Hypoglycemic and antihyperglycemic activities of the aqueous and the ethanolic extracts of Alpinia calcarata rhizomes in rats

Rhizomes of Alpinia calcarata Roscoe (Family: Zingiberaceae) is a common medicinal plant cultivated in Asian countries including Sri Lanka. The aim of this study is to evaluate the hypoglycemic and antihyperglycemic activities of A. calcarata which are not investigated so far. This was tested in normoglycemic and streptozotocin (STZ) - induced diabetic rats using oral administration of the hot water extract (HWE) and the hot ethanolic extract (HEE). In normoglycemic rats both HWE and HEE significantly lowered the blood glucose levels in a dose - dependent manner. Further, both HWE and HEE markedly improved the oral glucose tolerance in rats. The hypoglycemic activity of the HEE was generally higher than that of the HWE. However, the HWE or the HEE failed to reduce blood glucose levels of STZ - induced diabetic rats. Further, the HEE significantly inhibited the glucose absorption from the small intestine and increased the glycogen accumulation in both liver and skeletal muscle. It is concluded that A. calcarata rhizomes possess strong hypoglycemic and antihyperglycemic activities.