Identification of glucoside and carboxyl-linked glucuronide conjugates of mycophenolic acid in plasma of transplant recipients treated with mycophenolate mofetil

Br J Pharmacol. 1999 Mar;126(5):1075-82. doi: 10.1038/sj.bjp.0702399.


1. Mycophenolic acid (MPA), is primarily metabolized in the liver to 7-O-MPA-beta-glucuronide (MPAG). Using RP-h.p.l.c. we observed three further MPA metabolites, M-1, M-2, M-3, in plasma of transplant recipients on MMF therapy. To obtain information on the structure and source of these metabolites: (A) h.p.l.c. fractions containing either metabolite or MPA were collected and analysed by tandem mass spectrometry; (B) the metabolism of MPA was studied in human liver microsomes in the presence of UDP-glucuronic acid, UDP-glucose or NADPH; (C) hydrolysis of metabolites was investigated using beta-glucosidase, beta-glucuronidase or NaOH; (D) cross-reactivity of each metabolite was tested in an immunoassay for MPA (EMIT). 2. Mass spectrometry of M-1, M-2, MPA and MPAG in the negative ion mode revealed molecular ions of m/z 481, m/z 495, m/z 319 and m/z 495 respectively. 3. Incubation of microsomes with MPA and UDP-glucose produced M-1, with MPA and UDP-glucuronic acid MPAG and M-2 were formed, while with MPA and NADPH, M-3 was observed. 4. Beta-Glucosidase hydrolysed M-1 completely. Beta-Glucuronidase treatment led to a complete disappearance of MPAG whereas the amount of M-2 was reduced by approximately 30%. Only M-2 was labile to alkaline treatment. 5. M-2 and MPA but not M-1 and MPAG cross-reacted in the EMIT assay. 6. These results suggest that: (i) M-1 is the 7-OH glucose conjugate of MPA; (ii) M-2 is the acyl glucuronide conjugate of MPA; (iii) M-3 is derived from the hepatic CYP450 system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, High Pressure Liquid
  • Glucosides / isolation & purification
  • Glucuronates / isolation & purification
  • Glucuronides
  • Humans
  • Hydrolysis
  • Immunosuppressive Agents / pharmacology*
  • Mass Spectrometry
  • Microsomes, Liver / metabolism
  • Mycophenolic Acid / analogs & derivatives*
  • Mycophenolic Acid / isolation & purification
  • Mycophenolic Acid / metabolism*
  • Mycophenolic Acid / pharmacology
  • Organ Transplantation


  • Glucosides
  • Glucuronates
  • Glucuronides
  • Immunosuppressive Agents
  • mycophenolic acid glucuronide
  • Mycophenolic Acid