Gelatins and antioxidant peptides from Skipjack tuna (Katsuwonus pelamis) skins: Purification, characterization, and cytoprotection on ultraviolet-A injured human skin fibroblasts

For full use of Skipjack tuna (Katsuwonus pelamis) canning by-products, gelatins (STG) were extracted from tuna skins using acid (STG-A), enzyme (STG-E) and hot water (STG-H) methods with yields of 65.30 +/- 1.56%, 39.83 +/- 1.61%, and 50.97 +/- 1.44%, respectively. Due to the high imino acid contents (228, 216, and 213 residues/ 1000 residues for STG-A, STG-E, and STG-H, respectively), STG-A showed the highest transparency and gel strength properties. Amino acid analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), ultraviolet (UV) and Fourier transform infrared spectroscopy (FTIR) analysis confirmed that STG-A, STG-E, and STG-H kept the main structure of type I collagen, but enzyme and hot water extraction methods showed much stronger hydrolysis ability on alpha and beta chains. Moreover, neutrase hydrolysate (STG-AH) of STG-A showed the highest 1,1-diphenyl-2-picrylhydrazyl radical (DPPH center dot) scavenging activity and the fraction STG-AH-CYRILLIC CAPITAL LETTER BYELORUSSIAN-UKRAINIAN I (<3.5 kDa) from STG-AH prepared by ultrafiltration could significantly protect human skin fibroblasts (HSFBs) against ultraviolet-A (UVA) injury. Furthermore, nineteen peptides with high antioxidant activity were purified from STG-AH-CYRILLIC CAPITAL LETTER BYELORUSSIAN-UKRAINIAN I and identified. These results suggested that STG-AH and its derived antioxidant peptides could serve as potential ingredients applied in health benefiting products for preventing UVA injury.

Automated summary

Gelatins (STG) were extracted from skipjack tuna skins using acid, enzyme, and hot water methods. Acid extracted gelatin (STG-A) showed the highest transparency and gel strength. STG-AH, a neutrase hydrolysate of STG-A, exhibited the highest antioxidant activity and could protect human skin fibroblasts against UVA injury. Furthermore, nineteen peptides with high antioxidant activity were identified from STG-AH.