Antioxidant effect of casein phosphopeptides compared with fruit beverages supplemented with skimmed milk against H2O2-induced oxidative stress in Caco-2 cells

Casein phosphopeptides (CPPs) have been proposed as potential dietary antioxidants on designing new functional products. A fruit beverage, with/without milk, was subjected to in vitro digestion. Caco-2 cultures were preincubated with soluble fractions or isolated CPPs, the latter obtained from skimmed milk. The mitochondrial activities (MTT test), intracellular GSH and GSH-reductase activity (GSH-Rd), cell cycle analysis and RNA distribution in cycle phases were studied after inducing oxidative stress status (5 mM H2O2). MTT conversion was better preserved by soluble fractions of fruit beverages, either with or without milk. GSH concentration was equally decreased, and GSH-Rd was increased in all preincubations. However, failed to inhibit a decreased G1 cell population. CPPs produced RNA accumulation in the G2 phase, suggesting a modulating effect on cell response. We can postulate an antioxidant effect derived from dietary CPPs on a biological system which can be synergistic with other antioxidant compounds derived from fruit beverage.