Methyl salicylate

 

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Methyl salicylate (oil of wintergreen or wintergreen oil) is an organic ester that is naturally produced by many species of plants. Some of the plants which produce it are called wintergreens, hence the common name. This compound is used as a fragrance. It is also found in liniments (rubbing ointments).

Natural occurrence

Numerous plants produce methyl salicylate in very small amounts. Some plants, such as the following, produce more:

• some species of the genus Gaultheria in the family Ericaceae, including Gaultheria procumbens, the wintergreen or eastern teaberry;
• some species of the genus Betula in the family Betulaceae, particularly those in the subgenus Betulenta such as B. lenta, the black birch;
• all species of the genus Spiraea in the family Rosaceae, also called the meadowsweets.

This compound is produced most likely as an anti-herbivore defense. If the plant is infected with herbivorous insects, the release of methyl salicylate may function as an aid in the recruitment of beneficial insects to kill the herbivorous insects.^[1] Aside from its toxicity, methyl salicylate may also be used by plants as a pheromone to warn other plants of pathogens such as tobacco mosaic virus.^[2]

Commercial production

Methyl salicylate can be produced by esterifying salicylic acid with methanol. Commercial methyl salicylate is now synthesized, but in the past, it was commonly distilled from the twigs of Betula lenta (sweet birch) and Gaultheria procumbens (eastern teaberry or wintergreen).

Uses

• in high concentrations as a rubefacient in deep heating liniments (such as Bengay) to treat joint and muscular pain. Randomised double blind trial reviews report evidence of its effectiveness that is weak, but stronger for acute pain than chronic pain, and that effectiveness may be due entirely to counter-irritation. However, in the body it metabolizes into salicylates, including salicylic acid, a known NSAID.^[3][4][5]
• in low concentrations as a flavoring agent, The highest amount of methyl salicylate typically used in candy flavoring is 0.04%.^[6]
• providing fragrance to various products and as an odor-masking agent for some organophosphate pesticides.^{[citation needed]} If used excessively, it can cause stomach and kidney problems.^[7]
• attracting male orchid bees, who apparently gather the chemical to synthesize pheromones; it is commonly used as bait to attract and collect these bees for study.^[8]
• clear plant or animal tissue samples of color, and as such is useful for microscopy and immunohistochemistry when excess pigments obscure structures or block light in the tissue being examined. This clearing generally only takes a few minutes, but the tissue must first be dehydrated in alcohol.^[9]
• a mint flavoring in some kinds of chewing gum and candy, as an alternative to the more common peppermint and spearmint oils. It can also be found as a flavoring of root beer. It is also a potentially entertaining source of triboluminescence; when mixed with sugar and dried, it gains the tendency to build up electrical charge when crushed or rubbed. This effect can be observed by crushing wintergreen Life Savers candy in a dark room.^[10][11]
• as a transfer agent, to produce a manual copy of an image on a surface.^[12]
• in small amounts, to lower the freezing point of glacial acetic acid for transport.
• a simulant or surrogate for the research of chemical warfare agent sulfur mustard, due to its similar chemical and physical properties.^[13]
• an antiseptic in Listerine mouthwash produced by the Johnson & Johnson company.
• restoring (at least temporarily) the elastomeric properties of old rubber rollers, especially in printers.

Safety and toxicity

In pure form, methyl salicylate is toxic, especially when taken internally. A single teaspoon (5ml) of methyl salicylate contains 7g of salicylate,^[14] which is equivalent to more than twenty-three 300 mg aspirin tablets. The lowest published lethal dose is 101 mg/kg body weight in adult humans,^[15] (or 7.07 grams for a 70-kg adult). It has proven fatal to small children in doses as small as 4 ml.^[6] A seventeen-year-old cross-country runner at Notre Dame Academy on Staten Island, died in April 2007, after her body absorbed methyl salicylate through excessive use of topical muscle-pain relief products.^[16]

Most instances of human toxicity due to methyl salicylate are a result of over-application of topical analgesics, especially involving children. Some people have intentionally ingested large amounts of oil of wintergreen. Salicylate, the major metabolite of methyl salicylate, may be quantitated in blood, plasma or serum to confirm a diagnosis of poisoning in hospitalized patients or to assist in an autopsy.^[17]

The entire wiki article can be found at: http://en.wikipedia.org/wiki/Methyl_salicylate