Antioxidative and angiotensin I-converting enzyme inhibitory activities of Eastern eel (Anguilla japonica)

This study was designed to investigate the antioxidative and angiotensin I-converting enzyme (ACE) inhibitory activities of Eastern eel (Anguilla japonica). Hot water extracts were prepared over a period of 25 h at 100°C from the meat and whole body of the Eastern eel. Protein hydrolysates of Eastern eel were prepared over a period of 10 h using different hydrolytic enzymes, such as Alcalase®, Protamex®, and Alcalase® + Protamex®. The antioxidative and ACE inhibitory activities of the eel hydrolysates were higher than those of the extracts, and showed similar trends for hydrolysis time on each assay system due to similar enzyme specificity. The hydrolysates produced using Alcalase® exhibited the highest DPPH scavenging activity (IC50=3.02 mg/mL), while the Protamex® hydrolysates exhibited the highest ABTS (IC50=1.13 mg/mL), hydroxyl radical (IC50=1.30 mg/mL), and hydrogen peroxide (IC50=1.11 mg/mL) scavenging activities and ACE inhibitory activity (IC50=110.37 μg/mL). These results revealed that the Eastern eel hydrolysates exhibited strong radicals (DPPH, ABTS, superoxide, hydroxyl, and hydrogen peroxide) scavenging properties and ACE inhibitory activity, indicating that they can be potentially used as functional food ingredients with potential to prevent oxidation and reduce blood pressure.