Solvent-dependent extraction of antioxidants and polyphenolics of quince (Cydonia oblonga Mill.) leaves in conventional and deep eutectic solvents: Response surface methodology, LC-MS phenolic characterization, and mineral assessment.

This study evaluates the performance of water, ethanol, and a choline chloride:urea deep eutectic solvent (DES) for the extraction of antioxidant and polyphenolic compounds of quince (Cydonia oblonga Mill.) leaves. The DES system yielded the highest antioxidant capacity (46.62 mg AAE/g) and total phenolic content (66.30 mg GAE/g) at 120 °C. The response surface methodology (RSM) demonstrated adequate predictive performance (R2 > 0.9) with a cubic model for the water extraction, while the quadratic model provided good fits for ethanol and DES systems. The LC-ESI-QTOF-MS analyses characterized the phenolic profiles of the quince leaf extracts. The ICP-OES mineral analyses indicated that the water extract contained nutritionally relevant levels of Mg(II), K(I), Mn(II), Fe(III), and Zn(II), contributing appreciably to the recommended daily intake (DRI) values. These findings emphasize the promise of water extracts for dietary applications, whereas ethanol and DES extracts offer greater potential for pharmaceutical and nutraceutical usages.