Biological effect of nutritional antioxidants: What to measure in foods and what to measure in plasma

The two analytical approaches described here are addressed to the evaluatio n of health protective or challenging aspects of different diets and could contribute to determine the "Recommended Optimal Intake" for different nutr itional antioxidants. A competition kinetics procedure for measuring plasma antioxidant capacity is described. This procedure is based on the "crocin bleaching test" modified for analyzing the antioxidant capacity of complex mixtures. This kinetic analysis has the advantage of accounting for by the average between antioxidant effect (reduction of peroxy radicals) and possi ble prooxidant effect (oxidation by the radical of the antioxidant of the t arget supposed to be protected) if any. The result of this analysis provide s a more precise evaluation of the efficiency of antioxidant defence. The v alidated procedure has been used to show that plasma antioxidant capacity i s deeply influenced by the assumption of wine. A new procedure for the meas urement of lipid hydroperoxides, based on chemiluminescence emission, is al so described. An innovative very sensitive "single photon counting" instrum ent was used, allowing the direct analysis of lipid hydroperoxides in plasm a or intact lipoproteins without the preliminary steps of purification nece ssary to avoid the presence of inhibitors of the chemiluminescent reaction. This procedure was adopted for analysing post-prandial plasma. The results indicate that the level of peroxides increases after each meal and were ma rkedly less pronounced when meals were consumed with red wine.