Identification of phenobarbital N-glucuronides as urinary metabolites of phenobarbital in mice

Department of Medicinal Chemistry, School of Pharmacy, Virginia Commonwealth University, Richmond 23298-0540, USA.
Drug Metabolism and Disposition (Impact Factor: 3.25). 06/1995; 23(5):548-52.
Source: PubMed


Mice were evaluated for their ability to form phenobarbital N-glucuronides. Following oral administration of [14C]phenobarbital to mice, a radiolabeled phenobarbital metabolite cochromatographed with synthetic standards of phenobarbital N-glucuronides. The phenobarbital N-glucuronides were partially purified from the mouse urine as phenobarbital N-methylglucuronates. The phenobarbital N-methylglucuronates isolated from mouse urine had similar chromatographic and spectroscopic properties as synthetic standards. The diastereomers of phenobarbital N-glucuronides and phenobarbital N-glucosides accounted for 7.8 +/- 2.3% and 1.6 +/- 0.6%, respectively, of the radioactivity excreted in mouse urine in the first 48 hr after dosing. This study indicates that the mouse may be a suitable species to study both N-glucosidation and N-glucuronidation simultaneously as metabolic pathways for barbiturates.

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    • "Regarding the metabolism of barbiturate derivatives, the N-glucoside forms of phenobarbital [5] and amobarbital [6] are known as the main metabolites in humans, but no Nglucuronide forms of these compounds have been confirmed . Neighbors et al. [7] reported the presence of Nglucuronide and N-glucoside in urine of mice treated with phenobarbital, and Mohri et al. [8] reported the "
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    ABSTRACT: Bucolome N-glucuronide (BCP-NG, main metabolite of bucolome (BCP) is the first N-glucuronide of barbituric acid derivatives isolated from rat bile. The objective of this study was to identify the main tissue producing BCP-NG and the molecular species of BCP-NG-producing UGT. Four target tissues were investigated: the liver, small and large intes-tines, and kidney. To identify the UGT molecular species responsible for BCP-NG formation, yeast microsomes ex-pressing each rat UGT isoform were prepared. BCP-NG formation was detected in all microsomal fractions of the 4 tissues. The liver microsomal BCP-NG-producing activity was the highest, followed by that in the small intestinal mi-crosomes, showing about 41% of the liver microsomal activity level. BCP-NG-producing activity (min-1) was deter-mined in yeast microsomal fractions expressing rat UGT isoforms, and the activity was detected in UGT1A1 (0.059), UGT1A2 (0.318), UGT1A3 (0.001), UGT1A7 (0.003), UGT2B1 (0.004), UGT2B3 (0.091), and UGT2B6 (0.031), show-ing particularly high levels for UGT1A1 and UGT1A2 among the UGT1A isoforms. It was clarified that UGT1A1, widely distributed in rat tissues, is the molecular species responsible for BCP-NG formation.
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    ABSTRACT: A HPLC assay using UV detection and post-column alkalinization was developed to quantify possible urinary excretion products of phenobarbital in human urine. After filtration the urine was injected directly onto the HPLC column for analysis of phenobarbital, p-hydroxyphenobarbital, phenobarbital N-glucosides and phenobarbital N-glucuronides. The accuracy and precision of the assay were within +/- 15% and the limit of detection (LOD) was 1 microM, suitable for pharmacokinetic studies. Phenobarbital was administered orally to five male subjects and urine was collected for a period of 96-108 h. Phenobarbital, p-hydroxyphenobarbital, and phenobarbital N-glucosides were detected and quantified in the urine of all five subjects. The phenobarbital N-glucuronides were not detected in the urine. This assay provides a rapid method with improved selectivity to analyze urine for phenobarbital and its metabolites.
    Journal of chromatography. B, Biomedical sciences and applications 04/1997; 691(1):111-7. DOI:10.1016/S0378-4347(96)00437-9
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    ABSTRACT: A study was undertaken to determine if humans excrete both amobarbital N-glucuronides and N-glucosides in urine after an oral dose of amobarbital. Amobarbital N-glucuronides were synthesized and characterized. A reverse phase LC method using post-column pH adjustment and UV detection at 240 nm was developed and used for the quantification of the amobarbital N-glucosides and N-glucuronides in human urine. Amobarbital was administered orally to seven male subjects and the total urine was collected for a period of 48-53 h after dosing. After filtration, the urine was injected directly onto the HPLC column to analyze for the presence of metabolites. The previously identified (5S)-amobarbital N-glucoside was detected in all seven subjects. The (5R)-amobarbital N-glucoside was detected at lower concentrations in only four of the subjects. At the levels at which amobarbital N-glucosides were detected, there was no evidence for the formation and excretion of the amobarbital N-glucuronides. Amobarbital N-glucuronidation is not a quantitatively significant pathway for the biodisposition of amobarbital in humans.
    Journal of Pharmaceutical and Biomedical Analysis 06/1997; 15(8):1187-95. DOI:10.1016/S0731-7085(96)01936-X · 2.98 Impact Factor
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