Abstract
In China, a large amount of fish bones are produced during the processing of tuna cans production. For full use of those by-products, gelatin (STB-G) with a yield of 6.37 ± 0.64% was extracted from skipjack tuna (Katsuwonus pelamis) bone using water at 60 °C for 8 h. Amino acid analysis showed that STB-G contained Gly (340.3 residues/1000 residues) as the major amino acid and its imino acid content was 177.3 residues/1000 residues. Amino acid composition, SDS-PAGE, and Fourier transform infrared (FTIR) spectrum investigations confirmed that the physicochemical properties of STB-G were similar to those of type I collagen from skipjack tuna bone (STB-C), but partial high molecular weight components of STB-G were degraded during the extraction process, which induced that the gelatin was easier to be hydrolyzed by protease than mammalian gelatins and was suitable for preparation of hydrolysate. Therefore, STB-G was hydrolyzed under in vitro gastrointestinal digestion (pepsin-trypsin system) and five antioxidant peptides were purified from the resulted hydrolysate (STB-GH) and identified as GPDGR, GADIVA, GAPGPQMV, AGPK, and GAEGFIF, respectively. Among the gelatin hydrolysate, fractions, and isolated peptides, GADIVA and GAEGFIF exhibited the strongest scavenging activities on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical (EC50 0.57 and 0.30 mg/mL), hydroxyl radical (EC50 0.25 and 0.32 mg/mL), superoxide anion radical (EC50 0.52 and 0.48 mg/mL), and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical (EC50 0.41 and 0.21 mg/mL). Moreover, GADIVA and GAEGFIF showed a high inhibiting ability on lipid peroxidation in a linoleic acid model system. The strong activities of five isolated peptides profited by their small molecular sizes and the antioxidant amino acid residues in their sequences. These results suggested that five isolated peptides (STP1–STP5), especially GADIVA and GAEGFIF, might serve as potential antioxidants applied in health food industries.
Highlights
Gelatin is produced by partial hydrolysis of collagen with a molecular weight (MW) ranging between 80 and 250 kDa [1]
Sun et al evaluated the effect of tilapia gelatin peptides (TGP) on UV-induced damages to mice skin, and the results indicated that TGP could significantly prevent a decrease of antioxidase activity in a dose-dependent manner
The results indicated that the impurities in the bones of skipjack tuna were effectively removed through the extraction process of gelatin
Summary
Gelatin is produced by partial hydrolysis of collagen with a molecular weight (MW) ranging between 80 and 250 kDa [1]. Gelatin has been isolated from the skin and bone collagens of. Mar. Drugs 2019, 17, 78 mammalian species, primarily cows and pigs [2]. The application of gelatin from mammalian species may be a concern among consumers because of dietary restrictions and infectious disease [3]. These sociocultural and safety concerns have led to intensive research to identify and develop alternatives to mammal derived gelatin [1]. Gelatin has been extensively extracted from different fish by-products, such as golden carp skin [2], lizardfish scale [6], unicorn leatherjacket skin [7], cuttlefish skin [8], cod head [9], shark cartilage [10], and red snapper and grouper bones [11]
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