The determination of the Paraxanthine/Caffeine ratio as a metabolic biomarker for CYP1A2 activity in various human matrices by UHPLC-ESIMS/MS

The Cytochrome P450 CYP1A2 is a central enzyme in the metabolism of drugs and xenobiotics. overall activity this influenced by complex array biochemical, dietary, genetic factors. One simplest ways to probe output measure ratio between concentration precursor product its activity. With growing interest Paraxanthine/Caffeine ratio, need arises develop improved analytical methods specifically optimized for rapid sensitive determination paraxanthine caffeine biological samples. We report new method various human matrices. involved direct following protein precipitation based on ultra high performance liquid chromatographic separation with tandem mass spectrometric detection (UHPLC-ESIMS/MS). offers an improvement limit over previously published at least 10-fold (0.1 pg), (ca. 5 min), utilization green solvent (5% v/v ethanol), little sample preparation, employment isotopically labeled internal standards qualifier ions ensure accuracy. Method validation urine, saliva, plasma was performed spiking levels where recovery repeatability were within ±15% ±10%, respectively. applied investigate volunteers controlled administration inter- intra-individual variability paraxanthine/caffeine unrestricted diet. In conclusion, developed UHPLC-ESIMS/MS simultaneous multiple matrices, several advantages current methods, well suitable application large clinical studies.