Menthol

OVERVIEW

Menthol (MEN-thol) occurs naturally in the peppermint plant. In pure form it occurs as a white crystalline material with a cooling taste and odor. Peppermint is one of the oldest known herbal remedies. Dried peppermint leaves have been found in Egyptian pyramids dating to at least 1000 bce, and its use among the Greeks and Romans in cooking and medical preparations is well known. Peppermint was not introduced to western Europe, however, until the eighteenth century, when it was used to treat a variety of ailments ranging from toothaches to morning sickness. It was first brought to the United States about a century later.

KEY FACTS

OTHER NAMES:

Hexahydrothymol; methylhydroxyisopropylcyclohexane; peppermint camphol

FORMULA:

CH₃C₆H₉ (C₃H₇)OH

ELEMENTS:

Carbon, hydrogen, oxygen

COMPOUND TYPE:

Organic

STATE:

Solid

MOLECULAR WEIGHT:

156.26 g/mol

MELTING POINT:

41°C to 43°C (106°F to 109°F)

BOILING POINT:

212°C (414°F)

SOLUBILITY:

Slightly soluble in water; very soluble in alcohol, chloroform, and ether

HOW IT IS MADE

Peppermint oil is extracted from the leaves of the peppermint plant, Mentha piperita, by steam distillation, by which various oils in the plant are separated from each other. The peppermint oil is then frozen to extract the menthol from other components of the oil. Menthol can also be produced synthetically by the reduction of thymol [(CH₃)₂CHC₆H₃(CH₃)OH] with hydrogen.

COMMON USES AND POTENTIAL HAZARDS

Menthol smells like mint and creates a soothing and sometimes tingling sensation when it touches the skin. Scientists theorize that menthol creates the cooling sensation by triggering the same receptors on skin that tell the body's nerves to respond to cold temperatures.

The cooling sensation makes menthol a desirable additive to aftershave lotions, skin cleansers, lotions, sore throat lozenges, and lip balms. Menthol is also used in a variety of cosmetics applied to the skin and medications for the relief of itching. It is also added to foods such as chewing gums and candies to impart a mint-like flavor.

When inhaled or ingested as a lozenge, menthol can relieve nasal congestion and coughs, as well as cool and numb the throat to ease the pain of sore throats. It can also be used in ointments with camphor and eucalyptus to produce cooling and antiseptic properties. These ointments can be applied to the chest and/or nostrils to clear the nose and reduce coughing. One of the most famous menthol-containing products is Vicks® VapoRub, which is used to relieve coughs and congestion.

Although menthol is soothing and cooling in small quantities, it produces a quite different effect in larger quantities. Gargling with a large amount of menthol-containing mouthwash, for example, can create an unpleasant burning sensation.

Interesting Facts

• Menthol was first added to cigarettes in the early 1900s to make a cooler tasting product. Tobacco companies claimed that menthol cigarettes were less irritating to the throat and an effective way of treating sore throats. Today, about 25 percent of all cigarettes sold in the United States are mentholated.

Although menthol has been classified as a "generally recognized as safe" (GRAS) product and approved for use in foods by the U.S. Good and Drug Administration, some side effects have been reported. On contact with the skin, menthol may cause irritation. Ingesting large quantities can cause abdominal pain, nausea, vomiting, dizziness, drowsiness, and even coma. These effects are more likely to occur in infants and children than in adults.

Words to Know

DISTILLATION

A process of separating two or more substances by boiling the mixture of which they are composed and condensing the vapors produced at different temperatures.

REDUCTION

The chemical reaction in which oxygen is removed from a substance or electrons are added to a substance.

SYNTHESIS

A chemical reaction in which some desired chemical product is made from simple beginning chemicals, or reactants.

FOR FURTHER INFORMATION

"Cool Menthol 1" and "Cool Menthol 2." Great Moments in Science. http://www.abc.net.au/science/k2/moments/s537539.htm and http://www.abc.net.au/science/k2/moments/s537548.htm (accessed on October 12, 2005).

Cummings, Linda Scott. "M2258 Menthol." Paleoresearch Institute. http://www.paleoresearch.com/MSDS/MENTHOL%20-%20SIGMA%20CHEMICAL%20-%2005-19-1997.htm (accessed on October 12, 2005).

"Menthol and Tobacco Smoking." http://goodhealth.freeservers.com/MethTobaccoIntro.html (accessed on October 12, 2005).

"Menthol-Its Chemistry and Many Uses." http://goodhealth.freeservers.com/MenthUseThisOne.htm (accessed on October 12, 2005).

Travis, J. "Cool Discovery: Menthol Triggers Cold-Sensing Protein." Science News (February 16, 2002): 101-102.

See AlsoCamphor

men·thol / ˈmenˌ[unvoicedth]ôl; -ˌ[unvoicedth]äl/ • n. a crystalline compound, C₁₀H₁₉OH, with a cooling minty taste and odor, found in peppermint and other natural oils. It is used as a flavoring and in decongestants and analgesics.

menthol (C₁₀H₁₉OH) White, waxy crystalline compound having a strong odour of peppermint. Its main source is oil of peppermint from the plant Mentha arvensis. It is an ingredient of decongestant ointments and nasal sprays, and as a flavouring in toothpaste and cigarettes.

menthol XIX. — G. menthol, f. mentha MINT2; see -OL.

menthol (men-thol) n. a compound extracted from peppermint oil, used in inhalants to relieve cold symptoms, in ointments and liniments, and to relieve itching. Formula: C₁₀H₂₀O.