Vitamin E
In 1922, H. Evans and K. Bishop discovered vitamin E in green leafy vegetables and wheat germ while performing growth experiments with laboratory rats. Vitamin E refers to a mixture of several related fat-soluble compounds known as tocopherols. Vitamin E is a generic descriptor for all tocol [2-methyl-2-(4,8,12-trimethyltridecyl)chroman-6-ol(I, R1 = R2 = R3 = H)] and tocotrienol derivatives exhibiting qualitatively the biologi- cal activity of a.-tocopherol. Chemically related to sex hormones, vitamin E is stored primarily in muscle and adipose (fat) tissue, and to a lesser ex- tent the reproductive organs, within the body. Found largely in plant materials, including wheat germ, vegetable oils, nuts, seeds, whole grains, and dark green leafy vegetables, this vitamin tends to be resistant to heat, light, and acid exposure but is unstable in the presence of oxygen. Other sources of vitamin E include meats, milk, and eggs. The a.-tocopherol [2,5, 7,8-tetramethyl-2-(4',8',12'-trimethyltridecyl)-6-chromanol; C29H50O2] molecule is the most potent of the tocopherols. Vitamin E is absorbed from the intestines and subsequently delivered to the tissues and liver, and it easily accumulates in cellular membranes, fat deposits, and other lipoproteins within the bloodstream. Its major function is to act as an antioxidant in preventing the peroxidation of polyunsaturated membrane fatty acids and cholesterol by scavenging free radicals and molecular oxy- gen. Thus, vitamin E, along with the antioxidant capabilities of vitamin C, assists in preventing oxidative damage to cell membranes and atherosclerosis. Vitamin E also has been used to promote fertility.
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