The use of stable isotope labelling for the analytical chemistry of drugs

Abstract

This perspective reviews the potential for stable isotope labelling to examine the metabolic transformations of drugs. The increased sensitivity and widespread availability of modern nuclear magnetic resonance (NMR) and high-resolution mass spectrometers will increase the application of stable isotopes to study drug metabolism. Creating mass doublets by mixing a natural isotopic abundance compound with a labelled isotopomer and applying stable isotope filtering to high resolution mass spectrometry allows one to rapidly identify drug metabolites in very complex samples, such as blood or urine. Applying this approach to drug metabolism will require a significant synthesis effort. The relatively small number of (13) C, (15) N, or (17,18) O-labelled precursors exacerbates this problem, making the synthesis of the labelled drug often more difficult than that of the parent compound. We have developed new strategies for stable isotope labelling of complex molecules based on the rich chemistry of [(13) C]methyl phenyl sulfide, where the phenylthio group acts as a stable, non-volatile carrier for the valuable (13) C-label. For example we have used [(13) C]methyl phenyl sulfide to prepare the three possible (13) C-isotopomers ([1-(13) C]-, [2-(13) C]-, [1,2-(13) C(2) ]) of the two carbon precursors, ethyl 2-(phenylthio) acetate and ethyl N,N-dimethyl oxamate. In each case, these two-carbon labelling precursors are asymmetric and the differential reactivity of the carbons allows for either/or (13) C-labelling in the products. We demonstrate the utility of these two carbon precursors in the synthesis of aromatic ring-labelled N-(4-hydroxyphenyl)acetamide (acetaminophen or paracetamol).

Profiling primaquine metabolites in primary human hepatocytes using UHPLC‐QTOF‐MS with 13C stable isotope labeling

“…Detailed structural information on drugs and related molecules can be obtained employing cone voltage fragmentation with single MS instrumentation, collision‐induced dissociation with triple quadrupole MS instruments, to MS n techniques using quadrupole ion‐trap instrumentation or time‐of‐flight MS (TOF‐MS) . A wide range of different MS techniques including accurate mass electrospray ionization (ESI)‐MS, accurate mass tandem MS, and desorption ESI (DESI) have been applied to different types of antimalarials . MS has a number of advantages over other analytical methods including high speed and sensitivity.…”

“…However, the metabolites generated in low quantities require sensitive technologies for more accurate phenotyping of the metabolites. Availability of high‐resolution mass spectrometers coupled with application of drugs labeled with stable isotopes has addressed these challenges . Creating mass doublets by mixing a natural isotopic abundance compound with a labeled isotopomer and applying stable isotope filtering to high‐resolution MS allows one to rapidly identify drug metabolites in very complex samples .…”

“…Availability of high‐resolution mass spectrometers coupled with application of drugs labeled with stable isotopes has addressed these challenges . Creating mass doublets by mixing a natural isotopic abundance compound with a labeled isotopomer and applying stable isotope filtering to high‐resolution MS allows one to rapidly identify drug metabolites in very complex samples . The general aims of the current study are: (1) to phenotype metabolites of PQ (identify and determine their chemical structures through metabolite prediction software) generated in in vitro incubation of PQ with primary human hepatocytes and (2) to generate information on the MS‐MS fragmentation pathway of each metabolite.…”

Deuterium‐ und tritiummarkierte Verbindungen: Anwendungen in den modernen Biowissenschaften

“…Falls HIE-Methoden auf das Endmoleküls elbst angewendet werden, muss der Austausch hocheffizient sein, um eine massenspektrometrische Signalüberschneidung mit dem verbleibenden M 0 zu vermeiden. [150] Verglichen mit Radioaktivitätsdetektion erfordert die LC/MS-Analyse typischerweise eine aufwendigere Methodenentwicklung und Va lidierung,u me ine vergleichbare Sensitivität( LOQ) zu erreichen. Schema 12.…”

Editorial: Analysis of drugs for the therapy of anticholinesterase poisoning

“…[10] The valuable properties of classic Ellman-based assays to explore inhibition and reactivation kinetics of cholinesterases are also outlined in a concise review. [15] Regarding this diversity of presented techniques and applications, we hope that this special issue will be of interest not only to toxicologists, pharmacologists, pharmacists, and medicinal chemists but to researchers with an interest in analytical chemistry in general. [12] In addition, perspective papers point out current technical and methodological trends and progress in mass spectrometry instrumentation [13] as well as use of attenuated-total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) [14] and stable isotope labelling for synthesis of internal standards for mass spectrometry, applications in nuclear magnetic resonance (NMR) spectroscopy and for studying drug biotransformation.…”