2–3.2 g/L in water
Five to eight times the solubility of menthol at 25 °C, which is what makes an alcohol-free aqueous spray possible.
Technology & research
One ester. Cooling and antimicrobial activity from the same dose.
Menthol citrate ester is a mono-ester of L-menthol and citric acid. Esterification turns a volatile, oil-soluble alcohol into an amphiphilic molecule that disperses in water, resists crystallising, and stays in the formula instead of leaving the bottle.
Looking for the development service rather than the data? See Formulation R&D.
Technical data
MC‑01 · mono‑ester
Menthol citrate ester
L-menthol × citric acid, Fischer esterification
Molecular formula
C₁₆H₂₆O₇
Molecular weight
330.38 g/mol
Water solubility
2–3.2 g/L at 25 °C · 5–8× menthol
Volatility
Reduced >90% boiling range 320–350 °C
Partition coefficient
logP ≈ 2.3 menthol ≈ 3.8
Supply forms
Oil · 10% Na salt solution · Na salt powder
Synthesis route and in‑vitro microbiology disclosed in published patent application CN 121731277 A.
The chemistry
Why we esterify instead of just using menthol.
L-menthol is a good sensate and a poor ingredient: it volatilises, it barely dissolves in water, and it crystallises out of a formula at low temperature. Reacting one of its hydroxyl groups with citric acid fixes those three problems at once.
L-MENTHOLC₁₀H₂₀O · 156.27volatile alcohol
+
CITRIC ACIDC₆H₈O₇ · 192.12tri-carboxylic acid
↓ esterification · − H₂O
MENTHYL CITRATEC₁₆H₂₆O₇ · 330.38amphiphilic mono-ester
Volatility down >90%
The boiling range moves from 216 °C to 320–350 °C. That is the difference between a five-minute sensation and an eight-hour one.
No bloom at 4 °C
Lower molecular symmetry and higher steric hindrance break the packing that makes menthol crystallise out of a formula on a cold shelf.
Physicochemical values are from in-house characterisation of the supplied grade. Methods and raw data are included in the technical dossier.
Supply forms
Three grades for three formulation needs.
The free acid suits oil-phase and emulsion work. The sodium salt is what makes a clear aqueous spray or a shampoo possible without a solubiliser.
| Property | Free acid | Sodium salt, 10% solution | Sodium salt, powder |
|---|---|---|---|
| Appearance | Pale yellow to amber oil | Slightly hazy mobile liquid | White powder |
| Odour | Characteristic menthol | ||
| pH | 3–4 (2% dilution) | 8–9 (neat) | 9–10 (1% dilution) |
| Best suited to | Emulsions, balms, oil gels, patches | Clear sprays, toners, shampoos | Powder systems, concentrates, dry blends |
| Handling note | Add to the oil phase before emulsification | Add cold, after the thickener | Pre-dissolve in water or glycol |
Mechanism
Why an amphiphile behaves differently from a solvent.
Menthol acts on cold receptors and then evaporates. The ester does that, and also interacts with microbial membranes — not by poisoning a single target, but by three physical routes that are difficult for a microorganism to mutate around.
It inserts
The menthyl ring partitions into the phospholipid bilayer while the citrate head stays at the interface. Membrane integrity and permeability break down, and intracellular ions leak out.
It sequesters
Unreacted carboxyl groups bind Ca2+, Mg2+ and Fe3+, cofactors for respiratory-chain and nucleic-acid enzymes. Enzyme activity falls without any direct binding to the enzyme.
It acidifies
Residual acidity pulls the local microenvironment to pH 5.0–5.5, away from the 7.2–7.6 optimum of many bacteria, and destabilises the outer membrane of Gram-negatives.
The fungal route: in fungi, the ester is proposed to interfere with the lanosterol 14α-demethylase step of ergosterol synthesis — consistent with the MIC data below.
Performance data
What the in-vitro work actually shows.
Contact time decides more than concentration in rinse-off formats. The data below separates the two, because a shampoo touches the scalp for one to three minutes.
1.25 mg/mL
MIC₈₀ for Malassezia furfur, agar dilution, ≥80% growth inhibition
89.66%
Inhibition at 1% after three minutes' contact
>99.99%
Broad-spectrum inhibition at 15–25 mg/mL over 15 minutes
>90%
Volatility reduction versus L-menthol
| Contact time | Inhibition |
|---|---|
| 1 minute | 50.60% |
| 3 minutes | 89.66% |
| Concentration | mg/mL | Inhibition |
|---|---|---|
| 1.5% | 15 | 90.59% |
| 2.0% | 20 | 95.29% |
| 2.5% | 25 | 97.65% |
Both tables reproduce data disclosed in CN 121731277 A. Plates, controls and the ketoconazole comparator are in the dossier.
| Organism | Inhibition |
|---|---|
| Staphylococcus aureus Gram-positive | >99.99% |
| Escherichia coli Gram-negative | >99.99% |
| Candida albicans Yeast | >99.99% |
Ketoconazole 10 µg/mL used as positive control.
Cooling performance
The cooling holds when you raise the dose.
An eight-hour mean temperature drop on cooling patches, comparing the ester against L-menthol and a synthetic cooling agent at two use levels.
0.2% w/w
0.5% w/w
Menthol citrate esterthis ingredient
6.35
6.20
−0.15 °Cstable
Synthetic coolantmarket reference
6.10
5.50
−0.60 °Cfalls
L-Mentholincumbent
6.20
5.40
−0.80 °Cfalls
5.05.56.06.5 °C
The interesting column is the second one.
At the low use level all three ingredients look similar. Push to 0.5% and the two incumbents lose between 0.6 and 0.8 °C of mean performance, while the ester holds its level.
That difference is a formulation consequence, not a sensory opinion: menthol and the synthetic coolant reach a solubility ceiling and start to bloom or volatilise out of the patch matrix, so extra dose stops becoming extra cooling.
- No alcohol required in aqueous systems
- Stable at 4 °C — no precipitation or water separation over four weeks
- Dose response linear across 0.1–0.5% in the patch series (r = 0.977)
In the formula
Use levels, handling and what it tolerates.
Guidance from our development work, adjusted with you on your own base.
| Parameter | Recommendation | Reason |
|---|---|---|
| Rinse-off systems | 1.0–3.0% w/w | Compensates for the short contact window in shampoo and body wash |
| Leave-on systems | 0.3–1.5% w/w | Continuing exposure means less material is needed |
| Contact window | 1–3 minutes | Where the antimicrobial effect is concentrated; design the claim around it |
| Compatible actives | Niacinamide, panthenol, PCA-zinc, glycerin, cationic polymers | Tested together in reference formulas |
| Stability observed | 4 °C, 25 °C and 40 °C for 4 weeks | No clouding, precipitation or odour change in the reference shampoo and gel |
Research programme
Where the work comes from.
The chemistry was developed in academic laboratories and is published. We manufacture the material and run the formulation work.
- Published patent application — CN 121731277 A, “Menthol citrate ester, its preparation and use”, filed 11 December 2025, published 27 March 2026. The compound, the synthesis routes and the microbiology are on the public record.
- Two synthesis routes — Fischer esterification with an acid catalyst and molecular sieve, or EDCI/DMAP coupling, both followed by silica chromatography to the mono-ester.
- Ongoing formulation research — sensory profiling, surfactant compatibility and long-term stability in shampoo, spray and patch formats.
Ownership and licensing terms for the patent application are stated in writing in the technical dossier.
Image note: laboratory visuals are illustrative renderings.
Toxicology
Acute oral and acute inhalation studies, completed.
Both endpoints have been run by an accredited third-party laboratory. The full reports — protocol, raw observations and conclusion — are released to qualified buyers on request, for review by your own toxicologist.
Oral toxicity study
A single-dose oral study with a 14-day observation period. Report on file with the laboratory's own conclusion.
- Third-party accredited laboratory
- Full report available on request
Inhalation toxicity study
A single-exposure inhalation study on the same observation schedule. Report on file with the laboratory's own conclusion.
- Third-party accredited laboratory
- Full report available on request
How to get them: ask for the toxicology pack with your grade and destination market. Both reports go out with the laboratory's credentials. Request the toxicology pack
Evidence map
Three columns: what ships today, what we commission, what you hold.
Three categories decide your timeline and your budget. This is where each one sits.
Records from our own work
- Specification with test methods and acceptance limits
- Batch CoA against that specification
- SDS in GHS format, plus transport classification
- Synthesis route and process description
- Solubility, pH window and volatility measurements
- The in-vitro Malassezia set shown above
- Acute oral and inhalation toxicology reports — available on request
Tests we can run or buy in
- OECD 439 / 492 irritation and ocular work
- OECD 442C / 442E sensitisation
- OECD 423 / 436 in GLP format, if your dossier needs the OECD route
- Zone IVb real-time and accelerated stability
- Preservative challenge in your base
- Compatibility against your surfactant system
Quoted at cost, with the laboratory's price passed through unchanged.
Files only the brand owner can own
- CPNP and ACD notifications
- US OTC drug listing and monograph compliance
- Halal, organic and similar certifications
- Clinical efficacy claims
- Finished-product safety assessment
We supply the ingredient inputs and the records behind them.
This map is updated per project. Anything in column 02 can be moved into column 01 with a quotation and a date — ask for both before you plan the launch.
The file
What travels with the material.
Four documents a formulator or a reviewer will ask for, and where each one comes from.
Identity and assay
Specification, a certificate of analysis against that specification for the batch you receive, and the analytical methods behind both.
Microbiology
Time-kill and MIC data generated in vitro, with plates, controls and the positive comparator — ready for a structure–activity discussion with your technical team.
Toxicology
Acute oral and acute inhalation reports from an accredited third-party laboratory, released on request for the grade and the market you are working in.
Market status
Listing and naming status confirmed in writing per destination, alongside the tests your submission needs and the laboratory quotation for them.
In-vitro results support formulation decisions and structure–activity work; label claims are built on the testing your market requires.
Go deeper
Three places this page leads.
Product customisation
Grade, dose, base, fragrance, pack and fill size — and the eighteen formats already on the bench.
Open the customisation pageWhy more can feel like less
The four mechanisms behind the dose-response curve, including the solubility ceiling and receptor desensitisation.
Read the noteZPT-free scalp care
The EU ban, the three reformulation routes, and what an in-vitro Malassezia dataset supports.
Read the briefWant the dossier for a specific grade?
Tell us the grade, the application and the market, and we will send what exists for it.