Fractionation of angiotensin I converting enzyme inhibitory activity from pea and whey protein in vitro gastrointestinal digests

Abstract In vitro gastrointestinal digestion of pea and whey protein produced high angiotensin I converting enzyme (ACE) inhibitory activity with IC 50 values of 0.070 and 0.041 mg protein ml −1 respectively. Ultrafiltration/centrifugation using a membrane with a molecular weight cut‐off of 3000 Da decreased the IC 50 value to 0.055 mg protein ml −1 for pea permeate and 0.014 mg protein ml −1 for whey permeate. Further fractionation by reverse phase HPLC gave IC 50 values as low as 0.016 mg protein ml −1 for pea and 0.003 mg protein ml −1 for whey. Consequently, these purification steps enriched the ACE inhibitory activity of the pea digest more than four times and that of the whey digest more than 13 times. HPLC profiles after digestion and ultrafiltration indicate that high ACE inhibitory activity is due to short and more hydrophobic peptides. The results also suggest that potent ACE inhibitory peptides were present alongside low active peptides in whey hydrolysate, while all peptides had more or less the same ACE inhibitory activity in pea hydrolysate. In addition, the hydrolysates and enriched fractions will resist in vivo gastrointestinal digestion after oral administration. Hence these ACE inhibitory peptides, as part of functional foods, can play significant roles in the prevention and treatment of hypertension. Copyright © 2004 Society of Chemical Industry