Sustainable extraction of apple and pear polyphenols using natural deep eutectic solvents: functional activity, cytotoxicity and sustainability assessment.

Apples and pears are widely consumed, polyphenol-rich fruits, yet whole-fruit extraction using green solvents remains underexplored relative to by-product-focused approaches. Natural deep eutectic solvents (NADES) were investigated as green extraction media for polyphenols from apple and pear. NADES were characterized (FTIR, DSC, viscosity, density) and extracts were evaluated for polyphenol content and profile (HPLC, LC-MS/MS), antioxidant activity (DPPH, ABTS, square-wave voltammetry) and cytotoxicity. Hydrophilic choline chloride-based NADES significantly enhanced polyphenol recovery compared with ethanol and menthol-based systems, with stronger radical-scavenging and electrochemical responses. Fluorescence spectroscopy indicated improved polyphenol solubilization. Cytotoxicity assays in tongue-derived and intestinal cell lines (HSC-3, Caco-2) showed high viability for choline chloride-based systems, whereas menthol-based NADES showed reduced tolerance. Sustainability assessment showed reduced solvent use, waste generation, and processing complexity versus conventional extraction. Solvent polarity and hydrogen-bonding capacity governed extraction efficiency, supporting food-grade NADES-based extraction as a proof-of-concept green alternative for whole-fruit polyphenol recovery.