Bioactive peptides of amaranth: isolation and determination of antioxidant and hypocholesterolemic properties

Abstract

Hydrolysis of the amaranth protein isolate (Amaranthus hypochondriacus L., Voronezh variety) protein isolate by trypsin, papain and alkalase was carried out in order to obtain biologically active peptides with antioxidant and hypocholesterolemic activities. A high degree of protein hydrolysis was shown by trypsin during the first two hours, papain between three and four hours, and alkalase after four hours of hydrolysis. The rate of cleaved protein increased from the first two hours of hydrolysis from 40%, 30% and 15% to 78%, 70% and 60% when trypsin, papain, alkalase were applied, respectively. Maximum hydrolysis of the amaranth protein was observed after 6 h of proteolysis by all enzyme preparations. The molecular weights of the hydrolysis products of the amaranth protein after 2, 4 and 6 h of hydrolysis were determined. All hydrolysates showed a high content of polypeptides with molecular masses of 33 kDa, 18-23 kDa, 52-54 kDa, 40-54 kDa, 6.5-15 kDa. Short-chain peptides with molecular masses of 624 to 2817 Da were detected in the hydrolysates after 6 h of proteolysis. It was determined by capillary electrophoresis method that all protein hydrolysates after 6 h of hydrolysis contain amino acids (tyrosine, phenylalanine, alanine, leucine, valine, proline, alanine) responsible for antioxidant activity of peptides in the studied hydrolysates. The antioxidant activity of peptides in all hydrolysates of amaranth protein isolate was determined by ABTS cation radical reduction method for 6 min. Hypocholesterolemic activity of peptides was shown in protein hydrolysates by trypsin and papain.