rac-alpha-Tocopherol

Alpha-tocopherol is one of the eight forms of vitamin E and contains three methyl groups attached to the chromonal ring. Of all the forms of vitamin E, alpha-tocopherol is preferentially retained by the liver in animals and undergoes slower catabolism in cells. It has been found that alpha-tocopherol inhibits the activity of protein kinase C, an enzyme involved in cell proliferation and differentiation in smooth muscle cells, platelets, and monocytes. Other functions of alpha-tocopherol include gene regulation, up-regulation of mRNA or protein synthesis, and preventing the uptake of the harmful 7- hydroxycholesterol into cells.1 Although the antioxidant activity of alpha-tocopherol in vitro has long been established it appears that this may not be one of its primary functions in vivo.2 Vitamin E is involved in immune function, cell signaling, regulation of gene expression, and other metabolic processes. Vitamin E also inhibits lipid oxidation by donating its phenolic hydrogen to lipid free radicals.3 Antioxidant activity in vivo is normally alpha>beta>delta>gamma but the antioxidant potency may depend on various chemical and physical situations.4 The ortho-methyl substitution of the chroman head plays a vital role in the antioxidant activity of tocopherols while the phytyl tail is very important for proper positioning in the biomembranes. The antioxidant properties of vitamin E may delay memory loss in Down’s syndrome patients due to their protection from harmful oxidation caused by excess activity of superoxide dismutase. Vitamin E is only naturally produced in plants, algae, and some cyanobacteria and is therefore an important dietary nutrient for humans and animals.