Angiotensin-Converting Enzyme Inhibition <i>In Vitro</i> by Protein Hydrolysates and Peptide Fractions from Mojarra of Nile Tilapia ( <i>Oreochromis niloticus</i> ) Skeleton

Abstract

Mojarra of Nile tilapia (Oreochromis niloticus) skeleton was used as protein source for the preparation of protein hydrolysates and peptide fractions with angiotensin-converting enzyme (ACE) inhibitory activity. The flour presented a content of 34.92% protein and a brightness (luminosity, L*) of 82.29. Protein hydrolysates were obtained from the protein-rich flour with the enzymes Flavourzyme^® and Alcalase^® reaching degree of hydrolysis (%DH) of 52% and 67% at 100 min of reaction, respectively. Both hydrolysates showed low-molecular-weight (MW) peptides estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The hydrolysates obtained with Flavourzyme at 60 min and at 80 min with Alcalase showed greater ACE inhibitory activity with IC₅₀ values of 0.238 and 0.344 mg/mL, respectively. The peptide fraction A (MW >10 kDa) with Flavourzyme and fraction B (MW = 10-5 kDa) with Alcalase obtained by ultrafiltration of hydrolysates with higher DH presented IC₅₀ of 0.728 and 0.354 mg/mL, respectively, whereas peptide fraction C (MW = 5-3 kDa) with both enzymes hydrolysates with greater ACE inhibitory activity showed IC₅₀ values of 0.470 and 0.634 mg/mL. The components obtained in this study could be used as functional ingredients in the design and development of functional foods.