Modulation of plasma non enzimatic antioxidant capacity (NEAC) by plant foods: the role of polyphenols.

A large body of evidence has described the antioxidant properties of phytochemicals such as PolyPhenols (PP) in different in vitro and ex vivo models. PP have been shown to scavenge oxygen and nitrogen derived free radicals, modulating antioxidant enzymes and cellular redox transcription factors. Dietary intervention studies have shown that consumption of plant foods modulate plasma Non Enzymatic Antioxidant Capacity (NEAC), biomarker of endogenous antioxidant network, in human subjects. However the identification of the molecules responsible for this effect is far to be obtained and evidences of an antioxidant in vivo action of PP are contrasting. There is a clear discrepancy between PP concentration in body fluids and the extent of increase of plasma NEAC. The low degree of absorption and the extensive metabolism of PP within the body have raised questions about their contribution to the in vivo antioxidant network. The available evidence from human intervention studies on the role of plant foods as modulators of plasma/serum NEAC and the involvement of PP will be presented and critically discussed.