Efficient extraction of Cercis chinensis seeds polysaccharides by ultrasound-assisted deep eutectic solvent: Process optimization, identification, kinetics and bioactivity

This study employed an ultrasound-assisted deep eutectic solvent (DES) method to extract Cercis chinensis seeds polysaccharides (CCSPs). Among 19 synthesized DES, DES-9 composed of betaine and ethylene glycol (Bet-Eg) had the highest extraction efficiency during the initial screening, with a yield of 47.7 mg/g, which is 3.5 times higher than that obtained by water extraction (13.6 mg/g). A structural characterization by IR and ¹H NMR revealed a robust hydrogen bonding network in DES-9. This enhanced the solubility and extraction of CCSPs. Extraction conditions were optimized via the Response Surface Methodology (RSM), yielding an experimentally validated yield of 66.3 mg/g following optimum parameters: water content 37%, temperature 72 °C, time 61 min, solid-liquid ratio 1:25 g/mL, and ultrasonic power 240 W. After four cycles of reuse experiments, DES-9 maintained over 74% extraction efficiency, demonstrating good recyclability. CCSPs extracted by DES-9 had higher Mw (46.22 kDa), higher content of Gal, and better stability under different temperatures. At concentrations of 0.03125-1 mg/mL, CCSPs extracted by DES-9 exhibited moderate antioxidant activity and α-glucosidase inhibitory ability, indicating potential as a natural food preservative. These findings confirm that ultrasound-assisted DES extraction is an efficient and green process for extracting CCSPs, providing theoretical and technical support for the utilization of C. chinensis seed resources and the preparation of functional polysaccharides.