Microwave assisted extraction of flavonoids from Terminalia bellerica: Study of kinetics and thermodynamics

Microwave-assisted solid liquid extraction (MAE) of flavonoids from Terminalia bellerica Roxb. has been investigated to understand the influence of solvent-to-feed ratio (5-40 mL/g) and temperature (40-100 degrees C) on kinetics and thermodynamics of extraction. The flavonoid concentration time data were analysed using a second order kinetic model to determine extraction constant. A diffusion model was utilized to determine diffusion coefficient taking into account of both washing and diffusion phases together. Solvent-to-feed ratio and temperature were observed to show a significant effect on flavonoid yield, extraction rate and effective diffusion coefficient with the highest solvent-to-feed ratio and temperature providing the maximum flavonoid yield of 25.21 mgQE/g using water as the solvent. An empirical equation has been developed to predict extraction kinetics. Thermodynamic parameters revealed MAE process to be spontaneous and endothermic. The kinetic and diffusion models provided valuable insights into the microwave assisted extraction process. T. bellerica was observed to be a good source of flavonoids. Therefore, MAE is a suitable method for extraction of flavonoids from T. bellerica when water alone is to be used as the solvent, as in the case of traditional Indian medicinal preparations. (C) 2015 Elsevier B.V. All rights reserved.