Background: Current methods to estimate antioxidant status of plasma have many associated difficulties including questionable sensitivity, unreliability, non-reproducible results and procedural difficulties. In addition, there is no significant elevation in the measured value of biomarkers of oxidative stress until pathological disease is already evident. We have developed a new method that eliminates many of these problems.
Methods: This new method includes 3 steps: (1) enzymatic removal of uric acid; (2) ex vivo free radical oxidation of plasma by the addition of a free-radical generator such as SIN-1 or AAPH; and (3) measurement of a marker of lipid peroxidation, 8-isoprostanes.
Results: It has been shown in an in vitro experiment that the addition of various antioxidants to plasma significantly reduced the amount of free-radical induced 8-isoprostanes. In a human single dose supplementation clinical study with vitamin C, vitamin E, and grape seed and green tea extracts (on separate days) 8-isoprostane formation was also significantly reduced compared to no supplementation (74.2 to 53.8+/-5.1 pg/ml for vitamin C).
Conclusions: The reduction in 8-isoprostane formation demonstrates that the total amount of antioxidant protection in the plasma can be increased with supplementation of antioxidants and this new method can effectively measure the plasma antioxidant reserve (PAR) in healthy subjects.