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.

F2-isoprostanes are a biomarker of lipid peroxidation, and their measurement has emerged as a reliable approach to assess oxidative stress. However, dietary intervention studies in humans have provided contrasting results following supplementation with antioxidant-rich foods or supplements. In this paper, we have systematically reviewed the evidence about the effect of supplementation with antioxidant-rich foods and galenic antioxidants on isoprostanes levels in humans. Moreover, the association with nonenzymatic antioxidant capacity (NEAC), a biomarker of endogenous antioxidant status, has also been investigated.MEDLINE database was searched using the terms "(isoprostane * OR isoP OR iso-PGF OR epi-PGF) AND (intervention * OR consumption * OR administration * OR supplementation * )," with limits activated "humans" and "English." Abstracts and full texts were screened, from which were selected human intervention studies reporting isoprostanes measurement in biological fluids. The total of the studies carried out with antioxidant-rich foods and antioxidant galenic supplements was 113, reporting 154 interventions. Results suggest that dietary antioxidants modulate successfully the levels of isoprostanes in less than 45% of the interventions. A correspondence between the effect on isoprostane and NEAC has been evidenced, and this correspondence suggests the importance of measuring different biomarkers to obtain a better outline of the redox events following supplementation.

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An innovative procedure to separate the 3 isomeric sn-monoacylglycerols (MAG) classes (sn-1-, sn-2-, sn-3-MAG) is described. MAGs, obtained by chemical deacylation of triacylglycerols (TAGs), have been derivatized with (S)-(+)-1-(1-naphtyl)- ethyl-isocyanate, and the resulting urethane derivatives have been separated by normal-phase high-performance liquid chromatography. This procedure allows resolution as diasteroisomers of the 2 enantiomeric classes (sn-1-MAG and sn-3-MAG), without the need of a chiral column, and to separate also the isomeric sn-2-MAG class; moreover, by introducing a chromophoric moiety, this reagent makes possible the ultraviolet detection of the analyte molecules. This procedure has been used to obtain the stereospecific analysis of the TAG fraction of extra virgin olive oil samples. The use of a nondestructive detector permitted the collection of the individual urethane classes; the fatty acid composition of each was determined by high-resolution gas chromatography, obtaining directly from the data the fatty acid distribution within each sn- position of TAGs. To validate this new method, the results have been compared with those obtained by 2 other procedures for TAG stereospecific analysis, and the obtained results were satisfactory since the proposed method gave data very similar to the other procedures.

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