17α-E2; Alpha-Estradiol; Alfatradiol; 17-Epiestradiol; Estra-1,3,5(10)-triene-3,17α-diol; β-Estradiol (obsolete, misleading)
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||272.388 g·mol−1|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
17α-Estradiol (also known as 17α-E2, 17-epiestradiol, alfatradiol, or estra-1,3,5(10)-triene-3,17α-diol) is a minor and weak endogenous steroidal estrogen that is related to 17β-estradiol (better known simply as estradiol). It is the C17 epimer of estradiol. It has approximately 100-fold lower estrogenic potency than 17β-estradiol. The compound shows preferential affinity for the ERα over the ERβ. Although 17α-estradiol is far weaker than 17β-estradiol as an agonist of the nuclear estrogen receptors, it has been found to bind to and activate the brain-expressed ER-X with a greater potency than that of 17β-estradiol, suggesting that it may be the predominant endogenous ligand for the receptor.