Isolation and identification of an antioxidant collagen peptide from skipjack tuna (Katsuwonus pelamis) bone

Abstract

To date, many researchers have developed active components that are derived from seafood processing for the purposes of healthcare. Here, an antioxidant collagen peptide was obtained from skipjack tuna (Katsuwonus pelamis) bone by using a combination of trypsin and chymotrypsin as the catalyst. The amino acid sequence of the peptide was identified as Ser-Ser-Gly-Pro-Pro-Val-Pro-Gly-Pro-Met-Gly-Pro-Met-Gly-Pro-Arg (SSGPPVPGPMGPMGPR) by liquid chromatography-electrospray ionization quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS) analysis. We found that the as-prepared collagen peptide can efficiently scavenge DPPH radical (IC₅₀ 3.149 mM), superoxide anion radical (IC₅₀ 3.803 mM) and ABTS radical (IC₅₀ 9.489 mM). In addition, it has been found that the methionine (Met) residue in the collagen peptide could provide a precise active site during the scavenging of DPPH radicals by Fourier transform infrared spectroscopy (FTIR) analysis and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry analysis. These results suggest that the peptide can find wide uses in the food, cosmetic and pharmaceutical industries.

Fig. 1. (A) Elution profile of STCH obtained using DEAE-52 cellulose chromatography; (B) inhibition of DPPH radicals in the fractions was determined (1 mg mL⁻¹); (C) elution profile of Frac.1 obtained using RP-HPLC; (D) DPPH radical scavenging activity of the active fraction based on the RP-HPLC chromatogram (1 mg mL⁻¹).

Fig. 2. Antioxidant activities of the peptides in terms of: (A) DPPH radical scavenging activity; (B) superoxide anion radical scavenging activity; (C) ABTS radical scavenging activity; (D) ESR spectra in the presence of DPPH radicals.

Fig. 3. Effects of the peptides on H₂O₂-induced cytotoxicity in HepG2 cells.

Fig. 4. The mechanism utilized by SSGPPVPGPMGPMGPR peptide during scavenging of DPPH radicals. (A) CD spectra; (B) FTIR-ATR spectra.

Fig. 5. (A) MALDI-TOF mass spectrometry of the SSGPPVPGPMGPMGPR peptide after the reaction with DPPH radicals; (B) MALDI-TOF/TOF mass spectrometry of the SSGPPVPGPMGPMGPR peptide; (C) MALDI-TOF/TOF mass spectrometry of the SSGPPVPGPMGPMGPR peptide after the reaction with DPPH radicals.

Fig. 6. (A) DPPH radical scavenging activity of the SSGPPVPGPMGPMGPR peptide and SSGPPVPGPGGPMGPR peptide; (B) ESR spectra of DPPH radicals in the presence of the SSGPPVPGPMGPMGPR peptide and SSGPPVPGPGGPMGPR peptide; (C) structure of the SSGPPVPGPMGPMGPR peptide.