Abstract: Bioactive peptides were prepared from Porphyra yezoensis by hydrolysis with papain, trypsin or pepsin, their in vitro antioxidant activity was assessed based on reducing power and scavenging effects against hydroxyl radicals and DPPH radicals, and their molecular weight distribution was also measured. The results showed that three enzymes could better hydrolyze Porphyra yezoensis proteins, producing hydrolysates with obvious reducing power. The three hydrolysates had dose-dependent positive scavenging effects on hydroxyl radicals and DPPH radicals, among which, the papain hydrolysate had the best hydroxyl radical scavenging activity, with a half-scavenging concentration (IC50) of 0.397 mg/mL, and the pepsin hydrolysate was the best scavenger against DPPH radicals with an IC50 of 0.261 mg/mL. The molecular weight distribution of small-molecule antioxidant peptides in the three hydrolysates was determined to be in the range of 148 to 1963 u.

Key words: Porphyra yezoensis, hydrolysis, bioactive peptides, antioxidant activity