17α-Epiestriol, or simply 17-epiestriol, also known as 16α-hydroxy-17α-estradiol or estra-1,3,5(10)-triene-3,16α,17α-triol, is a minor and weak endogenous estrogen, and the 17α-epimer of estriol (which is 16α-hydroxy-17β-estradiol).[1][2][3] It is formed from 16α-hydroxyestrone.[4][5] In contrast to other endogenous estrogens like estradiol, 17α-epiestriol is a selective agonist of the ERβ.[6] It is described as a relatively weak estrogen, which is in accordance with its relatively low affinity for the ERα.[7] 17α-Epiestriol has been found to be approximately 400-fold more potent than estradiol in inhibiting tumor necrosis factor α (TNFα)-induced vascular cell adhesion molecule 1 (VCAM-1) expression in vitro.[8]
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| Names | |
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| IUPAC name Estra-1,3,5(10)-triene-3,16α,17α-triol | |
| Systematic IUPAC name (1S,2R,3aS,3bR,9bS,11aS)-11a-Methyl-2,3,3a,3b,4,5,9b,10,11,11a-decahydro-1H-cyclopenta[a]phenanthrene-1,2,7-triol | |
| Other names 17-Epiestriol; 16α-Hydroxy-17α-estradiol; 3,16α,17α-Trihydroxy-1,3,5(10)-estratriene | |
| Identifiers | |
3D model (JSmol) | |
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CompTox Dashboard (EPA) | |
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| Properties | |
| C18H24O3 | |
| Molar mass | 288.38136 g/mol |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Compound | PR | AR | ER | GR | MR | SHBG | CBG | ||
|---|---|---|---|---|---|---|---|---|---|
| Estradiol | 2.6 | 7.9 | 100 | 0.6 | 0.13 | 8.7 | <0.1 | ||
| Alfatradiol | <1 | <1 | 15 | <1 | <1 | ? | ? | ||
| Estriol | <1 | <1 | 15 | <1 | <1 | ? | ? | ||
| 16β-Epiestriol | <1 | <1 | 20 | <1 | <1 | ? | ? | ||
| 17α-Epiestriol | <1 | <1 | 31 | <1 | <1 | ? | ? | ||
| Values are percentages (%). Reference ligands (100%) were progesterone for the PR, testosterone for the AR, E2 for the ER, DEXA for the GR, aldosterone for the MR, DHT for SHBG, and cortisol for CBG. | |||||||||