Pharmaceutical Research

, Volume 6, Issue 2, pp 125–132

Procedures to Characterize In Vivo and In Vitro Enantioselective Glucuronidation Properly: Studies with Benoxaprofen Glucuronides

  • Hildegard Spahn
  • Seigo Iwakawa
  • Emil T. Lin
  • Leslie Z. Benet
Article

DOI: 10.1023/A:1015976425031

Cite this article as:
Spahn, H., Iwakawa, S., Lin, E.T. et al. Pharm Res (1989) 6: 125. doi:10.1023/A:1015976425031

Abstract

The diastereoisomeric glucuronic acid conjugates of R/S-benoxaprofen are the major benoxaprofen metabolites and are found in urine at high concentrations. The conjugates of R- and S-benoxaprofen can be separated directly on a C18 reversed-phase column using a mixture of acetonitrile and tetrabutylammonium hydroxide buffer, pH 2.5 (28:72, v/v), as the mobile phase. The k′ values of S- and R-benoxaprofen glucuronides are 57.5 and 63.0, respectively. Diluted urine or deproteinized plasma samples were injected without further treatment. With fluorescence detection at 313/365 nm, quantifiable limits of 50 ng equiv./ml were found for the conjugates. The intra- and interday variability was below 12%. Utilizing this analytical procedure it is possible to characterize enantioselective glucuronidation both in vivo and in vitro. For in vitro procedures, apparent rates of formation and the R/S ratio may be substrate (benoxaprofen) and cosubstrate (UDPGA) dependent. Moreover, enantioselective cleavage of the formed benoxaprofen glucuronides by alkaline hydrolysis, hydrolytic enzymes, and acyl migration must be controlled for both in vitro and in vivo studies since R-benoxaprofen glucuronide is degraded faster than the S-diastereomer under certain conditions.

stereospecific assay benoxaprofen glucuronides enantiomers diastereoisomers 

Copyright information

© Plenum Publishing Corporation 1989

Authors and Affiliations

  • Hildegard Spahn
    • 1
    • 2
  • Seigo Iwakawa
  • Emil T. Lin
  • Leslie Z. Benet
  1. 1.School of Pharmacy, Department of PharmacyUniversity of CaliforniaSan Francisco
  2. 2.Pharmakologisches Institut für Naturwissenschaftler derJohann Wolfgang Goethe-UniversitätFrankfurt/M. 70F.R.G