Characterization and quantification of metabolites of racemic ketoprofen excreted in urine following oral administration to man by 1H-NMR spectroscopy, directly coupled HPLC-MS and HPLC-NMR, and circular dichroism

1. The identity of the human metabolites of ketoprofen (2-(3-benzoylphenyl)-propanoic acid) excreted via urine was investigated after a single oral dose of the racemic drug. 2. Drug metabolites were concentrated and partially purified from urine using solid-phase extraction chromatography before separation and identification by directly coupled HPLC-MS and HPLC-NMR. 3. The metabolites identified were the ester glucuronides of the parent drug and its phase I metabolites, 2-[3-(3-hydroxybenzoyl)plenl]-propanoic acid, 2-[3-(4-hydroxy-benzoyl)phenyl]-propanoic acid and 2-[3-(hydroxy,(phenyl)methyl)phenyl]-propanoic acid, the latter formed by reduction of the ketone group of ketoprofen. In addition, two novel minor metabolites were identified as the ether glucuronides of 2-[3-(3-hydroxybenzoyl)phenyl]-propanoic acid and 2-[3-(4-hydroxybenzoyl)phenyl]-propanoic acid. These conjugates were all observed as diastereoisomeric pairs of unequal proportions. 4. Purification of these metabolites by preparative chromatography allowed stereochemistry assignments. 5. Metabolites were quantified by H-1-NMR spectroscopy after spectral simplification achieved by hydrolysis of the conjugates.