Angiotensin I-converting enzyme-inhibitory peptide fractions from albumin 1 and globulin as obtained of amaranth grain

A number of biopeptides promoting health benefits have been isolated from food-protein hydrolysates and can be released during enzymatic digestion. Antihypertensive peptides can be part of protein fractions from amaranth grain. The objective of this work was to obtain ACE-inhibitory peptide fractions from albumin 1 and the globulin of amaranth (Amaranthus hypochondriacus) grain. Albumin 1 and globulin were hydrolysed with alcalase; hydrolysis was monitored by proteolytic degradation and by ACE-inhibitory activity. The highest ACE-inhibitory activity was 40% and 35% as obtained after 18 and 15 h hydrolysis for albumin 1 and globulin, respectively. Further separation and purification of the ACE-inhibitory peptide fractions were carried out by gel filtration and C18 RP–HPLC. The IC50 was 0.35 ± 0.02 mg/ml for albumin 1 peptide fraction and 0.15 ± 0.03 mg/ml for globulin peptide fraction. Albumin 1 peptide fraction showed an competitive mode of ACE inhibition, whereas the globulin peptide fraction was competitive. The globulin peptide fraction may have one of the most active naturally-occurring ACE-inhibitory peptides.