Two novel peptides with angiotensin I converting enzyme inhibitory and antioxidative activities from Scorpaena notata muscle protein hydrolysate

Fish protein hydrolysate was prepared from muscle of small red scorpionfish ( Scorpaena notata ) by treatment with a protease from the fungus Penicillium digitatum . Protein hydrolysate was found to strongly inhibit the angiotensin I converting enzyme and exhibited high antioxidative activity through 1,1‐diphenyl‐2‐picrylhydrazyl free radical scavenging assay. After ultrafiltration, peptides were isolated by a two‐step procedure: size exclusion chromatography on a Toyopearl HW‐40 followed by reversed‐phase high‐performance liquid chromatography with a high purification yield of 2.5 mg of peptide per gram of initial protein. Two major peptides were then identified by nanoscale liquid chromatography coupled to tandem mass spectrometry (nano‐LC‐MS/MS), corresponding to the following sequences: Leu‐Val‐Thr‐Gly‐Asp‐Asp‐Lys‐Thr‐Asn‐Leu‐Lys (1,204.665 Da) and Asp‐Thr‐Gly‐Ser‐Asp‐Lys‐Lys‐Gln‐Leu (992.511 Da). These peptides, mainly composed of hydrophilic amino acids, showed high antioxidative and angiotensin I converting enzyme inhibitory activities. These data suggest that the two novel peptides isolated from the muscle hydrolysate of small red scorpionfish can be a beneficial ingredient for functional foods or pharmaceuticals against hypertension and oxidative stress.