HYPOGLYCEMIC ACTIVITY OF THE AQUEOUS EXTRACT OF CAESALPINIA PULCHERRIMA FLOWERS IS INDEPENDENT OF INSULIN STIMULATION AND SUPPRESSED IN THE PRESENCE OF METFORMIN

Abstract

Considering the high prevalence of insulin resistance, antidiabetic strategies that enhance insulin action or act independent of insulin are desirable. Caesalpinia pulcherrima (CP) flowers are known to have antidiabetic properties, but more work is required with respect to this action in insulin resistant adipocytes, particularly, its dependence on insulin and its therapeutic equivalence and/or interactions with other antidiabetic drugs. The purpose of this study was therefore to investigate the insulindependency of the water extract of CP flowers (CP extract) hypoglycemic effects, compare its antidiabetic action in diabetic and non-diabetic glucose loads, and explore its therapeutic equivalence and interactions with metformin. CP extract was prepared by boiling the air-dried flowers in cell culture media prepared in Krebs Ringer Bicarbonate buffer for 5mins. Metformin solution was prepared from a Metformin hydrochloride extended-release tablet to obtain low and therapeutic levels of metformin (0.8-2.4mg/L and). Insulin resistant (IR) adipocytes were exposed to CP extract in cell culture containing either 8mM or 18mM glucose and one of three insulin concentrations. CPextract allowed an efficient glucose disposal in the IR adipocytes in an insulin independent manner (p<0.0001). The percentage of glucose uptake did not significantly differ by models of diabetic and non-diabetic conditions (p=0.4727) although the significantly higher glucose concentration taken up by the IR adipocytes in the presence of IR adipocytes suggest an enhancement of antidiabetic action in hyperglycemic conditions. Expectedly metformin had a higher potency than the CP extract with its therapeutic dose of 1.8-2.4mg/L corresponding to 280mg/l of CP extract (p=0.9996). Additionally, metformin and CP extract appear to compete for similar sites which suppressed the hypoglycemic activity of CPextract.