title: Determination of urinary 13C-caffeine metabolites by liquid chromatography-mass spectrometry: the use of metabolic ratios to assess CYP1A2 activity.
abstract: A method using liquid chromatography coupled with mass spectrometry with an atmospheric pressure electrospray source was developed for analysis of labelled caffeine and fourteen of its metabolites in urine. Caffeine metabolic ratios were determined after an oral bolus of labelled caffeine in 20 healthy subjects with different characteristic CYP1A2 activity, relative to smoking habit and oral contraceptive intake. The use of labelled caffeine for the calculation of metabolic ratios avoided taking into account the important background of endogenous caffeine metabolites, very difficult to eliminate even after a specific diet. The selectivity and high sensitivity of mass spectrometry detection allowed urine collections for only a 3h period. Comparison between characteristic groups showed that labelled caffeine metabolic ratios were sensitive markers of changes in CYP1A2 activity.
authors.affiliation: Faculté de Pharmacie, University of Montreal, Montreal, Que., Canada H3C 3J7.
authors.forename: Marie-Sophie
authors.initials: MS
authors.lastname: Caubet
authors.forename: Blandine
authors.initials: B
authors.lastname: Comte
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Brazier
mesh_terms: D000293:Adolescent; D000328:Adult; D002110:Caffeine / Q000652:urine*; D002247:Carbon Isotopes / Q000652:urine; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D019388:Cytochrome P-450 CYP1A2 / Q000652:urine*; D004789:Enzyme Activation / Q000502:physiology; D005260:Female; D006801:Humans; D007527:Isoenzymes / Q000652:urine; D008297:Male; D018709:Statistics, Nonparametric
chemical_list: D002247:Carbon Isotopes; D007527:Isoenzymes; D002110:Caffeine; D019388:Cytochrome P-450 CYP1A2