Vitamin E

Literature References: General term referring to 2 groups of closely related 6-chromanol derivatives known as tocopherols and tocotrienols, each comprised of four homologs (a, b, g, and d) that differ in the position and number of methyl substituents on the chromanol ring. All eight compounds are found in nature, occurring as the R,R,R- or R,Z,Z- forms. Dietary sources include vegetable oils and green leafy vegetables. a-Tocopherol, q.v., is the most abundant and has the greatest bioactivity. Vitamin E acts as an antioxidant to prevent free radical damage to tissues and unsaturated lipids; also thought to stabilize membrane structures. Deficiency in healthy humans is rare and is characterized by peripheral neuropathy and spinocerebellar ataxia. Discovery as nutritional factor required for normal reproduction in animals: H. M. Evans, K. S. Bishop, Science 56, 650 (1922). Comparison of bioactivities of tocopherols and tocotrienols: T. Leth, H. Sondergaard, J. Nutr. 107, 2236 (1977). HPLC determn in infant formula: B. R. Mendoza et al., J. Chromatogr. A 1018, 197 (2003). Review of chemistry, nomenclature and activity: W. Friedrich, "Vitamin E" in Vitamins (Walter de Gruyter, Berlin, 1988) pp 217-283. Review of biological occurrence and functions: R. S. Parker, Adv. Food Nutr. Res. 33, 157-232 (1989); of nutritional requirements: E. E. J. Valk, G. Hornstra, Int. J. Vitam. Nutr. Res. 70, 31-42 (2000); of metabolism: F. Brigelius-Flohé, M. G. Traber, FASEB J. 13, 1145-1155 (1999). Review of antioxidant functions and role in membranes: X. Wang, P. J. Quinn, Prog. Lipid Res. 38, 309-336 (1999); of non-antioxidant roles: A. Azzi, A. Stocker, ibid. 39, 231-255 (2000).