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). It is formed from 16α-hydroxyestrone. In contrast to other endogenous estrogens like estradiol, 17α-epiestriol is a selective agonist of the ERβ. It is described as a relatively weak estrogen, which is in accordance with its relatively low affinity for the ERα. 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.

CAS：1228-72-4
中文别名：17-雌二醇;雌三醇杂质E;
英文别名：16a-Hydroxy-17a-estradiol;epi-Oestriol;16a,17a-Estriol;17-epioestriol;16ALPHA-HYDROXY-17ALPHA-ESTRADIOL;17-EPIESTRIOL (16ALPHA,17ALPHA);17a-Estriol;
分子式：C18H24O3
分子量：288.381
精确质量：288.173
Psa：60.69
Logp：2.58

UNII：4G7IHY560Z

密度：1.255g/cm3
沸点：469ºC at 760mmHg
熔点：230 - 235 °C
闪点：220.8ºC
折射率：1.624
蒸汽压：1.34E-09mmHg at 25°C