TY - JOUR T1 - Identification of Novel Metabolites of Colchicine in Rat Bile Facilitated by Enhanced Online Radiometric Detection JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 731 LP - 739 DO - 10.1124/dmd.107.019463 VL - 36 IS - 4 AU - Lin Xu AU - Bruce Adams AU - Valentina V. Jeliazkova-Mecheva AU - Laird Trimble AU - Gloria Kwei AU - Andreas Harsch Y1 - 2008/04/01 UR - http://dmd.aspetjournals.org/content/36/4/731.abstract N2 - Three novel conjugation metabolites of colchicine were identified in rat bile facilitated by enhanced on-line liquid chromatography-accurate radioisotope counting. The known 2- and 3-demethylcolchicines (DMCs) underwent O-sulfate conjugation in addition to the previously described O-glucuronidation. 2-DMC was preferably O-glucuronidated, whereas 3-DMC predominantly yielded O-sulfation conjugates, indicating phase II conjugation regiopreferences. Moreover, M1 was identified as a novel glutathione conjugate and a possible biotransformation pathway for its formation was proposed. The known 2-DMC (M6), 3-DMC (M7), 2-DMC glucuronide (M4), and novel 3-DMC sulfate (M3) were confirmed as the major metabolites. Radiometric data were acquired by the XFlow liquid chromatography-accurate radioisotope counting (XFlow LC-ARC) system, a novel technology for dynamic control of both on-column and postcolumn high-performance liquid chromatography flow rates to maximize sensitivity and resolution of radiochromatograms. A comparative evaluation was also performed between the XFlow LC-ARC system and a conventional flow radiometric detection system using bile samples from an in vivo disposition study of colchicine in male Sprague-Dawley rats. Results demonstrated a 20-fold sensitivity improvement of the XFlow LC-ARC system in comparison with radioactivity detection by conventional flow scintillation analyzers. The dynamic flow mode also provided the best chromatographic resolution. Unambiguous metabolite identification was performed by high-resolution mass spectrometry and nuclear magnetic resonance analysis. ER -