Effects of physicochemical factors and in vitro gastrointestinal digestion on antioxidant activity of R-phycoerythrin from red algae Bangia fusco-purpurea

R-phycoerythrin (R-PE) was purified from the red algae Bangia fusco-purpurea after 35-50% ammonium sulphate fractionation followed by ion-exchange column chromatography on DEAE-Sepharose, resulting in a purity (A(565)/A(280)) ratio of 5.1. The circular dichroism spectroscopy results suggested that the structure of R-PE is predominately helical. The antioxidant activity of R-PE was studied and revealed changes in conformation and antioxidant activity at different temperatures and pH values. After in vitro-simulated gastrointestinal (GI) digestion of R-PE, the scavenging activity of ABTS radical (EC50, 769.9gmL(-1)), DPPH radical (EC50, 421.9gmL(-1)), hydroxyl radical (EC50, 32.4gmL(-1)) and reducing power (A(700)=0.5, 625.8gmL(-1)) were measured. Gel filtration chromatography analysis showed that the molecular weight distribution of the final GI digest that still contained high antioxidant activity was <3kDa. Our present results indicate that digestion-resistant antioxidant peptides of R-PE may be obtained by in vitro GI proteinases degradation.