Optimization of extraction conditions for the recovery of phenolic compounds and antioxidants from Syrian olive leaves

Abstract

In this study the effect of extraction conditions, solvent (type, composition), time and temperature, on the amount of phenolic compounds extracted from olive leaves obtained from Safita /Syria was investigated and the radical scavenging activity of these extracts was evaluated. The total phenolic content and the radical scavenging activity of olive leaves extracts were determined by Folin-Ciocalteu reagent and scavenging of DPPH (2,2-diphenyl-1-picrylhydrazyl) radical, respectively. It was found that concentration of solvents (40% ethanol, 40% methanol, 80% acetone, and 6:2: acetone: ethanol: water) gave the highest total phenolic content and possess strong activity against the DPPH radicals (IC50 18.92, 25.01, 33.15, 37.19 μg Gallic acid /ml), respectively. Temperature and time of extraction were also found to have a significant effect on the total phenolic content and IC50. The aqueous solutions of ethanol 40%, extraction temperature of 60 °C and extraction time of 60 min were the most efficient for the extraction of polyphenols from olive leaves. Therefore, these conditions could be applied for further extraction and isolation of phenolic compounds from olive leaves for their use in the preparation of medicinal products or functional food.