Antioxident effects of caseinophosphopeptides (CPP) and associated conjugates in chemical models and cell culture systems in vitro

Caseinophosphopeptides (CPP) derived from tryptic digests of bovine milk casein were evaluated for potential antioxidant activity. Two different commercially available (Meiji Seika Kaisha Ltd. Japan) CPP fractions, CPP-I and III, were shown to interact with ferrous iron, ferric iron and calcium ions. CPP-I and III exhibited significant (p<0.01) inhibition of both site-specific and non site-specific degradation of deoxyribose in a Fenton reaction oxidation test and protected liposomes from oxidation induced by ferrous iron and free radical AAPH . CPP-I was more effective (p<0.01) at quenching ABTS radicals than CPP-III. Laboratory synthesized CPP and CPP-saccharide conjugates were also analyzed for antioxidant activity. Different preparation techniques yield CPP of different calcium concentrations and peptide sizes. It appears that all CPP peptides carry the required polar, acidic Ser-P-Ser-P-Ser-P-Glu-Glu domain for ideal conformation for metal binding. CPP III was shown to be the most effective (p<0.01) at binding iron and lowering deoxyribose oxidation, while CPP-IJ was more effective (p<0.01) at sequestering ABTS radicals. All of the CPP preparations were equally effective (p>0.05) at quenching peroxyl radicals in the liposome peroxidation model. Conjugation of CPP with polysaccharide galactomannan and oligosaccharide xyloglucan did not enhance the bioactivity of CPP as predicted. Hence, both commercially available and laboratory synthesized CPP can act as a primary and also a secondary antioxidant by displaying both metal sequestering and free radical quenching activity in aqueous and emulsion models. Using a reduced serum culture system, laboratory synthesized CPP-III was also shown to be relatively non-toxic to intestinal cells and to successfully protect human intestinal embryonic Int-407 and colon carcinoma Caco-2 cells from ferrous sulphate-induced cytotoxicity. With a selective affinity to sequester free metal ions, such as iron, and a low toxicity in intestinal cells, bioactive casein derived peptides can act as a potential antioxidant co-nutrient that serves to remove pro-oxidative metal catalysts and free radicals from oxidizable lipids in labile food systems or biomembrane lipid bilayer systems in vivo, especially at the site of the intestine.Land and Food Systems, Faculty ofGraduat