Know More About Vitamin E

By Author: Abinash Mallick
Total Articles: 21
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Vitamin E refers to a group of ten lipid-soluble compounds that include both tocopherols and tocotrienols.[1] Of the many different forms of vitamin E, γ-tocopherol is the most common in the North American diet.[2] γ-Tocopherol can be found in corn oil, soybean oil, margarine, and dressings.[3][4] α-tocopherol, the most biologically active form of vitamin E, is the second-most common form of vitamin E in the diet. This variant can be found most abundantly in wheat germ oil, sunflower, and safflower oils.[4][5] As a fat-soluble antioxidant, it stops the production of reactive oxygen species formed when fat undergoes oxidation.[6][7][8] Regular consumption of more than 1,000 mg (1,500 IU) of tocopherols per day[9] may be expected to cause Hypervitaminosis E, with an associated risk of vitamin K deficiency and consequently of bleeding problems.

The ten forms of vitamin E are divided into two groups; five are tocopherols and five are tocotrienols. They are identified by prefixes alpha- (α-), beta- (β-), gamma- (γ-), delta- (δ-), and epsilon (ε-). Natural tocopherols occur in ...
... the RRR-configuration only. The synthetic form contains eight different stereoisomers and is called 'all-rac'-α-tocopherol.

α-Tocopherol is an important lipid-soluble antioxidant. It performs its functions as antioxidant in the glutathione peroxidase pathway,[11] and it protects cell membranes from oxidation by reacting with lipid radicals produced in the lipid peroxidation chain reaction.[7][12] This would remove the free radical intermediates and prevent the oxidation reaction from continuing. The oxidized α-tocopheroxyl radicals produced in this process may be recycled back to the active reduced form through reduction by other antioxidants, such as ascorbate, retinol or ubiquinol.[13] However, the importance of the antioxidant properties of this molecule at the concentrations present in the body are not clear and the reason vitamin E is required in the diet is possibly unrelated to its ability to act as an antioxidant.[14] Other forms of vitamin E have their own unique properties; for example, γ-tocopherol is a nucleophile that can react with electrophilic mutagens.

Compared with tocopherols, tocotrienols are sparsely studied.[16][17][18] Less than 1% of PubMed papers on vitamin E relate to tocotrienols.[19] The current research direction is starting to give more prominence to the tocotrienols, the lesser known but more potent antioxidants in the vitamin E family. Some studies have suggested that tocotrienols have specialized roles in protecting neurons from damage[19] and cholesterol reduction[20] by inhibiting the activity of HMG-CoA reductase; δ-tocotrienol blocks processing of sterol regulatory element‐binding proteins (SREBPs).

Oral consumption of tocotrienols is also thought to protect against stroke-associated brain damage in vivo.[21] Until further research has been carried out on the other forms of vitamin E, conclusions relating to the other forms of vitamin E, based on trials studying only the efficacy of α-tocopherol, may be premature.

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