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Essay on Vitamin E
- Historical Review of Vitamin E
- Properties of Vitamin E
- Distribution of Vitamin E
- Function and Mode of Action of Vitamin E
- Deficiency of Vitamin E
Essay # 1. Historical Review of Vitamin E:
Since 1922 effects of vitamin E deficiency was studied in rats. When Bishop and Evans announced the existence of a substance X, the absence of which in the diet, results failure in the reproductive capacity of rats.
In 1936 Evans and Emerson isolated and synthesised vitamin E from the unsaponifiable fraction of wheat-germ oil which was found to be a mixture of three closely related compounds. A fourth was discovered in 1955, and recently two other compounds have been detected.
There are three varieties of tocopherol—(Tokos = child-birth, Phero = to bear, suffix Ol signifies alcohol)—α, β and γ. They are unsaturated alcohols. The most active compound is α-tocopherol, C29H50O2 β-tocopherol contains one less methyl group—C28H48O2. The composition of ϒ-tocopherol is the same as β-tocopherol. Recently γ – tocopherol and few more compounds have been isolated.
Essay # 2. Properties of Vitamin E:
They are soluble in fat and fat- solvents, heat-stable and exists naturally as a yellow oil. These tocol types of vitamin can stand cooking and they are extraordinarily stable in heat in the absence of oxygen, and withstand acids at elevated temperatures.
The vitamin activity is destroyed by ultraviolet light as well as by oxidation. They are excellent antioxidants. They prevent other vitamins present in food (e.g., vitamin A) from oxidative destruction. Free tocopherols and their ester are readily absorbed from the small intestine. Bile acids are necessary for absorption.
Essay # 3. Distribution of Vitamin E:
This vitamin remains in blood in the α-lipoprotein fraction. The average blood level is 1.0 mgm per 100 ml of serum.
i. Animal Sources:
Egg, milk, fish and muscles contain this vitamin.
ii. Vegetables Sources:
It is abundantly present in vegetable seed oils, especially wheat, soya-bean, corn and leafy vegetables. It has also been synthetically prepared.
Essay # 4. Function and Mode of Action of Vitamin E:
i. Tocopherols have got anti-oxidative effects and prevent unwanted oxidation in the body.
ii. Required for the normal reproductive function in rats.
iii. Essential for normal function of muscle. Deficiency produces muscular dystrophy.
iv. The increased uptake of O2 in the dystrophic muscles produced by the deficiency of this vitamin is prevented by administration of tocopherols.
v. Peroxidation and brown pigmentation due to formation of highly unsaturated fatty acids are prevented by the tocopherols.
vi. Massive hepatic necrosis produced by deficiency of sulphur-containing amino acids and selenium are also prevented by tocopherols.
vii. The development of encephalomalacia in chicks (cerebellar disorder) and exudative diathesis is due to deficiency of vitamin E and is relieved by administration of tocopherols.
viii. It acts as a cofactor in the electron transfer system operating between cytochromes b and c.
Essay # 5. Deficiency of Vitamin E:
In the female rats implantation of the ovum occurs, but after some time the foetus dies (resorption sterility). The changes however are reversible. Vitamin E therapy is of some promise in the prevention of habitual miscarriage in women. In rats there are increased metabolic rates, development of muscular dystrophy, electrocardiographic changes in cardiac muscle indicating degenerative lesions.
Excessive intake does not increase fertility but may cure sterility. Male rats show atrophy of testes and spermatogenic failure and both of which are irreversible in prolonged deficiency. Erythrocytes are affected in vitamin E deficiency. Combined deficiency of this vitamin and selenium (Se) produces hepatic necrosis. Goat, sheep and rabbit do not show deficiency signs.
Probably they may synthesise sufficient quantities. Vitamin E also remains stored in the tissues. It has been observed that members of the coenzyme Q group have protective action against vitamin E deficiency in some species of animals.
Average daily intake through normal diet is about 15 to 20 mgm, which satisfies the requirement.