TY - JOUR T1 - Glucuronidation of labetalol at the two hydroxy positions by bovine liver microsomes. Isolation, purification, and structure elucidation of the glucuronides of labetalol. JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 20 LP - 23 VL - 19 IS - 1 AU - N R Niemeijer AU - T K Gerding AU - R A De Zeeuw Y1 - 1991/01/01 UR - http://dmd.aspetjournals.org/content/19/1/20.abstract N2 - Glucuronidation is known to be a major metabolic pathway for labetalol. As the drug contains a phenolic and an alcoholic hydroxy group, in principle two regio isomeric glucuronides can be formed. By incubating the substrate labetalol with bovine liver microsomes, in the presence of the co-substrate UDP-glucuronic acid, both hydroxy positions were glucuronidated. The different glucuronides were isolated from the incubation mixture using Bond-Elut extraction cartridges and separated by means of high performance liquid chromatography. The formation of glucuronides was confirmed by performing reference incubations using radiolabeled UDP-glucuronic acid. Structure elucidation of the various glucuronides was done by nuclear magnetic resonance, ultraviolet spectroscopy, and mass spectrometry. ER -