Methyl salicylate (oil of wintergreen orwintergreen oil) is anorganic compound with the formula C8H8O3. It is the methylester ofsalicylic acid. It is a colorless,viscous liquid with a sweet, fruity odor reminiscent ofroot beer (in which it is used as a flavoring),[4] but oftenassociatively called "minty", as it is an ingredient in mint candies.[5] It is produced by many species ofplants, particularlywintergreens. It is also produced synthetically, used as afragrance and as a flavoring agent.
Many plants produce methyl salicylate in small quantities. Methyl salicylate levels are often upregulated in response to biotic stress, especially infection by pathogens, where it plays a role in the induction ofresistance. Methyl salicylate is believed to function by being metabolized to the plant hormone salicylic acid. Since methyl salicylate is volatile, these signals can spread through the air to distal parts of the same plant or even to neighboring plants, whereupon they can function as a mechanism ofplant-to-plant communication, "warning" neighbors of danger.[9] Methyl salicylate is also released in some plants when they are damaged by herbivorous insects, where they may function as a cue aiding in the recruitment of predators, notablyhoverflies,lacewings, andlady beetles.[10][11]
Some plants produce methyl salicylate in larger quantities, where it likely involved in direct defense against predators or pathogens. Examples of this latter class include: some species of the genusGaultheria in the familyEricaceae, includingGaultheria procumbens, the wintergreen or eastern teaberry; some species of the genusBetula in the familyBetulaceae, particularly those in the subgenusBetulenta such asB. lenta, the black birch; all species of the genusSpiraea in the familyRosaceae, also called the meadowsweets; species of the genusPolygala in the familyPolygalaceae. Methyl salicylate can also be a component offloral scents, especially in plants dependent on nocturnal pollinators like moths,[12] scarab beetles, and (nocturnal) bees.[13]
Chickembryo that was treated withmethylene blue to stain the skeleton, then cleansed with two or threeethanol washes, and treated with methyl salicylate to make the surroundingtissues transparent
Methyl salicylate is used in high concentrations as arubefacient andanalgesic in deep heatingliniments (such asBengay) to treat joint and muscular pain. Randomised double blind trials report that evidence of its effectiveness is weak, but stronger for acute pain than chronic pain, and that effectiveness may be due entirely tocounterirritation. However, in the body it metabolizes into salicylates, including salicylic acid, a knownNSAID.[15][16][17]
Methyl salicylate is also used as a bait for attracting maleorchid bees for study, which apparently gather the chemical to synthesize pheromones,[22] and to clear plant or animal tissue samples of color, and as such is useful for microscopy andimmunohistochemistry 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.[23] It has also been discovered that methyl salicylate works as akairomone that attracts some insects, such as thespotted lanternfly. Unlike some other kairomone's, Methyl Salicylate attracts all stages of the spotted lanternflies life.[24]
Other niche uses include:
as a simulant or surrogate for the research of chemical warfare agentsulfur mustard, due to its similar chemical and physical properties;[25]
restoring (at least temporarily) the elastomeric properties of old rubber rollers, especially in printers;[26]
as a transfer agent in printmaking (to release toner from photocopied images and apply them to other surfaces);[27]
as a historical substitute forcedar oil as animmersion oil in microscopy, given its refractive index (1.538) being close to that of crown glass (1.515) and being less prone todrying than cedar oil;[28]
Methyl salicylate is potentially deadly, especially for young children who may accidentally ingest preparations containing methyl salicylate, such as anessential oil solution. A single teaspoon (5 mL) of methyl salicylate contains approximately 6 g of salicylate,[29] which is equivalent to almost twenty 300 mgaspirin tablets (5mL × 1.174g/mL = 5.87g). 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 140mg/kg of salicylates for a 10kg child (22lbs).[30] The lowest published lethal dose is 101 mg/kg body weight in adult humans,[31][32] (or 7.07 grams for a 70 kg adult). It has proven fatal to small children in doses as small as 4 mL.[18] A seventeen-year-oldcross-country runner atNotre Dame Academy onStaten Island died in April 2007 after her body absorbed methyl salicylate through excessive use of topical muscle-pain relief products (using multiple patches against the manufacturer's instructions).[33]
Most instances of human toxicity due to methyl salicylate are a result of overapplication of topical analgesics, especially involving children. Salicylate, the major metabolite of methyl salicylate, may accumulate inblood,plasma orserum which may help professionals to confirm a diagnosis of poisoning in hospitalized patients or to assist in anautopsy.[34]
^James, D. G.; Price, T. S. (2004). "Field-testing of methyl salicylate for recruitment and retention of beneficial insects in grapes and hops".Journal of Chemical Ecology.30 (8):1613–1628.doi:10.1023/B:JOEC.0000042072.18151.6f.PMID15537163.S2CID36124603.
^Rodriguez-Saona, C., Kaplan, I., Braasch, J., Chinnasamy, D., & Williams, L. (2011). Field responses of predaceous arthropods to methyl salicylate: A meta-analysis and case study in cranberries. Biological Control, 59(2), 394-303.https://doi.org/10.1016/j.biocontrol.2011.06.017
^Knudsen, J. T.; Tollsten, L. (1993). "Trends in floral scent chemistry in pollination syndromes: floral scent composition in moth-pollinated taxa".Botanical Journal of the Linnean Society.113 (3). Oxford Academic:263–284.doi:10.1111/j.1095-8339.1993.tb00340.x.
^Cordeiro, G. D.; Fernandes dos Santos, I. G.; da Silva, C. I.; Schlindwein, C.; Alves-dos-Santos, I.; Dötterl, S. (2019). "Nocturnal floral scent profiles of Myrtaceae fruit crops".Phytochemistry.162:193–198.doi:10.1016/j.phytochem.2019.03.011.PMID30939396.S2CID92997657.
^Altman, J. S.; Tyrer, N. M. (1980). "Filling selected neurons with cobalt through cut axons". In Strausfeld, N. J.; Miller, T. A. (eds.).Neuroanatomical Techniques. Springer-Verlag. pp. 373–402.
^Bartlet-Hunt, S. L.; Knappe, D. R. U.; Barlaz, M. A. (2008). "A Review of Chemical Warfare Agent Simulants for the Study of Environmental Behaviour".Critical Reviews in Environmental Science and Technology.38 (2):112–136.doi:10.1080/10643380701643650.S2CID97484598.
^Baselt, R. (2008).Disposition of Toxic Drugs and Chemicals in Man (8th ed.). Foster City, CA: Biomedical Publications. pp. 1012–1014.ISBN978-0-9626523-7-0.
^The British Pharmacopoeia Secretariat (2009)."Index, BP 2009"(PDF). Archived fromthe original(PDF) on 11 April 2009. Retrieved5 July 2009.
^"NIHS Japan". Moldb.nihs.go.jp.Archived from the original on 2013-02-17. Retrieved2013-07-01.
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