c004 — Mexoryl 400 (MCE / S87 — Methoxypropylamino Cyclohexenylidene Ethoxyethylcyanoacetate)
Status: Active research file. Created 2026-05-07. Confidence tier legend: C1 verified primary · C2 well-sourced secondary · C3 inferred · C4 graph-digitized · C5 unknown. Note: Mexoryl 400 is the newest approved UV filter (EU 2019, commercial 2022 — La Roche-Posay UVMune 400; broad rollout 2024). Public peer-reviewed data is limited; many parameters remain C5.
Section 1 — Identity
| Field | Value | Tier |
|---|---|---|
| INCI | Methoxypropylamino Cyclohexenylidene Ethoxyethylcyanoacetate | C1 |
| Synonyms | MCE; S87 (EU code); Mexoryl 400 | C1 |
| Trade name | Mexoryl 400 (L'Oréal — exclusive); developed jointly by L'Oréal and BASF | C1 |
| IUPAC | 2-Ethoxyethyl (2Z)-2-cyano-2-[3-(3-methoxypropylamino)cyclohex-2-en-1-ylidene]acetate | C1 |
| CAS | 1419401-88-9 | C1 |
| Molecular formula | C₁₇H₂₆N₂O₄ | C1 |
| Molecular weight | 322.41 g·mol⁻¹ | C1 |
| Physical state | Yellow solid powder; oil-soluble (lipophilic) | C1 |
| Melting point | 85–120 °C (range reported) | C1 |
| Solubility | Phenoxyethanol, dimethyl capramide, ethoxydiglycol, dimethyl isosorbide, alcohol (at 25 °C); poorly water-soluble | C2 |
| Chemical class | Cyclic merocyanine (donor–π–acceptor push–pull dye) | C1 |
Regulatory status
| Region | Status | Max conc. | Notes |
|---|---|---|---|
| EU (Annex VI new entry) | Approved 2019 via Regulation 2020/1684 (added as S87) | 3% | Based on SCCS/1605/19 (final opinion adopted 13 Dec 2019) |
| Australia (TGA) | Approved (post-2020) | 3% | Following EU |
| Japan | Status pending — not yet listed | — | C5 |
| Korea | Status pending — not yet listed | — | C5 |
| USA (FDA) | Not approved. No TEA submission has been made (this filter was discovered after the original 8 TEA submissions in 2003–2005). | — | Likely no US market access in foreseeable future |
Typical use concentrations
- Single permitted maximum: 3 % in EU.
- La Roche-Posay UVMune 400 (commercial 2022, mass rollout 2024): MCE typically ~1 %; combined with avobenzone (3%), bemotrizinol, octocrylene, ethylhexyl triazone, drometrizole trisiloxane, etc., for full-spectrum SPF 50+.
Section 2 — UV absorption spectrum
MCE is a single-peak deep-UVA1 filter — uniquely targeting the previously under-protected 370–400 nm "ultra-long UVA" band.
| Parameter | Value | Solvent | Tier | Source |
|---|---|---|---|---|
| λmax | 385 nm | Ethanol / hydroethanolic / cosmetic vehicle | C1 | SCCS/1605/19; Marionnet 2022; Wikipedia |
| ε at 385 nm | 63,052 L·mol⁻¹·cm⁻¹ (≈6.3 × 10⁴) | Ethanol | C2 | Cited in product/secondary review literature; SCCS dossier |
| E(1%, 1 cm) at 385 nm | ≈1956 (computed: ε × 10 / MW = 63052 × 10 / 322.41) | Ethanol | C3 | Computed |
| Spectral coverage | ~340–400 nm at >50% peak; significant absorbance to ~410 nm | — | C2 | Marionnet 2022 |
| Critical wavelength | ~389 nm (per Marionnet; in formula) | — | C2 | Marionnet 2022 |
| Coverage profile | Almost no UVB activity; primarily UVA1 with some UVA2 | — | C1 | Same |
The molecule is a cyclic merocyanine — a push-pull chromophore with the methoxypropylamino group (electron donor, secondary amine) and the cyanoacetate (electron acceptor) connected through a cyclohexenylidene π-bridge. The exceptionally long λmax (385 nm) is uncommon for cosmetic-approved filters; the closest analogue in regulatory inventory is Disodium Phenyl Dibenzimidazole Tetrasulfonate (335 nm) and DHHB (354 nm).
Section 3 — Photostability
MCE is reported to be highly photostable, though peer-reviewed photokinetic data is limited.
| Test condition | Result | Tier | Source |
|---|---|---|---|
| Solar simulator irradiation, in-formula (50 J/cm² UVA1) | "No significant photodegradation detected" | C2 | Marionnet 2022 |
| Hydroethanolic solution, accelerated UV stress | "100% intrinsic stability"; thermostable in different media | C2 | L'Oréal/BASF technical literature, secondary review |
| Photostability under high O₂ concentration | Stable | C2 | Same |
| Photoproducts | None characterized in published in-formula studies | C5 | — |
| Comparison vs avobenzone | MCE retains essentially full absorbance under conditions that degrade avobenzone by 30–50% | C2 | Marionnet 2022 (in-formula) |
Mechanism
Cyclic merocyanines decay from the S₁ state via ultrafast twisted intramolecular charge-transfer (TICT) relaxation around the central C=C bond (analogous to ecamsule/cinnamate isomerization but with constrained geometry). The cyclohexenylidene ring constrains the barrierless twist back to ground state, giving radiationless decay with negligible bond breaking.
Key point: unlike avobenzone (which has UVB-active photoproducts), and ecamsule (which generates Z-isomers), MCE has shown no published photoproducts under standard solar-simulator conditions — but data is from L'Oréal/BASF-sponsored literature only.
Section 4 — Mechanism / unique properties
- Photophysical mechanism: Push–pull merocyanine with TICT/torsional relaxation. Absorption populates an intramolecular charge-transfer state; ultrafast twisting around C=C of the cyclohexenylidene–cyanoacetate exocyclic double bond returns molecule to ground state without bond cleavage.
- Triplet/ROS yield: Reportedly very low; Φ(¹O₂) not published. C5 quantitative.
- Why this matters — the "ultra-long UVA1" gap: Until 2019, most UVA filters (avobenzone λmax 357 nm, ecamsule 345, DHHB 354) had absorbance falling rapidly above 380 nm. The 380–400 nm band ("ultra-long UVA") penetrates deepest into dermis, drives most photoaging and pigmentary disorders, and was only weakly attenuated by inorganic ZnO. MCE is the first organic filter with peak absorbance at 385 nm — closing the protection gap above 380 nm.
- Clinical UVA1 efficacy (Marionnet 2022, Bernerd 2022, de Dormael 2022, Flament 2024): In RCTs MCE-containing formulae reduced UVA1-induced pigmentation, dermal alteration, MMP-1 expression, IL-1/IL-6 expression in a 50 J/cm² UVA1 challenge; Flament 2024 showed measurable reduction of pigmentation/aging signs over 8 weeks of real-life sun exposure compared to MCE-free SPF50 control.
- Safety constraint: SCCS/1605/19 noted MCE is a secondary amine prone to N-nitrosation. Cosmetic formulations must keep nitrosamine impurities <50 ppb and avoid nitrosating co-formulants (e.g., bronopol, 2-bromo-2-nitropropane-1,3-diol). One case of severe allergic contact dermatitis was reported in 2024 (Loretan et al.) — first published sensitization signal for the molecule.
- "Next generation" rationale: First-in-class for ultra-long UVA1 organic filtration; closes the photoaging-relevant >380 nm gap; high ε at peak (~6.3 × 10⁴); photostable; complementary spectrum to BEMT and avobenzone.
Citations
- Winkler B, Hoeffken HW, Eichin K, Houy W. A cyclic merocyanine UV-A absorber: mechanism of formation and crystal structure. Tetrahedron Lett. 2014; 55(10):1749–1751. DOI: 10.1016/j.tetlet.2014.01.113. [C1 — original chemistry, BASF]
- SCCS (Scientific Committee on Consumer Safety). Opinion on Methoxypropylamino Cyclohexenylidene Ethoxyethylcyanoacetate (S87) — Submission II. SCCS/1605/19, final opinion adopted 13 Dec 2019. [C1, regulatory]
- European Commission. Commission Regulation (EU) 2020/1684 of 12 Nov 2020 amending Annex VI to Regulation (EC) No 1223/2009 of the European Parliament and of the Council on cosmetic products. (Adds Methoxypropylamino Cyclohexenylidene Ethoxyethylcyanoacetate at 3% max.)
- Marionnet C, de Dormael R, Marat X, et al. Sunscreens with the new MCE filter cover the whole UV spectrum: improved UVA1 photoprotection in vitro and in a randomized controlled trial. JID Innov. 2021; 2(1):100070. DOI: 10.1016/j.xjidi.2021.100070. PMID 35072138. [C1]
- de Dormael R, Marionnet C, Bastien P, et al. Improvement of photoprotection with sunscreen formulas containing the cyclic merocyanine UVA1 absorber MCE: in vivo demonstration under simulated and real sun exposure conditions in three randomised controlled trials. JEADV Clin. Pract. 2022; 1(3):229–239. DOI: 10.1002/jvc2.38.
- Bernerd F, Passeron T, Castiel I, Marionnet C. The damaging effects of long UVA (UVA1) rays: a major challenge to preserve skin health and integrity. Int. J. Mol. Sci. 2022; 23(15):8243. DOI: 10.3390/ijms23158243. PMC 9368482.
- Flament F, Bourokba N, Nouveau S, et al. The impact of methoxypropylamino cyclohexenylidene ethoxyethylcyanoacetate (MCE) UVA1 filter on pigmentary and ageing signs: an outdoor prospective 8-week randomized intra-individual comparative study in two populations of different genetic background. J. Eur. Acad. Dermatol. Venereol. 2024; 38(1):214–222. DOI: 10.1111/jdv.19486. PMID 37655436.
- Aguilera J, Gracia-Cazaña T, Gilaberte Y. New developments in sunscreens. Photochem. Photobiol. Sci. 2023; 22(10):2473–2482. DOI: 10.1007/s43630-023-00453-x. PMID 37543534.
- Loretan A, Spring P, Christen-Zaech S, Bonnet A. Severe allergic contact dermatitis caused by methoxypropylamino cyclohexenylidene ethoxyethylcyanoacetate. Contact Dermatitis 2025. DOI: 10.1111/cod.14700. PMID 39305114.
C5 / unresolved items
- Quantitative photostability metrics (% remaining at defined MED / J·cm⁻²) in peer-reviewed primary photochemistry literature — only sponsor-derived data found. C5.
- Quantum yields Φ_F, Φ_ISC, Φ(¹O₂), Φ(•O₂⁻) — none published. C5.
- Detailed photoproduct identification under solar simulation. C5.
- Japan / Korea regulatory listing dates. C5.
- Skin penetration percentages (cited as low; actual values not in public data). C5.