Antiradical effect of low-molecular peptides in extracts and hydrolyzates from tissues of water organisms

Abstract

Molecular-weight composition of peptides in extracts and hydrolyzates from soft tissues of the clams Corbicula japonica and Mercenaria mercenaria and liver of chum salmon is investigated. Antiradical activity is defined for low-molecular peptides, as well as for high-molecular proteins and free amino acids in the extracts. The maximum activity is detected for the extracts of salmon liver; all protein fractions in the water extract of the liver have antiradical activity. Low-molecular peptides and free amino acids have antiradical activity in all samples. The peptides with molecular weight 4.3 kDa have the highest activity in the water extract from C. japonica (43 units) and the peptides with molecular weight 4.7 kDa - in the water extract from M. mercenaria (5.6 units). After hydrolysis, the portion of low-molecular peptides increases for C. japonica , M. mercenaria , and salmon liver in 22.1, 14.5, and 11.1 %, respectively. Hence antiradical activity for hydrolyzates from C. japonica and M. mercen aria is in 1.9 times higher and for hydrolyzates from salmon liver - in 1.3 times higher than for water extracts from their tissues. Only the peptides with molecular weight 2.8-4.7 kDa have antiradical activity in the hydrolyzates; its value is 1-24 activity units for M. mercenaria ; 13-76 units for C. japonica and about 40 units for the chum salmon liver. Correlation is found between the content of peptides with molecular weight 3-4 kDa in hydrolyzates and their antiradical activity.

Antiradical Potential of Food Products as a Comprehensive Measure of Their Quality

“…According to the literature and our own data, protein hydrolysates have a higher ARP than pure protein preparations. For example, it has been previously shown that the reducing ability of proteins increases with the degradation of the molecular weight of the protein [ 26 , 28 ]. In other words, the ARP of the native protein is less (with a reservation about some enzymes) than that of the hydrolysis products of its molecule.…”

“…For example, whey protein hydrolyzate is 9.5–10 times more active than wheat gluten protein from bakery products made from premium flour. We attribute this both to an increase in the spatial availability of the amino acid side chains of polypeptides and to an increase in the concentration of C- and N-terminal fragments of polypeptides per volume of reacting mixtures [ 12 , 28 ]. With some exceptions, all studied samples are distributed in the following order according to the increase in their activity: native proteins < less protein-enriched hydrolysates < more protein-enriched hydrolysates < a mixture of molecular amino acids.…”