Anti hyperglycemic and insulin secretory activity of Costus pictus leaf extract in streptozotocin induced diabetic rats and in in vitro pancreatic islet culture

Aim of the study: The leaves of Costus pictus D. Don were used extensively for its anti hyperglycemic activity by the people in Kerala, India. In the present study, the antihyperglycemic and insulin secretory activity of an aqueous extract of Costus pictus leaf extract was investigated in streptozotocin induced diabetic rats. Materials and methods: Oral Glucose Tolerance Test was done to determine the effective close of Costus pictus extract. Aqueous extract of Costus pictus leaves was given orally to the diabetic rats for 14 days. The insulin secretory action of the leaf extract was investigated using isolated pancreatic islets from rat. Liver glucose uptake activity was measured using D-[C-14] glucose, Results: The oral administration of an aqueous extract of Costus pictus at a dose of 250 mg/kg body weight significantly decreased the blood glucose with significant increase in plasma insulin level in diabetic rats at the end of 14 days treatment. The Costus pictus leaf extract significantly increased glucose induced insulin secretion at both 4 mM and 20 mM glucose concentrations which represents normal physiological and diabetic condition respectively. The decreased glucose uptake activity of the liver of diabetic rats was reverted to near normal levels after the treatment with Costus pictus leaf extract. Conclusion: Our results suggest the glucose lowering effect of Costus pictus to be associated with the potentiation of insulin release from pancreatic islets and enhancement of peripheral utilization of glucose. (C) 2009 Elsevier Ireland Ltd. All rights reserved.