ArticleAnalytical chemistry2025
Distinguishing Isomeric Caffeine Metabolites through Protomers and Tautomers Using Cryogenic Gas-Phase Infrared Spectroscopy.
Article in Analytical chemistry, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 6 papers.
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Who cites it
6 citing papers in PubMed.
- Topology Switching in Polymetallic Fragments Governed by Metal Encapsulation.Journal of the American Chemical Society · 2026Article
- Steroid Fingerprinting with Cryogenic Gas-Phase Infrared Spectroscopy.ACS measurement science au · 2026Article
- Evaluating Participation Modes in Peracetylated Glycosyl Cations.Organic letters · 2026Article
- Infrared Ion Spectroscopy Combined with Ion Mobility Spectrometry for Identification of Caffeine Metabolite Isomers and Protomers.Journal of the American Society for Mass Spectrometry · 2026Article
- How to Use Quantum Chemistry for Analyzing Mass Spectrometry Data.Mass spectrometry (Tokyo, Japan) · 2026Review
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Authors and funding
7 authors.
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Abstract
Caffeine is metabolized through various pathways in the human body, with the primary two steps yielding isomeric products. Distinguishing these metabolites is crucial for mass spectrometry-based metabolomics, for example, to assess specific drug interactions. Here, we investigate the gas-phase structures of caffeine and its metabolites─theophylline, theobromine, paraxanthine, 1-methylxanthine, 3-methylxanthine, and 7-methylxanthine─in their respective protonated ions using cryogenic gas-phase infrared spectroscopy, supported by density functional theory. The analytes exhibit varying preferences for protonation and tautomerism, particularly N9 protonation and, where applicable, a tendency for N3O2 and N1O2 amide-imidic acid and N7N9 imine-imine tautomerism. We further demonstrate that the two isomeric sets of caffeine metabolites can easily be distinguished with gas-phase IR spectroscopy, paving the way for robust identification of such molecules in metabolomics using hyphenated gas-phase techniques.
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