title: Elucidation of the in vitro metabolic profile of stable isotope labeled BAL19403 by accurate mass capillary liquid chromatography/quadrupole time-of-flight mass spectrometry and isotope exchange.
abstract: The in vitro metabolic pattern of BAL19403, a novel macrolide antibiotic, was investigated by capillary liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/QTOF-MS) in incubations with human microsomes. For the elucidation of the metabolic pathway, BAL19403 labeled with four deuterium atoms (D4) was used, and detection of metabolites performed using mixtures of the unlabeled (H4) BAL19403 and its D4 analogue (1:1) as substrate. All metabolites appeared with similar chromatographic behavior. MS/MS spectra of BAL19403 and its metabolites are dominated by non-informative fragment ions. Therefore, the structure of the metabolites was elucidated mainly by accurate mass measurements with subsequent proposals of elemental compositions. Main biotransformations were N-demethylation, lactone ring hydrolysis, and oxidation. Additionally, N-dealkylation of the aromatic moiety was identified. This dealkylation results not only in formation of an aldehyde, according to the classical pathway, but also in formation of the corresponding alcohol and carboxylic acid. Final elucidation of their structures was possible, since this dealkylation takes place vicinal to the deuterium-labeled part of BAL19403 and interferes with D/H exchange. The degree of D/H exchange, determined by analysis of the metabolite isotopic pattern, was used to elucidate the adjacent functional group.
authors.affiliation: Analytics, Basilea Pharmaceutica Ltd, Basel, Switzerland. mathias.wind@basilea.com
authors.forename: Mathias
authors.initials: M
authors.lastname: Wind
authors.forename: Klaus
authors.initials: K
authors.lastname: Gebhardt
authors.forename: Helge
authors.initials: H
authors.lastname: Grunwald
authors.forename: Jochen
authors.initials: J
authors.lastname: Spickermann
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Donzelli
authors.forename: Laurenz
authors.initials: L
authors.lastname: Kellenberger
authors.forename: Marc
authors.initials: M
authors.lastname: Muller
authors.forename: Pascal
authors.initials: P
authors.lastname: Fullhardt
authors.forename: Anne
authors.initials: A
authors.lastname: Schmitt-Hoffmann
authors.forename: Michael
authors.initials: M
authors.lastname: Schleimer
mesh_terms: D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D018942:Macrolides / Q000737:chemistry* / Q000493:pharmacokinetics*; D008657:Metabolic Clearance Rate; D008861:Microsomes / Q000737:chemistry* / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: C515877:BAL 19403; D018942:Macrolides