Enzymatic degradation of polysaccharide from Enteromorpha prolifera: an efficient way to enhance its antioxidant and tyrosinase inhibitory activities

In order to improve the biological activities of polysaccharides from Enteromorpha prolifra (EP), the crude EP was degraded in the presence of pectinase and glucoamylase. The reaction conditions for the hydrolysis of EP were optimized as: hydrolysis temperature 45.2 °C, total enzyme concentration 48.5 U/mL, with an activity ratio of pectinase to glucoamylase 3.4:1, pH 4.5, degradation time 3 h. In vitro antioxidant activity of the enzymatic degraded polysaccharides from E. prolifra (EEP) obtained under the optimal conditions was significantly improved when compared to that of EP. The IC 50 values of EEP to scavenge DPPH, hydroxyl and superoxide anion radicals were found to be 3.31, 3.02 and 3.90 mg/mL, respectively, while those values for EP were 19.57, 5.96 and 5.51 mg/mL, respectively. At 5 mg/mL, the ferric iron reducing power of EEP was 1.41 times higher than that of EP; the ferrous chelating ability of EEP was 89.6%, being much than that of EP (54.9%). Furthermore, EEP was found to have stronger tyrosinase inhibitory effects than EP. At 3.0 mg/mL, the inhibition rates of EEP on monophenolase and diphenolase activity of mushroom tyrosinase were measured as 32.7% and 39.1%, respectively, while those values for EP were 16.3% and 21.1%, respectively. The inhibition of EEP on diphenolase activity of mushroom tyrosinase was reversible and of competitive-uncompetitive mixed-type. EEP prepared in this study may find application in food industry and cosmetics.