Identification of drug glucuronides in human urine by RP-HPLC after derivatization

Glucuronic acid conjugates

The methods of assay in body fluids of 1-beta-alkyl, 1-beta-phenyl and 1-beta-acyl glucuronic acids ("glucuronide conjugates") have been reviewed. Most of the 78 references cited (from the literature of the period 1990-1997) concern the glucuronide conjugates of drug metabolites, and these have been considered, for reasons of accessibility, within sections of individual drug classes such as analgesics, anti-cancer agents and opioids. Other glucuronide conjugates are considered under "miscellaneous compounds". A few gas chromatography and capillary electrophoresis methods are described, but the major technique of assay (62 citations) is reversed-phase high-performance liquid chromatography.

Chromatographic resolution of ciprofibrate and interaction of the racemate and both enantiomers with rat liver microsomes in vitro

The enantiomers of ciprofibrate may be achieved by enantioselective HPLC separation of its methylesters using a OD - Daicel column. Ciprofibrates (racemate and both enantiomers) bind to oxidized cytochrome P-450 in rat liver microsomes according type II like aniline or most probably as inversed type I, but less pronounced and with a general shift to the left. Ethylmorphine N-demethylation, ethoxycoumarin and ethoxyresorufin O-deethylation are all inhibited by the ciprofibrates, most effectively ethoxyresorufin O-deethylation by S(-)-ciprofibrate even in microM concentrations. Microsomal luminol and lucigenin amplified chemiluminescence indicating the formation of reactive oxygen species, microsomal hydrogen peroxide formation and NADPH/Fe stimulated lipid peroxidation were inhibited in a concentration dependent manner in concentration ranges between mM and microM. This might be due to distinct scavenger activities of all 3 compounds: the zymosan stimulated chemiluminescence of whole blood was completely inhibited in mM concentrations and influenced significantly down to concentrations of 10 microM, whereas burst and phagocytosis tests with human polynuclear leucocytes were not influenced.

Direct monitoring of enzyme reactions using micellar electrokinetic capillary chromatography. Optimisation of drug glucuronide and sulfate conjugate hydrolysis

This paper demonstrates the use of micellar electrokinetic capillary chromatography (MECC) to monitor enzyme reaction conditions. The hydrolysis reactions of model conjugated substrates (morphine and reduced flunixin glucuronides, napthyl sulfate), by proprietary beta-glucuronidase preparations, were studied under varied experimental conditions. Reactions were carried out in autosampler vials with incubation in a thermostatted CE autosampler tray. MECC was performed using borax buffer (17.5 mM, pH 9.3) modified with sodium dodecyl sulfate (70 mM). Repetitive injections were made from the sample vial throughout the course of the reactions at a frequency of up to 10 h-1. MECC provided a rapid and reproducible assay for the model substrates. Baseline interference from the enzymes prevented measurement of product increase, therefore substrate decrease was measured from the peak areas. Monitoring of reactions in this way has proved valuable in the optimisation of hydrolysis conditions used in sample preparation for drug analysis. beta-Glucuronidase preparations from Helix pomatia were found to give the best performance of those evaluated in terms of deconjugation efficiency.

Determination of phase II drug metabolites in equine urine by micellar electrokinetic capillary chromatography

Micellar electrokinetic capillary chromatography (MECC) using diode array detection has been investigated for the determination of phase I and phase II metabolites of drugs in biofluids. Methods were optimised for the determination of morphine, morphine-3-glucuronide, morphine-6-glucuronide, normorphine, meclofenamic acid and its metabolites in equine urine. Solid-phase extraction procedure were developed to concentrate and purify the analytes from spiked and post administration urines for MECC analysis. A simple on-line procedure for monitoring the kinetics of hydrolysis of morphine-glucuronide conjugates by beta-glucuronidase was demonstrated.