High-performance liquid chromatography-based determination of total isothiocyanate levels in human plasma: application to studies with 2-phenethyl isothiocyanate.
Dietary and pharmacologic isothiocyanates (ITCs) may play a role in reducing the risk of certain cancers. The quantification of ITCs in humans is important both for epidemiological and pharmacokinetic studies. We describe a modification of an HPLC-based assay of urinary ITCs for use with human plasma. The assay utilizes the cyclocondensation reaction of 1,2-benzenedithiol with ITCs present in human plasma, followed by a two-step hexane extraction and analysis by HPLC using UV detection at 365 nm. The method shows linearity and reproducibility with human plasma over a range of 49-3003 nM phenethyl isothiocyanate (PEITC) (r(2) = 0.996 +/- 0.003). A similar degree of linearity was seen with two other biologically occurring conjugates of PEITC: PEITC--N-acetylcysteine (PEITC--NAC) and PEITC--glutathione (PEITC--GSH). The recovery of PEITC assessed on multiple days was 96.6 +/- 1.5% and was 100% for PEITC--GSH and PEITC--NAC. The reproducibility of the assay on multiday samplings showed a mean %CV of 6.5 +/- 0.3% for PEITC, 6.4 +/- 4.3 for PEITC--NAC and 12.3 +/- 3.9 for PEITC--GSH. In clinical studies, mean plasma ITC level of 413 +/- 193 nM PEITC equivalents was determined for a non-dietary-controlled group of 23 subjects. Multiday analysis data from pharmacokinetic plasma sets of 3 subjects taking a single dose of PEITC at 40 mg showed a good CV (range: 16-21%). The applicability of the methodology to pharmacokinetic studies of PEITC in humans is demonstrated.
Liebes
L
L
Division of Oncology, Department of Medicine, New York University Medical Center, New York, New York 10016, USA. Liebel01@gcrc.med.nyu.edu
Conaway
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CC
Hochster
H
H
Mendoza
S
S
Hecht
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Crowell
J
J
Chung
F L
FL
D002851:Chromatography, High Pressure Liquid; D017321:Clinical Trials, Phase I as Topic; D004032:Diet; D006801:Humans; D017879:Isothiocyanates / Q000097:blood* / Q000737:chemistry / Q000493:pharmacokinetics; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D017879:Isothiocyanates; C037152:isothiocyanic acid; C058305:phenethyl isothiocyanate