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Titolo:
ANALYSIS OF URINARY CAFFEINE METABOLITES TO ASSESS BIOTRANSFORMATION ENZYME-ACTIVITIES BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY
Autore:
KRUL C; HAGEMAN G;
Indirizzi:
UNIV MAASTRICHT,DEPT HLTH RISK ANAL & TOXICOL,POB 616 NL-6200 MD MAASTRICHT NETHERLANDS UNIV MAASTRICHT,DEPT HLTH RISK ANAL & TOXICOL NL-6200 MD MAASTRICHT NETHERLANDS
Titolo Testata:
Journal of chromatography B. Biomedical sciences and applications
fascicolo: 1, volume: 709, anno: 1998,
pagine: 27 - 34
SICI:
0378-4347(1998)709:1<27:AOUCMT>2.0.ZU;2-C
Fonte:
ISI
Lingua:
ENG
Soggetto:
CYTOCHROME P4501A2; CYP1A2 ACTIVITY; VARIABILITY; ASSAYS; PROBE;
Keywords:
ENZYMES; CAFFEINE; PARAXANTHINE; 1,7-DIMETHYLURATE; 1-METHYLXANTHINE; 1-METHYLURATE; 5-ACETYLAMINO-6-FORMYLAMINO-3-METHYLURACIL;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
18
Recensione:
Indirizzi per estratti:
Citazione:
C. Krul e G. Hageman, "ANALYSIS OF URINARY CAFFEINE METABOLITES TO ASSESS BIOTRANSFORMATION ENZYME-ACTIVITIES BY REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY", Journal of chromatography B. Biomedical sciences and applications, 709(1), 1998, pp. 27-34

Abstract

An isocratic high-performance liquid chromatography procedure was developed for the analysis of five urinary metabolites of caffeine; caffeine or 1,3,7-trimethylxanthine (137X), paraxanthine or 1,7-dimethylxanthine (17X), 1,7-dimethylurate (17U), 1-methylxanthine (1X), 1-methylurate (1U) and 5-acetylamino-6-formylamino-3-methyluraci (AFMU). A standardized procedure was used for oral intake of caffeine and for urine collection. Conditions for sample storage and preparation were optimized, resulting in no detectable loss of caffeine metabolites after storage of the urine samples for four months. Urine samples were extractedwith chloroform-2-propanol (4:1, v/v) and separated on a reversed-phase column with acetic acid (33%)-tetrahydrofuran-acetonitrile-water (1:2.5:44:925.5, v/v) as the eluent. Peaks were monitored at 280 nm. Peak heights were measured and the five metabolites were quantified usingcalibration curves. Cytochrome P4501A2 (CYP1A2) activity was calculated from the molar ratio (AFMU+1X+1U)/17U, N-acetyltransferase (NAT) from the ratio AFMU/1X, XO from the ratio 1U/1X+1U and cytochrome P4502A6 (CYP2A6) from the ratio 17U/(17U+17X+1U+1X+AFMU). The inter-assay coefficients of variation ranged from 1.7% for 17U to 5.7% for 1X. The intra-individual variation in metabolite ratios determined in two people, with intervals of a few days to several weeks between measurements,ranged from 2.1% for XO to 11.0% for CYP2A6. Using this procedure, metabolic ratios were determined for four groups of subjects; healthy, non-smoking females using oral contraceptives (OC users, n=5) and non-users (n=5), healthy nonsmoking males (n=9) and children (n=7). Resultsfound in this study were comparable to results reported in the literature for subjects with similar characteristics. A significantly higherCYP1A2 ratio was found for males (4.87+/-0.47) compared to females (3.62+/-0.91; p=0.005, Mann-Whitney). For the other enzyme activities, no significant differences were found between the groups of subjects inthis study. (C) 1998 Elsevier Science B.V.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 28/09/20 alle ore 18:38:21