Glucose lowering effect of aqueous extract of Enicostemma littorale Blume in diabetes: A possible mechanism of action

Diabetes mellitus is a chronic metabolic disorder characterized by hyperglycemia. Enicostemma littorale Blume is a small herb and recently we have reported its blood glucose lowering potential in alloxan induced diabetic rats. A single dose of aqueous extract of E. littorale (15 g dry plant equivalent extract per kg) had shown significant increase in the serum insulin levels in alloxan-induced diabetic rats at 8 h. The insulinotropic action of aqueous extract of E. littorale was further investigated using rat pancreatic islets. Extract has the potential to enhance glucose-induced insulin release at 11.1 mM glucose from isolated rat pancreatic islets and was partially able to reverse the effect of diazoxide (0.25 mM). Incubation with Ca²⁺ chelator (EGTA) and Ca²⁺ channel blocker (nimodipine) did not affect the glucose-induced insulin release augmented by the extract. Above results suggest the glucose lowering effect of aqueous extract of E. littorale to be associated with potentiation of glucose-induced insulin release through K⁺-ATP channel dependent pathway but did not require Ca²⁺ influx.