Optimization of ultrasound-assisted extraction of polyphenolic compounds from pomegranate peel using response surface methodology

The pomegranate peel is discarded as waste although it contains high amount of biologically active phenolics and has high value for recycling. In this study we have determined optimal conditions for ultrasound-assisted extraction (UAE) of polyphenols from pomegranate peel using response surface methodology (RSM). The influence of extraction time (X1: 10–60 min), ethanol concentration (X2: 10–90%), solid to solvent ratio (X3: 1:10–1:50) and extraction temperature (X4: 20–80 °C) on total polyphenols content (TPC) as well on content of individual polyphenolic compounds (ellagic acid, gallic acid, punicalagin and punicalin) was investigated. The optimal extraction process conditions were as follows: extraction time of 25 min, ethanol concentration of 59%, solid to solvent ratio of 1:44, and extraction temperature of 80 °C. Experimentally obtained values were in agreement with those predicted by RSM model, indicating suitability of the employed model and the success of RSM in optimizing the extraction conditions.