Vitamin E activity

They are widely distributed in vegetable lipids, and in the body fat of animals, though animals cannot synthesize them. They have vitamin E activity and can protect unsaturated lipids against oxidation. Four are found naturally ... 

Label claims for tocopherol levels in preparations can be based on milligrams or International Units. Only the RRR or all-rac-International Units ate also used in some reference books and compendia, eg. Food Chemicals Codex (40,53), which is of particular importance for specifications for food fortification. 

Several different tocopherols are known to have vitamin E activity, but a-tocopherol, a trimethyltocol (Figure 12.9) is the most biologically active. Other less potent forms are the /3-, y- and S-tocopherols, which contain fewer methyl groups. They all have antioxidant properties and a deficiency results in a lack of protection of the unsaturated fatty acids in the membrane phospholipids against oxidation by molecular oxygen. 

AOAC official method 992.03. Vitamin E activity (all-rac-a-tocopherol) in milk-based infant formula. Liquid chromatographic method. In MP Bueno, ed. Official Methods of Analysis of AOAC International. 16th ed. Arlington, VA AOAC International, 1995, p. 50-4-50-5. 

Vitamin E is an effective scavenger of lipid peroxy radicals and is efficient at protecting unsaturated fatty acids against lipid peroxidation. The chemistry of vitamin E is rather complex as there are eight compounds, four tocopherols and four tocotrienols, which exhibit vitamin E activity. The relative bioactivity of the various compounds varies considerably, from 1.0 for a-tocopherol to 0.03 for 8-tocopherol. In milk, a-tocopherol accounts for virtually all of vitamin E, although very small amounts of (3-tocopherols and y-tocopherols are present. Also, the concentration of a-tocopherol in milk fat varies widely, with the level in samples of commercial butter ranging from 18 to 35 pg/g fat (MAFF, 1999). These concentrations equate to a low level of vitamin E bioactivity, 0.025 to 0.05 IU/g fat. 

Manufacturers also commonly convert the phenol form of the vitamins (with a free hydroxyl group) to esters, using acetic or succinic acid. The fortification of foods and feeds with oc-tocopherol esters is common because they are more stable and provide vitamin E activity when consumed. 

Until the year 2000, all tocopherols and tocotrienols were considered to have the same biological activity of a-tocopherol, i.e. vitamin E activity. a-Tocopherol was considered to have the highest activity followed by 3- and y-tocopherol with 50% and 10% of the activity of a-tocopherol. Nutrition data was often reported in a-tocopherol equivalents (a-TE) that were expressed as follows (McLaughlin and Weihrauch, 1979 Schakel et al., 1997) amounts of a-TE were calculated as mg of a-tocopherol, 0.5 x mg of 3-tocopherol, 0.1 x mg... 

Soybean tocopherols are the major source of natural fat-soluble antioxidants and Vitamin E. The Vitamin E activity of natural d-cx-tocopherol is much greater that that of synthetic Vitamin E, which is a mixture of eight stereoisomers (203). Phytosterols are used as raw materials for over 75% of the world s steroid production. The more recent application of phytosterol, phytostanol, and their fatty acid esters in margarine and table spreads is based on the blood cholesterol-lowering effect of these compounds (204,205). The recent development of functional foods containing phytosterols has been reviewed by Hollingsworth (206) and Hicks and Moreau (207). 

Aside from their antioxidant activity, tocopherols also have an important Vitamin E activity, generally expressed as ... 

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