Alpha-Tocopherol

OVERVIEW

Alpha-tocopherol (AL-fa toe-KOF-er-ol) is also known as 2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)chroman-6-ol and 3,4-Dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyl-tridecyl)-2H-1-benzopyran-6-ol, as well as by many other systematic names. It is one of a family of compounds, the tocopherols, that makes up vitamin E. Other members of the family include the beta (β), gamma (γ), delta (δ), and epsilon (ε) tocopherols. All tocopherols share the same basic molecular structure, differing only in slightly different arrangements of methyl (CH₃-) and hydroxyl (OH-) groups. In terms of biological activity, α-tocopherol is the most important member of the tocopherol family. The tocopherols are all pale yellow, viscous oils found in a variety of plants, including almonds, mustard greens, green and red peppers, spinach, and sunflower seeds. The most important source for the vitamin is wheat germ.

KEY FACTS

OTHER NAMES:

See Overview.

FORMULA:

C₂₉H₅₀O

ELEMENTS:

Carbon, hydrogen, oxygen

COMPOUND TYPE:

Organic

STATE:

Liquid

MOLECULAR WEIGHT:

430.69 g/mol

MELTING POINT:

2.5°C to 3.5°C (36°F to 38°F)

BOILING POINT:

350°C (660°F; decomposes)

SOLUBILITY:

Insoluble in water; soluble in alcohol, ether, acetone, oils, and most organic solvents

Vitamin E was discovered in 1922 by two scientists at the University of California at Berkeley, Herbert McLean Evans (1882–1971) and Katherine Scott Bishop (1889–1976). Evans and Bishop found that rats whose diet was deficient in a-tocopherol did not reproduce normally. Scientists are now aware that the primary function of vitamin D in the human body is as an antioxidant. An antioxidant is a substance that reacts with and prevents the harmful effects of chemical strictures known as free radicals. A free radical is an atom or group of atoms with a single unpaired electron, making the atom or atoms unusually reactive. Free radicals are thought to be a primary cause of cell damage leading to cardiovascular disease, cancer, and aging.

Vitamin E was first produced synthetically (artificially) in 1938 by Swiss chemist Paul Karrer (1889–1971), who had been awarded the Nobel Prize in chemistry a year earlier for his studies of vitamin A, vitamin B₂, and other important biological compounds.

HOW IT IS MADE

A variety of methods is now available for the synthesis (artificial production) of the tocopherols. In the most commonly used procedure, 2,3,5-trimethylhydroquinone is reacted with isophytol over one of many possible catalysts. A small amount of the vitamin is still obtained from natural sources, usually as the by-product in the treatment of one of its natural sources.

Interesting Facts

As a general rule, vitamins and minerals are equally potent (effective) whether they come from natural sources or synthetic procedures. Vitamin E is an exception to that general rule. Synthetic forms of the vitamin are generally less potent than natural forms. The reason for this fact is that natural vitamin E exists in only one stereoisomeric form. Stereoisomers are two or more forms of a compound with the same kind and number of atoms. But the atoms in stereoisomers have somewhat different orientations in space. These slight differences in geometric shape are responsible for slight differences in biological activity. Natural vitamin E consists of only one stereoisomer, which is very active biologically. Synthetic vitamin E consists of two stereoisomers, only one of which (the one that occurs in natural vitamin E) is biologically active. So synthetic vitamin E tends to be about half as active biologically as natural vitamin E.

COMMON USES AND POTENTIAL HAZARDS

Vitamin E deficiency disorders are rare in humans. The vast majority of people get all the vitamin E they need in their daily diets. Three groups of people may, however, require vitamin E supplements. The first group consists of individuals who are unable to absorb fat in their diets, so that the vitamin E they ingest is immediately eliminated from their bodies. The second group consists of a small fraction of people who have genetic disorders that make it impossible for them to utilize α-tocopherol. The third group of individuals consist of premature and very young babies. All babies are born deficient in vitamin E, but they normally overcome that deficiency in the first few weeks of their lives. Premature babies and some babies born at term may experience a variety of health problems as a result of vitamin E deficiency. Lack of normal reflexes, inability to orient itself, muscle weekness, and loss of balance are typical symptoms of vitamin E deficiency in babies. Deficiency problems for individuals in all three groups can be overcome by taking supplementary vitamin E.

In addition to its use as a vitamin supplement for normal individuals and those at risk for vitamin E deficiency, the tocopherols have a few other uses:

• In the curing of meat to block the action of nitrosamines, a group of compound that occurs naturally in meats and may be carcinogenic;
• As an additive to animal feed to replace vitamins lost during feed processing; and
• As a food additive in vegetable oils and shortening to prevent oxidation (spoilage).

Words to Know

CARCINOGEN

A chemical that causes cancer in humans or other animals.

VISCOUS

Describes a syrupy liquid that flows slowly.

FOR FURTHER INFORMATION

Challem, Jack, and Melissa Diane Smith. Basic Health Publications User's Guide to Vitamin E: Don't Be a Dummy: Become an Expert on What Vitamin E Can Do for Your Health. North Bergen, NJ: Basic Health Publications, 2002.

Packer, Lester, and Carol Colman. The Antioxidant Miracle: Put Lipoic Acid, Pycogenol, and Vitamins E and C to Work for You. New York: Wiley, 1999.

"Vitamin E." National Institutes of Health, Office of Dietary Supplements. http://ods.od.nih.gov/factsheets/vitamine.asp (accessed on September 17, 2005).

"Vitamin E (tocopherol)." Vitamin and Health Supplements Guide. http://www.vitamins-supplements.org/vitamin-E.php (accessed on September 17, 2005).