Specific extraction of bioactive flavonoids from Torreya grandis pomace using magnetic nanoparticles modified with a ChCl/acetamide deep eutectic solvent

Deep eutectic solvent (DES) is a highly efficient, environmentally friendly, and safe solvent for extraction. However, the application of magnetic nanoparticles modified with DES in flavonoid extraction remain largely unexplored. In our study, we first used ultrasound-assisted DES to extract total flavonoids from T. grandis pomace. The extraction process was thoroughly investigated and optimized to maximize flavonoid yield. Among the 12 DESs tested, 80% ChCl/acetamide proved to be the most effective in flavonoid extraction. Utilizing response surface plots, we determined the optimum extraction conditions and the yield of total flavonoids from T. grandis pomace reached 12.741 mg/g. Furthermore, our analysis revealed that these flavonoids possess remarkable antioxidant activity. Finally, we successfully prepared magnetic nanomaterials using ChCl/acetamide (Fe 3 O 4 @TiO 2 @DES) and utilized them for the selective adsorption of T. grandis pomace extracts. LC-MS analysis of the absorption peaks indicated that the primary compound adsorbed was leucodelphinidin 3-glucoside with strong antioxidant activity. Integrating magnetic Fe 3 O 4 nanoparticles with the DES offers a novel and efficient approach for extracting specific flavonoids from T. grandis pomace, and presenting a potential application of the DES for the enrichment and separation of flavonoids in plants. Highlights • DES composed of 80% ChCl/acetamide showed the highest flavonoids extraction efficiency from T. grandis pomace. • The flavonoids desorbed from T. grandis pomace exhibited remarkable antioxidant activity. • The maximum extraction rate of flavonoids from T. grandis pomace by optimizing the reaction conditions. • Leucodelphinidin 3-glucoside can be specifically adsorbed by MSPE (Fe 3 O 4 @TiO 2 @DES). • Leucodelphinidin 3-glucoside enrichment by Fe 3 O 4 @TiO 2 @DES has strong antioxidant activity.