Antioxidant properties oxygen radicals

Some colors are nutrients in their own right, and they have antioxidant properties that are beneficial to health. Beta-carotene, annatto, saffron, and turmeric all have these good properties in addition to their color. In fact, the same chemistry that makes them absorb light also helps them to absorb and neutralize dangerous oxygen free radicals in the body. 

Thus the competition between stimulatory and inhibitory effects of NO depends on the competition between two mechanisms the direct interaction of NO with free radicals formed in lipid peroxidation and the conversion of NO into peroxynitrite or other reactive NO metabolites. Based on this suggestion, Freeman and his coworkers [42-44] concluded that the prooxidant and antioxidant properties of nitric oxide depend on the relative concentrations of NO and oxygen. It was supposed that the prooxidant effect of nitric oxide originated from its reaction with dioxygen and superoxide ... 

The lung also possesses nonenzymatic antioxidants such as vitamin E, beta-carotene, vitamin C, and uric acid. Vitamin E is lipid-soluble and partitions into lipid membranes, where it is positioned optimally for maximal antioxidant effectiveness. Vitamin E converts superoxide anion, hydroxyl radical, and lipid peroxyl radicals to less reactive oxygen metabolites. Beta-carotene also accumulates in cell membranes and is a metabolic precursor to vitamin A. Furthermore, it can scavenge superoxide anion and react directly with peroxyl-free radicals, thereby serving as an additional lipid-soluble antioxidant. Vitamin C is widely available in both extracellular and intracellular spaces where it can participate in redox reactions. Vitamin C can directly scavenge superoxide and hydroxyl radical. Uric acid formed by the catabolism of purines also has antioxidant properties and primarily scavenges hydroxyl radical and peroxyl radicals from lipid peroxidation. 

In addition to demonstrating the occurrence of acute post-traumatic oxygen radical reactions and their association with pathophysiological events, the establishment of their importance, relative to other factors, is ultimately dependent upon a demonstration that by interrupting them, chronic neurological recovery can be enhanced. Thus, attempts have been made to show that early treatment of spinal-cord injured animals with bonafide antioxidants or agents with antioxidant properties can beneficially affect sensory and motor recovery. 

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. 

Interactions between lycopene and oxygen radicals can be considered second-order rate reactions. Lycopene is less efficient, and electron transfer is observed in both directions (Conn et al., 1992). The potential reduction of the antioxidant property of lycopene is related to the formation of the superoxide radical anion, CV (Palozza, 1998). 

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