Estradiol

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Cat Number

API50282

CAS Number

50-28-2

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CAS Number

50-28-2

EINECS

200-023-8

Storage

Store at room temperature

Synonyms

17beta-Estradiol; Oestradiol; Dihydrofolliculin; Estrace; Aquadiol; Diogynets; Divigel; Vivelle; Diogyn; Dihydrotheelin

Molecular Formula

C18H24O2

Molecular Weight

272.4

Smiles

C[C@]12CC[C@H]3[C@H]([C@@H]1CC[C@@H]2O)CCC4=C3C=CC(=C4)O

Appearance

White to off-white crystalline powder

Melting Point

173°C

Boiling Point

445.9°C at 760 mmHg

Relative Density

1.17

General Description

Estradiol (E2) is a natural steroid hormone, the principal estrogen in humans, with a phenolic A-ring and a 17β-hydroxyl group. Its chemical structure is 3,17β-dihydroxyestra-1,3,5(10)-triene. Estradiol is a white to off-white crystalline powder, practically insoluble in water but soluble in organic solvents. It is the most potent endogenous estrogen.

Mechanism of Action

Estradiol binds to estrogen receptors (ERα and ERβ) in target tissues, and the receptor-ligand complex translocates to the nucleus, modulating gene transcription. This leads to the regulation of various physiological processes, including the development of secondary sex characteristics, maintenance of the reproductive system, bone mineralization, and cardiovascular function.

Application

Estradiol is indicated for the treatment of menopausal symptoms (vasomotor symptoms, vulvovaginal atrophy), for hormone replacement therapy (HRT) in hypogonadism, and for the prevention of osteoporosis. It is also used as a component of combined oral contraceptives. The drug is effective in relieving hot flashes, vaginal dryness, and preventing bone loss.

In male castrated rats, daily estradiol benzoate (EB) increased cocaine choice over food in a concurrent access paradigm, increased cocaine intake under progressive ratio, and enhanced acquisition of cocaine (but not food) reinforcement within the EB‑treated group. These effects mirror those previously observed in females, demonstrating that estradiol promotes cocaine preference and motivation in males as well.

Fig. 1 Impact of EB on cocaine and food acquisition. (Bagley JR, et al., 2019)

References

Bagley JR, et al. Estradiol increases choice of cocaine over food in male rats. Physiol Behav. 2019;203:18-24.

Single-nucleus RNA sequencing of aged male rat hypothalamus showed that 17α-estradiol treatment attenuated aging-induced elevation of neuronal metabolism, stress, and reduction of synapse formation pathways. It increased serum oxytocin, GnRH, testosterone, and HPG axis activity. GnRH1 upregulation mediated effects on energy homeostasis and stress response. CRH neurons showed prominent stress phenotypes distinct from Agrp/Ghrl neurons. Supervised clustering based on neuropeptides effectively assessed hypothalamic neuron subtype responses to aging and treatment.

Fig. 2 Two opposing regulatory signaling networks in neuron metabolism. (Li L, et al., 2025)

References

Li L, et al. The effects of 17α-estradiol treatment on endocrine system revealed by single-nucleus transcriptomic sequencing of hypothalamus. Elife. 2025;13:RP100346.

Does Estradiol require protection from light during long-term storage?

Yes, it is photosensitive. UV exposure can cause photodegradation and isomerization of the steroid ring. Store in light-resistant containers, preferably amber glass.

What is the recommended storage temperature for Estradiol?

Store at controlled room temperature (15-25°C). Avoid excessive heat above 30°C, which can accelerate oxidation of the phenolic A-ring.

Is Estradiol stable in transdermal and oral formulations?

Yes, when formulated with antioxidants and protected from light.

How is the impurity estrone (an oxidative degradation product) monitored?

This primary degradation product is specifically quantified using a stability-indicating HPLC method, ensuring it remains within pharmacopoeial limits.