Effect of deep eutectic solvent extraction on Auricularia auricula polysaccharide solubilization and antioxidant potential

This study was conducted to assess the potential of a green and eco-friendly technique: ultrasound-assisted natural deep eutectic extraction (UAE-DES) for the preparation of Auricularia auricula polysaccharides (AAPs), and to evaluate the antioxidant capacity of the products. Firstly, the optimal parameters for AAPs by Box-Behnken using deionized water as the solvents, and the yield was 25.07% ± 0.43% at 50 °C, 70 mL/g of liquid-to-material ratio and 150 W of ultrasonic power. Next, the effects of five types of DES on the output of the AAPs under this parameter were investigated. DES (ethylene glycol-choline chloride, molar ratio of 2:1) containing 40% water increased the yield by 18.68%. The molecular weight of AAPs-UW (using deionized water as solvents) was 851.029 kDa, while the UAE-DES fractured AAPs-UD (using DES as solvents) into three polysaccharides, 811.895, 277.178 and 15.520 kDa, respectively. AAPs-UD showed significantly stronger ABTS+/OH·/DPPH· scavenging capacity than AAPs-UW. Compared with AAPs-UW, AAPs-UD treatment prolonged the maximum lifespan and the mean survival time of C. elegans at low concentration. In addition, qRT-PCR results indicated that AAPs-UD could up-regulate the expression levels of antioxidant related genes such as daf-16, sir-2.1 and sod-3 in the insulin and IGF-1 signaling pathway (>1.50, p < 0.05), and the expression of skn-1 in the target of rapamycin pathway (>1.70, p < 0.05).