Casein hydrolysates as a source of antimicrobial, antioxidant and antihypertensive peptides

Abstract

The aim of this work was to investigate the presence of antioxidant and ACE-inhibitory activity in ovine αs2-casein and bovine κ-casein hydrolysates with antibacterial activity. Several peptides which had been previously identified in these hydrolysates were selected in order to fulfil certain structural requirements and they were chemically synthesised to evaluate their antioxidant and ACE-inhibitory activity. Hydrolysates of ovine αs2-casein and bovine κ-casein with pepsin strongly inhibited ACE activity, with IC50 values of 41.8 and 9.97 μmol·L−1, respectively. The κ-casein hydrolysate also exhibited a significant oxygen radical absorbance capacity, seven times higher than that of Trolox. From the chemically synthesised peptides, two of them, LKKISQ and PYVRYL, both from ovine αs2-casein, exerted potent ACE-inhibitory activity in the range of the most potent food-derived antihypertensive peptides described to date (IC50 values of 2.6 and 2.4 μmol·L−1, respectively). The latter sequence, corresponding to the C-terminal hexapeptide of the ovine αs2casein molecule, also had antioxidant activity. The activity found is discussed in relation to the peptide sequences.