Green Extraction of Antioxidant Polyphenols from Strawberry Tree (Arbutus unedo L. ) Fruits and Leaves: Application of Deep Eutectic Solvents in the Ultrasound-Assisted Extraction

Deep eutectic solvents combined with ultrasound assisted extraction (DES-UAE) was successfully performed to extract polyphenols from strawberry tree (<italic>Arbutus unedo</italic>). Choline chloride (ChCl)-glycerol and ChCl-lactic acid were chosen as the most effective DESs for <italic>A.unedo</italic> leaves and fruits, respectively. DES-UAE parameters (DES molar ratio, solvent:solid ratio, extraction temperature, extraction time) impacting the total phenolic content (TPC), total flavonoid content (TFC), total antioxidant activity (TAA) results of both fruit and leaf extracts were investigated at different conditions. The optimal conditions for leaf sample were determined as 1:2 ChCl:Glycerol, 30:1 ml/g solvent:solid ratio, 50 min time, and 60 °C temperature, whereas for fruit sample they were 1:2 ChCl:Lactic acid, 30:1 ml/g, 40 min and 50 °C, respectively. Under these conditions, leaf extracts contained TPC (46.94±0.13 mg GAE/g), TFC (20.14±0.46 mg CAT/g), DPPH (75.13±1.96%), ABTS (0.520±0.003 mmol TR/g) and FRAP (0.231±0.000 mmolTR/g) while fruit extracts contained TPC (10.17±0.18 mg GAE/g), TFC (2.30±0.05 mg CAT/g), DPPH (84.19±1.49%), ABTS (0.128±0.002mmolTR/g) and FRAP (0.033±0.001mmolTR/g) results. Further research into the optimization of parameters of DES-UAE for the extraction of polyphenols from <italic>A. unedo</italic> fruits and leaves may enable scalable applications in the food, pharmaceutical and cosmetic industries where the demand for efficient and sustainable methods is increasing.