P-menthane-3,8-diol
Encyclopedia
p-Menthane-3,8-diol, also known as para-menthane-3,8-diol, PMD, or Menthoglycol, is an active ingredient used in insect repellent
s. It smells similar to menthol
and acts as a coolant
. PMD is found in very small quantities in the essential oil
within leaves of the Eucalyptus citriodora
tree. This tree is native to Australia
, but is now cultivated in many warm places around the world. This oil, when refined for use in insect repellents, is known in the United States as oil of lemon eucalyptus or under the registered tradename Citriodiol. This refined oil contains approximately 64% PMD (a mixture of the cis and trans isomer
s of p-menthane-3,8-diol). The refined oil has been notified under the European Biocidal Products Directive
(BPD) 98/8/EC under its trade name Citriodiol (PMDRBO) and is currently proceeding through the registration process with the Health and Safety Executive
in the UK. It is the only natural derived active ingredient that can now be used as an insect repellent in the United States and Europe.
Because there are R and S configurations possible at carbon atoms 1, 2, and 5, PMD has eight possible stereoisomers. Each of these, and many of the possible mixtures, have their own CID number.. However, the isomeric composition is rarely specified and is commonly assumed to be racemic.
The Center for Disease Control has recognized Oil of Lemon Eucalyptus (OLE) as the only effective naturally derived substance for deterring mosquitoes carrying West Nile Virus
. PMD can be synthetically manufactured; however, one study has found that repellents containing synthetic PMD mixtures are not as effective as those containing naturally derived PMD mixtures (oil of lemon eucalyptus). This study also shows that naturally-derived PMD is as effective as DEET
when used in like quantities.
Insect repellent
An insect repellent is a substance applied to skin, clothing, or other surfaces which discourages insects from landing or climbing on that surface. There are also insect repellent products available based on sound production, particularly ultrasound...
s. It smells similar to menthol
Menthol
Menthol is an organic compound made synthetically or obtained from peppermint or other mint oils. It is a waxy, crystalline substance, clear or white in color, which is solid at room temperature and melts slightly above. The main form of menthol occurring in nature is -menthol, which is assigned...
and acts as a coolant
Coolant
A coolant is a fluid which flows through a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor...
. PMD is found in very small quantities in the essential oil
Essential oil
An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile oils, ethereal oils or aetherolea, or simply as the "oil of" the plant from which they were extracted, such as oil of clove...
within leaves of the Eucalyptus citriodora
Eucalyptus citriodora
Corymbia citriodora is a tall tree, to 51 metres in height, from temperate and tropical north eastern Australia. It is also known as lemon-scented gum, blue spotted gum and lemon eucalyptus....
tree. This tree is native to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, but is now cultivated in many warm places around the world. This oil, when refined for use in insect repellents, is known in the United States as oil of lemon eucalyptus or under the registered tradename Citriodiol. This refined oil contains approximately 64% PMD (a mixture of the cis and trans isomer
Isomer
In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...
s of p-menthane-3,8-diol). The refined oil has been notified under the European Biocidal Products Directive
Biocidal Products Directive
The Biocidal Products Directive also known as the Biocides Directive is European Union Directive, , which concerns biocides...
(BPD) 98/8/EC under its trade name Citriodiol (PMDRBO) and is currently proceeding through the registration process with the Health and Safety Executive
Health and Safety Executive
The Health and Safety Executive is a non-departmental public body in the United Kingdom. It is the body responsible for the encouragement, regulation and enforcement of workplace health, safety and welfare, and for research into occupational risks in England and Wales and Scotland...
in the UK. It is the only natural derived active ingredient that can now be used as an insect repellent in the United States and Europe.
Because there are R and S configurations possible at carbon atoms 1, 2, and 5, PMD has eight possible stereoisomers. Each of these, and many of the possible mixtures, have their own CID number.. However, the isomeric composition is rarely specified and is commonly assumed to be racemic.
The Center for Disease Control has recognized Oil of Lemon Eucalyptus (OLE) as the only effective naturally derived substance for deterring mosquitoes carrying West Nile Virus
West Nile virus
West Nile virus is a virus of the family Flaviviridae. Part of the Japanese encephalitis antigenic complex of viruses, it is found in both tropical and temperate regions. It mainly infects birds, but is known to infect humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels, domestic...
. PMD can be synthetically manufactured; however, one study has found that repellents containing synthetic PMD mixtures are not as effective as those containing naturally derived PMD mixtures (oil of lemon eucalyptus). This study also shows that naturally-derived PMD is as effective as DEET
DEET
N,N-Diethyl-meta-toluamide, abbreviated DEET, is a slightly yellow oil. It is the most common active ingredient in insect repellents...
when used in like quantities.