Preparation and Characterization of Gelatin and Antioxidant Peptides from Gelatin Hydrolysate of Skipjack Tuna (Katsuwonus pelamis) Bone Stimulated by in vitro Gastrointestinal Digestion

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.

Antioxidant Peptides from the Protein Hydrolysate of Monkfish (Lophius litulon) Muscle: Purification, Identification, and Cytoprotective Function on HepG2 Cells Damage by H2O2

“…EC 50 values of MMP-4, MMP-7, and MMP-12 were 0.76, 0.94, and 0.48 mg/mL, respectively. The EC 50 value of MMP-12 was lower than those of MMP-4, MMP-7, and other APs from croceine croaker muscle (VLYEE: 0.69 mg/mL; MILMR: 0.99 mg/mL) [40], skipjack tuna bone (GADIVA: 0.52 mg/mL) [23], Spanish mackerel skins (PFGPD: 0.91 mg/mL, PYGAKG: 0.80 mg/mL, and YGPM: 0.73 mg/mL) [37], bluefin leatherjacket heads (WEGPK: 3.22 mg/mL; GPP: 4.67 mg/mL; GVPLT: 2.88 mg/mL) [32], and miiuy croaker swim bladders (YLPYA: 3.61 mg/mL; VPDDD:4.11 mg/mL) [20]. However, the EC 50 value of MMP-12 was higher than those of FPYLRH (0.34 mg/mL) and GIEWA (0.30 mg/mL) from miiuy croaker swim bladders [20] Figure 8 showed the inhibiting abilities of three isolated peptides (MMP-4, MMP-7, and MMP-12) on the lipid peroxidation system in the linoleic acid model.…”

“…The monkfish muscle was defatted according to our previous method [7]. Afterwards, the defatted muscle was hydrolyzed by pepsin, trypsin and in vitro GI digestion (pepsin-trypsin system) [2,9,23]. The hydrolytic process of the defatted monkfish muscles separately using pepsin and trypsin was performed following the previous methods [9].…”

“…The protein hydrolysate of monkfish muscles prepared using the in vitro GI digestion was performed according to the previous method [23]. The defatted muscle dispersions (pH 1.5, 1%, w/v) were hydrolyzed using pepsin at 37.0 • C with a total enzyme dose of 1% (w/w).…”

“…The EC 50 values of MMP-4, MMP-7, and MMP-12 were 0.39, 0.62, and 0.51 mg/mL, respectively, but their activities were still lower than that of the positive control of GSH at the same concentration. The EC 50 value of MMP-4 was lower than those of most APs from protein hydrolysates of red stingray cartilages (VPR: 4.61 mg/mL, IEPH: 1.90 mg/mL, LEEEE: 3.69 mg/mL, and IEEEQ: 4.01 mg/mL) [6], loach (PSYV: 17.0 mg/mL) [35], salmon pectoral fin (TTANIEDRR: 2.50 mg/mL) [36], Spanish mackerel skins (PFGPD: 0.80 mg/mL, PYGAKG: 3.02 mg/mL, and YGPM: 0.72 mg/mL) [37], skipjack tuna bone (GADIVA: 0.57 mg/mL) [23], and miiuy croaker swim bladders (FPYLRH: 0.51 mg/mL; GIEWA: 0.78 mg/mL; YLPYA: 3.63 mg/mL; VPDDD: 2.87 mg/mL) [20]. Therefore, the present result suggested that three isolated peptides (MMP-4, MMP-7, and MMP-12), especially MMP-4 could contribute an electron or hydrogen radical to suppress the DPPH• reaction.…”

Characterization and Antioxidant Activity of Collagen, Gelatin, and the Derived Peptides from Yellowfin Tuna (Thunnus albacares) Skin

“…In addition, the gelatin yield in this study (19.97%) was quite high when compared with that of skipjack tuna (K. pelamis) skin (11.3%) [22], emperor fish (Lethrinus sp.) skin (4.8%) [23], and K. pelamis bone (6.37%) [24]. The main structures of the skin inner layers and different harvesting ages could lead to differences in the yield [25].…”