Determination of optimal extraction conditions for phenolic compounds from Pistacia atlantica leaves using the response surface methodology

Abstract

Response surface methodology in combination with a Box-Behnken experimental design was performed to optimize the extraction conditions, resulting in a maximum yield for the total phenolic content (TPC) from leaves of Pistacia atlantica. The ranges of the examined independent variables (factors), i.e. the extraction time (24-72 hours), liquid-to-solid ratio (30:1-50:1 ml solvent per g dry leaf) and extraction temperature (35-55°C) were identified by preliminary experiments. Quadratic polynomial regression models were fitted through the experimental results. They showed acceptable coefficients of multiple determination. From the models, the liquid-to-solid ratio was found to have the most influence on the extraction of TPC. The optimum extraction conditions were found at 72 h extraction time and 50:1 ml/g liquid-to-solid ratio. For the extraction temperature, rather high values (about 50°C) were found best. Using the optimized conditions, the TPC varied from 256 to 306 mg gallic acid equivalents g dry leaf in different sample types.