Antioxidant and ACE Inhibitory Activities of Kawakawa (Euthynnus affinis) Protein Hydrolysate Produced by Skipjack Tuna Pepsin

ABSTRACT

Pepsin enzyme from skipjack tuna was extracted for the production of kawakawa (Euthynnus affinis) fish protein hydrolysate. Using ultra-fractionation, Kawakawa protein hydrolysates were separated into four different fractions, including fractioned protein hydrolysate I (FPH I) (< 1 kDa), FPH-II (1–3 kDa), FPH-III (3–10 kDa), and FPH-IV (> 10 kDa). The antioxidant activity was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, inhibition of linoleic acid oxidation, reducing power tests, and chelating activity of metal ions. Results indicated that FPH II fraction peptides had higher antioxidant activity in comparison with the other fractions, followed by FPH I. Further, the fractions were evaluated for angiotensin converting enzyme (ACE) inhibition, and IC₅₀ value ranged from 0.45 to 1.86 mg/ml with higher activity in FPH I (IC₅₀ 0.45). Finally, the amino acid profile of different fractions was analyzed. The fractions exhibited significant amounts of hydrophobic amino acids, which could perform as hydrogen donors, frustrate the free radicals, and inhibit the ACE. The recovered pepsin from the viscera was used to produce hydrolysates with good biological activities. Peptides lower than 3 KDa had antioxidant activity as positive controls and significant ACE activity. These are very important findings that could be used to conduct further research in a preclinical study of these peptides.

KEYWORDS:

• Antioxidant activity
• ACE inhibitory activity
• Kawakawa fish
• Pepsin
• Protein hydrolysate

Acknowledgments

The authors would like to thank the Chabahar Maritime University for financially supporting this research and Dr. Reza Tahergorabi from North Carolina A & T State University for help in English language editing.

Additional information

Funding

This work was supported by the Chabahar Maritime University.