Tocopherols, tocotrienols and vitamin

The general biochemistry of vitamin E has been extensively reviewed (Azzi and Stocker, 2000 Brigelius Flohe and Traber, 1999 Stone and Papas, 1997). This review will primarily focus on the biochemical and health aspects of vitamin E in food. It is important, however, to contrast the chemical forms of vitamin E found in plants with that found in mammals and in dietary supplements. Vitamin E is often equated with a-tocopherol, which is the primary lipid-soluble antioxidant in human plasma, and the most potent form in protecting the fetuses of pregnant female rats from death and resorption. We will explore the hypothesis that vitamin E supplements containing a chemical distribution of tocopherols and tocotrienols similar to that found in plant oils may be superior to supplements containing only a-tocopherol or a-tocopheryl acetate. Finally, this review will summarize the very recent application of nutritional genomics to vitamin E synthesis in plants. 

---

Heinonen, M. and Piironen, V. 1991. The Tocopherol, Tocotrienol, and Vitamin E Content of the Average Finnish Diet. Int. J. Vitam. Nutr. Res. 61 27-32. 

Oil extracted from rice bran and com fiber is especially rich in tocopherols, tocotrienols and sterols. Extraction of these valuable compounds is remarkably enhanced by heat pretreatment (Lane et al., 1999). For example, the level of extracted y-tocophcrol increased from 0.3% to 3.6% by subjecting com fiber to temperatures of 100-175°C (Moreau et al., 1999). Tocopherol- and tocotrienol-rich oils may be used as such as important sources of vitamin E, or the vitamers can be purified from them following the same protocols as above. 

The fat-soluble vitamins can be divided into four different groups, based on biological activity vitamin A (retinol and carotenoids), vitamin D (chole-calciferol and ergocalciferol), vitamin E (tocopherols and tocotrienols), and vitamin K (phylloquinone and menaquinone), all of which may be present in a munber of closely related forms. 

Puah C.W., Choo Y.M., Ma A.N., Chuah H.C. The effect of physical refining on palm vitamin E. (tocopherol, tocotrienol and tocomo-noenol). American Journal of Applied Sciences, 4 374-377 (2007). 

Several comprehensive reviews have been published on the existing chromatographic methods for the analysis of lipophilic antioxidants (tocopherols, tocotrienols, and carotenoids) in various sample matrices (Abidi, 2000 Aust et al., 2001) on electrochemical approaches in the sensing of natural or biological antioxidants and antioxidant capacity (mainly polyphenols and vitamins C and E) using cyclic voltammetry on flow injection analysis (FIA) with amperometric detection in food and biological samples (Blasco et al., 2007) and on chemiluminescence (CL) and fluorescence (FL) methods for the analysis of oxidative stability, antioxidant activity, and lipid hydroperoxide content in edible oils (Christodouleas et al., 2012). 

Szydlowski, J. (2002). Phase Behaviour of Room Temperature Ionic Liquid Solutions An Unusually Large Co-Solvent Effect in (Water Plus Ethanol). Physical Chemistry Chemical Physics, Vol. 4, No. 10, pp. 1701-1703, ISSN 1463-9076 Ng, M. H., Choo, Y. M., Ma, A. N., Cheng, H. C. Hashim, M. A. (2004). Separation of Vitamin E (Tocopherol, Tocotrienol, and Tocomonoenol) in Palm Oil. Eipids, Vol. 39, No. 10, pp. 1031-1035, ISSN 0024-4201... 

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. 

Wehmeyer et al. (1969) published results on the content of B vitamins (thiamine, riboflavin, and nicotinic acid), vitamin C, and p-carotene and foimd that the morama bean is a good source of both B vitamins and vitamin C, but a poor source of p-carotene. Holse et al. (2010) investigated the content of the eight vitamin E isomers and found that the vitamin E composition in morama beans is dominated by y-tocopherol with 59-234 ng/g, followed by a- and p-tocopherols with 14- 8 gg/g and 1.1-3.3 ng/g, respectively. Eurthermore, traces of 8-tocopherol as well as p- and y-tocotrienols were present in some samples. The remaining two tocotrienols (a- and 8-) were not present in the beans. The presence of a-, p-, and y-tocopherols in the morama bean was also foimd by Mitei et al. (2009) who examined morama oil and by Dubois et al. (1995) who examined two samples of T.fassoglense. 

Research Council defined 1 mg of a-tocopherol as 1 unit of a-TE (mg x 1). The activities as a-TE of other vitamers were (3-tocopherol, mg x 0.5 y-tocopherol, mg xO. 1 8-tocopherol, mg x 0.03 a-tocotrienol, mg x 0.3 and (3-to-cotrienol, mg x 0.05. The activities of y- and 8-tocotrienol were undetectable. The Recommended Dietary Allowances (RDAs) are only based on intake of the 2R-stereoisomeric forms of a-tocopherol (RRR-, RSR-, RRS-, and RSS-tocopherol) from food, fortified food, and vitamin supplements (Food and Nutrition Board, 2000). The 2S-stereoisomeric forms of a-tocopherol and the other tocopherols ((3-, y-, and 5-tocopherol) and tocotrienols are not used to estimate the RDAs. 

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... 

Muller, L. Theile, K. Bohm, V. 2010. In vitro antioxidant activity of tocopherols and tocotrienols and comparison of vitamin E concentration and lipophilic antioxidant capacity in human plasma. Mol. Nutr. Food Res. 54 731-742. 

The affinities of a-tocopherol transfer protein for the other vitamers (relative to l l l -o -tocopherol = 1, and based on competition with RRR-oc-toco-pherol) are /8-tocopherol, 0.38 y-tocopherol, 0.09 5-tocopherol, 0.02 SRR-oc-tocopherol, 0.11 and a-tocotrienol, 0.09. As a result, whereas the hedf-life of a-tocopherol in the circulation is 48 hours, that of /3- emd y-tocopherol (emd the other vitamers) is only of the order of 13 to 15 hours. In patients with attixia and vitamin E deficiency caused by a genetic lack of a-tocopherol tremsfer... 

Palm oil, both crude and refined, is a rich source of vitamin E, which consists of a mixture of tocotrienols and tocopherols. A technology for the preparation of a locotrinol-rich fraction (TRF) from palm fatty acid distillate has been developed. Palm Vitee (TRF in superolein and encapsulated) has been evaluated in a number of nutritional studies in both animals and humans. The nutritional properties of TRF are as follows ... 

---