Vitamin E as antioxidants

The use of vitamins in humans consumes ca 40% of vitamins made worldwide. The majority of the vitamins, particularly in countries outside the United States, are used in animal husbandry. It is well estabUshed (21) that vitamins are critical to animal productivity, especially under confined, rapid growth conditions. Newer information (22) has shown that vitamin E added to catde feed has the additional effect of significantly prolonging beef shelf life in stores. Additional appHcations of vitamins exist. A small but growing market segment involves cosmetics (qv) (23). The use of the chemical properties of the vitamins, particularly as antioxidants (qv) in foods and, more recently, in plastics (vitamin E (24)), has emerged as a growing trend. 

The mechanism of prooxidant effect of a-tocopherol in aqueous lipid dispersions such as LDLs has been studied [22], This so-called tocopherol-mediated peroxidation is considered in detail in Chapter 25, however, in this chapter we should like to return once more to the question of possible prooxidant activity of vitamin E. The antioxidant effect of a-tocopherol on lipid peroxidation including LDL oxidation is well established in both in vitro and in vivo systems (see, for example, Refs. [3,4] and many other references throughout this book). However, Ingold et al. [22] suggested that despite its undoubted high antioxidant efficiency in homogenous solution a-tocopherol can become a chain transfer agent in aqueous LDL... 

Vitamin E, a natural antioxidant, is essential for growth, disease prevention, tissue integrity and reproduction in all fauna. Natural vitamin E, as it occurs in plants, consists mainly of a-tocopherol (III, R = H) with minor amounts of y-tocopherol (IV), although this ratio can vary as for example in the vegetable oil composition shown in Fig. 5a. In animal husbandry, such as dairy farms or cattle feed lots, the stock diets are commonly supplemented with vitamin E, because processed grain-based cereal fodder, hay, and silage are deficient in vitamin This results in higher levels of a-tocopherol... 

Many food constituents including peppermint, spearmint, and tea contain 4-phenylpyridine, another close relative.775 While administration of L-dopa to replace the deficit in the basal ganglia seemed the ideal treatment for Parkinson disease, mental deterioration is not stopped, and for some patients the drug loses its effectiveness in about three years. Based on the new information about MPTP, treatment with extra vitamin E as an antioxidant along with an MAO inhibitor is being tested as a way to prevent further damage from environmental toxins.776... 

Foods are supplemented with vitamin A in the form of standardized preparations of synthetic fatty acyl esters, nowadays chiefly retinyl palmitate. The preparations are available commercially as either dilutions in high-quality vegetable oils containing added vitamin E as an antioxidant or as dry, stabilized beadlets in which the vitamin A is dispersed in a solid matrix of gelatin and sucrose or gum acacia and sucrose. The oily preparations are used to supplement fat-based foods such as margarines the dry preparations are used in dried food products such as milk powder, infant formulas, and dietetic foods (24). 

T Byers, G Perry. Dietary carotenes, vitamin C, and vitamin E as protective antioxidants in human cancers. Ann Rev Nutr 12 139-159, 1992. 

Packer, L. and Valacchi, G., Antioxidants and the response of skin to oxidative stress vitamin E as a key indicator, Skin Pharmacol. Appl. Skin Physiol., 15, 282, 2002. 

Reduction of the Vitamin E Radical by Ascorbate Asdiscussed in Section 4.3.1, one of the major roles of vitamin E is as a radical-trapping antioxidant in membranes and lipoproteins. a-Tocopherol reacts with lipid peroxides forming the a-tocopheroxyl radical, which reacts with ascorbate in the aqueous phase, regenerating a-tocopherol, and forming monodehydroascorbate. Vitamin C may have a vitamin E-sparing antioxidant action, coupling lipophilic and hydrophilic reactions. 

A variety of antioxidants are added to food including vitamin C and vitamin E. Two antioxidants that may occasionally cause problems are butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA), which have been associated with symptoms such as eczema, skin rash, runny nose, wheezing, headache, chest pain, flushing of the skin, and red eyes. At the same time, it has been reported that these antioxidants may be helpful in preventing cancer, possibly by removing damaging free radicals such as reactive oxygen and its by-products from fatty acids. 

Noguchi, N., Gotoh, N., and Niki, E. (1998). Action of vitamin E as an antioxidant against oxidative modification of low-density lipoprotein. Biofactars 7,41-50. 

Without doubt vitamin E is the most important lipid-soluble chain-breaking antioxidant in the human body. It is able to interact with lipid peroxyl radicals and is also able to react with singlet oxygen. The role of vitamin E as an antioxidant in vivo has been established several times by measuring tissue lipid peroxidation in vitamin E-deficient or in vitamin E-supplemented animals. 

Ernster L, Forsmark P, Nordenbrand K (1992) The mode of action of lipid-soluble antioxidants in biological membranes. Relationship between the effects of ubiquinol and vitamin E as inhibitors of lipid peroxidation in submitochondrial particles. J Nutr Sci Vitaminol (Tokyo) Sp. Issue, pp 548-551... 

Vitamin E, as an antioxidant choice for Polyethylene Medical Packaging, Anthony O Driskoll, Ciba speciality Chemical Inc. Basel, Switzerland. 

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