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Quantitative assay of plasma homocysteine thiolactone by gas chromatography/mass spectrometry
Author(s) -
Daneshvar Parham,
Yazdanpanah Mehrdad,
Cuthbert Carla,
Cole David E. C.
Publication year - 2003
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.915
Subject(s) - chemistry , thiolactone , chromatography , selected ion monitoring , derivatization , detection limit , mass spectrometry , chemical ionization , gas chromatography–mass spectrometry , gas chromatography , homocysteine , selected reaction monitoring , metabolite , quantitative analysis (chemistry) , solid phase extraction , tandem mass spectrometry , ion , organic chemistry , ionization , biochemistry
Enzymatic cyclization of homocysteine forms a reactive thiolactone that may play an important role in its cardiovascular toxicity, but reliable quantitation of the free thiolactone metabolite in physiological fluids has not been reported. We have therefore used a highly selective gas chromatography/mass spectrometry (GC/MS) technique combined with the sensitivity of negative chemical ionization (NCI) to develop a quantitative method for the detection of homocysteine thiolactone (HcyTL) in plasma. To improve accutacy the deuterated isomer d 4 ‐HcyTL was synthesized and added to plasma as internal standard. The plasma was then treated with silica solid‐phase extraction and derivatized with heptafluorobutyric anhydride. The derivative was analyzed by GC/MS in NCI mode with methane as the reagent gas and quantified by analyzing for the HcyTL ion [M − HF] and its d 4 ‐HcyTL counterpart in single‐ion monitoring mode. The calibration curve showed a dynamic linear range up to 40 nmol/L. Within‐day precision (n = 20, nominal concentration 5.2 nmol/L) was 0.96% and between‐day precision was 3.9%, with a detection limit of 1.7 nmol/L and quantification limit of 5.2 nmol/L. Two human plasma samples had HcyTL concentrations of 18 and 25 nmol/L. This facile method for quantitation of homocysteine thiolactone opens the way for more detailed clinical studies of its potential role in homocysteine‐induced arteriosclerosis and vaso‐occlusive disease. Copyright © 2003 John Wiley & Sons, Ltd.