Ultrasound-assisted deep eutectic solvent extraction of polyphenols from peach leaves and their compositional...

This work reports the extraction of polyphenols from peach leaves via ultrasound-assisted deep eutectic solvent extraction (UAE-DES) coupled with subsequent resin-based purification, along with comprehensive characterization of the resulting phenolic profile. Screening of various DES formulations identified the choline chloride-lactic acid system as the most effective for this purpose. Based on single-factor experiments and Box-Behnken response surface design, the optimal UAE-DES extraction parameters were determined as follows: liquid-to-solid ratio of 26.61 mL/g, ultrasonic temperature of 40 °C, choline chloride-to-lactic acid molar ratio of 1:3.715, water content of 20%, and sonication time of 10 min. Under these optimal settings, the total phenolic content (TPC) attained 16.79 mg gallic acid equivalents (GAE)/g, closely approaching the model-predicted value of 16.92 mg GAE/g. The crude extract was subsequently purified using AB-8 macroporous resin, and Fourier transform infrared spectroscopy (FTIR) analysis confirmed the presence of functional groups characteristic of phenolic and flavonoid structures. UPLC-MS/MS profiling further identified 25 distinct phenolic compounds, with flavonol glycosides representing the dominant category, accounting for 91.07% of the total quantified polyphenols. Among these, quercetin-3-O-glucoside (50.75%), kaempferol-3-O-glucoside (20.71%), and rutin (19.61%) were identified as the most abundant components. in vitro antioxidant evaluation revealed that the purified peach leaf polyphenols possessed potent concentration-dependent radical-scavenging capacity against both ABTS⁺ and DPPH radicals. Collectively, these results demonstrate that the UAE-DES/resin purification approach offers a green and effective means of recovering polyphenols from peach leaves, thereby providing a scientific foundation for the valorization of peach leaf resources and the production of natural antioxidant agents.