-induced diabetic rats. Diabetes was induced in male albino rats of Wistar strain (180–200 g) by a single intraperitoneal injection of streptozotocin at a dose of 40 mg/kg body weight. d-limonene was administered orally at doses of 50, 100 and 200 mg/kg body weight and glibenclamide at a dose of 600 μg/kg body weight daily for 45 days. Plasma glucose and glycosylated hemoglobin levels were increased, the activities of gluconeogenic enzymes such as, glucose 6-phosphatase and fructose 1, 6-bisphosphatase were increased and the glycolytic enzyme, glucokinase activity was decreased along with liver glycogen in the diabetic rats. Graded doses of d-limonene reverse all the above changes towards normal level. The effect of d-limonene was more pronounced in 100 mg/kg body weight than the other two doses. The antidiabetic effect of d-limonene was comparable with glibenclamide. These findings suggest that d-limonene has potential antihyperglycemic activity in streptozotocin-induced diabetic rats.