Effect of Enzyme-Assisted Extraction on the Chemical Properties and Antioxidant Activities of Polysaccharides Obtained from the Wood Ear Mushroom, Auricularia auricula (Agaricomycetes).

An effective method of polysaccharide extraction from Auricularia auricula (AAPs) by mannanase was developed and optimized by response surface methodology in which the ABTS+ [diammonium 2,2'-azino-bis(3-ethylben-zothiazoline-6-sulfonate radical] scavenging rate was the response. AAPs were graded by stepwise ethanol precipitation with concentrations of 5, 10, 15, and 20% ethanol successively. The fractions with a strong radical scavenging rate were obtained, and then their antioxidant stress effect was studied using Caenorhabditis elegans as a model organism. The ABTS+ scavenging rate of AAPs could reach 37.95 ± 0.53% at a temperature of 55°C, a time of 4 h, a liquid-to-material ratio of 58 mL/1 g, and an enzyme-to-substrate ratio of 2.97%. AAP-20 obtained by 20% ethanol with a strong radical scavenging rate was a heteropolysaccharide composed of mannose, glucose, galactose, xylose, and glucuronic acid. AAP-20 could significantly prolong the lifespan of C. elegans under oxidative stress conditions induced by methyl viologen or hydrogen peroxide, and it could also enhance the activity of antioxidant enzymes including catalase, glutathione reductase, and superoxide dismutase at 0.50 mg/mL (P < 0.05). These studies showed that AAPs prepared with mannanase had a significant protective effect against damage induced by intracellular radical generating agents.