Caseins and Casein Hydrolysates. 2. Antioxidative Properties and Relevance to Lipoxygenase Inhibition

Abstract

The antioxidant activity of caseins and casein-derived peptides was evaluated by using three free radical producing reactions-the lipoxygenase- and AAPH-catalyzed oxidation of linoleic acid and the hemoglobin-catalyzed oxidation of linoleic acid hydroperoxide. Caseins and casein-derived peptides were able to inhibit enzymatic and nonenzymatic lipid peroxidation, suggesting they were preferred targets for the free radical intermediates. The antioxidative feature was not lost with the dephosphorylation or the proteolysis of the proteins. The fractionation of the tryptic beta-casein digest yielded peptides with antioxidant activity. A structure-function relationship between the amino acid sequence and the antioxidant capacity and effectiveness is proposed. In addition, indirect evidence suggested that the trapping of free radicals by the proteins/peptides was accompanied by the oxidation of proteins/peptides, according to a sequence-specific mechanism.

The impact of milk proteins and peptides on blood pressure and vascular function: a review of evidence from human intervention studies

“…Several studies reported antioxidant effects of both casein and whey hydrolysates produced by different enzymes (80,81) . Many tripeptides (other than LTP, for example, Xaa -Xaa-Trp/Tyr, Tyr-His-Tyr) that show high scavenging activity and strong synergistic effects with phenolic antioxidants have been identified in milk (82) .…”

Isolation and Characterization of Peptides with Antioxidant Activity Derived from Wheat Gluten.

“…Much physiological damage may be directly imputable to the hydroxyl radical, because it is highly reactive, and so many hydroxyl radicals produced in vivo react at or close to their site of formation. The biochemical literature is full of claims that reactive species are involved in different diseases (Southorn & Powis, 1988).Many proteins have been reported to have antioxidant activities against the peroxidation of lipids or fatty acids upon hydrolysis (Rival et al, 2001, Suetsuna, 2000Chen et al, 1998;Hattori et al, 1998;Bishov & Henick, 1972). Gluten has a unique amino acid composition, with Glu/Gln and Pro accounting for more than 50% of the amino acid residues.…”

?-Caseinophosphopeptide (f1-25) confers on ?-casein tryptic hydrolysate an antioxidant activity during iron/ascorbate-induced oxidation of liposomes

“…This could result from the binding of iron to the phosphopeptide, limiting both initiation of the reaction and breakage of the hydroperoxides. Free radical scavenging by the peptides, or reactions of peroxidizing lipids with amino groups of the protein hydrolysate, causing losses in reacting amino acids, cannot be excluded [23,52]. Loss of methionine during storage of casein and of lysyl, tryptophanyl and histidyl residues of whey proteins were observed previously in the presence of oxidizing methyl linoleate [7,45,55].…”

“…The antioxidant activity of milk proteins such as lactoferrin, transferrin and caseins has been demonstrated in various systems [2,25,46,49,54,56]. Casein hydrolysates and caseinderived peptides have been shown to inhibit enzymatic and non-enzymatic lipid peroxidation [52]; caseinophosphopeptides were demonstrated to exhibit antioxidant properties in oil-in-water emulsions [14]. Iron chelation, scavenging of free radicals, and reactions of some side-chains of amino acids with hydroperoxides or secondary oxidation products, such as malonaldehyde and other aldehydes, are the main mechanisms involved in the antioxidant activity of amino acids, peptides and proteins [12,23,24,26,33,34,44,45].…”