Oxygen radical absorbance capacity values

In a test-tube method called ORAC (oxygen radical absorbance capacity), freeze-dried agaf powder scored the highest ORAC level yet determined among fruits, a result that incited a storm of marketing literature declaring that a af products have the highest antioxidant health value of any food. The bad news is that there are limitations to that ORAC value as we know it (see Appendix A). Antioxidant properties determined in test tubes are unlikely to have the same antioxidant roles in the human body. Further, the comparisons of aqa ORAC with other fruits are not valid since the fruit preparations were not identical across all tests. 

Free radical scavengers are molecules that react with free radicals and render them harmless. There is considerable interest in foods rich in vitamins A, C and E (Chapters 51, 52 and 56) and those with an abundance of phytochemicals such as the phenols, polyphenols and flavonoids, which have high oxygen radical absorbance capacity (ORAC) values. These are potent free radical scavengers that are thought to reduce the risk of several chronic degenerative disorders. 

The antioxidant capacity of red grapes was evaluated in HepG2 (human hepatocellular liver carcinoma) cells and positively correlated with the total phenolic content and the oxygen radical absorbance capacity (ORAC) values of grape extracts. Results suggest that increasing fruit consumption is a suitable strategy to counteract oxidative stress [106]. 

Figure 5 Correlation between total phenolics (milligrams gallic acid equivalents/ 100 g and measurements of antioxidant activity, TEAC, FRAP, and ORAC, of fruit and vegetables extracts. The correlation coefficients (r) and the correspondent significance values (P) are indicated. TEAC, Trolox equivalent antioxidant capacity FRAP, ferric reducing ability of plasma ORAC, oxygen radical absorbance capacity.

Furthermore, the oxygen radical absorbance capacity (ORAC) assay has been used to evaluate the total antioxidant activity of polyaniline/ PE blends by monitoring the oxidation of fluorescein, a fluorescence probe, into non-fluorescent products by the peroxy radicals generated in the analysis mixture [3]. The relative ORAC values, converted to trolox equivalents, indicated the antioxidant efficacy of the blend samples. As shown in Figure 4.6, the ORAC values and hence the total antioxidant activity, of the blend samples increased with increasing polyaniline content in the blend. 

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