Angiotensin I-converting enzyme (ACE) inhibitory peptides derived from arachin by simulated gastric digestion

In silico analysis of the sequences of arachin, the major storage protein of peanut suggests that it is laden with antihypertensive peptides. Physiological proteases pepsin, trypsin, chymotrypsin and pancreatin were used to release these peptides. The degree of proteolysis and in vitro angiotensin I-converting enzyme (ACE) inhibition was maximum with pepsin. The ACE inhibitor index of human gastric juice catalysed digestion was similar to pepsin demonstrating that such peptides can be produced in vivo following ingestion of arachin. Three peptides purified from the simulated gastric fluid digests were synthesized. Among them, the pentapeptide, NAQRP was the most potent with an IC50 of 32 ± 2 μM. Molecular docking simulation with human tACE indicate that in addition to a favourable C-terminal Pro residue, the length of the peptides advocate ACE inhibitor potency. These results further potentiate the use of arachin/peanut proteins as functional ingredients in auxiliary therapeutic foods toward blood pressure management.