Abstract: Peptides were prepared by enzymatic hydrolysis of abalone visceral proteins with alcalase followed by ultrafiltration. The molecular weights of most peptides were in the range of 192-938 Da as measured by high performance liquid chromatography (HPLC), accounting for 76.3% of the total. The peptides were able to scavenge free radicals in vitro but the activity was much weaker than that of vitamin C (VC). The maximum percentage of DPPH radical scavenging activity was 32.7%, and the half maximal inhibitory concentration (IC50) for hydroxyl radical scavenging was 2.1 mg/mL. Furthermore, the peptides exhibited significant antioxidant activity in vivo by increasing the activity of superoxide dismutase (SOD) and the content of glutathione (GSH) in injured mice, and reducing the contents of malonaldehyde (MDA) and protein carbonyl group content in a dose-dependent manner. The peptides augmented SOD activity and GSH content by 33.2% and 130%, and decreased MDA and protein carbonyl group content by 43.9% and 40.7%, respectively. The effect was close to or even better than that of the positive control. The immunomodulatory activity assay proved that the peptides increased voix pedis swelling by 77.1%, antibody level by 28.0%, splenic index by 24.9% and spleen index by 120%. Accordingly, we concluded that the peptides derived from abalone visceral proteins could enhance immune function in mice with respect to cellular immunity, humoral immunity, nonspecific immunity and immune organs and the effect was better than that of the positive control.

Key words: abalone viscera, peptides, antioxidant activity, immunoregulatory activity