Novel antioxidant peptide from tilapia skin: identification and structure elucidation

In recent years, a variety of antioxidant peptides have been isolated and purified from diverse food sources. These peptides have attracted significant interest due to their potential therapeutic benefits in managing cardiovascular diseases and their favorable safety profiles. In this study, tilapia skin protein was hydrolyzed using alcalase to generate a peptide hydrolyzate with antioxidant activity. The hydrolyzate was subsequently fractionated through a series of methods including dialysis, Sephadex G-100 gel filtration, DEAE-Sepharose fast-flow ion-exchange chromatography, and reversed-phase high-performance liquid chromatography (RP-HPLC). RP-HPLC analysis indicated that the purity of the enriched antioxidant peptides reached 92.91%. The primary structure of the peptides was characterized by liquid chromatography – tandem mass spectrometry (LC – MS/MS), while circular dichroism (CD) spectroscopy was employed to elucidate the secondary structure of the major peptide component, designated P1-2. Six peptide segments were identified within P1-2, with the following amino acid sequences: ADQLTDDQISEFK, VFDKDQNGFISAAELR, LTDEEVDEMIR, DTDSEEELKEAFR, EADVDGDGQINYDEFVK, and SLGQNPTEAELQDMINEVDADGNGTIDFPEFLNLMARK. Hydrophobic and aromatic amino acids accounted for 40.14% and 11.32% of the total composition, respectively. Database searching with Mascot software followed by alignment analysis using the NCBI database revealed that P1-2 exhibits 72% sequence similarity to a peptide encoded under the accession gi|194716545|gb|ACF93134.1|. These results indicate that tilapia skin-derived antioxidant peptides hold promise as functional ingredients in nutraceuticals or pharmaceuticals aimed at the prevention and management of hypertension and related disorders.