Optimization of a green ultrasound-assisted extraction of phenolics and in vitro antioxidant potential of date fruit (Phoenix dactylifera l.)

Abstract

The fruit of the date palm, Phoenix dactylifera L., is one of the richest fruit-based in biologically functional phytochemicals. The efficient extraction of phenolic compounds in this fruit by means of rapid, low cost, environment-free methods would be a desirable achievement. A deep eutectic solvent (DES) based on lactic acid and sucrose was considered as extraction solvent. DES are green solvents composed of natural compounds and characterized by their negligible volatility, high solubilization ability and tunable selectivity. In this line, the present study was based on a step-by-step optimization of the extraction, taking into consideration basic parameters, including solvent composition (lactic acid/sucrose ratio), solvent concentration (0–100%) sample/solvent ratio (100/15 to 300/15 mg/ml) and extraction time (3-40 min). The total phenolic compound content (TPC) was used to evaluate antioxidant content of the extracts. DPPH radical scavenging activity was used to evaluate antioxidant potential. Experimental results showed that all extraction parameters investigated had significant effects (p < 0.05) on TPC and antioxidant activity of the extracts. The best antioxidant activity (948.1mgAAE)/100 g) and the highest TPC (1393.5mgGAE)/100 g) were obtained with double extraction using lactic acid/sucrose mixture with ratio of 3:1 at a concentration of 100%, with a sample/solvent ratio of 100mg/15ml, for 40 min. These results suggested that the mixture lactic acid/sucrose may be an ideal candidate for use in eco-friendly extraction processes. As a function of investigated extraction parameters, phenolic contents were positively correlated with the antioxidant activity.