Desirability Function Approach for the Optimization of Hydroalcoholic Solvent Extraction Conditions for Antioxidant Compounds from Olive Leaves

Abstract

The goal of this work was to obtain a rich olive leaf extract with high antioxidant activity due to its content of oleuropein (OLE), hydroxytyrosol (HT) and other phenolics, which have a synergistic effect on total antioxidant activity (TAA).The extraction parameters in the solvent extraction were investigated using response surface methodology (RSM) to produce the best results of HT and TAA in olive leaf extracts. A Box Wilson-CCD design was applied, the multi-objective optimization (MOO) was computed with Pareto solutions, and the desirability function (DF) was employed to define the best process variables. The optimized conditions (solvent concentration, temperature, time, solvent:solid ratio) were as follows: 63.30 %, 36 °C, 62 min, 11.80 mL/g for MeOH:H 2 O extracts and 43.80 %, 52 °C, 58 min, 9.40 mL/g for EtOH:H 2 O extracts. Under these conditions, the highest results of HT were reached to 0.809±0.110 mg/g dw and 0.175±0.004 mg/g dw for MeOH:H 2 O and EtOH:H 2 O extracts, respectively. Similarly, the best results for TAA were obtained at higher concentrations in MeOH:H 2 O extracts (451±2.32 mM Trolox) than in EtOH:H 2 O extracts (297±0.817 mM Trolox). Overall, the synergistic effect of OLE, HT, and flavonoids could make the olive leaf extract a potential cheap source for high value-added products.