Microwave-assisted extraction of polyphenols from Clinacanthus nutans Lindau medicinal plant: Energy perspective and kinetics modeling

Abstract

Clinacanthus nutans Lindau (C. nutans, “snake grass”) is a well-known medicinal plant in South-East Asia that recently has attracted attention for its high polyphenol content and its medical and nutraceutical applications. In this work, polyphenols have been recovered from C. nutans by microwave-assisted extraction (MAE). The influence of the main process parameters has been analyzed: ethanol concentration in the extraction solvent mixture, microwave energy applied and solvent-to-feed ratio. Model results have been correlated with mathematical models of the extraction process, that allow linking the observed variations in extraction curves with modifications of mass transfer and equilibrium parameters. Moreover, in order to assess the energy efficiency of the process, results were studied and explained in view of the specific energy absorbed during the microwave treatment (J/g). Results indicate that microwave pre-treatment improves extraction rate by a factor of 2–5, yielding the best results when a water–ethanol solvent mixture with 50%vol of ethanol is used at a solvent-to-feed ratio (S/F) of 14 mL/g.