Vitamin E was first found to be essential for reproduction in 1922, but it was not until 1936 that Herbert McLean Evans discovered vitamin E and its chemistry through a series of rat-feeding studies and named it tocopherol.1 The name “tocopherol” is from the Greek words tokos, meaning “childbirth,” and pherein meaning “to carry.” The “ol” at the end of the word designates it as an alcohola.
Chemistry of tocopherols
Vitamin E can be divided into two basic forms—tocopherols and tocotrienols.
Tocopherols. Figure 1 illustrates the four structural forms of tocopherol. On the left is a ring structure called the chromanol ring, which includes carbon atoms in a circle with a side attachment, also in a ring form, containing an oxygen atom. Look carefully at the molecule, and you will see an OH group and the left side of the larger ring. This is the business end of the vitamin E molecule. Notice that it does not change position in all form types of tocopherols. Concentrate on this OH group, called a hydroxyl group, and then look at the three other groups of atoms attached to the chromanol ring. The position of these groups, known as methyl groups, gives the name to the various types of tocopherol.