The present invention relates to the development of stable microemulsion to enhance solubility and bioavailability of BCS II and IV class drugs by using dried latex of Jatropha curcas as a surfactant. The formulated microemulsion was thermodynamically stable, biocompatible and environment friendly with enhanced solubility and bioavailability. Thus, plant-derived surfactant can replace synthetic surfactant as they are used in lower concentrations, with minimum cytotoxic side effects.