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Substance Name: Alfatradiol [INN]
RN: 57-91-0
UNII: 3VQ38D63M7


  • /Estradiol/ Generally refers to the 17-beta-isomer of estradiol, an aromatized C18 steroid with hydroxyl group at 3-beta- and 17-beta-position. Estradiol-17-beta is the most potent form of mammalian estrogenic steroids. In humans, it is produced primarily by the cyclic ovaries and the PLACENTA. It is also produced by the adipose tissue of men and postmenopausal women. The 17-alpha-isomer of estradiol binds weakly to estrogen receptors ( RECEPTORS, ESTROGEN) and exhibits little estrogenic activity in estrogen-responsive tissues. Various isomers can be synthesized.
  • Used for treating androgenetic alopecia.

Molecular Formula

  • C18-H24-O2

Molecular Weight

  • 272.3856

Classification Codes

  • 5-alpha Reductase Inhibitors
  • Dermatologic Agents
  • Enzyme Inhibitors
  • Hormone
  • Hormone Antagonists
  • Mutation Data
  • Steroid Synthesis Inhibitors
  • Tumor Data
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Names and Synonyms

Name of Substance

  • Alfatradiol [INN]


  • 1,3,5-Estratriene-3,17-alpha-diol
  • 17alpha-Estradiol
  • 3,17-alpha-Dihydroxyoestra-1,3,5(10)-triene
  • 3,17-Dihydroxyestratriene
  • 3,17alpha-Dihydroxyestra-1,3,5(10)-triene
  • 3,17alpha-Dihydroxyoestra-1,3,5(10)-triene
  • 4-06-00-06611 (Beilstein Handbook Reference)
  • Alfatradiol
  • alpha-Estradiol
  • BRN 2698044
  • CCRIS 7203
  • EINECS 200-354-8
  • Epiestradiol
  • Estra-1,3,5(10)-triene-3,17alpha-diol
  • NSC 20293
  • Oestra-1,3,5(10)-triene-3,17alpha-diol
  • Oestradiol-17-alpha
  • Oestradiol-17alpha
  • UNII-3VQ38D63M7

Systematic Names

  • 17-alpha-Estradiol
  • 17alpha-Estradiol
  • Estra-1,3,5(10)-triene-3,17-diol, (17-alpha)-
  • Estra-1,3,5(10)-triene-3,17alpha-diol

Registry Numbers

CAS Registry Number

  • 57-91-0


  • 3VQ38D63M7

System Generated Number

  • 0000057910

Structure Descriptors







Physical Properties

Physical Property Value Units Temp (deg C) Source
Melting Point 221.5 deg C   EXP
log P (octanol-water) 3.940 (none)   EST
Water Solubility 3.9 mg/L 25 EXP
Atmospheric OH Rate Constant 1.23E-10 cm3/molecule-sec 25 EST

Physical property data is provided to ChemIDplus by SRC, Inc.