Hypoglycaemic effect of Teucrium polium: studies with rat pancreatic islets

The aquous extract of Teucrium polium (Labiatae) has long being used in Iran as a hypoglycaemic aid without any knowledge about its probable side effects and mode of action. In an effort to assess the claimed hypoglycaemic property of the crude drug and to get some knowledge about the mechanism of action, the crude extract (0.5 g plant powder per kg body weight) was administered orally to a group of streptozotocin diabetic rats for six consecutive weeks. A significant decrease (64%) in blood glucose concentration was observed in the treated animals compared to the untreated diabetic rats, without any measurable effects on the major biochemical factors. In addition, the crude extract significantly enhanced the blood insulin level by almost 160% compared to the untreated diabetic rats. The insulinotropic property of the Teucrium polium extract was further assessed by an in vitro investigation using isolated pancreatic rat islets. Our data indicated that Teucrium polium crude extract is able to enhance insulin secretion by almost 135% after a single dose of plant extract (equivalent to 0.1 mg plant leaf powder per mL of the culture medium) at high glucose concentration (16 mmol/L). Meanwhile, the time pattern of insulin secretion was not affected by the plant extract compared to the untreated islets. These data clearly show that the plant extract, probably without metabolic transformation, is able to reduce high blood glucose levels through enhancing insulin secretion by the pancreas.