Menthone

Menthone at a Glance

Menthone is a monoterpene ketone and the compound the mint plant makes on the way to making menthol. It is the oxidised, ketone form of the same p-menthane skeleton: reduce its C3 carbonyl to an alcohol and you have menthol.

That relationship is the most interesting thing about it, and it is visible in the plant. Peppermint oil harvested before the glands mature is comparatively menthone-rich; oil from mature leaves is menthol-rich, because a second wave of enzyme expression has reduced the ketone ^{1Reference 1Davis EM et al. · 2005Monoterpene metabolismView study →}. Pharmacopoeial composition limits for peppermint oil put menthone at 14–32% and menthol at 30–55% ^{6,11Reference 6Chumpitazi BP et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →Reference 11Grigoleit HG · 2005ReviewPharmacology and preclinical pharmacokinetics of peppermint oil — reviewView study →}.

Its own pharmacology is thin. Menthone has no cold receptor, no clinical trials and no established dose. Where it has been tested as an isolate it is a weak, membrane-active antimicrobial — the MRSA minimum inhibitory concentration is 3,540 µg/mL, more than three milligrams per millilitre ^{3Reference 3Zhao W et al. · 2023In vitroMenthone exerts its antimicrobial activity against methicillin resistant Staphylococcus aureus by affecting cell membrane properties and lipid profile — in vitroView study →} — and against plant-pathogenic fungi it was less active than the menthol it turns into ^{4Reference 4Makkar MK et al. · 2018In vitroEvaluation of Mentha arvensis essential oil and its major constituents for fungitoxicity — in vitroView study →}. It is best understood as a biosynthetic intermediate and a flavour constituent rather than an active in its own right.

The Hinge of the Menthol Pathway

Menthol biosynthesis in mint runs through menthone, and the enzymes on either side of it have both been cloned, which makes this one of the better-characterised terpene pathways in plants.

Upstream: pulegone reductase stereoselectively reduces the Δ2,8 double bond of pulegone to give menthone. Because the reduction sets the stereochemistry, this enzyme is what determines which menthol the plant ends up with — a Nepeta tenuifolia enzyme characterised in 2021 converts (−)-pulegone to (+)-menthone, the mirror-image outcome of the peppermint route ^{2Reference 2Liu C et al. · 2021Functional characterization and structural insights into stereoselectivity of pulegone reductase in menthol biosynthesisView study →}.

Downstream: two short-chain dehydrogenase/reductase enzymes act on menthone, and peppermint expresses them at different times. Menthone:(−)-(3R)-menthol reductase makes menthol; menthone:(+)-(3S)-neomenthol reductase makes neomenthol. They share 73% sequence identity but differ enormously in affinity — Km for menthone is 3.0 µM for the menthol-forming enzyme and 674 µM for the neomenthol-forming one — and between them they account for all the menthol isomers found in peppermint oil ^{1Reference 1Davis EM et al. · 2005Monoterpene metabolismView study →}. The menthol-forming enzyme belongs to a later oil-maturation programme that begins around flower initiation, which is why harvest timing changes the oil’s menthol:menthone ratio.

Both menthone reductases also accept isomenthone, menthone’s C1 epimer, at lower affinity — which is how the minor menthol isomers arise ^{1Reference 1Davis EM et al. · 2005Monoterpene metabolismView study →}.

The practical consequence for anyone reading an oil analysis: a high menthone figure is usually a statement about the harvest, not about the chemotype.

What It's Used For

Very little has been tested on menthone alone. What exists is in vitro, and the honest summary is that the isolate is weaker than the oils it comes from are usually credited with being.

Evidence by IndicationStrength of support · Beta

01AntibacterialShaky28%One in-vitro isolate study against MRSA with a defined membrane mechanism and a very high MIC ^{3Reference 3Zhao W et al. · 2023In vitroMenthone exerts its antimicrobial activity against methicillin resistant Staphylococcus aureus by affecting cell membrane properties and lipid profile — in vitroView study →}

02AntifungalShaky20%In vitro against plant-pathogenic fungi; weaker than menthol and than the standard comparator ^{4Reference 4Makkar MK et al. · 2018In vitroEvaluation of Mentha arvensis essential oil and its major constituents for fungitoxicity — in vitroView study →}

03Smooth-Muscle RelaxationShaky16%Guinea-pig ileum work on buchu oils, not the isolate ^{7Reference 7Lis-Balchin M et al. · 2001Buchu (Agathosma betulina and A. crenulata, Rutaceae) essential oils: their pharmacological action on guinea-pig ileum and antimicrobial activity on microorganismsView study →}; the isolate-level calcium-channel data belong to menthol ^{12Reference 12Hawthorn M et al. · 1988The actions of peppermint oil and menthol on calcium channel dependent processes in intestinal, neuronal and cardiac preparationsView study →}

Mechanisms

Menthone’s two best-characterised interactions are both with plant enzymes. That is an accurate picture of the molecule: it is a well-understood intermediate and a poorly-characterised drug.

Pharmacokinetics

Nothing specific is established for isolated menthone in humans — no absorption fraction, no bioavailability figure, no half-life. What is known is generic to the mint ketones: they are lipophilic, readily absorbed, and cleared by hepatic oxidation and conjugation. Menthone has been assessed as a fragrance ingredient under the RIFM programme ^{9Reference 9Api AM et al. · 2023ReviewRIFM fragrance ingredient safety assessment, menthone, CAS Registry Number 10458-14-7 — reviewView study →} and, together with carvone, is one of the alicyclic ketones on which the FEMA GRAS re-evaluation of mint, buchu, dill and caraway flavour complexes was built ^{8Reference 8Cohen SM et al. · 2020ReviewFEMA GRAS assessment of natural flavor complexes: mint, buchu, dill and caraway derived flavoring ingredients — reviewView study →}; those assessments are exposure-based and do not substitute for clinical pharmacokinetics.

Clinical Trials

Last checked: September 2026.

Isolate vs. Plant Studies

The split here is unusually lopsided. Menthone’s plant biochemistry has been studied as the isolate, precisely and repeatedly — recombinant enzymes, Km values, stereochemical outcomes ^{1,2Reference 1Davis EM et al. · 2005Monoterpene metabolismView study →Reference 2Liu C et al. · 2021Functional characterization and structural insights into stereoselectivity of pulegone reductase in menthol biosynthesisView study →}. Its pharmacology has barely been studied as the isolate at all: two in-vitro antimicrobial papers ^{3,4Reference 3Zhao W et al. · 2023In vitroMenthone exerts its antimicrobial activity against methicillin resistant Staphylococcus aureus by affecting cell membrane properties and lipid profile — in vitroView study →Reference 4Makkar MK et al. · 2018In vitroEvaluation of Mentha arvensis essential oil and its major constituents for fungitoxicity — in vitroView study →}, and otherwise a supporting mention inside work on peppermint or buchu oil ^{5,7,10Reference 5Saharkhiz MJ et al. · 2012In vitroChemical composition, antifungal and antibiofilm activities of the essential oil of Mentha piperita L. — in vitroView study →Reference 7Lis-Balchin M et al. · 2001Buchu (Agathosma betulina and A. crenulata, Rutaceae) essential oils: their pharmacological action on guinea-pig ileum and antimicrobial activity on microorganismsView study →Reference 10Zhao H et al. · 2022ReviewPeppermint essential oil: its phytochemistry, biological activity, pharmacological effect and application — reviewView study →}.

Because menthone is abundant in oils that do have effects, it inherits credit easily. The IBS, headache and antispasmodic literature that mint is known for was generated with enteric-coated peppermint oil and with menthol, and both the calcium-channel mechanism and the clinical outcomes are attributed there ^{6,11,12Reference 6Chumpitazi BP et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →Reference 11Grigoleit HG · 2005ReviewPharmacology and preclinical pharmacokinetics of peppermint oil — reviewView study →Reference 12Hawthorn M et al. · 1988The actions of peppermint oil and menthol on calcium channel dependent processes in intestinal, neuronal and cardiac preparationsView study →}. Nothing in that record isolates menthone’s contribution.

Prevalence in Nature

Menthone is a Lamiaceae molecule with one notable outlier in an unrelated family.

Peppermint (Mentha × piperita) carries it at 14–32% of the leaf oil under pharmacopoeial composition limits, second only to menthol ^{6,11Reference 6Chumpitazi BP et al. · 2018ReviewReview article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — reviewView study →Reference 11Grigoleit HG · 2005ReviewPharmacology and preclinical pharmacokinetics of peppermint oil — reviewView study →}. The ratio moves with harvest date, because the menthol-forming reductase belongs to a late oil-maturation programme ^{1Reference 1Davis EM et al. · 2005Monoterpene metabolismView study →}; a measured sample of cultivated M. piperita found menthol at 53.3% with menthone not among the top three components at all ^{5Reference 5Saharkhiz MJ et al. · 2012In vitroChemical composition, antifungal and antibiofilm activities of the essential oil of Mentha piperita L. — in vitroView study →}, which is how wide the spread can be.

Cornmint / field mint (Mentha canadensis, published as M. arvensis) is bred for menthol, and menthone falls accordingly — one cultivar analysis found isomenthone at 5.2% with menthol at 77.9% ^{4Reference 4Makkar MK et al. · 2018In vitroEvaluation of Mentha arvensis essential oil and its major constituents for fungitoxicity — in vitroView study →}.

Buchu (Agathosma betulina, Rutaceae) is the outlier: a South African shrub, unrelated to the mints, whose oil is dominated by menthone together with its epimer isomenthone ^{7,8Reference 7Lis-Balchin M et al. · 2001Buchu (Agathosma betulina and A. crenulata, Rutaceae) essential oils: their pharmacological action on guinea-pig ileum and antimicrobial activity on microorganismsView study →Reference 8Cohen SM et al. · 2020ReviewFEMA GRAS assessment of natural flavor complexes: mint, buchu, dill and caraway derived flavoring ingredients — reviewView study →}. Buchu also carries the genus-signature ketone diosphenol and, depending on chemotype, substantial pulegone — which is where that herb’s real safety question sits.

Smaller amounts occur across the mint family, including in Clinopodium douglasii, where menthone is one of several chemotype-defining ketones.

Discovery & Synthesis

Menthone has been known as a peppermint-oil constituent since the nineteenth-century work that characterised the mint terpenes, and its chemistry has never been mysterious: it is menthol’s oxidation product and is prepared straightforwardly by oxidising menthol, which is the industrial route to it today. Commercially it is a flavour and fragrance material rather than a pharmaceutical, produced in far smaller volume than menthol.

The part of its story that was genuinely settled recently is biological rather than chemical. The two peppermint menthone reductases were cloned, expressed in E. coli and kinetically characterised in 2005, resolving how a single ketone gives rise to all four menthol stereoisomers found in the oil ^{1Reference 1Davis EM et al. · 2005Monoterpene metabolismView study →}; the structural basis of the pulegone reductase step upstream was worked out in 2021 ^{2Reference 2Liu C et al. · 2021Functional characterization and structural insights into stereoselectivity of pulegone reductase in menthol biosynthesisView study →}.

Patents: not yet researched.

Toxicity & Safety

Menthone carries a low flag. It is consumed daily in mint-flavoured products, has a published fragrance-ingredient safety assessment ^{9Reference 9Api AM et al. · 2023ReviewRIFM fragrance ingredient safety assessment, menthone, CAS Registry Number 10458-14-7 — reviewView study →}, and is one of the constituents on which the FEMA expert panel based its affirmation of GRAS status for peppermint, spearmint, buchu, dill and caraway oils ^{8Reference 8Cohen SM et al. · 2020ReviewFEMA GRAS assessment of natural flavor complexes: mint, buchu, dill and caraway derived flavoring ingredients — reviewView study →}.

Safety at a Glance

✅ Low / no toxicity

• A long-standing food and fragrance constituent. Assessed under both the FEMA GRAS and RIFM programmes at flavour and fragrance exposure levels.
• Concentrated oils are irritant. Buchu leaf oil is classified as irritant to skin and eyes and as a skin and respiratory sensitiser; the caution belongs to the oil, and menthone is a major part of it.
• Menthone is not the safety problem in a mint oil. The hepatotoxicity and the regulatory intake limits attached to mint oils belong to pulegone and its metabolite menthofuran.

Full Safety & Interactions Detail

What is established. Menthone’s safety record is an exposure record rather than a toxicology package: it is evaluated as a flavouring and fragrance constituent at the levels people actually encounter ^{8,9Reference 8Cohen SM et al. · 2020ReviewFEMA GRAS assessment of natural flavor complexes: mint, buchu, dill and caraway derived flavoring ingredients — reviewView study →Reference 9Api AM et al. · 2023ReviewRIFM fragrance ingredient safety assessment, menthone, CAS Registry Number 10458-14-7 — reviewView study →}. No isolated-molecule clinical toxicity data exist.

What belongs to the oil rather than the molecule. Buchu oil, in which menthone is a dominant component, is classified as an irritant and a skin and respiratory sensitiser. Concentrated mint and buchu oils should be diluted for topical use and are not interchangeable with the herb.

What belongs to a different molecule entirely. The hepatic toxicity, the abortifacient reputation and the EU intake limits attached to mints run through pulegone and its bioactivated metabolite menthofuran. Menthone is chemically adjacent to pulegone — it is pulegone’s reduction product — but the reactive-metabolite chemistry that makes pulegone hepatotoxic requires pulegone’s α,β-unsaturated ketone, which menthone does not have. Reading pulegone’s risk onto menthone overstates it.

Reproductive note. No reproductive-toxicity dataset for isolated menthone is characterised here. Pregnancy and lactation decisions belong to the herb or product page.

Interactions. None documented for the isolated molecule; no clinical pharmacokinetic study exists against which an interaction could be assessed.

Dosage

No therapeutic dose has been established for isolated menthone, and there are no human trials from which one could be derived. Human exposure is dietary and cosmetic, as a constituent of the oils below.

These are composition figures, not doses, and are not a personal recommendation.

References

1. Davis EM, Ringer KL, McConkey ME, et al. (2005). Monoterpene metabolism. Cloning, expression, and characterization of menthone reductases from peppermint. Plant Physiol. https://pubmed.ncbi.nlm.nih.gov/15728344/
2. Liu C, Gao Q, Shang Z, et al. (2021). Functional characterization and structural insights into stereoselectivity of pulegone reductase in menthol biosynthesis. Front Plant Sci. https://pubmed.ncbi.nlm.nih.gov/34917113/
3. Zhao W, Yang C, Zhang N, et al. (2023). Menthone exerts its antimicrobial activity against methicillin resistant Staphylococcus aureus by affecting cell membrane properties and lipid profile — in vitro. Drug Des Devel Ther. https://pubmed.ncbi.nlm.nih.gov/36721663/
4. Makkar MK, Sharma S, Kaur H (2018). Evaluation of Mentha arvensis essential oil and its major constituents for fungitoxicity — in vitro. J Food Sci Technol. https://pubmed.ncbi.nlm.nih.gov/30150845/
5. Saharkhiz MJ, Motamedi M, Zomorodian K, et al. (2012). Chemical composition, antifungal and antibiofilm activities of the essential oil of Mentha piperita L. — in vitro. ISRN Pharm. https://pubmed.ncbi.nlm.nih.gov/23304561/
6. Chumpitazi BP, Kearns GL, Shulman RJ (2018). Review article: the physiological effects and safety of peppermint oil and its efficacy in irritable bowel syndrome and other functional disorders — review. Aliment Pharmacol Ther. https://pubmed.ncbi.nlm.nih.gov/29372567/
7. Lis-Balchin M, Hart S, Simpson E (2001). Buchu (Agathosma betulina and A. crenulata, Rutaceae) essential oils: their pharmacological action on guinea-pig ileum and antimicrobial activity on microorganisms. J Pharm Pharmacol. https://pubmed.ncbi.nlm.nih.gov/11341377/
8. Cohen SM, Eisenbrand G, Fukushima S, et al. (2020). FEMA GRAS assessment of natural flavor complexes: mint, buchu, dill and caraway derived flavoring ingredients — review. Food Chem Toxicol. https://pubmed.ncbi.nlm.nih.gov/31604112/
9. Api AM, Belsito D, Botelho D, et al. (2023). RIFM fragrance ingredient safety assessment, menthone, CAS Registry Number 10458-14-7 — review. Food Chem Toxicol. https://pubmed.ncbi.nlm.nih.gov/37758049/
10. Zhao H, Ren S, Yang H, et al. (2022). Peppermint essential oil: its phytochemistry, biological activity, pharmacological effect and application — review. Biomed Pharmacother. https://pubmed.ncbi.nlm.nih.gov/35994817/
11. Grigoleit HG, Grigoleit P (2005). Pharmacology and preclinical pharmacokinetics of peppermint oil — review. Phytomedicine. https://pubmed.ncbi.nlm.nih.gov/16121523/
12. Hawthorn M, Ferrante J, Luchowski E, et al. (1988). The actions of peppermint oil and menthol on calcium channel dependent processes in intestinal, neuronal and cardiac preparations. Aliment Pharmacol Ther. https://pubmed.ncbi.nlm.nih.gov/2856502/

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