Angiotensin I-converting enzyme inhibitory properties and SDS-PAGE of red lentil protein hydrolysates

Several research studies have shown that protein hydrolysates from milk and soy contain peptides that possess angiotensin I converting enzyme (ACE) inhibitory properties and may help to prevent hypertension. To date, no studies have been conducted to determine if red lentil (Lens culinaris) proteins contain peptides with ACE-inhibitory properties. The objective of the present work was to characterize the proteins present in red lentils and determine if tryptic hydrolysis could liberate peptides with ACE-inhibitory properties. Red lentil protein extracts were prepared and fractionated to obtain enriched albumin, legumin and vicilin fractions. Protein/peptide profiles were studied by electrophoresis and ACE-inhibitory activity was measured using the HPLC hippuryl-His-Leu (HHL) substrate method. Our results revealed that red lentil protein hydrolysates posses ACE-inhibitory properties. Furthermore, we demonstrated that the ACE-inhibitory property of the hydrolysates varied as a function of the protein fraction with the total lentil protein hydrolysate having the lowest half maximal inhibitory concentration (IC50) (111 ± 1 μmol/L) (i.e., highest ACE-inhibitory activity), followed by the enriched legumin (119 ± 0.5 μmol/L), albumin (127 ± 2 μmol/L) and vicilin (135 ± 2 μmol/L) fractions, respectively.