Abstract: The chemical components and in vivo antioxidant activity of peptides prepared from Apostichopus japonicus
sperm were detected. The best enzyme to prepare antioxidant peptides from Apostichopus japonicus sperm was selected
by comparing the hydroxyl radical scavenging activities of five protein hydrolysates obtained with papain, protamex and
flavourzyme. After ultrafiltration of the hydrolysates, the weight distribution, soluble protein and polypeptide contents and
hydroxyl radical scavenging capacity of the fractions were determined. The low molecular weight component of the peptide
with higher hydroxyl radical scavenging capacity was analyzed for its amino acid composition, and then it was orally
administered to mice at low, middle and high dosages (100, 200, 600 mg/kg), respectively. The administration period for the
three dosage groups as well as the model control and blank control groups lasted for 42 days. At the end of administration,
superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities, GSH, malondialdehyde (MDA) and protein
carbonyl contents were measured in the serum of mice. Results showed that the peptide prepared by papain hydrolysis and
ultrafiltration with molecular weight cut-off of < 1 000 u had better hydroxyl radical scavenging capacity in vitro with half
maximal inhibitory concentration of 6.02 mg/mL, accounting for 58% of the total peptides. The acidic amino acid glutamic
acid and the hydrophobic amino acid tyrosine dominated its amino acid composition. The results of antioxidant tests with
a mouse model showed that all experimental mice could normally growth, and serum SOD activity and GSH content in the
mice from the high-dosage group were improved significantly (P < 0.05) and highly significantly (P < 0.01), respectively.
The activity of GSH-Px also exhibited a dosage-dependent improvement, but did not show a significant difference (P > 0.05).
The contents of MDA and protein carbonyl were both reduced and the latter was significant (P < 0.05). All these results
demonstrated that the peptide with a molecular weight less than 1 000 u could enhance antioxidant function in mice, and
therefore it has potential as an ingredient of functional foods.

Key words: Apostichopus japonicus sperm, peptide, antioxidation, mouse