Resumen
Vitamin E refers to a family of compounds that function as lipid-soluble antioxidants capable of preventing lipid peroxidation. Naturally occurring forms of vitamin E include tocopherols and tocotrienols. Vitamin E in dietary supplements and fortified foods is often an esterified form of a-tocopherol, the most common esters being acetate and succinate. The vitamin E esters are hydrolyzed and converted into free a-tocopherol prior to absorption in the intestinal tract. Because its functions are relevant to many chronic diseases, vitamin E has been extensively studied in respect to a variety of diseases as well as cosmetic applications. The forms of vitamin E most studied are natural a-tocopherol and the esters a-tocopheryl acetate and a-tocopheryl succinate. A small number of studies include or focus on another ester form, a-tocopheryl nicotinate, an ester of vitamin E and niacin. Some of these studies raise the possibility of differences in metabolism and in efficacy between vitamin E nicotinate and other forms of vitamin E. Recently, through metabolomics studies, we identified that a-tocopheryl nicotinate occurs endogenously in the heart and that its level is dramatically decreased in heart failure, indicating the possible biological importance of this vitamin E ester. Since knowledge about vitamin E nicotinate is not readily available in the literature, the purpose of this review is to summarize and evaluate published reports, specifically with respect to a-tocopheryl nicotinate with an emphasis on the differences from natural a-tocopherol or a-tocopheryl acetate.