15-Desmethyl FK-506 and 15,31-desmethyl FK-506 from human liver microsomes: isolation, identification (by fast atom bombardment mass spectrometry and NMR), and evaluation of in vitro immunosuppressive activity

Clin Chem. 1994 May;40(5):740-4.


15-Desmethyl FK-506 and 15,31-desmethyl FK-506 metabolites extracted from incubated human liver microsomes were separated by normal and reversed-phase HPLC. The metabolites were identified by fast atom bombardment/mass spectrometry and nuclear magnetic resonance spectroscopy. The in vitro 50% inhibitory concentration, tested against bidirectional mixed lymphocyte reactions, was 325 mg/L for 15,31-desmethyl FK-506 and 4 mg/L for 15-desmethyl FK-506, indicating that these products of FK-506 demethylation retain in vitro immunosuppressive activity.

MeSH terms

  • Chromatography, High Pressure Liquid
  • Humans
  • Immunosuppression Therapy*
  • Lymphocyte Culture Test, Mixed
  • Magnetic Resonance Spectroscopy
  • Methylation
  • Microsomes, Liver / chemistry*
  • Spectrometry, Mass, Fast Atom Bombardment
  • Tacrolimus / analogs & derivatives*
  • Tacrolimus / analysis
  • Tacrolimus / metabolism*
  • Tacrolimus / pharmacology


  • 15,31-desmethyl FK-506
  • 15-desmethyl FK-506
  • Tacrolimus