Effect of in vitro gastrointestinal digestion on the Angiotensin Converting Enzyme (ACE) inhibitory activity of pigeon pea protein isolate

The content of certain bioactive peptides in the gastrointestinal digestive products from legume proteins is expected to provide added value to the function of proteins (beyond the scope of nutrition). In vitro gastrointestinal digestion (GID) involves the hydrolysis of proteins by a mixture of proteases (pepsin, trypsin, and chymotrypsin) to produce protein hydrolysate. The present work aimed to evaluate the angiotensin converting enzyme (ACE) inhibitory activity of protein hydrolysate produced through a simulated in vitro GID of pigeon pea protein isolates, and to fractionate its bioactive peptide component. The protein content of pigeon pea protein isolate was 81.34%. The highest value of the degree of hydrolysis and the ACE inhibitory activity was obtained using P120TC120 treatment (120 min of pepsin followed by 120 min of trypsin-chymotrypsin mixture) with an IC50 value of 64.22 µg/mL. The fractionation of the protein hydrolysate using ultra-filtration method resulted in a peptide fraction with the molecular weight below 3 kDa as the most active fraction, which had an IC50 value of 11.76 µg/ mL and contained 10 peptide components with molecular weight between 400-1,000 Da. These results indicated that the pigeon pea protein hydrolysate has the potential as an ACE inhibitory functional ingredient.