 Chemical Structure.png)
Physicochemical Properties
| Molecular Formula | C₁₈H₂₀O₂ |
| Molecular Weight | 268.35 |
| Exact Mass | 268.146 |
| CAS # | 474-86-2 |
| Related CAS # | Equilin-d4;285979-79-5 |
| PubChem CID | 223368 |
| Appearance | White to off-white solid |
| Density | 1.2±0.1 g/cm3 |
| Boiling Point | 459.1±45.0 °C at 760 mmHg |
| Melting Point | 238-240ºC(lit.) |
| Flash Point | 195.4±21.3 °C |
| Vapour Pressure | 0.0±1.2 mmHg at 25°C |
| Index of Refraction | 1.626 |
| LogP | 3.53 |
| Hydrogen Bond Donor Count | 1 |
| Hydrogen Bond Acceptor Count | 2 |
| Rotatable Bond Count | 0 |
| Heavy Atom Count | 20 |
| Complexity | 466 |
| Defined Atom Stereocenter Count | 3 |
| SMILES | OC1C=C2CC=C3[C@@]4([H])[C@@](C(CC4)=O)(CC[C@]3([H])C2=CC=1)C |
| InChi Key | WKRLQDKEXYKHJB-HFTRVMKXSA-N |
| InChi Code | InChI=1S/C18H20O2/c1-18-9-8-14-13-5-3-12(19)10-11(13)2-4-15(14)16(18)6-7-17(18)20/h3-5,10,14,16,19H,2,6-9H2,1H3/t14-,16+,18+/m1/s1 |
| Chemical Name | (9S,13S,14S)-3-hydroxy-13-methyl-9,11,12,14,15,16-hexahydro-6H-cyclopenta[a]phenanthren-17-one |
| Synonyms | 7-Dehydroestrone; Equilin |
| HS Tariff Code | 2934.99.9001 |
| Storage |
Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month |
| Shipping Condition | Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs) |
Biological Activity
| Targets |
- `Equilin (7-Dehydroestrone)` exhibits estrogenic activity, presumably targeting estrogen receptors (ERs) [1] - `Equilin (7-Dehydroestrone)` activates NMDA receptors to promote cortical neuron growth, with an EC50 of ~10 nM for neuron survival promotion [2] - `Equilin (7-Dehydroestrone)` activates the NF-κB signaling pathway to increase monocyte-endothelial adhesion, with an EC50 of ~25 nM for NF-κB p65 nuclear translocation [3] |
| ln Vitro |
Equilin in conjugated equine estrogen promotes monocyte-endothelial adhesion via NF-κB signaling[3]. - In primary rat cortical neuron cultures, treatment with `Equilin (7-Dehydroestrone)` (1 nM-1 μM) for 72 hours increased neuron viability dose-dependently: 10 nM increased viability by 35%, 100 nM by 62%, and 1 μM by 78% (MTT assay). This effect was completely blocked by MK-801 (1 μM, an NMDA receptor antagonist) [2] - In human umbilical vein endothelial cells (HUVECs) co-cultured with THP-1 monocytes, `Equilin (7-Dehydroestrone)` (1 nM-100 nM) for 24 hours increased monocyte-endothelial adhesion rate: 10 nM increased adhesion by 41%, 100 nM by 73% (flow cytometry). Western blot showed 100 nM `Equilin` upregulated NF-κB p65 (2.1-fold) and ICAM-1 (3.4-fold) protein expression [3] |
| ln Vivo |
- In ovariectomized female rats (n=5 per group), subcutaneous injection of `Equilin (7-Dehydroestrone)` (0.1 mg/kg/day or 0.5 mg/kg/day) for 14 days increased uterine weight by 52% (0.1 mg/kg) and 98% (0.5 mg/kg) compared to the vehicle group [1] - In adult male mice (n=6 per group), intraperitoneal injection of `Equilin (7-Dehydroestrone)` (1 mg/kg) for 3 days increased liver glycogen content by 38% vs. vehicle [1] - In ovariectomized female rats with cortical neuron injury (n=6 per group), oral gavage of `Equilin (7-Dehydroestrone)` (0.3 mg/kg/day) for 21 days increased surviving cortical neurons by 45% vs. vehicle; this effect was abolished by co-administration of MK-801 (0.1 mg/kg/day) [2] |
| Enzyme Assay |
- NMDA receptor activity assay (to verify `Equilin (7-Dehydroestrone)` targeting): Primary rat cortical neurons were seeded in 24-well plates (1×10⁵ cells/well) and treated with `Equilin` (10 nM) ± MK-801 (1 μM) for 48 hours. Intracellular Ca²⁺ concentration was measured using a Ca²⁺-sensitive fluorescent dye (excitation at 488 nm, emission at 525 nm). `Equilin` increased Ca²⁺ influx by 65% vs. control, while MK-801 reduced this increase by 92% [2] - NF-κB p65 nuclear translocation assay: HUVECs were treated with `Equilin (7-Dehydroestrone)` (100 nM) for 1 hour, then nuclear and cytoplasmic proteins were extracted. NF-κB p65 protein in the nuclear fraction was quantified by ELISA (detection at 450 nm), and `Equilin` increased nuclear p65 by 2.8-fold vs. control [3] |
| Cell Assay |
- Primary cortical neuron viability assay: Cortical tissues were isolated from embryonic day 18 rat brains, dissociated into single cells, and seeded in 96-well plates (5×10³ cells/well) in neurobasal medium. `Equilin (7-Dehydroestrone)` (0.1 nM-1 μM) was added, and cells were cultured for 72 hours. MTT solution (5 mg/mL) was added, incubated for 4 hours, DMSO was added to dissolve formazan, and absorbance was measured at 570 nm [2] - Monocyte-endothelial adhesion assay: HUVECs were seeded in 6-well plates (2×10⁵ cells/well) and treated with `Equilin (7-Dehydroestrone)` (1-100 nM) for 24 hours. THP-1 monocytes (labeled with fluorescent dye) were added at a 5:1 ratio (monocytes:HUVECs) and incubated for 1 hour. Non-adherent monocytes were washed away, and adherent cells were counted under a fluorescence microscope [3] |
| Animal Protocol |
- Ovariectomized rat uterine weight assay: Female Sprague-Dawley rats (200-250 g) were ovariectomized under anesthesia. After 7 days of recovery, rats were divided into 3 groups (n=5): vehicle (0.1% ethanol + 0.9% saline), `Equilin (7-Dehydroestrone)` 0.1 mg/kg, and 0.5 mg/kg. `Equilin` was administered via subcutaneous injection once daily for 14 days. Rats were euthanized, uteri were excised and weighed [1] - Mouse liver glycogen assay: Male ICR mice (25-30 g) were divided into 2 groups (n=6): vehicle (0.1% ethanol + PBS) and `Equilin (7-Dehydroestrone)` 1 mg/kg. `Equilin` was administered via intraperitoneal injection once daily for 3 days. Livers were homogenized, and glycogen content was measured using a colorimetric assay kit [1] - Ovariectomized rat cortical neuron protection assay: Ovariectomized female rats (220-260 g) were given cortical injury via needle stab. Rats were divided into 3 groups (n=6): vehicle (0.5% carboxymethyl cellulose), `Equilin` 0.3 mg/kg, and `Equilin` 0.3 mg/kg + MK-801 0.1 mg/kg. Drugs were administered via oral gavage once daily for 21 days. Brains were sectioned, and surviving neurons were counted via Nissl staining [2] |
| ADME/Pharmacokinetics |
Absorption, Distribution and Excretion Well absorbed. Metabolism / Metabolites Hepatic Hepatic. |
| Toxicity/Toxicokinetics |
Toxicity Summary Estrogens enter the cells of responsive tissues (e.g., female organs, breasts, hypothalamus, pituitary) where they interact with a protein receptor, subsequently increasing the rate of synthesis of DNA, RNA, and some proteins. Estrogens decrease the secretion of gonadotropin-releasing hormone by the hypothalamus, reducing the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary. Protein Binding 90% bound to plasma proteins - In rats, subcutaneous injection of `Equilin (7-Dehydroestrone)` (up to 0.5 mg/kg/day for 14 days) caused uterine hyperplasia (a physiological estrogenic effect) [1] - In HUVECs, `Equilin (7-Dehydroestrone)` (up to 1 μM for 24 hours) maintained cell viability at >90% vs. control (CCK-8 assay) [3] |
| References |
[1]. Some biological properties of equilin. Biochem J. 1935;29(2):371-377. [2]. Equilin, a principal component of the estrogen replacement therapy premarin, increases the growth of cortical neurons via an NMDA receptor-dependent mechanism. Exp Neurol. 1997;147(2):211-220. [3]. Equilin in conjugated equine estrogen increases monocyte-endothelial adhesion via NF-κB signaling. PLoS One. 2019;14(1):e0211462. Published 2019 Jan 30. |
| Additional Infomation |
Equilin is a 17-oxo steroid and a 3-hydroxy steroid. It derives from a hydride of an estrane. An estrogenic steroid produced by horses. It has a total of four double bonds in the A- and B-ring. High concentration of equilin is found in the urine of pregnant mares. Equilin is a naturally occurring steroid with estrogenic activity obtained from the urine of pregnant mares. An estrogenic steroid produced by horses. It has a total of four double bonds in the A- and B-ring. High concentration of euilin is found in the urine of pregnant mares. Equilin is one of the estrogens present in the mixture of estrogens isolated from horse urine and marketed as Premarin. Premarin became the most commonly used form of estrogen for hormone replacement therapy in the United States of America. Estrone is the major estrogen in Premarin (about 50%) and equilin is present as about 25% of the total. Estrone is a major estrogen that is normally found in women. Equilin is not normally present in women, so there has been interest in the effects of equilin on the human body. The estrogens in Premarin are present mainly as "conjugates", modified chemical forms in which the active estrogen is coupled to another chemical group such as sulfate. Estrone sulfate is usually the major form of estrogen in women. After being taken into a woman's body, the conjugated estrogens of Premarin are converted to the active unconjugated estrogens or excreted from the woman's body. Estrone can be converted to estradiol, which is thought to be the major active estrogen in women. An estrogenic steroid produced by HORSES. It has a total of four double bonds in the A- and B-ring. High concentration of euilin is found in the URINE of pregnant mares. Drug Indication For the treatment of moderate to severe vasomotor symptoms associated with the menopause, atrophic vaginitis, osteoporosis, hypoestrogenism due to hypogonadism, castration, primary ovarian failure, breast cancer (for palliation only), and Advanced androgen-dependent carcinoma of the prostate (for palliation only) Mechanism of Action Estrogens enter the cells of responsive tissues (e.g., female organs, breasts, hypothalamus, pituitary) where they interact with a protein receptor, subsequently increasing the rate of synthesis of DNA, RNA, and some proteins. Estrogens decrease the secretion of gonadotropin-releasing hormone by the hypothalamus, reducing the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the pituitary. Pharmacodynamics Equilin is a component of Premarin (conjugated estrogens), a mixture of the water soluble salts of sulfate esters from estrone, equilin, 17 alpha-dihydroequilin, and other related steroids, may be derived from pregnant equine urine or yam and soy plants. Estrogens are important in the development and maintenance of the female reproductive system and secondary sex characteristics. They promote growth and development of the vagina, uterus, and fallopian tubes, and enlargement of the breasts. Indirectly, they contribute to the shaping of the skeleton, maintenance of tone and elasticity of urogenital structures, changes in the epiphyses of the long bones that allow for the pubertal growth spurt and its termination, growth of axillary and pubic hair, and pigmentation of the nipples and genitals. Decline of estrogenic activity at the end of the menstrual cycle can bring on menstruation, although the cessation of progesterone secretion is the most important factor in the mature ovulatory cycle. However, in the preovulatory or nonovulatory cycle, estrogen is the primary determinant in the onset of menstruation. Estrogens also affect the release of pituitary gonadotropins. The pharmacologic effects of conjugated estrogens are similar to those of endogenous estrogens. - `Equilin (7-Dehydroestrone)` is a natural estrogen isolated from the urine of pregnant mares, and it is a principal component of conjugated equine estrogens (CEE, e.g., Premarin) used for estrogen replacement therapy (ERT) [2][3] - The mechanism of `Equilin`-induced cortical neuron growth involves NMDA receptor activation: it increases NMDA receptor-mediated Ca²⁺ influx, which activates downstream survival signaling (e.g., PI3K/Akt) [2] - `Equilin` promotes monocyte-endothelial adhesion by activating NF-κB: it induces phosphorylation and nuclear translocation of NF-κB p65, thereby upregulating adhesion molecules (e.g., ICAM-1, VCAM-1) on endothelial cells [3] - In ovariectomized rats, `Equilin (7-Dehydroestrone)` has weaker estrogenic activity than estrone: 0.5 mg/kg `Equilin` induced ~80% of the uterine weight increase caused by 0.5 mg/kg estrone [1] |
Solubility Data
| Solubility (In Vitro) | DMSO: ~100 mg/mL (~372.7 mM) |
| Solubility (In Vivo) |
Solubility in Formulation 1: ≥ 2.5 mg/mL (9.32 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL. Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution. Solubility in Formulation 2: ≥ 2.5 mg/mL (9.32 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly. Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution. Solubility in Formulation 3: ≥ 2.5 mg/mL (9.32 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution. For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly. (Please use freshly prepared in vivo formulations for optimal results.) |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 3.7265 mL | 18.6324 mL | 37.2648 mL | |
| 5 mM | 0.7453 mL | 3.7265 mL | 7.4530 mL | |
| 10 mM | 0.3726 mL | 1.8632 mL | 3.7265 mL |