Angiotensin-I converting enzyme inhibitory and antioxidant activities of peptide fractions extracted by ultrafiltration of cowpea Vigna unguiculata hydrolysates

BACKGROUND: Enzymatic proteolysis of food proteins is used to produce peptide fractions with the potential to act as physiological modulators. Fractionation of these proteins by ultrafiltration results in fractions rich in small peptides with the potential to act as functional food ingredients. The present study investigated the angiotensin-I converting enzyme (ACE-I) inhibitory and antioxidant activities for hydrolysates produced by hydrolyzing Vigna unguiculata protein extract as well as ultrafiltered peptide fractions from these hydrolysates. RESULTS: Alcalase (R), Flavourzyme (R) and pepsin-pancreatin were used to produce extensively hydrolyzed V. unguiculata protein extract. Degree of hydrolysis (DH) differed between the enzymatic systems and ranged from 35.7% to 58.8%. Fractionation increased in vitro biological activities in the peptide fractions, with IC50 (hydrolysate concentration in mu g protein mL(-1) required to produce 50% ACE inhibition) value ranges of 24.3-123 (Alcalase hydrolysate, AH), 0.04-170.6 (Flavourzyme hydrolysate; FH) and 44.7-112 (pepsin-pancreatin hydrolysate, PPH) mu g mL(-1), and TEAC (Trolox equivalent antioxidant coefficient) value ranges of 303.2-1457 (AH), 357.4-10211 (FH) and 267.1-2830.4 (PPH) mmol L-1 mg(-1) protein. CONCLUSION: The results indicate the possibility of obtaining bioactive peptides from V. unguiculata proteins by means of a controlled protein hydrolysis using Alcalase (R), Flavourzyme (R) and pepsin-pancreatin. The V. unguiculata protein hydrolysates and their corresponding ultrafiltered peptide fractions might be utilized for physiologically functional foods with antihypertensive and antioxidant activities. (c) 2010 Society of Chemical Industry