Status, antioxidant assessment

This assay has been used to determine the antioxidant activity of common vegetables, fruits including apples and strawberries (Eberhardt and others 2000 Chu and others 2002 Sun and others 2002 MacLean and others 2003 Meyers and others 2003), and fruit juices (Lichtenthaler and Marx 2005). No studies have yet reported the application of TOSC assay for the assessment of in vivo antioxidant status. 

Analytical applications of the malonaldehyde and Maillard fluorescent product formation to assessment of abuse status of oxidizing oils, relative effectiveness of antioxidants, and sugar-amine browning potential are available. 

G6. Ghiselli, A., Serafini, M., Natella, F., and Scaccini, C., Total antioxidant capacity as a tool to assess redox status Critical view and experimental data. Free Radio. Biol. Med. 29, 1106—1114... 

Overall antioxidant status, as opposed to specifically vitamin E stams, can be assessed by a variety of measures of lipid peroxidation, including measurement of ... 

The assays most widely employed are the measurement of thiobarbituric acid-reactive species (TBARS) and the formation of conjugated dienes, markers of lipid peroxidation [31-33] the determination of advanced oxidation protein products (AOPP), a marker of protein oxidation, and of advanced glycation end-products (AGE) [34-37] the measurement of erythrocyte antioxidant potential [38]. Of particular importance is the isoprostanes determination, since these compounds are formed by the free radical catalysed peroxidation of arachidonic acid, which is independent of the cyclooxygenase enzyme, giving rise to stable compounds, measurable in urine [39]. As recently assessed in a Workshop on markers of oxidative damage and antioxidant protection [40], currently available methods for the determination of antioxidant and redox status are not yet generally suitable for routine clinical applications, essentially for the lack of standardized tests. 

Panayiotidis, M. and Collins, A.R., Ex vivo assessment of lymphocyte antioxidant status using the Comet assay. Free RaJic. Res., 21, 533, 1997. 

Glutathione reductase has selenium at the catalytic site, as a selenocysteine residue (section 11.15.2.5) this explains the role of selenium as an antioxidant nutrient. Glutathione reductase is a flavoprotein, and is especially sensitive to riboflavin (vitamin B ) depletion as discussed in section 11.7.4.1, measurement of glutathione reductase is used as a means of assessing riboflavin status. 

An alternative method of assessing functional antioxidant status, again one that is affected by both vitamin E and other antioxidants, is by measuring the exhalation of pentane arising from the metabolism of the peroxides of 0)-6 polyunsaturated fatty acids or ethane from peroxides of co-3 polyunsaturated fatty acids. 

The applications surveyed in Tables 4 through 9 illustrate the general principles of vitamin E assays outlined in I.E. 1. Specifically, each matrix puts a different emphasis on the E vitamers to be determined. Thus, in serum/plasma a-tocoph-erol is clearly the main compound of interest. Accordingly, leversed-phase chromatography with UV detection is the indicated technique for this purpose. In addition, as part of the assessment of the antioxidant status of humans, tocopher-ols are determined concurrently with retinoids (retinol, retinyl palmitate) and carotenoids (particularly p-carotene). a-Tocopherol is also the principal target compound in erythrocytes and platelets but here, predictably, the quantitation of a-tocopherolquinone may also be meaningful as an indicator of oxidative stress (7). The need to assay this minor constituent in turn justifies coulometric detection. The analysis of tissues is complementary to that of plasma and red blood cells and mainly concerns the determination of a-tocopherol as well as retinoids, carotenoids, and ubiquinones (Table 6). 

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