Most Popular in:
Vitamin E: A Skin Care Ally
By: Peter T. Pugliese, MD
Posted: August 27, 2009, from the September 2009 issue of Skin Inc. magazine.
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.
Note that in the alpha form, there are three methyl groups on the chromanol ring: one at the top and one at the bottom of the ring, and a third one on the carbon below the hydroxyl groupb. In the other forms illustrated in Figure 1, the only difference among the tocopherols are the number of methyl groups and their positions. Note that when a methyl group is removed, as in beta tocopherol, a hydrogen (H) atom must be added to balance the whole molecule. Now you can see that by removing methyl groups and adding hydrogen atoms, four different tocopherols have been created. They are known as alpha, beta, gamma and delta tocopherols with the corresponding Greek letters α, β, γ, δ.
Tocotrienols. There are also four forms of tocotrienols. When you see a chemical named with the designation -ene, it means that a double bond is present in the molecule between two carbon atoms. For example, -C-C- is a single-bond carbon structure, but C=C is a double-bond carbon structure. If there is more than one double bond in a string of carbons, the number can be figured out by using a prefix before the -ene designation. For example, C=C is known as a diene, while C=C=C is known as a triene. It is not necessary that they follow in sequence since C=C-C-C=C-C=C is also a triene. Now you have mastered the last half of tocotrienols. It is nothing more than the tocopherol molecule with three double bonds in the carbon chain. Because the chromogen ring is the same, there are four variations also in the tocotrienols. See Figure 2 for an illustration of these four types. Now look at the long carbon chain hooked onto the chromogen ring.