17α-Estradiol

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).[2] It is the C17 epimer of estradiol.[2] It has approximately 100-fold lower estrogenic potency than 17β-estradiol.[3] The compound shows preferential affinity for the ERα over the ERβ.[2][4] 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.[5]

Affinities of estrogen receptor ligands for the ERα and ERβ
LigandOther namesRelative binding affinities (RBA, %)aAbsolute binding affinities (Ki, nM)aAction
ERαERβERαERβ
EstradiolE2; 17β-Estradiol1001000.115 (0.04–0.24)0.15 (0.10–2.08)Estrogen
EstroneE1; 17-Ketoestradiol16.39 (0.7–60)6.5 (1.36–52)0.445 (0.3–1.01)1.75 (0.35–9.24)Estrogen
EstriolE3; 16α-OH-17β-E212.65 (4.03–56)26 (14.0–44.6)0.45 (0.35–1.4)0.7 (0.63–0.7)Estrogen
EstetrolE4; 15α,16α-Di-OH-17β-E24.03.04.919Estrogen
Alfatradiol17α-Estradiol20.5 (7–80.1)8.195 (2–42)0.2–0.520.43–1.2Metabolite
16-Epiestriol16β-Hydroxy-17β-estradiol7.795 (4.94–63)50??Metabolite
17-Epiestriol16α-Hydroxy-17α-estradiol55.45 (29–103)79–80??Metabolite
16,17-Epiestriol16β-Hydroxy-17α-estradiol1.013??Metabolite
2-Hydroxyestradiol2-OH-E222 (7–81)11–352.51.3Metabolite
2-Methoxyestradiol2-MeO-E20.0027–2.01.0??Metabolite
4-Hydroxyestradiol4-OH-E213 (8–70)7–561.01.9Metabolite
4-Methoxyestradiol4-MeO-E22.01.0??Metabolite
2-Hydroxyestrone2-OH-E12.0–4.00.2–0.4??Metabolite
2-Methoxyestrone2-MeO-E1<0.001–<1<1??Metabolite
4-Hydroxyestrone4-OH-E11.0–2.01.0??Metabolite
4-Methoxyestrone4-MeO-E1<1<1??Metabolite
16α-Hydroxyestrone16α-OH-E1; 17-Ketoestriol2.0–6.535??Metabolite
2-Hydroxyestriol2-OH-E32.01.0??Metabolite
4-Methoxyestriol4-MeO-E31.01.0??Metabolite
Estradiol sulfateE2S; Estradiol 3-sulfate<1<1??Metabolite
Estradiol disulfateEstradiol 3,17β-disulfate0.0004???Metabolite
Estradiol 3-glucuronideE2-3G0.0079???Metabolite
Estradiol 17β-glucuronideE2-17G0.0015???Metabolite
Estradiol 3-gluc. 17β-sulfateE2-3G-17S0.0001???Metabolite
Estrone sulfateE1S; Estrone 3-sulfate<1<1>10>10Metabolite
Estradiol benzoateEB; Estradiol 3-benzoate10???Estrogen
Estradiol 17β-benzoateE2-17B11.332.6??Estrogen
Estrone methyl etherEstrone 3-methyl ether0.145???Estrogen
ent-Estradiol1-Estradiol1.31–12.349.44–80.07??Estrogen
Equilin7-Dehydroestrone13 (4.0–28.9)13.0–490.790.36Estrogen
Equilenin6,8-Didehydroestrone2.0–157.0–200.640.62Estrogen
17β-Dihydroequilin7-Dehydro-17β-estradiol7.9–1137.9–1080.090.17Estrogen
17α-Dihydroequilin7-Dehydro-17α-estradiol18.6 (18–41)14–320.240.57Estrogen
17β-Dihydroequilenin6,8-Didehydro-17β-estradiol35–6890–1000.150.20Estrogen
17α-Dihydroequilenin6,8-Didehydro-17α-estradiol20490.500.37Estrogen
Δ8-Estradiol8,9-Dehydro-17β-estradiol68720.150.25Estrogen
Δ8-Estrone8,9-Dehydroestrone19320.520.57Estrogen
EthinylestradiolEE; 17α-Ethynyl-17β-E2120.9 (68.8–480)44.4 (2.0–144)0.02–0.050.29–0.81Estrogen
MestranolEE 3-methyl ether?2.5??Estrogen
MoxestrolRU-2858; 11β-Methoxy-EE35–435–200.52.6Estrogen
Methylestradiol17α-Methyl-17β-estradiol7044??Estrogen
DiethylstilbestrolDES; Stilbestrol129.5 (89.1–468)219.63 (61.2–295)0.040.05Estrogen
HexestrolDihydrodiethylstilbestrol153.6 (31–302)60–2340.060.06Estrogen
DienestrolDehydrostilbestrol37 (20.4–223)56–4040.050.03Estrogen
Benzestrol (B2)114???Estrogen
ChlorotrianiseneTACE1.74?15.30?Estrogen
TriphenylethyleneTPE0.074???Estrogen
TriphenylbromoethyleneTPBE2.69???Estrogen
TamoxifenICI-46,4743 (0.1–47)3.33 (0.28–6)3.4–9.692.5SERM
Afimoxifene4-Hydroxytamoxifen; 4-OHT100.1 (1.7–257)10 (0.98–339)2.3 (0.1–3.61)0.04–4.8SERM
Toremifene4-Chlorotamoxifen; 4-CT??7.14–20.315.4SERM
ClomifeneMRL-4125 (19.2–37.2)120.91.2SERM
CyclofenilF-6066; Sexovid151–152243??SERM
NafoxidineU-11,000A30.9–44160.30.8SERM
Raloxifene41.2 (7.8–69)5.34 (0.54–16)0.188–0.5220.2SERM
ArzoxifeneLY-353,381??0.179?SERM
LasofoxifeneCP-336,15610.2–16619.00.229?SERM
OrmeloxifeneCentchroman??0.313?SERM
Levormeloxifene6720-CDRI; NNC-460,0201.551.88??SERM
OspemifeneDeaminohydroxytoremifene2.631.22??SERM
Bazedoxifene??0.053?SERM
EtacstilGW-56384.3011.5??SERM
ICI-164,38463.5 (3.70–97.7)1660.20.08Antiestrogen
FulvestrantICI-182,78043.5 (9.4–325)21.65 (2.05–40.5)0.421.3Antiestrogen
PropylpyrazoletriolPPT49 (10.0–89.1)0.120.4092.8ERα agonist
16α-LE216α-Lactone-17β-estradiol14.6–570.0890.27131ERα agonist
16α-Iodo-E216α-Iodo-17β-estradiol30.22.30??ERα agonist
MethylpiperidinopyrazoleMPP110.05??ERα antagonist
DiarylpropionitrileDPN0.12–0.256.6–1832.41.7ERβ agonist
8β-VE28β-Vinyl-17β-estradiol0.3522.0–8312.90.50ERβ agonist
PrinaberelERB-041; WAY-202,0410.2767–72??ERβ agonist
ERB-196WAY-202,196?180??ERβ agonist
ErteberelSERBA-1; LY-500,307??2.680.19ERβ agonist
SERBA-2??14.51.54ERβ agonist
Coumestrol9.225 (0.0117–94)64.125 (0.41–185)0.14–80.00.07–27.0Xenoestrogen
Genistein0.445 (0.0012–16)33.42 (0.86–87)2.6–1260.3–12.8Xenoestrogen
Equol0.2–0.2870.85 (0.10–2.85)??Xenoestrogen
Daidzein0.07 (0.0018–9.3)0.7865 (0.04–17.1)2.085.3Xenoestrogen
Biochanin A0.04 (0.022–0.15)0.6225 (0.010–1.2)1748.9Xenoestrogen
Kaempferol0.07 (0.029–0.10)2.2 (0.002–3.00)??Xenoestrogen
Naringenin0.0054 (<0.001–0.01)0.15 (0.11–0.33)??Xenoestrogen
8-Prenylnaringenin8-PN4.4???Xenoestrogen
Quercetin<0.001–0.010.002–0.040??Xenoestrogen
Ipriflavone<0.01<0.01??Xenoestrogen
Miroestrol0.39???Xenoestrogen
Deoxymiroestrol2.0???Xenoestrogen
β-Sitosterol<0.001–0.0875<0.001–0.016??Xenoestrogen
Resveratrol<0.001–0.0032???Xenoestrogen
α-Zearalenol48 (13–52.5)???Xenoestrogen
β-Zearalenol0.6 (0.032–13)???Xenoestrogen
Zeranolα-Zearalanol48–111???Xenoestrogen
Taleranolβ-Zearalanol16 (13–17.8)140.80.9Xenoestrogen
ZearalenoneZEN7.68 (2.04–28)9.45 (2.43–31.5)??Xenoestrogen
ZearalanoneZAN0.51???Xenoestrogen
Bisphenol ABPA0.0315 (0.008–1.0)0.135 (0.002–4.23)19535Xenoestrogen
EndosulfanEDS<0.001–<0.01<0.01??Xenoestrogen
KeponeChlordecone0.0069–0.2???Xenoestrogen
o,p'-DDT0.0073–0.4???Xenoestrogen
p,p'-DDT0.03???Xenoestrogen
Methoxychlorp,p'-Dimethoxy-DDT0.01 (<0.001–0.02)0.01–0.13??Xenoestrogen
HPTEHydroxychlor; p,p'-OH-DDT1.2–1.7???Xenoestrogen
TestosteroneT; 4-Androstenolone<0.0001–<0.01<0.002–0.040>5000>5000Androgen
DihydrotestosteroneDHT; 5α-Androstanolone0.01 (<0.001–0.05)0.0059–0.17221–>500073–1688Androgen
Nandrolone19-Nortestosterone; 19-NT0.010.2376553Androgen
DehydroepiandrosteroneDHEA; Prasterone0.038 (<0.001–0.04)0.019–0.07245–1053163–515Androgen
5-AndrostenediolA5; Androstenediol6173.60.9Androgen
4-Androstenediol0.50.62319Androgen
4-AndrostenedioneA4; Androstenedione<0.01<0.01>10000>10000Androgen
3α-Androstanediol3α-Adiol0.070.326048Androgen
3β-Androstanediol3β-Adiol3762Androgen
Androstanedione5α-Androstanedione<0.01<0.01>10000>10000Androgen
Etiocholanedione5β-Androstanedione<0.01<0.01>10000>10000Androgen
Methyltestosterone17α-Methyltestosterone<0.0001???Androgen
Ethinyl-3α-androstanediol17α-Ethynyl-3α-adiol4.0<0.07??Estrogen
Ethinyl-3β-androstanediol17α-Ethynyl-3β-adiol505.6??Estrogen
ProgesteroneP4; 4-Pregnenedione<0.001–0.6<0.001–0.010??Progestogen
NorethisteroneNET; 17α-Ethynyl-19-NT0.085 (0.0015–<0.1)0.1 (0.01–0.3)1521084Progestogen
Norethynodrel5(10)-Norethisterone0.5 (0.3–0.7)<0.1–0.221453Progestogen
Tibolone7α-Methylnorethynodrel0.5 (0.45–2.0)0.2–0.076??Progestogen
Δ4-Tibolone7α-Methylnorethisterone0.069–<0.10.027–<0.1??Progestogen
3α-Hydroxytibolone2.5 (1.06–5.0)0.6–0.8??Progestogen
3β-Hydroxytibolone1.6 (0.75–1.9)0.070–0.1??Progestogen
Footnotes: a = (1) Binding affinity values are of the format "median (range)" (# (#–#)), "range" (#–#), or "value" (#) depending on the values available. The full sets of values within the ranges can be found in the Wiki code. (2) Binding affinities were determined via displacement studies in a variety of in-vitro systems with labeled estradiol and human ERα and ERβ proteins (except the ERβ values from Kuiper et al. (1997), which are rat ERβ). Sources: See template page.
Selected biological properties of endogenous estrogens in rats
EstrogenER RBA (%)Uterine weight (%)UterotrophyLH levels (%)SHBG RBA (%)
Control100100
Estradiol100506 ± 20+++12–19100
Estrone11 ± 8490 ± 22+++?20
Estriol10 ± 4468 ± 30+++8–183
Estetrol0.5 ± 0.2?Inactive?1
17α-Estradiol4.2 ± 0.8????
2-Hydroxyestradiol24 ± 7285 ± 8+b31–6128
2-Methoxyestradiol0.05 ± 0.04101Inactive?130
4-Hydroxyestradiol45 ± 12????
4-Methoxyestradiol1.3 ± 0.2260++?9
4-Fluoroestradiola180 ± 43?+++??
2-Hydroxyestrone1.9 ± 0.8130 ± 9Inactive110–1428
2-Methoxyestrone0.01 ± 0.00103 ± 7Inactive95–100120
4-Hydroxyestrone11 ± 4351++21–5035
4-Methoxyestrone0.13 ± 0.04338++65–9212
16α-Hydroxyestrone2.8 ± 1.0552 ± 42+++7–24<0.5
2-Hydroxyestriol0.9 ± 0.3302+b??
2-Methoxyestriol0.01 ± 0.00?Inactive?4
Notes: Values are mean ± SD or range. ER RBA = Relative binding affinity to estrogen receptors of rat uterine cytosol. Uterine weight = Percentage change in uterine wet weight of ovariectomized rats after 72 hours with continuous administration of 1 μg/hour via subcutaneously implanted osmotic pumps. LH levels = Luteinizing hormone levels relative to baseline of ovariectomized rats after 24 to 72 hours of continuous administration via subcutaneous implant. Footnotes: a = Synthetic (i.e., not endogenous). b = Atypical uterotrophic effect which plateaus within 48 hours (estradiol's uterotrophy continues linearly up to 72 hours). Sources: See template.
17α-Estradiol
Names
IUPAC name
(8R,9S,13S,14S,17R)-13-Methyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthrene-3,17-diol
Other names
17α-E2; Alpha-Estradiol; Alfatradiol; 17-Epiestradiol; Estra-1,3,5(10)-triene-3,17α-diol; β-Estradiol (obsolete, misleading)[1]
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.000.322
UNII
Properties
C18H24O2
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).
Infobox references

See also

References

  1. J. Elks (14 November 2014). The Dictionary of Drugs: Chemical Data: Chemical Data, Structures and Bibliographies. Springer. pp. 897–. ISBN 978-1-4757-2085-3.
  2. Zhu BT, Han GZ, Shim JY, Wen Y, Jiang XR (2006). "Quantitative structure-activity relationship of various endogenous estrogen metabolites for human estrogen receptor alpha and beta subtypes: Insights into the structural determinants favoring a differential subtype binding". Endocrinology. 147 (9): 4132–50. doi:10.1210/en.2006-0113. PMID 16728493.
  3. Ralph M. Trüeb; Won-Soo Lee (13 February 2014). Male Alopecia: Guide to Successful Management. Springer Science & Business Media. pp. 93–. ISBN 978-3-319-03233-7.
  4. Kuiper GG, Carlsson B, Grandien K, Enmark E, Häggblad J, Nilsson S, Gustafsson JA (1997). "Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors alpha and beta". Endocrinology. 138 (3): 863–70. doi:10.1210/endo.138.3.4979. PMID 9048584.
  5. Toran-Allerand CD, Tinnikov AA, Singh RJ, Nethrapalli IS (2005). "17alpha-estradiol: a brain-active estrogen?". Endocrinology. 146 (9): 3843–50. doi:10.1210/en.2004-1616. PMID 15947006.


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