A comparison of methods employed to evaluate antioxidant capabilities

Three different methodologies frequently employed to evaluate the indexes that report the antioxidant capabilities of pure compounds and/or complex mixtures of antioxidants are applied to a series of mono- and polyphenols, as well as to two wine (red and white) samples. These methodologies are based on the bleaching of a stable radical, the effect of the additive upon luminol chemiluminescence induced by peroxyl radicals, and the effect of the additive upon the bleaching of the fluorescence from a dye molecule. Widely different responses are obtained from the different methodologies. These differences are interpreted in terms of the different factors (stoichiometric factors and/or reactivities) that determines the indexes evaluated by these different methodologies.

The reaction between ABTS radical cation and antioxidants and its use to evaluate the antioxidant status of serum samples

The 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical cation can be generated by incubation of ABTS and 2,2'-azo-bis(2-amidinopropane) at 45 degrees Celsius. The ABTS radical cation is stable for several minutes at room temperature and reacts quantitatively and instantaneously with several antioxidants, such as Trolox, ascorbic acid, uric acid, cysteine, glutathione and bilirubin. In contrast, the ABTS radical cation reacts slowly with albumin. When serum is added to a solution of the ABTS radical cation, the bleaching of the radical follows biphasic kinetics, with a fast decay followed by a slow decay that takes place within several minutes. The fast decay is primarily due to uric acid, while the slow decay is related to the protein content of the sample. We propose that this procedure can provide an independent and simultaneous evaluation of the low molecular weight and protein antioxidants present in biological samples such as serum.

Spontaneous urinary visible luminescence: characteristics and modification by oxidative stress-related clinical conditions

Urinary visible luminescence is the result of the excretion of oxidized biomolecules and, as such, could provide a valuable index of systemic oxidative stress. The characteristics of the urinary luminescence that support this proposal are reviewed and the data obtained for patients with hyperthyroidism and children with Duchenne muscular dystrophy are also discussed. Enhanced urinary chemiluminescence was observed in both pathologies. A similar enhancement was obtained when the urinary luminescence of smokers was compared to that of non-smokers. The possibilities and limitations of this noninvasive methodology for the evaluation of systemic oxidative stress is critically evaluated.