Optimization of subcritical water extraction for total phenolics from pomegranate ( Punica granatum L.) leaves by response surface methodology

The aim of this study was to optimize the technology parameters of subcritical water extraction for extracting total phenolics from pomegranate leaves by response surface methodology. On the basis of single-factor experiments, three-factors and three-level response surface methodology was applied to investigate the effects of extraction temperature, extraction time and solvent/solid ratio on the total phenolics contents. The results showed that model regression was significant, and the established regression equation for phenolics contents had an excellent of fit.The optimized extraction temperature was 134 ℃, extracting time was 31 minutes, and solvent/solid ratio was 52∶ 1 m L/g.Under the optimized conditions, the total phenolics content was 169.24 mg GAE/g, which was consistent with the predictive value of 173.31 mg GAE/g. In addition, the total phenolic content of the optimized extracts was higher than the reflux extraction using aqueous-organic solvent, and the time was shortened.