Characterization of the antioxidant and angiotensin I-converting enzyme inhibitory activities of lizardfish Saurida wanieso viscera sauce and their correlation with the amino acid profiles

The biological activities of lizardfish viscera sauce under three different fermentation conditions were characterized, and the amino acid profiles of the peptides were investigated to determine their contribution to these biological activities. The lizardfish viscera sauce, with a low salt level prepared under alkaline fermentation conditions of pH 11.0 and 40 °C, had remarkable angiotensin I-converting enzyme (ACE) inhibitory and antioxidant activities, including scavenging of 2.2-diphenyl-1-picrylhydrazy (DPPH), hydroxyl and superoxide anion radicals, and chelating ferric ions. The biological peptides in lizardfish viscera sauce with molecular weights < 3 kDa accounted for more than 50% of its peptide content, ultimately contributing to the biological activities of the fish sauce. The large molecular weight (> 10 kDa) peptides promoted ACE inhibitory activities that might result from the steric hindrance of peptides to block the active site of ACE. Moreover, aliphatic and positively charged amino acid residues in peptides can improve their antioxidant and ACE inhibitory activities. Collectively, our findings indicate the biological activities of fish sauce fermented with a low salt content, and reveal the potential structure–activity relationship of these specific amino acid residues in peptides.