Optimization of Ultrasound Extraction of Phenolic Compounds from Tarragon (Artemisia dracunculus L.) Using Box–Behnken Design

In this study, ultrasound extraction of bioactive compounds from tarragon was examined as a sustainable technology. Pure water, which is a green solvent, was used as solvent. Box–Behnken was used in the experimental design, and ultrasonic power, extraction time and solvent-to-sample ratio were determined to be independent variables. The physicochemical properties were determined by physical (color, pH, Brix) and chemical analyses (antioxidant activity, total flavonoid and total phenolic compound (TPC)) in the extracts obtained under different conditions. Optimum conditions were found to be 73.9% ultrasonic power, 43.2 min sonication time and 10 mL/g solvent-to-sample ratio. The composite desirability (R2) of optimum conditions was 99.3% after optimization. Since high efficiency was obtained in a short time with ultrasound extraction, it was found to be quite good in terms of energy savings. That is, the highest TPC was obtained with a sonication time of 45 min with this method, while similar TPC in the control group (maceration) was obtained in 24 h. In the optimum conditions, extraction with other green solvents (ethanol and deep eutectic solvent—DES) was carried out and bioactive compound yields were compared. For different solvents compared under optimum conditions, ethanol gave higher yields in terms of TPC, while higher yields were obtained in samples using water as solvent for some antioxidant activity values. The results obtained with DES were not as high as expected, and this resulted in the conclusion that a hydrogen bond donor is not suitable for obtaining bioactive compounds from tarragon.