TY - JOUR
T1 - Quantitative determination of isothiocyanates, dithiocarbamates, carbon disufide, and related thiocarbonyl compounds by cyclocondensation with 1,2- benzenedithiol
AU - Zhang, Yuesheng
AU - Wade, Kristina L.
AU - Prestera, Tory
AU - Talalay, Paul
N1 - Funding Information:
These studies were supported by a grant (PO1 CA44530) from the National Cancer Institute, Department of Health and Human Services. Additional support was provided by the American Institute for Cancer Research, Washington, DC, and by the Rex Foundation (The Grateful Dead), San Anselmo, CA. The acquisition of the Photodiode Array Detector and accessories was made possible by a gift from Rick and Faith Kash and the Kash Family Foundation, Chicago. We thank Dr. Mikio Shikita for help in the analysis of volatile isothiocyanates and Gale Doremus for preparing the manuscript and illustrations.
PY - 1996/8/1
Y1 - 1996/8/1
N2 - A recently developed UV spectroscopic method for quantitating isothiocyanates (R-N=C=S) at the nanomole level is based on the observation that the highly electrophilic central carbon atom of the -N=C = S group can undergo successive nucleophilic additions with reagents containing two sulfhydryl groups on adjacent carbon atoms to form a cyclic thiocarbonyl product and release the nitrogen atom as a primary amine (Y. Zhang, C.-G. Cho, G. H. Posner, and P. Talalay, Anal. Biochem. 205, 100-107, 1992). The assay utilizes 1,2-benzenedithiol as the vicinal dithiol reagent and measures the reaction product, 1,3-benzodithiole-2-thione, spectroscopically (a(m) of 23,000 M-1 cm-1 at λ(max) = 365 nm). This paper reports a dramatic improvement in the analytical sensitivity of this method. By separating the cyclocondensation product by a simple isocratic HPLC method and using an automatic integrator, the sensitivity of detection has been lowered to a few picomoles of isothiocyanate. Furthermore, we now find that the chemical specificity of the cyclocondensation reaction is not restricted to isothiocyanates, but includes dithiocarbamates, and related thiocarbonyl compounds such as carbon disulfide, certain substituted thiourea derivatives, and xanthates. The availability of such analytical methods is important not only because isothiocyanates (and their glucosinolate precursors) are present in edible plants and are consumed by humans in substantial quantities, but also because some dithiocarbamates are toxic, and are widely used in the rubber industry as vulcanization accelerators and in agriculture as fungicides, insecticides, and herbicides. The analysis of many isothiocyanates is complicated by their extreme volatility. This difficulty can be circumvented by converting isothiocyanates quantitatively into dithiocarbamates (by facile addition of a mercaptan such as N-acetylcysteine) and quantitating the nonvolatile dithiocarbamate by the cyclocondensation reaction.
AB - A recently developed UV spectroscopic method for quantitating isothiocyanates (R-N=C=S) at the nanomole level is based on the observation that the highly electrophilic central carbon atom of the -N=C = S group can undergo successive nucleophilic additions with reagents containing two sulfhydryl groups on adjacent carbon atoms to form a cyclic thiocarbonyl product and release the nitrogen atom as a primary amine (Y. Zhang, C.-G. Cho, G. H. Posner, and P. Talalay, Anal. Biochem. 205, 100-107, 1992). The assay utilizes 1,2-benzenedithiol as the vicinal dithiol reagent and measures the reaction product, 1,3-benzodithiole-2-thione, spectroscopically (a(m) of 23,000 M-1 cm-1 at λ(max) = 365 nm). This paper reports a dramatic improvement in the analytical sensitivity of this method. By separating the cyclocondensation product by a simple isocratic HPLC method and using an automatic integrator, the sensitivity of detection has been lowered to a few picomoles of isothiocyanate. Furthermore, we now find that the chemical specificity of the cyclocondensation reaction is not restricted to isothiocyanates, but includes dithiocarbamates, and related thiocarbonyl compounds such as carbon disulfide, certain substituted thiourea derivatives, and xanthates. The availability of such analytical methods is important not only because isothiocyanates (and their glucosinolate precursors) are present in edible plants and are consumed by humans in substantial quantities, but also because some dithiocarbamates are toxic, and are widely used in the rubber industry as vulcanization accelerators and in agriculture as fungicides, insecticides, and herbicides. The analysis of many isothiocyanates is complicated by their extreme volatility. This difficulty can be circumvented by converting isothiocyanates quantitatively into dithiocarbamates (by facile addition of a mercaptan such as N-acetylcysteine) and quantitating the nonvolatile dithiocarbamate by the cyclocondensation reaction.
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U2 - 10.1006/abio.1996.0311
DO - 10.1006/abio.1996.0311
M3 - Article
C2 - 8811900
AN - SCOPUS:0030219693
SN - 0003-2697
VL - 239
SP - 160
EP - 167
JO - Analytical biochemistry
JF - Analytical biochemistry
IS - 2
ER -