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

Abstract

The response surface methodology in combination with a Box–Behnken experimental design was performed to optimize the extraction conditions, resulting in a maximum yield of the total phenolic content (TPC) from the leaves of Pistacia atlantica. The ranges of the examined independent variables (factors), i.e. 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 determinations. 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 to be 72 h extraction time and 50 : 1 ml g⁻¹ liquid-to-solid ratio. For the extraction temperature, rather high values (about 50 °C) were found to be the best. Using the optimized conditions, the TPC varied from 256 to 306 mg gallic acid equivalents per g dry leaf in different sample types.