ABSTRACT
The term "vitamin E" is now used to describe all tocopherol and tocotrienol derivatives that exhibit the general physiological activity of alleviating any symptoms related with vitamin E deficiency. Tocopherols and tocotrienols are present in various components of human diet. Tocopherols are found in polyunsaturated vegetable oils and in the germ of cereal seeds, whereas tocotrienols are found in the aleurone and subaleurone layers of cereal seeds and in palm oil. Tocopherol and tocotrienol were tested for chemopreventive activity in two chemically induced rat mammary tumor models. Initiation of lipid peroxidation often involves an oxygen activation stage during which reactive oxygen species, including superoxide, are formed. In heterogeneous membrane systems the efficiency of inhibiting lipid peroxidation is dependent on the chemical reactivity of the antioxidant, its distribution between the aqueous and nonpolar phases and into the lipid bilayer, and the mobility of membrane lipids.
