Estradiol 3-glucuronide

Estradiol 3-glucuronide (E2-3G), also known as 17β-estradiol 3-(β-D-glucuronide), is a naturally occurring and endogenous estrogen conjugate. It is specifically the C3 glucuronide conjugate of estradiol, the major estrogen in the body. It is formed from estradiol in the liver by UDP-glucuronosyltransferase via attachment of glucuronic acid and is eventually excreted in urine and bile. Similarly to estrogen sulfates like estrone sulfate, estrogen glucuronides have much higher water solubility than do unconjugated estrogens like estradiol.

Estradiol 3-glucuronide
Names
IUPAC name
17β-Hydroxyestra-1,3,5(10)-trien-3-yl β-D-glucopyranosiduronic acid
Systematic IUPAC name
(2S,3S,4S,5R,6S)-3,4,5-Trihydroxy-6-{[(1S,3aS,3bR,9bS,11aS)-1-hydroxy-11a-methyl-2,3,3a,3b,4,5,9b,10,11,11a-decahydro-1H-cyclopenta[a]phenanthren-7-yl]oxy}oxane-2-carboxylic acid
Other names
E2-3G; 17β-Estradiol 3-(β-D-glucuronide)
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
KEGG
  • InChI=1S/C24H32O8/c1-24-9-8-14-13-5-3-12(10-11(13)2-4-15(14)16(24)6-7-17(24)25)31-23-20(28)18(26)19(27)21(32-23)22(29)30/h3,5,10,14-21,23,25-28H,2,4,6-9H2,1H3,(H,29,30)/t14-,15-,16+,17+,18+,19+,20-,21+,23-,24+/m1/s1
    Key: MUOHJTRCBBDUOW-QXYWQCSFSA-N
  • C[C@]12CC[C@H]3[C@H]([C@@H]1CC[C@@H]2O)CCC4=C3C=CC(=C4)O[C@H]5[C@@H]([C@H]([C@@H]([C@H](O5)C(=O)O)O)O)O
Properties
C24H32O8
Molar mass 448.512 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Estrogen glucuronides can be deconjugated into the corresponding free estrogens by β-glucuronidase in tissues that express this enzyme, such as the mammary gland. As a result, estrogen glucuronides have estrogenic activity via conversion into estrogens.

Estradiol 3-glucuronide is a positional isomer of estradiol 17β-glucuronide.

Affinities and estrogenic potencies of estrogen esters and ethers at the estrogen receptors
Estrogen Other names RBATooltip Relative binding affinity (%)a REP (%)b
ER ERα ERβ
Estradiol E2 100 100 100
Estradiol 3-sulfate E2S; E2-3S  ? 0.02 0.04
Estradiol 3-glucuronide E2-3G  ? 0.02 0.09
Estradiol 17β-glucuronide E2-17G  ? 0.002 0.0002
Estradiol benzoate EB; Estradiol 3-benzoate 10 1.1 0.52
Estradiol 17β-acetate E2-17A 31–45 24  ?
Estradiol diacetate EDA; Estradiol 3,17β-diacetate  ? 0.79  ?
Estradiol propionate EP; Estradiol 17β-propionate 19–26 2.6  ?
Estradiol valerate EV; Estradiol 17β-valerate 2–11 0.04–21  ?
Estradiol cypionate EC; Estradiol 17β-cypionate  ?c 4.0  ?
Estradiol palmitate Estradiol 17β-palmitate 0  ?  ?
Estradiol stearate Estradiol 17β-stearate 0  ?  ?
Estrone E1; 17-Ketoestradiol 11 5.3–38 14
Estrone sulfate E1S; Estrone 3-sulfate 2 0.004 0.002
Estrone glucuronide E1G; Estrone 3-glucuronide  ? <0.001 0.0006
Ethinylestradiol EE; 17α-Ethynylestradiol 100 17–150 129
Mestranol EE 3-methyl ether 1 1.3–8.2 0.16
Quinestrol EE 3-cyclopentyl ether  ? 0.37  ?
Footnotes: a = Relative binding affinities (RBAs) were determined via in-vitro displacement of labeled estradiol from estrogen receptors (ERs) generally of rodent uterine cytosol. Estrogen esters are variably hydrolyzed into estrogens in these systems (shorter ester chain length -> greater rate of hydrolysis) and the ER RBAs of the esters decrease strongly when hydrolysis is prevented. b = Relative estrogenic potencies (REPs) were calculated from half-maximal effective concentrations (EC50) that were determined via in-vitro β‐galactosidase (β-gal) and green fluorescent protein (GFP) production assays in yeast expressing human ERα and human ERβ. Both mammalian cells and yeast have the capacity to hydrolyze estrogen esters. c = The affinities of estradiol cypionate for the ERs are similar to those of estradiol valerate and estradiol benzoate (figure). Sources: See template page.
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