Inhibitory effects of isoflavonoids on rat prostate testosterone 5α-reductase

J Acupunct Meridian Stud. 2012 Dec;5(6):319-22. doi: 10.1016/j.jams.2012.07.022. Epub 2012 Aug 9.


Testosterone 5α-reductase inhibitors represent important therapeutic drugs for use against androgen-dependent diseases such as benign prostatic hyperplasia, male pattern baldness, and acne. We have searched for inhibitors of rat prostate testosterone 5α-reductase in the cultured broths of many kinds of soil bacteria, and have found that cultured soybean-casein digest broths of certain bacterial strains have a potent inhibitory effect on the enzyme. We tested 10 selected isoflavonoids, including isoflavones and O-methylated isoflavones, for inhibitory effects on rat prostate testosterone 5α-reductase to determine the important structural elements for inhibition of the enzyme. Genistein, biochanin A, equol, and 3',4',7-trihydroxyisoflavone showed considerably higher inhibitory effects whereas daidzein, formononetin, glycitein, prunetin, ipriflavone, and 4',7-dimethoxyisoflavone showed lower inhibitory effects. The IC(50) values of genistein, biochanin A, equol, 3',4',7-trihydroxyisoflavone, and riboflavin, a positive control, for rat prostate testosterone 5α-reductase were 710 μm, 140 μm, 370 μm, 690 μm, and 17 μm, respectively. Daidzein, genistein, biochanin A, formononetin, and equol are already known to be testosterone 5α-reductase inhibitors, but this is the first characterization of 3',4',7-trihydroxyisoflavone as an inhibitor of the enzyme.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3-Oxo-5-alpha-Steroid 4-Dehydrogenase / metabolism*
  • 5-alpha Reductase Inhibitors / pharmacology*
  • Animals
  • Bacteria
  • Caseins
  • Inhibitory Concentration 50
  • Isoflavones / pharmacology*
  • Male
  • Plant Extracts / pharmacology*
  • Prostate / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Soil
  • Soybeans / chemistry*


  • 5-alpha Reductase Inhibitors
  • Caseins
  • Isoflavones
  • Plant Extracts
  • Soil
  • 3-Oxo-5-alpha-Steroid 4-Dehydrogenase
  • 3',4',7-trihydroxyisoflavone