{"doi":"10.1002/bmc.1419","title":"Caffeine and paraxanthine HPLC assay for CYP1A2 phenotype assessment using saliva and plasma","abstract":"<jats:title>Abstract</jats:title><jats:p>Caffeine has been extensively used as a probe to measure CYP1A2 activity in humans with caffeine clearance or the paraxanthine (major metabolite of caffeine) to caffeine concentration ratio being regarded as the preferred metric. A simple reverse‐phased C<jats:sub>18</jats:sub> HPLC assay using ethyl acetate liquid–liquid extraction was developed to quantitate caffeine and paraxanthine concentrations in saliva and plasma. The mobile phase consisted of acetonitrile–acetic acid–H<jats:sub>2</jats:sub>O (100:1:899) and analytes were quantitated with UV detection at 280 nm. The extraction recovery for paraxanthine and caffeine was approximately 70% in both saliva and plasma. The assay was linear over the concentration ranges 0.05–2.50 and 0.05–5.00 µg/mL, for paraxanthine and caffeine, respectively, in saliva. In plasma the assay was linear over the ranges 0.025–2.50 and 0.025–5.00 µg/mL for paraxanthine and caffeine, respectively. Intra‐ and inter‐assay precision and accuracy were less than 15%. Detection limits were 0.015 µg/mL for paraxanthine and caffeine in saliva, while it was 0.005 µg/mL for paraxanthine and caffeine in plasma. Utility was established in samples collected from two healthy volunteers who abstained from caffeine for 24 h and received a single 100 mg oral dose of caffeine. The assay developed is a robust, simple and precise technique to measure caffeine and paraxanthine in saliva and plasma of healthy volunteers after a single oral dose of caffeine. Copyright © 2010 John Wiley &amp; Sons, Ltd.</jats:p>","journal":"Biomedical Chromatography","year":2010,"id":687892,"datarank":0.586803450814222,"base_score":3.912023005428146,"endowment":3.912023005428146,"self_citation_contribution":0.586803450814222,"citation_network_contribution":0.0,"self_endowment_contribution":0.586803450814222,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":49,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_data_producer":false,"deposit_databanks":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":559330,"name":"Annette S. Gross","orcid":"0000-0001-9567-0127","position":1,"is_corresponding":false},{"id":1092722,"name":"Andrew J. McLachlan","orcid":"0000-0003-4674-0242","position":2,"is_corresponding":false},{"id":154717,"name":"Vidya Perera","orcid":null,"position":0,"is_corresponding":false}],"reference_count":0,"raw_metadata":{"has_enrichment":true,"resolved":true,"title":"Caffeine and paraxanthine HPLC assay for CYP1A2 phenotype assessment using saliva and plasma","abstract":"<jats:title>Abstract</jats:title><jats:p>Caffeine has been extensively used as a probe to measure CYP1A2 activity in humans with caffeine clearance or the paraxanthine (major metabolite of caffeine) to caffeine concentration ratio being regarded as the preferred metric. A simple reverse‐phased C<jats:sub>18</jats:sub> HPLC assay using ethyl acetate liquid–liquid extraction was developed to quantitate caffeine and paraxanthine concentrations in saliva and plasma. The mobile phase consisted of acetonitrile–acetic acid–H<jats:sub>2</jats:sub>O (100:1:899) and analytes were quantitated with UV detection at 280 nm. The extraction recovery for paraxanthine and caffeine was approximately 70% in both saliva and plasma. The assay was linear over the concentration ranges 0.05–2.50 and 0.05–5.00 µg/mL, for paraxanthine and caffeine, respectively, in saliva. In plasma the assay was linear over the ranges 0.025–2.50 and 0.025–5.00 µg/mL for paraxanthine and caffeine, respectively. Intra‐ and inter‐assay precision and accuracy were less than 15%. Detection limits were 0.015 µg/mL for paraxanthine and caffeine in saliva, while it was 0.005 µg/mL for paraxanthine and caffeine in plasma. Utility was established in samples collected from two healthy volunteers who abstained from caffeine for 24 h and received a single 100 mg oral dose of caffeine. The assay developed is a robust, simple and precise technique to measure caffeine and paraxanthine in saliva and plasma of healthy volunteers after a single oral dose of caffeine. Copyright © 2010 John Wiley &amp; Sons, Ltd.</jats:p>","is_dataset_classified":null,"base_score":3.912023005428146,"endowment":3.912023005428146,"datacite_reuse_total":0,"file_count":0,"downloads":0,"views":0,"has_version_chain":false,"is_dataset":false,"is_oa":false,"pmid":"20853468","pmcid":null,"openalex_id":"https://openalex.org/W1977321058","authors":[],"funders":[],"total_grants":0,"fwci":4.0925,"citation_percentile":0.91926721,"influential_citations":0,"citation_trend":[{"year":2012,"count":6},{"year":2013,"count":3},{"year":2014,"count":6},{"year":2015,"count":4},{"year":2016,"count":5},{"year":2017,"count":1},{"year":2018,"count":2},{"year":2019,"count":4},{"year":2020,"count":1},{"year":2021,"count":4},{"year":2022,"count":3},{"year":2023,"count":3},{"year":2024,"count":3},{"year":2025,"count":3}],"oa_status":"closed","license":"http://onlinelibrary.wiley.com/termsAndConditions#vor","oa_locations":[{"url":"https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fbmc.1419","host_type":"publisher"},{"url":"https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/pdf/10.1002/bmc.1419","host_type":"publisher"},{"url":"https://doi.org/10.1002/bmc.1419","host_type":"journal"},{"url":"https://pubmed.ncbi.nlm.nih.gov/20853468","host_type":"repository"}],"fields_of_study":["Pharmacogenetics and Drug Metabolism","Diet and metabolism studies","Tryptophan and brain disorders"],"mesh_terms":["Caffeine","Chromatography, High Pressure Liquid","Drug Stability","Humans","Male","Phenotype","Saliva","Sensitivity and Specificity","Theophylline","Reproducibility of Results","Least-Squares Analysis","Cytochrome P-450 CYP1A2","Area Under Curve","Young Adult"],"keywords":["Paraxanthine","Caffeine","Chemistry","Saliva","Chromatography","Theobromine","CYP1A2","High-performance liquid chromatography","Theophylline","Pharmacology","Biochemistry","Endocrinology","In vitro","Medicine"],"sdg_mappings":[],"linked_datasets":[],"clinical_trials":[],"software_tools":[],"database_accessions":[],"source":"live","citation_network_status":"fetched"},"created_at":"2026-08-19T09:25:37.940861Z","pmid":null,"pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}