Optimization of the polysaccharide hydrolysate from Auricularia auricula with antioxidant activity by response surface methodology.

An efficient acid-hydrolysis method was developed and optimized for the hydrolyses of polysaccharide from Auricularia auricula with the ABTS· scavenging ability as the detective marker. Based on the single factor experimental results, Box-Behnken design (BBD) were applied for the optimization of acid-hydrolysis conditions. The possible antioxidant mechanism of the hydrolyses (AAPs-F) in vivo was performed using the C. elegans model. The acid-hydrolysis conditions were found to be the optimal hydrolyzing time 2.78h (166.8min), hydrolyzing temperature 95.04°C and the acid concentration 14.03mol/L, respectively. Under the optimal acid-hydrolysis conditions, the ABTS· scavenging ability of AAPs-H was 97.94±0.87%, which was well matched with the predicted value (99.77%) of the BBD model. AAPs-F was the main fraction of AAPs-H separated through Sephadex G-10 as the stationary phase. AAPs-F was a kind of heteropolysaccharide and comprised of glucose, galactose and fucose with the molar ratio of 50:1:2. The molecular weight of AAPs-F was 143.15kDa. AAPs-F showed a remarkable protective effect to the injury induced by hydrogen peroxide or paraquat (p<0.01), and it could up-regulate stress-resistance related enzymes including superoxide dismutase (SOD) by 109.74% and CAT by 106.84% at concentration of 0.2mg/mL in C. elegans.