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Names | |
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IUPAC name (3E)-1,7,7-Trimethyl-3-[(4-methylphenyl)methylene]-2-norbornanone | |
Other names 4-Methylbenzylidene camphor 3-(4-Methylbenzylidene)bornan-2-one 3-(4-Methylbenzylidene)-dl-camphor | |
Identifiers | |
3D model (JSmol) | |
Abbreviations | 4-MBC |
ChemSpider | |
ECHA InfoCard | 100.048.386 |
EC Number |
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PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
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Properties | |
C18H22O | |
Molar mass | 254.37 g/mol |
Appearance | White crystalline powder |
Melting point | 66 to 69 °C (151 to 156 °F; 339 to 342 K) |
Insoluble | |
Hazards | |
GHS labelling: | |
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Warning | |
H410 | |
P273, P391, P501 | |
Pharmacology | |
Legal status |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Enzacamene (INN; also known as 4-methylbenzylidene camphor or 4-MBC) is an organic camphor derivative that is used in the cosmetic industry for its ability to protect the skin against UV, specifically UV B radiation. As such, it is used in sunscreen lotions and other skincare products claiming a SPF value.
All camphor-derived sunscreens dissipate photon energy by cis-trans isomerisation. However, for enzacamene, the quantum yield for this isomerization is only between 0.13 and 0.3. This low quantum yield means that other photochemical processes are also occurring, which may contribute to its limited photostability compared to other UV filters. [2]
Studies have extensively documented that enzacamene acts as an endocrine disruptor. The scientific evidence demonstrates both estrogenic and thyroid-disrupting effects:
Multiple peer-reviewed studies have demonstrated that 4-MBC exhibits estrogenic activity through estrogen receptor binding and activation. Mueller et al. (2003) showed that 4-MBC activates both estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ) in human and rat cells, with preferential binding to ERβ. The compound stimulated estrogen-responsive alkaline phosphatase activity in human endometrial cells and showed measurable transactivation at concentrations above 1 μM. [3]
Schlumpf et al. (2004) demonstrated that 4-MBC and the related compound 3-benzylidene camphor displaced estradiol from estrogen receptors, particularly ERβ, with 4-MBC showing an IC₅₀ of 35.3 μM for ERβ binding. The compound stimulated MCF-7 breast cancer cell proliferation with an EC₅₀ of 3.9 μM. [4]
Developmental exposure studies by Durrer et al. (2005) found that prenatal and postnatal exposure to 4-MBC in rats altered expression of estrogen target genes including ERα, progesterone receptor, and insulin-like growth factor-I in the uterus. A related study by Maerkel et al. (2007) demonstrated sex- and region-specific alterations in estrogen target gene regulation in the brain following developmental 4-MBC exposure. [5] [6]
Research has demonstrated that 4-MBC significantly disrupts thyroid function. Wuttke et al. (2006) found that 4-MBC treatment in rats resulted in decreased serum T₄ levels and increased TSH levels, indicating thyroid disruption. The study showed that 4-MBC inhibited T₄ production while stimulating TSH release, effects that were distinct from estradiol treatment. [7]
A comprehensive study presented at the European Congress of Endocrinology (2008) demonstrated that 4-MBC causes effects comparable to primary hypothyroidism in rats. At concentrations ≥33 mg/kg, 4-MBC significantly elevated TSH levels while T₄ levels decreased and T₃ levels remained unchanged - a pattern typical of early hypothyroidism. The study found increased thyroid gland weights and altered expression of thyroid-related genes including TSH receptor, sodium-iodide symporter, and thyroid peroxidase. [8]
The European Union has completely banned 4-MBC in all cosmetic products through Commission Regulation (EU) 2024/996, adopted on April 3, 2024. The Scientific Committee on Consumer Safety (SCCS) concluded in their 2022 opinion that there is insufficient data to evaluate potential genotoxicity and sufficient evidence that 4-MBC acts as an endocrine disruptor affecting both thyroid and estrogen systems. [9] [10]
Implementation timeline:
The compound has been moved from Annex VI (permitted UV filters) to Annex II (prohibited substances) as entry 1730.
The SCCS has identified multiple safety concerns: