Determination of acetylated caffeine metabolites by high-performance exclusion chromatography

Tang, Boyu; Zubovits, T.K.; Kalow, W.

doi:10.1016/s0378-4347(00)83706-8

Cited by 29 publications

(5 citation statements)

References 5 publications

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“…In the chromatograms of urine extracts, however, it could not be assigned properly. This is in agreement with data of other laboratories which report the use of exclusion chromatography for the simultaneous HPLC determination of AAMU, AFMU and 1X [6,7].…”

Section: Resultssupporting

confidence: 93%

“…1). Although the decomposition reaction can be minimized by acidification immediately after urine collection, complete control and prevention of inaccurate results is only given when both AAMU and AFMU can be monitored, a task which was found to be difficult when using reversed-phase high-performance liquid chromatography (HPLC) but possible with exclusion chromatography [7].…”

Section: Introductionmentioning

confidence: 99%

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Acetylator phenotyping via analysis of four caffeine metabolites in human urine by micellar electrokinetic capillary chromatography with multiwavelength detection

Guo

Thormann

1993

Electrophoresis

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The simultaneous analysis of 5-acetylamino-6-formylamino-3-methyluracil (AFMU), 5-acetylamino-6-amino-3-methyluracil (AAMU), 1-methylxanthine (1X) and 1-methyluric acid (1U), the four urinary metabolites of caffeine employed for acetylator phenotyping in man, by micellar electrokinetic capillary chromatography (MECC) is reported. Using on-column fast scanning multiwavelength detection is shown to permit unambiguous identification of AAMU, AFMU, 1X and 1U in the three-dimensional electropherograms obtained with both direct urine injection or application of extracted urine. The phenotype status of a number of healthy volunteers, some with known acetylator status, were determined using peak height ratios of AFMU/1X, (AFMU + AAMU)/1X and compared to those obtained by high performance liquid chromatography (HPLC) employing the AFMU/1X peak height ratio. Another set of MECC data was obtained after deliberate conversion of AFMU to AAMU, the results being expressed by AAMU/1X,AAMU/(1U + 1X) or AAMU/(AAMU + 1U + 1X) ratios. The data suggest that most reliable data are obtained when phenotyping is conducted under conditions of complete conversion of AFMU to AAMU. Phenotyping employing caffeine and analysis of its urinary metabolites by MECC is shown to be simple and, with automated instruments, potentially suitable for routine use and large-scale population analysis. The agreement of MECC data obtained from three different instruments demonstrates the high level of maturity of this emerging technology.

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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Acetylator phenotyping via analysis of four caffeine metabolites in human urine by micellar electrokinetic capillary chromatography with multiwavelength detection

Guo

Thormann

1993

Electrophoresis

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“…ZnO direction. This inductive effect of lattice mismatch strain between ZnO and SnO 2 maybe may be potentially applied in fabricating SnO 2 quantum dots/wires on the ZnO surfaces, referring to other epitaxial systems [25][26][27][28]. 3.4 Cathodoluminescence property of ZnO/SnO 2 core-shell micropyramids Because both ZnO and SnO 2 are important optical materials, novel luminescence properties might be hopefully found by the epitaxial growth of SnO 2 on the ZnO template.…”

mentioning

confidence: 99%

Hexagonal ZnO/SnO2 core–shell micropyramids: epitaxial growth-based synthesis, chemical conversion, and cathodoluminescence

Kuang

Zhou

Zheng

2014

Inorg. Chem. Front.

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In this paper, ZnO/SnO 2 core-shell micropyramids were successfully prepared via a chemical vapor deposition process that is based on the epitaxial growth of SnO 2 on the surface of ZnO hexagonal micropyramids. Upon controlling appropriate deposition times and flow rates of the precursor, two epitaxial growth modes of SnO 2 , i.e. a continuous thick film and well-arranged one-dimensional nanostructures were observed in the ZnO/SnO 2 core-shell micropyramids. Taking advantages of the difference in acid resistance between ZnO and SnO 2 , the as-prepared ZnO/SnO 2 micropyramids were further converted into SnO 2 hollow micropyramids with a facile acid-etching treatment. Structural analysis revealed that the lattice mismatch degree between epitaxial planes determines the preferential growth direction of the SnO 2 epitaxial layer on the ZnO surface. Compared to the pristine ZnO template, interestingly, the ZnO/ SnO 2 core-shell micropyramids exhibited very strong green emission around 504 nm. Such enhanced green emission should be induced by high-density structural defects generated in the interfacial area during the epitaxial growth.

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“…Chlorzoxazone and 6-hydroxychlorzoxazone were measured according to the method of Frye and Stiff,20 except that our mobile phase consisted of acetonitrile-0.5% acetic acid (30/70, v/v) and our UV detector was set to 287 nm. The caffeine metabolites 1 -methylxanthine (1X), 1 -methylurate (1U) and 1,7dimethylurate (17U) were measured according to Dobrocky et al21 with sample preparation according to Krul and Hageman.22 5-Acetylamino -6-amino -3methyluracil (AAMU) was measured with exclusion chromatography according to Tang et al 23 Dextromethorphan and dextrorphan were measured according to the method of Ducharme et a]24 with minor modifications. Our mobile phase consisted of methanol, acetonitrile, 10 mM sodium phosphate buffer (pH 5.7, 13:27:60, v/v) and 2.5 mM octanesulfonic acid.…”

Section: Methodsmentioning

confidence: 99%

Metabolic capacity and interindividual variation in toxicokinetics of styrene in volunteers

Wenker¹,

Kežić²,

Monster

et al. 2001

Hum Exp Toxicol

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The aim of the present study was to assess the interindividual variation in styrene toxicokinetics and to correlate this variation with the individual metabolic capacity for cytochromeP450 (CYP), CYP2E1, CYP1A2 and CYP2D6. Twenty male volunteers were exposed on separate occasions to 104±3 and 360 ± 20 mg/m3 of styrene for 1 h while performing 50 W physical exercise on a bicycle ergometer. Styrene concentrations in blood and mandelic (MA) and phenylglyoxylic acid (PGA) in urine were measured. The metabolic capacity was assessed by phenotyping with chlorzoxazone (CYP2El), caffeine (CYP1A2), dextromethorphan (CYP2D6) and antipyrine (CYP450). In addition, for the main styrene-metabolising enzyme, CYP2E1, genotyping for the genetic polymorphisms of the gene was performed. The average pulmonary retention of styrene was 62 ± 7% at both exposure concentrations, and the 24-h excretion of MA and PGA accounted for 58% of the dose at both concentrations. The interindividual variation in styrene kinetics ranged from 19% for the terminal half-life (t1/2,β) of styrene to 41% for the cumulative excretion of MA and PGA. However, no correlation between the apparent blood clearance of styrene (CLapp), t1/2,β of styrene or excretion of MA and PGA on one hand, and the individual metabolic capacity on the other hand was found. Although other explanations cannot be excluded, this lack of correlation might be due to the high apparent blood clearance (1.4 1/ min) of styrene, indicating that styrene metabolism is liver–blood-flow-dependent.

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Determination of acetylated caffeine metabolites by high-performance exclusion chromatography

Cited by 29 publications

References 5 publications

Acetylator phenotyping via analysis of four caffeine metabolites in human urine by micellar electrokinetic capillary chromatography with multiwavelength detection

Acetylator phenotyping via analysis of four caffeine metabolites in human urine by micellar electrokinetic capillary chromatography with multiwavelength detection

Hexagonal ZnO/SnO2 core–shell micropyramids: epitaxial growth-based synthesis, chemical conversion, and cathodoluminescence

Metabolic capacity and interindividual variation in toxicokinetics of styrene in volunteers

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