A novel pH-switchable deep eutectic solvents system regulated by alkaline/acidic electrolytic water: Efficient extraction of polyphenolic compounds and solvent recycling

To enhance polyphenol extraction efficiency and enable rapid solvent separation, an innovative and eco-friendly extraction method using a switchable deep eutectic solvent based on alkaline/acidic electrolyzed water (AA-SDES) was firstly developed. This study also pioneers the application of a hydrophobic deep eutectic solvent (SDES) system, which consists of nonoic acid (RS) and n-octanoic acid (XS), for extracting polyphenol compounds from Taraxaci Herba (PGY). Optimized using the Newton-Raphson-based optimizer-Support vector regression-Sparrow search algorithm (NRBO-SVR-SSA) algorithm, the AA-SDES system achieved a polyphenol content of 7.74 mg/g, demonstrating an extraction efficiency approximately 1.5 times higher than the traditional acid-base method (NH-SDES) and 2.7 times higher than conventional methanol extraction. Over five consecutive cycles, the AA-SDES system demonstrated robust polyphenol extraction efficiency (92.9 %). The enhanced characterization of SDES-7 revealed that RS acts as a hydrogen bond donor (HBD) and XS acts as a hydrogen bond acceptor (HBA), mainly mediated by hydrogen bonding. The switching mechanism of SDES further confirms its effective switching properties. Additionally, the extraction mechanism demonstrates that AA-SDES exhibits superior cell wall disruption capabilities compared to NH-SDES and methanol. Notably, AA-SDES increases intermolecular hydrogen bonds (HB) and promotes van der Waals interactions between AA-SDES and active components. Furthermore, the HB formed with the target components provide a protective effect, contributing to the overall efficiency of the extraction process. The green sustainability of the method was validated using established assessment tools (AGREE/Complex GAPI). Overall, as one of the most environmentally friendly pH-responsive solvents, it demonstrates broad application prospects.