Antioxidant and Angiotensin Converting Enzyme-Inhibitory Properties of a Flaxseed Protein-Derived High Fischer Ratio Peptide Mixture

Hydrolysis of flaxseed proteins using thermolysin and pronase followed by mixing with activated carbon, centrifugation and filtration yielded a filtrate (peptide mixture) with a Fischer ratio (branched-chain amino acids/aromatic amino acids) of 23.65 and a phenylalanine + tyrosine content of 1.11%. Gel permeation chromatography showed that the flaxseed peptide sample contained mainly low molecular weight peptides (<4 kDa). The high Fischer ratio peptide sample exhibited antioxidant property by scavenging 2,2-diphenyl-1-picrylhydrazyl radical, superoxide radical, hydroxyl radical, and also by protecting linoleic acid from oxidation. In addition, the peptide mixture showed potential antihypertensive properties by inhibiting angiotensin I-converting enzyme in a mixed-type inhibition pattern. Protein hydrolysates with Fischer ratio higher than 20 and phenylalanine + tyrosine content lower than 2% have been used to treat patients with hepatic encephalopathy; thus, this multifunctional flaxseed peptide mixture could be used to formulate food products with multiple human health benefits during liver diseases, oxidative stress and hypertension.