Enzymatic Protein Hydrolysates, and Ultrafiltered Peptide Fractions from Two Molluscs: Tympanotonus fuscatus var. radula (L.) and Pachymelania aurita (M.), with Angiotensin-I-Converting Enzyme Inhibitory and DPPH Radical Scavenging Activities

CONTEXT: Multifunctional food protein-derived peptides attract a great deal of research interest due to their health-promoting benefits. Particularly, peptides that have both antihypertensive and antioxidant properties are desired, since both effects can be synergistic in prevention of cardiovascular diseases. AIM: The aim of this study was to investigate the angiotensin-I-converting enzyme (ACE) inhibitory and 2,2(′)-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of two species of the Nigerian periwinkles: Pachymelania aurita and Tympanotonus fuscatus. METHODS: The ACE inhibitory and 2,2(′)-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activities of simulated gastrointestinal digestion (SGID) hydrolysates and ultrafiltered (UF) fractions of T. fuscatus var. radula and P. aurita were determined. Human SGID of the protein extracts of T. fuscatus and P. aurita was carried out using pepsin, trypsin, and chymotrypsin, and the hydrolysates were fractionated into two by centrifugal ultrafiltration. The ACE inhibitory and DPPH radical scavenging activities of the crude hydrolysates and UF fractions were tested. The UF permeates were observed to have relatively higher activities and was subjected to gel filtration chromatography on Sephadex G-50. The chromatographic fractions showed absorbance at 215, 225, and 280 nm and were assayed for DPPH radical scavenging activity. RESULTS: The inhibitory effect of the fractions on ACE activity was reported as the minimum concentration of extract that caused 50% of the inhibition (IC(50)), where the IC(50) values of P. aurita UF permeate and P. aurita UF retentate were 65.2 ± 6.4 and 301.9 ± 59.1 μg/ml, respectively, and that of T. fuscatus UF permeate (TFUFP) and T. fuscatus UF retentate were 54.93 ± 2.83 and 291.7 ± 8.6 μg/ml, respectively. CONCLUSION: This study suggests the potential health benefits of consuming T. fuscatus var. radula and P. aurita in health maintenance.