17α-Epiestriol

17α-Epiestriol
Names
	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
CAS Number	1228-72-4;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:42156;
ChEMBL	ChEMBL1232445;
ChemSpider	225189;
DrugBank	DB07702;
PubChem CID	256737;
UNII	4G7IHY560Z;
CompTox Dashboard (EPA)	DTXSID00858947 ;
	InChI InChI=1S/C18H24O3/c1-18-7-6-13-12-5-3-11(19)8-10(12)2-4-14(13)15(18)9-16(20)17(18)21/h3,5,8,13-17,19-21H,2,4,6-7,9H2,1H3/t13-,14-,15+,16-,17-,18+/m1/s1 Key: PROQIPRRNZUXQM-PNVOZDDCSA-N;
	SMILES CC12CCC3C(C1CC(C2O)O)CCC4=C3C=CC(=C4)O;
Properties
Chemical formula	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). Infobox references

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.

Relative affinities (%) of 17α-epiestriol and related steroids
Compound	PRTooltip Progesterone receptor	ARTooltip Androgen receptor	ERTooltip Estrogen receptor	GRTooltip Glucocorticoid receptor	MRTooltip Mineralocorticoid receptor	SHBGTooltip Sex hormone-binding globulin	CBGTooltip Corticosteroid binding globulin
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 PRTooltip progesterone receptor, testosterone for the ARTooltip androgen receptor, E2 for the ERTooltip estrogen receptor, DEXATooltip dexamethasone for the GRTooltip glucocorticoid receptor, aldosterone for the MRTooltip mineralocorticoid receptor, DHTTooltip dihydrotestosterone for SHBGTooltip sex hormone-binding globulin, and cortisol for CBGTooltip Corticosteroid-binding globulin.