Synergistic Antioxidant Activity in Deep Eutectic Solvents: Extracting and Enhancing Natural Products

Many natural products (NPs) exhibit strong antioxidant activity, making them valuable for various applications. In this context, the emergence of deep eutectic solvents (DESs) is expected to help address the growing demand for innovative, efficient, and more sustainable methods for NPs extraction. DESs are designer solvents that provide higher yields and enhance the antioxidant activity of extracted phytochemicals compared with conventional volatile organic solvents. Antioxidant and naturally occurring molecules can also form DESs, either as hydrogen bond donors (HBD) or as acceptors (HBA), creating natural DES (NADES) with inherent antioxidant activity. Thus, DESs containing extracted NPs can exert synergistic antioxidant effects, making the entire system a promising active ingredient for food industry applications. The synergy arises from the enhanced solubilization and stabilization of NPs in DESs through hydrogen bonding, ionic interactions, and van der Waals forces. Collectively, DES and NPs enable the system to effectively neutralize oxidants (such as ROS and free radicals) and regulate their reactions with other molecules, achieving up to a 3-fold increase compared to extracts in regular solvents in vitro. This Account overviews the wide range of antioxidant molecules extracted from natural resources using DESs. The antioxidant activities of HBA, HBD, and DESs, along with their advantageous coupling with the antioxidant activities of NPs extracts, are thoroughly discussed. Finally, we envisage future directions and potential applications of DESs, harnessing their collective antioxidant activity to guide advances in sustainable food chemistry.