Conjugable oxidation products assay

Figure 1. Chemical reaction steps in conjugable oxidation products (COP) assay.

Parr, L. J. and Swoboda, P.A.T. The assay of conjugable oxidation products applied to lipid deterioration in stored foods. J. Food Technol. 11, 1-12 (1976). 

It should be noted that both linoleic and a-linolenic acids form hydroperoxides that absorb UV radiation at 233 nm (i.e., the same wavelength as that of CDs). Furthermore, CDs are formed upon decomposition of hydroperoxides from a-linolenic acid, absorbing at 233 nm, whereas secondary oxidation products, particularly ethylenic diketones and a-unsatu-rated ketones, show a maximum absorbance at -268 nm. Carotenoid-containing oils may interfere in the assay by giving higher than expected absorbance values at 233 nm, due to the presence of double bonds in the conjugated structures of carotenoids. 

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. 

The uptake of PAH is influenced by the properties of both organic chemicals and plant species (Li et al., 2002). Once the organic xenobiotic enters the plant system, it is partitioned to different plant parts through translocation then, any number of reactions within the following series may occm oxidations, reductions or hydrolysis. However, PAH can be conjugated to other products, transported and segregated into vacuoles or bound to the cell wall material (Kamath et al., 2004) as Figure 2 shows, PHE was absorbed into the roots and transported to the stem of both assayed plants. 

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