Prevention of in vitro oxidation of low density lipoproteins (LDL) by amaranth peptides released by gastrointestinal digestion

- Amaranth protein isolate was subjected to a simulated gastrointestinal digestion.
- Prevention of lipid and protein LDL oxidation induced by Cu+2/H2O2 was evaluated.
- Gastrointestinal digest activity was dependent upon the protein concentration.
- Most active peptide fractions presented MW in the 0.59-1.4 kDa range.
- Histidine, hydrophobic and aromatic amine acids would be involved in the activity.

The objective of this work was to analyze the capacity of amaranth peptides generated by gastrointestinal digestion to prevent LDL oxidation. A simulated gastrointestinal digest from protein isolate (Id); Id fractions separated by gel filtration FPLC, and synthetic peptides (products of digestion) were evaluated. The evolution of conjugated dienes (CD) and, for most active samples, TBARS, fluorescent compounds (FC) evolution and electrophoretic mobility (EM) during Cu+2/H2O2-induced-LDL-oxidation were evaluated. Id was able to increase the lag time and to decrease the propagation rate for CD and FC formation; however, EM was not modified. Most active FPLC fractions (0.59-1.4 kDa) attained a complete inhibition of CD, and partial or total prevention of FC formation and electrophoretic changes. Peptides evaluation indicated that the presence of histidine, hydrophobic and aromatic residues would be important in the inhibition of Cu+2/H2O2-induced LDL oxidation. The most active were cationic or neutral peptides.