Methyl salicylate (oil of wintergreen or wintergreen oil) is an organic compound with the formula C6H4(OH)(CO2CH3). It is the methyl ester of salicylic acid. It is a colorless, viscous liquid with a sweet odor. It is produced by many species of plants, particularly wintergreens. It is also synthetically produced, used as a fragrance, in foods and beverages, and in liniments.
Video Methyl salicylate
Biosynthesis and occurrence
The compound methyl salicylate was first isolated (from the plant Gaultheria procumbens) in 1843 by the French chemist Auguste André Thomas Cahours (1813-1891), who identified it as an ester of salicylic acid and methanol.
The biosynthesis of methyl salicylate arises via the hydroxylation of benzoic acid by a cytochrome P450 followed by methylation by a methylase enzyme.
Methyl salicylate is probably produced 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. 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.
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; species of the genus Polygala in the family Polygalaceae.
Maps Methyl salicylate
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
It is used in high concentrations as a rubefacient and analgesic 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.
It is used in low concentrations (0.04% and under) as a flavoring agent in chewing gum and mints. When mixed with sugar and dried it is a potentially entertaining source of triboluminescence, gaining the tendency to build up electrical charge when crushed or rubbed. This effect can be observed by crushing wintergreen Life Savers in a dark room. It is used as an antiseptic in Listerine mouthwash produced by the Johnson & Johnson company. It provides fragrance to various products and as an odor-masking agent for some organophosphate pesticides.
It is used as a bait for attracting male orchid bees for study, which apparently gather the chemical to synthesize pheromones.
It is used to 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.
It is used as a transfer agent, to produce a manual copy of an image on a surface.
It is used as a simulant or surrogate for the research of chemical warfare agent sulfur mustard, due to its similar chemical and physical properties.
It is used in restoring (at least temporarily) the elastomeric properties of old rubber rollers, especially in printers.
Safety and toxicity
Methyl salicylate is potentially deadly, especially in the pediatric population. A single teaspoon (5 ml) of methyl salicylate contains approximately 6 g of salicylate, which is equivalent to almost twenty 300 mg aspirin tablets (5 mL × 1.174 g/mL = 5.87 g). Toxic ingestions of salicylates typically occur with doses of approximately 150 mg/kg body weight. This can be achieved with 1 ml of oil of wintergreen, which equates to 140 mg/kg of salicylates for a 10 kg child (22 lbs). The lowest published lethal dose is 101 mg/kg body weight in adult humans, (or 7.07 grams for a 70-kg adult). It has proven fatal to small children in doses as small as 4 ml. 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.
Most instances of human toxicity due to methyl salicylate are a result of over-application of topical analgesics, especially involving children. 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.
Compendial status
- British Pharmacopoeia
- Japanese Pharmacopoeia
See also
- Trolamine salicylate
References
External links
- MedlinePlus - Methyl salicylate overdose
- MedlinePlus - Sports cream overdose
- CNN - Medical examiner: Sports cream caused teen's death Wayback machine link to this article
- NLM Hazardous Substances Databank - Methyl salicylate
Source of the article : Wikipedia
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