Selenium antioxidant properties

There are numerous synthetic and natural compounds called antioxidants which regulate or block oxidative reactions by quenching free radicals or by preventing free-radical formation. Vitamins A, C, and E and the mineral selenium are common antioxidants occurring naturally in foods (104,105). A broad range of flavonoid or phenoHc compounds have been found to be functional antioxidants in numerous test systems (106—108). The antioxidant properties of tea flavonoids have been characterized using models of chemical and biological oxidation reactions. 

Pure selenium deficiency, wilhoui concurrent vitamin E deficiency, is not generally seen except in animals on experimental diets. In China, selenium deficiency in humans has been associated w ith Keshan disease, a cardiomyopathy seen in children and in women of child-bearing ages, and Kashin-Beck disease, an endemic osteoarthritis in adolescents. Selenium may have amicarcinogenic effects possibly because of the antioxidant properties of selenium compounds. 

Although inorganic selenium does not have antioxidant properties, selenium has an important role in cellular antioxidant defenses as a necessary component of selenoproteins. Selenium is incorporated into selenoproteins as selenocysteine. The glutathione (GSH) peroxidases are the best-characterized selenoproteins, although other circulating selenoproteins also have antioxidant functions. 

The major functions of selenium can be attributed to its antioxidative properties and its role in the regulation of thyroid hormone metabolism. Selenium is important as a nutritional factor, and the US Food and Nutrition Board s Committee on Dietary Allowances has, perhaps somewhat arbitrarily, proposed a recommended daily intake of 50-200 micrograms/day. 

Selenium deficiency in experimental animal studies is exacerbated by vitamin E depletion. The antioxidant properties of tocopherol and glutathione peroxidase are similar and can to some extent overlap, although this is highly species dependent. °... 

It would be unusual for humans not to obtain 70 milligrams, the minimum daily requirement, of selenium in their diet, since selenium is found in seafood, meat, and grains. Selenium has antioxidant properties as well as beneficial protein functions in the blood and certain tissues. 

The results of animal experiments suggest that selenium may both protect against some cancers (thought to be associated with its antioxidant properties) whilst causing others. However, there is no evidence that selenium is carcinogenic to humans. The ACGIH TLV for selenium is 0.2 mg/m. ... 

Diselenolane-3-pentanoic acid, in which the sulphur atoms of a-lipoic acid are replaced with selenium, displayed markedly different antioxidant properties when compared to a-lipoic acid (Matsugo et al. 1997). l,2-Diselenolane-3-pentanoic acid was unable to inhibit protein oxidative modification of human low density hpoprotein and bovine serum albumin induced by copper ion or hydroxyl radical, whereas a-lipoic acid showed significant protection. However, l,2-diselenolane-3-pentanoic acid was able to inhibit the formation of Hpid peroxidation products in low density hpoprotein after oxidation by copper, while a-hpoic acid did not. 

About 300 individual compounds with antimutagenic properties are known. The frequency of mutations can be reduced by some amino acids (arginine, histidine, methionine, cysteamine etc ), vitamins and provitamins (a-tocopherol, ascorbic acid, retinol, p-carotene, phylloquinone, folic acid), enzymes (peroxidase, NADPH oxidase, glutathione peroxidase, catalase), complex compounds of plant and animal origin, chemical substances with antioxidant properties (derivatives of gallic acid, ionol, oxypyridines, selenium salts and others). 

The opinion offered is to add additional focus, mainly the potential therapeutic benefit that can be derived from cascade regulation of the inducible nitric oxide synthase (iNOS), NO, cyclooxygenase (COX-2), and hypoxia-inducible factor la (HIF-la) by non-toxic but a biologically effective and selective small multi-targeted molecule, selenium, with considerable antioxidant properties. 

Rubber. The mbber industry consumes finely ground metallic selenium and Selenac (selenium diethyl dithiocarbamate, R. T. Vanderbilt). Both are used with natural mbber and styrene—butadiene mbber (SBR) to increase the rate of vulcanization and improve the aging and mechanical properties of sulfudess and low sulfur stocks. Selenac is also used as an accelerator in butyl mbber and as an activator for other types of accelerators, eg, thiazoles (see Rubber chemicals). Selenium compounds are useflil as antioxidants (qv), uv stabilizers, (qv), bonding agents, carbon black activators, and polymerization additives. Selenac improves the adhesion of polyester fibers to mbber. 

Selenium is a significant component of the enzymatic system of the glutafion for antioxidant protection. It is included in the composition of 200 enzymes engaged in different biochemical reactions, demonstrates the immune-tropic, antiteratogenic and anticancer properties, betters the functional state of muscles, especially myocarditis, and takes part in hormones synthesis of the thyroid gland. Selenium s deficit in soil is the cause of hearth deficiency in endemic zones. 

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