Ultrasound-assisted deep eutectic solvent extraction of polysaccharides from Cercis chinensis bark: Optimization, kinetics and antioxidant activities

This study pioneers a green, efficient ultrasound-assisted extraction (UAE) technique using a deep eutectic solvent (DES) to isolate polysaccharides from Cercis chinensis bark, overcoming limitations of conventional methods. Through systematic screening of 15 DES systems, DES-11 (L-proline:ethylene glycol, 1:2 M ratio) was identified as optimal, achieving a polysaccharide yield of 64.7 mg/g-3.7-fold higher than water extraction. Extraction conditions were optimized via response surface methodology (RSM) to 39 % water content, 45 °C, 28 min, solid-liquid ratio 1:40 g/mL, and 240 W ultrasonic power. SEM analysis confirmed that DES-11 disrupts plant cell walls, enhancing mass transfer. Kinetic studies revealed the process follows pseudo-first-order kinetics (R² > 0.90) and is primarily controlled by intraparticle diffusion, with an apparent activation energy of 10.28 kJ·mol^-1. The DES-11 extracted polysaccharides exhibited moderate antioxidant activity, with IC₅₀ values of 0.54 mg/mL (DPPH), 0.24 mg/mL (ABTS) and 0.62 mg/mL (OH), suggesting potential as natural food preservatives. DES recyclability was validated over five cycles, retaining > 78 % efficiency. This work establishes DES-UAE as a sustainable strategy for high-yield polysaccharide extraction, with mechanistic insights into kinetics and diffusion control.