Insulinotrophic and insulin-like effects of a high molecular weight aqueous extract of 'Pterocarpus marsupium' Roxb. hardwood

Ethnopharmacological relevance: 'Pterocarpus marsupium' Roxb. (PM) is an Ayurvedic traditional medicine well known for its antidiabetic potential. Aim: To fractionate the antidiabetic constituent(s) of the aqueous of extract of PM hardwood (PME). Materials and methods: Bio-assay methods including, insulin secretion from mouse pancreas and glucose uptake by mouse skeletal muscle, were used to determine and fractionate the antidiabetic activity of PME. Results obtained from the in vitro experiments were then verified by examining the effect of PME on glucose clearance in normoglycemic, non-diabetic sheep in vivo. Results: Exposure of mouse pancreatic and muscle tissues to PME stimulated the insulin secretion and glucose uptake, respectively, in a concentration-dependent manner. PME-mediated muscle glucose uptake was not potentiated in the presence of insulin indicating that PME acts via pathways which are utilized by insulin. Bio-assay-guided fractionation of PME yielded a high molecular weight fraction which had potent antidiabetic properties in vitro, and in in vivo. Conclusions: Our findings, we believe for the first time, provide novel insights for the antidiabetic constituents of PM and demonstrate that a high molecular weight constituent(s) of PM has potent insulinotrophic and insulin-like properties.