Deep Eutectic Solvent-Assisted Ultrasonic Extraction of Anthocyanins from Blueberry Pomace: Optimization, Mechanistic Insights and In Vitro Antioxidant Activity

This study explores an innovative approach based on deep eutectic solvent (DES)-synergistic ultrasonic-assisted extraction (UAE) of anthocyanins from blueberry pomace (BP). Choline chloride–lactic acid (ChCl-LA, 1:2) was identified as the most efficient DES and provided the highest anthocyanin recovery. The optimal conditions for ChCl-LA-synergistic UAE (ChCl-LA-UAE) were obtained as follows: ultrasonic power of 270 W, extraction time of 30 min, liquid-to-solid ratio of 35:1, and water content in ChCl-LA of 40%, achieving a total anthocyanin content (TAC) of 3.5168 mg/g, with R2 = 0.9860. This value was significantly higher than those obtained with 70% ethanol (3.1962 mg/g) and pure water (1.9137 mg/g). SEM images revealed that ChCl-LA-UAE disrupted the surface structure of the samples, thereby promoting anthocyanin release. COSMO-RS simulations confirmed that ChCl-LA significantly enhanced the interaction between the solvent and the representative anthocyanin (cyanidin-3-O-glucoside, C3G), resulting in higher extraction efficiency. In vitro antioxidant assays further demonstrated that the synergistic system exhibited stronger antioxidant activity. Overall, ultrasonic-synergistic DES extraction could be an eco-friendly method for recovering high-value compounds from blueberry and its byproducts.