Antihyperglycemic activity of Prunella vulgaris L. in streptozotocin-induced diabetic mice.

Prunella vulgaris L. (Labiatae) has been reported to have a wide range of health benefits in oriental medicine. This study for the first time is to examine the antihyperglycemic effects of P. vulgaris in streptozotocin (STZ)-induced diabetic ICR mice (STZ diabetic mice). The effects of P. vulgaris L. aqueous-ethanol extract (PVE) on blood glucose, exogenous insulin sensitivity and plasma insulin levels were investigated. In four doses of extracts from the spikes of P. vulgaris, extract at dose of 100 mg/kg significantly suppressed the rise in blood glucose after 30 min in the acute glucose tolerance test. Furthermore, this dose was applied in the fellow experiments. A significant decrease in blood glucose levels was observed after treatment of PVE. A combination of PVE and glibenclamide produced a greater effect in blood glucose level than using glibenclamide or PVE alone. PVE enhanced and prolonged the antihyperglycemic effects of exogenous insulin on STZ diabetic mice. Plasma insulin levels were increased with glibenclamide treatment in STZ diabetic mice, whereas such effect was not observed with PVE. These results indicated that P. vulgaris enhances the antihyperglycemic effects of exogenous insulin without stimulating insulin secretion, indicating that insulin sensitivity is increased in STZ diabetic mice.