Caffeic acid phenethyl ester, a component of beehive propolis, is a novel selective estrogen receptor modulator

Phytother Res. 2010 Feb;24(2):295-300. doi: 10.1002/ptr.2966.


Caffeic acid phenethyl ester (CAPE) is an active ingredient of beehive propolis with a structure similar to phenolic acid. The estrogenic effects of propolis were previously demonstrated through the activation of an estrogen receptor. To identify the estrogenic properties of propolis, CAPE was evaluated using in vitro and in vivo methods. CAPE showed selective binding affinity to human estrogen receptor beta (hERbeta) rather than hERalpha. CAPE also reduced ERalpha expression in MCF-7 and MDA 231 cells. In the yeast estrogen receptor transcription assay, CAPE produced the transcriptional activity of estrogen-responsive element with EC(50) values of 3.72 x 10(-6) M. CAPE did not increase the growth of MCF-7 estrogen receptor-positive breast cancer cells in doses ranging from 10(-7) to 10(-5) M. In order to understand how CAPE acts in animals, CAPE was tested by a uterotrophic bioassay. Treatment with CAPE (100, 500 mg/kg) did not increase the uterine weight relative to 3 microg/kg 17beta-estradiol treatment. The results indicate that CAPE, which is a selective agonist to hERbeta, but does not show any estrogenic effect on estrogen receptor-positive breast cancer cells and in immature rat uterine tissue, is a potential selective estrogen receptor modulator.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Caffeic Acids / pharmacology*
  • Cell Line, Tumor
  • Cell Proliferation
  • Estrogen Receptor alpha / metabolism
  • Female
  • Humans
  • Phenylethyl Alcohol / analogs & derivatives*
  • Phenylethyl Alcohol / pharmacology
  • Propolis / pharmacology*
  • Rats
  • Rats, Sprague-Dawley
  • Selective Estrogen Receptor Modulators / pharmacology*
  • Uterus / drug effects


  • Caffeic Acids
  • Estrogen Receptor alpha
  • Selective Estrogen Receptor Modulators
  • Propolis
  • caffeic acid phenethyl ester
  • Phenylethyl Alcohol