delta-Tocopherol is one of the forms of vitamin E and in animal tissues has been found to have much less retention than alpha-tocopherol.1 Due to its having only one methyl group meta to the phenolic hydroxyl group and no ortho-methyl groups, delta-tocopherol has much less antioxidant activity in vivo than alpha-tocopherol which has two ortho-methyl groups and a meta-methyl group. 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.2 Antioxidant activity in vivo is normally alpha>beta>gamma>delta but the antioxidant potency may depend on various chemical and physical situations.3 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.
