Menthol

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Contents

Menthol
(-)-Menthol Menthol skeletal.svg
(−)-Menthol
Ball-and-stick model of (-)-menthol Menthol-from-xtal-1999-3D-balls.png
Ball-and-stick model of (−)-menthol
Menthol Crystals.JPG
Menthol crystals.jpg
Names
Preferred IUPAC name
5-Methyl-2-(propan-2-yl)cyclohexan-1-ol
Other names
2-Isopropyl-5-methylcyclohexan-1-ol
2-Isopropyl-5-methylcyclohexanol
3-p-Menthanol
Hexahydrothymol
Menthomenthol
Peppermint camphor
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.016.992 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 218-690-9
KEGG
PubChem CID
RTECS number
  • OT0350000, racemic
UNII
  • InChI=1S/C10H20O/c1-7(2)9-5-4-8(3)6-10(9)11/h7-11H,4-6H2,1-3H3/t8-,9+,10-/m1/s1 Yes check.svgY
    Key: NOOLISFMXDJSKH-KXUCPTDWSA-N Yes check.svgY
  • InChI=1S/C10H20O/c1-7(2)9-5-4-8(3)6-10(9)11/h7-11H,4-6H2,1-3H3/t8-,9+,10-/m1/s1
  • Key: NOOLISFMXDJSKH-KXUCPTDWSA-N
  • O[C@H]1[C@H](C(C)C)CC[C@@H](C)C1
Properties
C10H20O
Molar mass 156.269 g·mol−1
AppearanceWhite or colorless crystalline solid
Odor mint-licorice
Density 0.890 g·cm−3, solid
(racemic or (−)-isomer)
Melting point 36–38 °C (97–100 °F; 309–311 K) racemic
42–45 °C, (−)-isomer, α crystalline form
Boiling point 214.6 °C (418.3 °F; 487.8 K)
Slightly soluble, (−)-isomer
Hazards [1]
Occupational safety and health (OHS/OSH):
Main hazards
Irritant, flammable
GHS labelling:
GHS-pictogram-exclam.svg
Warning
H315, H319
P264, P280, P302+P352, P305+P351+P338, P332+P313, P337+P313, P362
NFPA 704 (fire diamond)
[2]
NFPA 704.svgHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2
2
0
Flash point 93 °C (199 °F; 366 K)
Safety data sheet (SDS) External MSDS
Related compounds
Related alcohols
Cyclohexanol, Pulegol,
Dihydrocarveol, Piperitol
Related compounds
 Menthone, Menthene, Menthane,Thymol,
p-Cymene, Citronellal
Supplementary data page
Menthol (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Menthol is an organic compound, specifically a monoterpenoid, that occurs naturally in the oils of several plants in the mint family, such as corn mint and peppermint. It is a white or clear waxy crystalline substance that is solid at room temperature and melts slightly above. The main form of menthol occurring in nature is (−)-menthol, which is assigned the (1R,2S,5R) configuration.

For many people, menthol produces a cooling sensation when inhaled, eaten, or applied to the skin, and mint plants have been used for centuries for topical pain relief and as a food flavoring. Menthol has local anesthetic and counterirritant qualities, and it is widely used to relieve minor throat irritation. Menthol also acts as a weak κ-opioid receptor agonist.

Structure

Natural menthol exists as one pure stereoisomer, nearly always the (1R,2S,5R) form (bottom left corner of the diagram below). The eight possible stereoisomers are:

Mentholisomere.svg

In the natural compound, the isopropyl group is in the trans orientation to both the methyl and hydroxyl groups. Thus, it can be drawn in any of the ways shown:

Menthol structures.svg Menthol-from-xtal-1999-chair-3D-balls.png

The (+)- and (−)-enantiomers of menthol are the most stable among these based on their cyclohexane conformations. With the ring itself in a chair conformation, all three bulky groups can orient in equatorial positions.

The two crystal forms for racemic menthol have melting points of 28 °C and 38 °C. Pure (−)-menthol has four crystal forms, of which the most stable is the α form, the familiar broad needles.

Biological properties

A macro photograph of menthol crystals Menthol Crystals close up.jpg
A macro photograph of menthol crystals
Menthol crystals at room temperature. Approx. 1 cm in length. Menthol crystals.jpg
Menthol crystals at room temperature. Approx. 1 cm in length.

Menthol's ability to chemically trigger the cold-sensitive TRPM8 receptors in the skin is responsible for the well-known cooling sensation it provokes when inhaled, eaten, or applied to the skin. [3] In this sense, it is similar to capsaicin, the chemical responsible for the spiciness of hot chilis (which stimulates heat sensors, also without causing an actual change in temperature).

Menthol's analgesic properties are mediated through a selective activation of κ-opioid receptors. [4] Menthol blocks calcium channels [5] and voltage-sensitive sodium channels, reducing neural activity that may stimulate muscles. [6]

Some studies show that menthol acts as a GABAA receptor positive allosteric modulator and increases GABAergic transmission in PAG neurons. [7] Menthol has anesthetic properties similar to, though less potent than, propofol because it interacts with the same sites on the GABAA receptor. [8] Menthol may also enhance the activity of glycine receptors and negatively modulate 5-HT3 receptors and nAChRs. [9]

Menthol is widely used in dental care as a topical antibacterial agent, effective against several types of streptococci and lactobacilli. [10] Menthol also lowers blood pressure and antagonizes vasoconstriction through TRPM8 activation. [11]

Occurrence

Mentha arvensis (wild mint) is the primary species of mint used to make natural menthol crystals and natural menthol flakes[ citation needed ]. This species is primarily grown in the Uttar Pradesh region in India.[ citation needed ]

Menthol occurs naturally in peppermint oil (along with a little menthone, the ester menthyl acetate and other compounds), obtained from Mentha × piperita (peppermint). [12] Japanese menthol also contains a small percentage of the 1-epimer neomenthol.[ citation needed ]

Biosynthesis

The biosynthesis of menthol has been investigated in Mentha × piperita and the enzymes involved in have been identified and characterized. [13] It begins with the synthesis of the terpene limonene, followed by hydroxylation, and then several reduction and isomerization steps.

More specifically, the biosynthesis of (−)-menthol takes place in the secretory gland cells of the peppermint plant. The steps of the biosynthetic pathway are as follows:

  1. Geranyl diphosphate synthase (GPPS) first catalyzes the reaction of IPP and DMAPP into geranyl diphosphate.
  2. (−)-limonene synthase (LS) catalyzes the cyclization of geranyl diphosphate to (−)-limonene.
  3. (−)-Limonene-3-hydroxylase (L3OH), using O2 and then nicotinamide adenine dinucleotide phosphate (NADPH) catalyzes the allylic hydroxylation of (−)-limonene at the 3 position to (−)-trans-isopiperitenol.
  4. (−)-trans-Isopiperitenol dehydrogenase (iPD) further oxidizes the hydroxyl group on the 3 position using NAD+ to make (−)-isopiperitenone.
  5. (−)-Isopiperitenone reductase (iPR) then reduces the double bond between carbons 1 and 2 using NADPH to form (+)-cis-isopulegone.
  6. (+)-cis-Isopulegone isomerase (iPI) then isomerizes the remaining double bond to form (+)-pulegone.
  7. (+)-Pulegone reductase (PR) reduces this double bond using NADPH to form (−)-menthone.
  8. (−)-Menthone reductase (MR) then reduces the carbonyl group using NADPH to form (−)-menthol. [13]
Menthol biosynthesis image.gif

Production

Natural menthol is obtained by freezing peppermint oil. The resultant crystals of menthol are then separated by filtration.

Total world production of menthol in 1998 was 12,000 tonnes of which 2,500 tonnes was synthetic. In 2005, the annual production of synthetic menthol was almost double. Prices are in the $10–20/kg range with peaks in the $40/kg region but have reached as high as $100/kg. In 1985, it was estimated that China produced most of the world's supply of natural menthol, although it appears that India has pushed China into second place. [14]

Menthol is manufactured as a single enantiomer (94% e.e.) on the scale of 3,000 tonnes per year by Takasago International Corporation. [15] The process involves an asymmetric synthesis developed by a team led by Ryōji Noyori, who won the 2001 Nobel Prize for Chemistry in recognition of his work on this process:

Menthol synthesis.png

The process begins by forming an allylic amine from myrcene, which undergoes asymmetric isomerisation in the presence of a BINAP rhodium complex to give (after hydrolysis) enantiomerically pure R-citronellal. This is cyclised by a carbonyl-ene-reaction initiated by zinc bromide to isopulegol  [ de ], which is then hydrogenated to give pure (1R,2S,5R)-menthol.

Another commercial process is the Haarmann–Reimer process (after the company Haarmann & Reimer, now part of Symrise) [16] This process starts from m-cresol which is alkylated with propene to thymol. This compound is hydrogenated in the next step. Racemic menthol is isolated by fractional distillation. The enantiomers are separated by chiral resolution in reaction with methyl benzoate, selective crystallisation followed by hydrolysis.

Haarmann-Reimer process.svg

Racemic menthol can also be formed by hydrogenation of thymol, menthone, or pulegone. In both cases with further processing (crystallizative entrainment resolution of the menthyl benzoate conglomerate) it is possible to concentrate the L-enantiomer, however this tends to be less efficient, although the higher processing costs may be offset by lower raw material costs. A further advantage of this process is that D-menthol becomes inexpensively available for use as a chiral auxiliary, along with the more usual L-antipode. [17]

Applications

Menthol is included in many products, and for a variety of reasons.

Cosmetic

Medical

Others

Organic chemistry

In organic chemistry, menthol is used as a chiral auxiliary in asymmetric synthesis. For example, sulfinate esters made from sulfinyl chlorides and menthol can be used to make enantiomerically pure sulfoxides by reaction with organolithium reagents or Grignard reagents. Menthol reacts with chiral carboxylic acids to give diastereomic menthyl esters, which are useful for chiral resolution.

Reactions

Menthol reacts in many ways like a normal secondary alcohol. It is oxidised to menthone by oxidising agents such as chromic acid, dichromate, [25] or by calcium hypochlorite, in a green chemistry route. [26] Under some conditions the oxidation using Cr(VI) compounds can go further and break open the ring. Menthol is easily dehydrated to give mainly 3-menthene, by the action of 2% sulfuric acid. Phosphorus pentachloride (PCl5) gives menthyl chloride.

Menthol reactions.png

History

In the West, menthol was first isolated in 1771, by the German, Hieronymus David Gaubius. [27] Early characterizations were done by Oppenheim, [28] Beckett, [29] Moriya, [30] and Atkinson. [31] It was named by F. L. Alphons Oppenheim (1833–1877) in 1861. [32]

Compendial status

Safety

The estimated lethal dose for menthol (and peppermint oil) in humans may be as low as LD=50–500 mg/kg. In the rat, 3300 mg/kg. In the mouse, 3400 mg/kg. In the cat, 800 mg/kg.

Survival after doses of 8 to 9 g has been reported. [36] Overdose effects are abdominal pain, ataxia, atrial fibrillation, bradycardia, coma, dizziness, lethargy, nausea, skin rash, tremor, vomiting, and vertigo. [37]

See also

Related Research Articles

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<span class="mw-page-title-main">Chirality (chemistry)</span> Geometric property of some molecules and ions

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References

  1. ↑ "l-Menthol". pubchem.ncbi.nlm.nih.gov.
  2. ↑ "Safety Data Sheet" (PDF). Reckitt Benckiser . 27 October 2016. Retrieved 3 August 2018.
  3. ↑ Eccles R (1994). "Menthol and Related Cooling Compounds". J. Pharm. Pharmacol. 46 (8): 618–630. doi:10.1111/j.2042-7158.1994.tb03871.x. PMID   7529306. S2CID   20568911.
  4. ↑ Galeotti N, Mannelli LD, Mazzanti G, Bartolini A, Ghelardini C, Di Cesare M (2002). "Menthol: a natural analgesic compound". Neurosci. Lett. 322 (3): 145–148. doi:10.1016/S0304-3940(01)02527-7. PMID   11897159. S2CID   33979563.
  5. ↑ Hawthorn M, Ferrante J, Luchowski E, Rutledge A, Wei XY, Triggle DJ (April 1988). "The actions of peppermint oil and menthol on calcium channel dependent processes in intestinal, neuronal and cardiac preparations". Alimentary Pharmacology & Therapeutics . 2 (2): 101–18. doi:10.1111/j.1365-2036.1988.tb00677.x. PMID   2856502. S2CID   24596984.
  6. ↑ Haeseler G, Maue D, Grosskreutz J, Bufler J, Nentwig B, Piepenbrock S, Dengler R, Leuwer M (2002). "Voltage-dependent block of neuronal and skeletal muscle sodium channels by thymol and menthol". Eur. J. Anaesthes. 19 (8): 571–579. doi:10.1017/S0265021502000923 (inactive 1 November 2024). PMID   12200946.{{cite journal}}: CS1 maint: DOI inactive as of November 2024 (link)
  7. ↑ Lau BK, Karim S, Goodchild AK, Vaughan CW, Drew GM (1 June 2014). "Menthol enhances phasic and tonic GABAA receptor-mediated currents in midbrain periaqueductal grey neurons". Br. J. Pharmacol. 171 (11): 2803–2813. doi:10.1111/bph.12602. ISSN   1476-5381. PMC   4243856 . PMID   24460753.
  8. ↑ Watt EE, Betts BA, Kotey FO, Humbert DJ, Griffith TN, Kelly EW, Veneskey KC, Gill N, Rowan KC (20 August 2008). "Menthol shares general anesthetic activity and sites of action on the GABAA receptor with the intravenous agent, propofol". Eur. J. Pharmacol. 590 (1–3): 120–126. doi:10.1016/j.ejphar.2008.06.003. ISSN   0014-2999. PMID   18593637.
  9. ↑ Oz M, El Nebrisi EG, Yang KH, Howarth FC, Al Kury LT (2017). "Cellular and Molecular Targets of Menthol Actions". Frontiers in Pharmacology. 8: 472. doi: 10.3389/fphar.2017.00472 . PMC   5513973 . PMID   28769802.
  10. ↑ Freires IA, Denny C, Benso B, de Alencar SM, Rosalen PL (22 April 2015). "Antibacterial Activity of Essential Oils and Their Isolated Constituents against Cariogenic Bacteria: A Systematic Review". Molecules. 20 (4): 7329–7358. doi: 10.3390/molecules20047329 . PMC   6272492 . PMID   25911964.
  11. ↑ Sun J, Yang T, Wang P, Ma S, Zhu Z, Pu Y, Li L, Zhao Y, Xiong S, Liu D, Zhu Z (June 2014). "Activation of cold-sensing transient receptor potential melastatin subtype 8 antagonizes vasoconstriction and hypertension through attenuating RhoA/Rho kinase pathway". Hypertension . 63 (6): 1354–63. doi: 10.1161/HYPERTENSIONAHA.113.02573 . PMID   24637663. S2CID   11029018.
  12. ↑ PDR for Herbal Medicines (4 ed.). Thomson Healthcare. 2007. p. 640. ISBN   978-1-56363-678-3.
  13. 1 2 Croteau RB, Davis EM, Ringer KL, Wildung MR (December 2005). "(−)-Menthol biosynthesis and molecular genetics". Naturwissenschaften. 92 (12): 562–577. Bibcode:2005NW.....92..562C. doi:10.1007/s00114-005-0055-0. PMID   16292524. S2CID   206871270.
  14. ↑ Charles S. Sell (2013), "Terpenoids", in Arza Seidel, et al. (eds.), Kirk-Othmer Chemical Technology of Cosmetics, John Wiley & Sons, pp. 247–374, ISBN   978-1-118-40692-2
  15. ↑ "Japan: Takasago to Expand L-Menthol Production in Iwata Plant". Flex News Food.
  16. ↑ Schäfer B (2013). "Menthol". Chemie in unserer Zeit. 47 (3): 174–182. doi:10.1002/ciuz.201300599.
  17. ↑ Sell C, ed. (2006). The Chemistry of Fragrances: From Perfumer to Consumer. Royal Society of Chemistry. ISBN   978-0-85404-824-3.[ page needed ]
  18. ↑ "Unexpected Link Between Menthol and Alzheimer's Discovered in Mice". 22 October 2024.
  19. ↑ Henderson BJ, Wall TR, Henley BM, Kim CH, Nichols WA, Moaddel R, Xiao C, Lester HA (2016). "Menthol Alone Upregulates Midbrain nAChRs, Alters nAChR Subtype Stoichiometry, Alters Dopamine Neuron Firing Frequency, and Prevents Nicotine Reward". J. Neurosci. 36 (10): 2957–2974. doi:10.1523/JNEUROSCI.4194-15.2016. PMC   4783498 . PMID   26961950.
  20. ↑ Biswas L, Harrison E, Gong Y, Avusula R, Lee J, Zhang M, Rousselle T, Lage J, Liu X (2016). "Enhancing effect of menthol on nicotine self-administration in rats". Psychopharmacology. 233 (18): 3417–3427. doi:10.1007/s00213-016-4391-x. PMC   4990499 . PMID   27473365.
  21. ↑ Wickham RJ (2015). "How Menthol Alters Tobacco-Smoking Behavior: A Biological Perspective". Yale J. Biol. Med. 88 (3): 279–287. PMC   4553648 . PMID   26339211.
  22. ↑ Hiki N, Kaminishi M, Hasunuma T, Nakamura M, Nomura S, Yahagi N, Tajiri H, Suzuki H (2011). "A Phase I Study Evaluating Tolerability, Pharmacokinetics, and Preliminary Efficacy of L-Menthol in Upper Gastrointestinal Endoscopy". Clin. Pharmacol. Ther. 90 (2): 221–228. doi: 10.1038/clpt.2011.110 . PMID   21544078. S2CID   24399887.
  23. ↑ "Make Sodium Metal with Menthol (And a bunch of other stuff...)". YouTube . 14 February 2019.
  24. ↑ Barwood MJ, Gibson OR, Gillis DJ, Jeffries O, Morris NB, Pearce J, Ross ML, Stevens C, Rinaldi K, Kounalakis SN, Riera F (1 October 2020). "Menthol as an Ergogenic Aid for the Tokyo 2021 Olympic Games: An Expert-Led Consensus Statement Using the Modified Delphi Method". Sports Medicine. 50 (10): 1709–1727. doi:10.1007/s40279-020-01313-9. ISSN   1179-2035. PMC   7497433 . PMID   32623642.
  25. ↑ Sandborn LT. "l-Menthone". Organic Syntheses ; Collected Volumes, vol. 1, p. 340.
  26. ↑ Surapaneni A, Surapaneni A, Wu J, Bajaj A, Reyes K, Adwankar R, Vittaladevuni A, Njoo E (2020). "Kinetic Monitoring and Fourier-Transform Infrared (FTIR) Spectroscopy of the Green Oxidation of (-)-Menthol to (-)-Menthone". Journal of Emerging Investigators. doi: 10.59720/20-058 .
  27. ↑ Adversoriorum varii argumentii. Vol. 1. Leiden. 1771. p. 99.
  28. ↑ Oppenheim A (1862). "On the camphor of peppermint". J. Chem. Soc. 15: 24. doi:10.1039/JS8621500024.
  29. ↑ Beckett GH, Alder Wright CR (1876). "Isomeric terpenes and their derivatives (Part V)". J. Chem. Soc. 29: 1. doi:10.1039/JS8762900001.
  30. ↑ Moriya M (1881). "Contributions from the Laboratory of the University of Tôkiô, Japan. No. IV. On menthol or peppermint camphor". J. Chem. Soc., Trans. 39: 77. doi:10.1039/CT8813900077.
  31. ↑ Atkinson RW, Yoshida H (1882). "On peppermint camphor (menthol) and some of its derivatives". J. Chem. Soc., Trans. 41: 49. doi:10.1039/CT8824100049.
  32. ↑ Oppenheim A (1861). "Note sur le camphre de menthe" [On the camphor of mint]. Comptes Rendus. 53: 379–380. Les analogies avec le bornéol me permettent de proposer pour ce corps le nom de menthol,… [Analogies with borneol allow me to propose the name menthol for this substance,…]
  33. ↑ Therapeutic Goods Administration (1999). "Approved Terminology for Medicines" (PDF). Archived from the original (PDF) on 22 May 2006. Retrieved 29 June 2009.
  34. ↑ "Japanese Pharmacopoeia". Archived from the original on 9 April 2008. Retrieved 29 June 2009.
  35. ↑ Sigma Aldrich. "DL-Menthol" . Retrieved 15 February 2022.
  36. ↑ James A. Duke (2002), "PEPPERMINT", Handbook of Medicinal Herbs (2nd ed.), pp. 562–564, ISBN   978-0-8493-1284-7
  37. ↑ Jerrold B. Leikin, Frank P. Paloucek, eds. (2008), "Peppermint Oil", Poisoning and Toxicology Handbook (4th ed.), Informa, p. 885, ISBN   978-1-4200-4479-9

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