Chlorotrianisene: Properties, Uses & Lab Handling Guide

Chlorotrianisene is a long-acting, nonsteroidal synthetic estrogen that acts as an estrogen receptor agonist and has been widely employed as a pharmacological tool compound in reproductive biology and hormone-related research.

Chemical Name

Chlorotrianisene (TACE); 1-chloro-2-[4-methoxyphenyl]-1,2-bis(4-methoxyphenyl)ethylene (systematic name varies by source)

CAS Number

569-57-3

Molecular Formula

C₂₃H₂₁ClO₃

Molecular Weight

380.86 g/mol

Mechanism of Action

Binds and activates estrogen receptors (ERα and ERβ); acts as a prodrug partially converted to active estrogenic metabolites in vivo

Solubility

Poorly soluble in water; soluble in ethanol, DMSO, and other organic solvents

Storage Condition

Store at 2–8 °C, protected from light, in a tightly sealed container

Chemical Identity and Physical Properties

Chlorotrianisene (CAS 569-57-3), also abbreviated as TACE, is a nonsteroidal synthetic estrogen belonging to the triphenylethylene class of compounds. Its molecular formula is C₂₃H₂₁ClO₃ with a molecular weight of approximately 380.86 g/mol. The compound features three para-methoxyphenyl groups and one chlorine substituent arranged around a central ethylene core, conferring structural similarity to other triphenylethylene estrogens such as tamoxifen and diethylstilbestrol analogues.

Chlorotrianisene appears as a white to off-white crystalline powder at room temperature. It exhibits poor aqueous solubility, which is typical for highly lipophilic nonsteroidal estrogens. For laboratory use, stock solutions are best prepared in anhydrous ethanol or DMSO at concentrations of 10–100 mM, followed by dilution into aqueous buffer immediately before use. The compound is stable when stored at 2–8 °C in a desiccated, light-protected environment.

Mechanism of Action and Pharmacological Profile

Chlorotrianisene functions as an estrogen receptor (ER) agonist, binding to both ERα and ERβ subtypes. Upon binding, it promotes receptor dimerization and nuclear translocation, leading to transcriptional activation of estrogen-responsive genes. The compound is frequently described as a prodrug: it is stored in adipose tissue and slowly released and metabolized in vivo to generate more potent estrogenic metabolites, which accounts for its characteristically long duration of action compared with endogenous estradiol.

Because of its prolonged half-life and tissue distribution profile, chlorotrianisene has served as a tool compound in research models investigating estrogen-dependent cellular proliferation, gene expression, and reproductive physiology. Researchers should note that, like other triphenylethylene compounds, chlorotrianisene may exhibit partial agonist or context-dependent activity depending on the cellular and receptor subtype context; appropriate controls including a full agonist (e.g., 17β-estradiol) and an ER antagonist (e.g., ICI 182,780) are recommended in experimental designs.

Laboratory Applications and Experimental Considerations

Chlorotrianisene is employed in a range of in vitro and in vivo research contexts, including: (1) estrogen receptor binding and transactivation assays; (2) studies of estrogen-responsive gene expression using reporter gene systems; (3) investigation of estrogen effects on cell proliferation in ER-positive cell lines (e.g., MCF-7); and (4) animal model studies of estrogenic activity and reproductive endocrinology.

When designing in vitro experiments, researchers should use estrogen-depleted (phenol-red-free, charcoal-dextran-stripped serum) culture media to minimize background estrogenic activity. Vehicle controls (matching solvent concentration ≤0.1% v/v DMSO or ethanol) must be included. Dose-response experiments spanning at least three log units of concentration are advisable to characterize potency. Given the lipophilic nature of the compound, adsorption to plasticware is possible; use of glass or low-binding labware is recommended for dilute working solutions.

Safe Handling, Hazards and Regulatory Notes

Chlorotrianisene is a hormonally active compound and should be treated as a potential endocrine disruptor in the laboratory setting. Personnel handling this reagent should wear appropriate personal protective equipment (PPE), including nitrile gloves, a laboratory coat, and eye protection. Operations generating dust or aerosols should be conducted in a chemical fume hood or biological safety cabinet.

The compound is not classified as acutely toxic under standard GHS criteria at typical laboratory exposure levels; however, chronic or repeated exposure to estrogenic compounds carries potential health risks, particularly for pregnant individuals or those with hormone-sensitive conditions. Researchers should consult the current Safety Data Sheet (SDS) supplied with the product before use. Disposal must comply with local and institutional regulations governing hormonally active substances; do not dispose of via standard drain or municipal waste streams.

Preparation, Reconstitution and Storage Recommendations

For routine laboratory use, prepare a concentrated stock solution of chlorotrianisene at 10–50 mM in anhydrous DMSO or absolute ethanol. Vortex thoroughly and warm gently (37 °C water bath, ≤5 min) if necessary to aid complete dissolution. Aliquot the stock solution into single-use volumes to avoid repeated freeze–thaw cycles, which may compromise compound integrity over time.

Working solutions should be prepared fresh by diluting stock into the appropriate aqueous buffer or culture medium immediately before use. Store unused stock aliquots at –20 °C under desiccating conditions and protected from light; for long-term storage beyond six months, –80 °C is preferred. The original sealed product should be stored at 2–8 °C as specified on the product label. Always allow cold vials to equilibrate to room temperature before opening to prevent moisture condensation on the compound.

Frequently asked questions

What is the recommended solvent for preparing chlorotrianisene stock solutions?

Anhydrous DMSO or absolute ethanol are the preferred solvents for preparing chlorotrianisene stock solutions, as the compound is poorly soluble in water. Working solutions can then be prepared by diluting the stock into aqueous media immediately before use, keeping the organic solvent concentration at or below 0.1% v/v.

How does chlorotrianisene differ mechanistically from 17β-estradiol?

Unlike 17β-estradiol, which is an endogenous steroidal estrogen that acts directly and rapidly, chlorotrianisene is a nonsteroidal triphenylethylene compound that behaves partly as a prodrug. It accumulates in adipose tissue and is slowly released and metabolized to generate active estrogenic metabolites, resulting in a prolonged duration of action. Its receptor binding affinity is generally lower than that of estradiol, and its activity may be context-dependent across cell types and receptor subtypes.

Is chlorotrianisene suitable for use in cell culture experiments?

Yes, chlorotrianisene is used in cell culture studies, particularly in ER-positive cell lines such as MCF-7. For reliable results, researchers should use phenol-red-free medium supplemented with charcoal-dextran-stripped serum to eliminate background estrogenic interference. Appropriate vehicle and positive controls should always be included. Glass or low-binding plasticware is recommended for dilute solutions to minimize compound adsorption.

What safety precautions are required when handling chlorotrianisene?

Chlorotrianisene should be handled as a hormonally active compound. Wear nitrile gloves, a lab coat, and safety glasses at all times. Conduct powder weighing or any dust-generating operations in a fume hood. Pregnant individuals or those with hormone-sensitive conditions should avoid direct exposure. Consult the current product SDS before use and dispose of waste in accordance with local regulations for hormonally active substances.

What controls should be included in chlorotrianisene estrogenic activity assays?

Experiments should include a vehicle-only negative control (matched solvent at the same concentration), a positive control with a well-characterized full ER agonist such as 17β-estradiol, and ideally an ER antagonist control (e.g., ICI 182,780 or fulvestrant) to confirm receptor-mediated activity. Including multiple concentrations of chlorotrianisene across at least three log units enables full dose-response characterization.

References

1. Inadomi CL, et al. Pharmacology of chlorotrianisene and related nonsteroidal estrogens. General reference — specific article details require verification.
2. Kuiper GG, et al. Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors α and β. Endocrinology. 1997;138(3):863–870. (General ER pharmacology reference; applicability to chlorotrianisene should be verified.) doi:10.1210/endo.138.3.4979
3. Shyam Sunder S, et al. Chlorotrianisene: clinical and pharmacological properties. General textbook reference — details require verification.
4. Goodman & Gilman's The Pharmacological Basis of Therapeutics. Nonsteroidal estrogens chapter. McGraw-Hill. (Exact edition and page numbers require verification.)

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