In vitro Antioxidant Bioactivity of Enzymatically-Produced Tilapia zillii and Oreochromis niloticus Muscle Protein Hydrolysates: Potential Application in Health and Nutrition

Abstract

Background & Aims:   Hydrolyzed food proteins contain bioactive peptides that can modulate physiological processes that promote good health. In this study, isolated Tilapia zillii muscle protein (TzMP) and Oreochromis niloticus muscle protein (OnMP) were enzymatically hydrolyzed, and their antioxidant properties were evaluated to determine their therapeutic potential in the treatment of oxidative stress-related illness. Methods: The protein hydrolysates of O. niloticus and T. zillii muscle were produced with digestive proteases: pepsin, trypsin, and chymotrypsin, and the degree of hydrolysis (DH) and average peptide chain length (APCL) were determined. The antioxidant activities of the TzMP and OnMP hydrolysates were evaluated by ferric reducing power, 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging, hydrogen peroxide scavenging, and metal chelating assays. Results: The degree of hydrolysis was dependent on the time of hydrolysis, indirectly proportional to APCL, and pepsin-produced hydrolysates of TzMP and OnMP displayed the highest hydrolysis degree of 54.27 ± 0.84% and 77.9 ± 3.97%, and lowest APCL value of 1.84 and 1.29, respectively. Chymotrypsin- and trypsin-produced protein hydrolysates showed the highest reductive potential for O. niloticus and T. zillii, respectively. The hydrolysates from OnMP were better DPPH scavengers than hydrolysates from TzMP, with the pepsin-produced hydrolysate from O. niloticus being the most potent scavenger exhibiting 45.99 ± 0.09% inhibition though statistically significant from glutathione (84.99 ± 0.83%). Furthermore, chymotrypsin-produced hydrolysate from TzMP scavenged peroxide better than pepsin- and trypsin-produced hydrolysates from TzMP. The hydrolysate from OnMP produced by pepsin displayed the strongest hydrogen peroxide scavenging potential. The trypsin-produced hydrolysate from TzMP gave the highest metal chelating activity, while chymotrypsin-produced had the highest activity for O. niloticus. Conclusion:     The hydrolysates obtained from TzMP and OnMP were found to contain biologically active peptides with significant antioxidative activities, indicating their potential as food functional components with nutritional and therapeutic relevance.