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

Key Findings:

Plasma amino acid imbalance has been found in patients with liver diseases, in particular high levels of aromatic amino acids (AAA; tyrosine and phenylalanine) and methionine, and decreased levels of branched-chain amino acids (BCAA; leucine, isoleucine and valine). The ratio of plasma BCAA to AAA is termed Fischer ratio and is used to measure abnormal amino acid metabolism during liver disease. In human beings, the normal plasma Fischer ratio is 3.5-4.0; this value decreases to <2.5 in liver diseases. Flaxseed proteins contain high levels of BCAA, with 50, 71, and 56 mg/g of isoleucine, leucine and valine, respectively. The authors describe the utilization of several methods to produce the highest Fischer ratio flaxseed peptide mixture from thermolysin-pronase treatment. This product showed antioxidant activity which could offer protection to cellular components. The BCAA-rich had antihypertensive property. Animal feeding experiments in a model of liver disease will be conducted to evaluate the in vivo effects of the peptides.

ABSTRACT:

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 (branchedchain amino acids/aromatic amino acids) of 23.65 and a phenylalanine þ 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 þ 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. (Author’s abstract)