Ultrasound-assisted lactic acid based deep eutectic solvent extraction of phenolic antioxidants from Thymus broussonetii: A Box – Behnken design approach for optimization

Abstract

Developing of an eco-friendly, sustainable and efficient solvents with low toxicity and cost has always been a tremendously important goal for industries. In this context, green solvent, such as natural deep eutectic solvent, have been developed as a promising solvent capable of replacing organic ones. The combination of lactic acid: glucose (5:1) was investigated as an extraction medium for bioactive phenolic compounds from Thymus broussonetii. The ultrasonication method was established and optimized by a systematic investigation of the influencing factors: water content in solvent (0/35/70 %), extraction time (30/60/90 min), and temperature (30/50/80°C). A Box – Behnken design was adopted including 17 experiments with three center points. The results obtained presented an excellent efficacy of polyphenols extraction ranging from 25.53 ± 0,02 to 153.23 ± 0,03 mg GAE/g dm and a high scavenging activity attending 80.64 %, the optimized conditions selected for both responses were 66.47 min, at 80°C and a 40.72 % of water, with an extraction yields of 144.394 ±0,02 mg GAE/g dm and 75.9 % for phenolic compounds and antioxidant activity, respectively. Regression analysis showed a good fit of the experimental data which indicates the suitability of the model employed and the successful application of Box – Behnken design in optimizing the extraction conditions. Furthermore, the developed procedure represents an excellent alternative for the extraction of natural products from sample matrices.