tocopherol

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tocopherol:

see vitaminvitamin,
group of organic substances that are required in the diet of humans and animals for normal growth, maintenance of life, and normal reproduction. Vitamins act as catalysts; very often either the vitamins themselves are coenzymes, or they form integral parts of coenzymes.
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Tocopherol

 

any vitamin of the E group. Tocopherols are similar in chemical structure and are contained in large quantities in vegetable oils. Eight tocopherols that have vitamin activity are known; they are designated by the Greek letters et, β, 7, and so on. Although only a tocopherol, which is the most active, was formerly considered to be vitamin E, the term subsequently came to include the entire group of natural and synthetic tocopherols, which have the activity of α-tocopherol to varying degrees (α-tocopherol was discovered in the 1920’s and was extracted in pure form in 1936; P. Karrer synthesized it chemically in 1938).

Chemically, tocopherols are derivatives of chromane (a two-ring aromatic system) combined with an isoprenoid side chain. Tocopherols are transparent, oily liquids that are soluble only in organic solvents; they remain stable upon heating. They are widespread in nature but are synthesized only by plants. Animals and man obtain them from food. The highest tocopherol content is found in the germs of cereals and in the oils extracted from them. With a normal diet, E avitaminosis and hypovitaminosis occur rarely. Insufficient intake of vitamin E in experimental animals leads to sterility, muscular dystrophy, disorders of the central nervous system, increased hemolysis, and hypothyroidism. Tocopherol deficiency causes increased permeability or complete disintegration of biological membranes, including the membranes of the mitochondria and lysosomes. It is assumed that one of the functions of tocopherols in cells is to prevent the formation of peroxides from unsaturated fatty acids—that is, to play the role of natural antioxidants. In many cases, pathological symptoms that result from a tocopherol-deficient diet may be eliminated or prevented by certain antioxidants. The biochemical functions of tocopherols are also associated with tissue respiration processes.

Tocopherols are used in medicine to treat certain nervous, skin, gynecological, and cardiovascular disorders. Supplements added to animal feeds sharply reduce miscarriages in cows and eliminate motor disorders and paralyses in young birds. Tocopherols are used as natural antioxidants to stabilize vitamins A and D and to prevent vegetable oils from becoming rancid.

REFERENCE

Shaternikov, V. A. “Vitamin E.” In Vitaminy. Moscow, 1974. Chapter 5.

N. N. ZAITSEVA

tocopherol

[tə′käf·ə‚röl]
(organic chemistry)
Any of several substances having vitamin E activity that occur naturally in certain oils; α-tocopherol possesses the highest biological activity.
References in periodicals archive ?
They also had a 13% greater concentration of delta-tocopherol than those of group D, and 11% greater gamma-tocopherol concentration than those of group C.
Our message is that the vitamin E form of gamma-tocopherols, the most abundant form of vitamin E in the American diet, and delta-tocopherols, also found in vegetable oils, are beneficial in preventing cancers while the form of vitamin E, alpha- tocopherol, the most commonly used in vitamin E supplements, has no such benefit.
Preliminary research, largely in animals, suggests that natural vitamin E rich in gammatocopherol and, depending on the oil source, delta-tocopherol, may be more cancer preventive than alphatocopherol alone, which is the only form in synthetic vitamin E.
Vitamin E is found in food in four different forms: alpha-, beta-, gamma-, and delta-tocopherol.
One possible explanation for the ineffectiveness of vitamin E in clinical trials is that the trials used only alpha-tocopherol, whereas the vitamin E that occurs naturally in food consists of alpha-, beta-, gamma-, and delta-tocopherol.
Foods are stripped of their naturally occurring vitamin E's--alpha-, beta-, gamma-, and delta-tocopherol and--tocotrienols--and replaced by a whopping dose of just one of the eight, alpha-tocopherol.