Carvone: between regulatory caution and reasoned use in phyto-aromatherapy

Carvone is a cyclic monoterpene ketone found in several essential oils commonly used in phyto-aromatherapy. Its ambiguous regulatory status, particularly in relation to possible neurotoxicity, raises legitimate questions about its safe use. Should carvone be classified as a substance of concern? Scientific data allow us to qualify this approach.

Carvone exists in two enantiomeric forms:
(R)-(-)-carvone, predominant in spearmint (Mentha spicata);
(S)-(+)-carvone, predominant in caraway (Carum carvi) and cumin.
These two molecules have the same gross formula, but opposite spatial orientations. This stereochemical difference leads to distinct pharmacological effects, making carvone a textbook case on the importance of molecular configuration in therapeutics.

Antimicrobial activity

Carvone exhibits antibacterial activity in vitro, notably against Staphylococcus aureus, Escherichia coli, Listeria monocytogenes and Bacillus subtilis, with antibiofilm action too. These effects are attributed to an alteration in bacterial membrane integrity. However, their clinical relevance remains limited by low bioavailability and significant variability between essential oils.

Anti-inflammatory and antispasmodic activity

Animal studies have highlighted a reduction in the production of pro-inflammatory cytokines (such as TNF-α or IL-6) following carvone administration. The antispasmodic action is also well documented in intestinal models. These effects are dose-dependent and could be linked to modulation of ion channels (Na⁺, Ca²⁺, K⁺) or to changes in membrane fluidity, as is the case for many monoterpenes.

The neuropharmacological effects of carvone are very different depending on the enantiomer used. Several animal models have highlighted the following observations:

Table - Comparative activity of carvone enantiomers

These results suggest involvement of the GABAergic system, without evidence of a direct effect or exclusive role. As with other monoterpenes, the effects could also involve modulation of ion channels, membrane interactions, or an influence on other neurotransmitters (glutamate, acetylcholine). It is therefore premature to speak of allosteric modulation in the strict sense.

Carvone is rapidly absorbed and undergoes extensive hepatic metabolism, notably by hydroxylation and conjugation (phase I and II), which limits its systemic concentration. It has a short half-life and high inter-individual variability in absorption.
These factors explain the low clinical transposition of effects observed in vitro or in animal models, particularly when used orally. Effects may, however, be more marked by inhalation or cutaneous routes, which partially bypass first-pass metabolism.

Carvone displays low acute toxicity, with no data indicating irreversible neurotoxicity or CMR effects. No teratogenic effects have been observed, but data remain insufficient to guarantee safety during pregnancy or breastfeeding, particularly for (R)-(-)-carvone. There are also no clinical studies exploring its use in vulnerable populations (children, the elderly, liver failure patients).
To date, no specific drug interactions have been described, but caution remains recommended in people undergoing anticoagulant treatment, due to the lipophilic and metabolically active nature of carvone.

The potential classification of carvone as a substance of concern is based on European risk assessment standards. These include:
- The ALARA (As Low As Reasonably Achievable) principle,
- Safety factors for animal → human extrapolation,
- Consideration of sensitive populations,
- The absence of formal clinical studies.
Regulatory caution therefore does not necessarily reflect proven dangerousness, but the application of a risk management policy. However, this approach can lead to confusion, by equating reversible pharmacological effect with toxicity.

The pharmacological evaluation of carvone is still lacking on several points:

• The synergistic or antagonistic effects between carvone and other essential oil compounds (alcohols, esters, sesquiterpenes...) are poorly documented.
• Metabolic variabilities linked to genetic polymorphisms (e.g. CYP2C9, CYP3A4, UGTs) have not been studied, but could influence individual tolerance.
• Human clinical data remain scarce, or even non-existent in monotherapy.
• The route of administration profoundly modifies pharmacokinetics and therefore risk interpretation: it is necessary to distinguish between oral, cutaneous and inhalation uses.
• Populations at risk require a finer assessment: children, pregnant women, frail or poly-treated subjects.

These limitations justify a cautious but not alarmist attitude on the part of the practitioner, bearing in mind that carvone, like any active molecule, requires rigor and discernment.

Carvone is a pharmacologically active molecule, differentiated according to its enantiomer, and generally well tolerated in conventional aromatherapeutic uses. The effects observed on the central nervous system are reversible, dose-dependent, and do not involve any known irreversible neurotoxicity.
The regulatory approach, although based on legitimate precautionary principles, would benefit from a clear distinction between potentially undesirable effects and documented therapeutic effects, notably according to enantiomer, route of administration, dose and patient's terrain.
For the phyto-aromatherapy practitioner, carvone is not an innocuous molecule. But properly used, it can offer real therapeutic value, provided we don't give in to either unwarranted regulatory alarm or simplistic enthusiasm.

Bouyahya, A., Mechchate, H., Benali, T., Ghchime, R., Charfi, S., Balahbib, A., Burkov, P., Shariati, M. A., Lorenzo, J. M., & El Omari, N. (2021). Health benefits and pharmacological properties of carvone. Biomolecules.

Koleva, Y. K., Iliev, I. Z., Gandova, V. D., & Stoyanova, A. S. (2024). Potential toxicity, physicochemical properties and environmental behavior of L-carvone. Bulgarian Chemical Communications.

Finefield, J. M., Sherman, D. H., Kreitman, M., & Williams, R. M. (2012). Enantiomeric natural products: Occurrence and biogenesis. Angewandte Chemie International Edition.

Lange, B. M. (2015). Biosynthesis and biotechnology of high-value p-menthane monoterpenes, including menthol, carvone, and limonene. Advances in Biochemical Engineering/Biotechnology.

Sell, C. (2020). Chemistry of essential oils. In Handbook of Essential Oils (2nd ed.). CRC Press.

Silva, P. M. (2018). Efeito anti-hiperalgésico do óleo essencial de Lippia grata livre e complexado em β-ciclodextrina em modelos animais de dor crônica não inflamatória e dor neuropática (Doctoral thesis, Universidade Estadual de Feira de Santana).

Chizzola, R. (2013). Regular monoterpenes and sesquiterpenes (essential oils). In Natural Products (pp. 2879-2892). Springer.

Mahboubi, M. (2019). Caraway as important medicinal plants in management of diseases. Natural Products and Bioprospecting, 9(3), 127-139.

Barba, C., Toledano, R. M., Santa-María, G., Herraiz, M., & Martínez, R. M. (2013). Enantiomeric analysis of limonene and carvone by direct introduction of aromatic plants into multidimensional gas chromatography. Talanta, 110, 63-69.

Mahboubi, M. (2023). Caraway, peppermint and their essential oils in management of irritable bowel syndrome (IBS). Bulletin of Faculty of Pharmacy Cairo University.

Wojtunik-Kulesza, K. A., Rudkowska, M., Klimek, K., Mołdoch, J., Agacka-Mołdoch, M., Budzyńska, B., & Oniszczuk, A. (2024). S-(+)-Carvone, a monoterpene with potential anti-neurodegenerative activity-In vitro, in vivo and ex vivo studies. Molecules, 29(18), 4365.

Bergman, M. A., & Matthew, E. (n.d.). Structural diversity and biosynthesis of plant-derived p-menthane monoterpenes. [Data incomplete].

Unknown author. (2011). Alternative solvents in carvone hydrogenation. CORE.

Smith, R. L., & Sipes, I. G. (2018). The safety evaluation of food flavouring substances: The role of metabolic studies. Toxicology Research, 7(6), 947-960.