TY - JOUR
T1 - Spectroscopic quantitation of organic isothiocyanates by cyclocondensation with vicinal dithiols
AU - Zhang, Yuesheng
AU - Cho, Cheon Gyu
AU - Posner, Gary H.
AU - Talalay, Paul
N1 - Funding Information:
These studies were supported by a U.S. Public Health Service Grant (PO1 CA 44530) awarded by the National Cancer Institute, Department of Health and Human Services. We thank Anders Kjzr, Technical University of Denmark, Lyngby, Denmark, for gifts of numerous isothiocyanates identified in the text; J. L. Kachinsky, The Johns Hopkins University, for carrying out the mass spectra; L.-S. Kan, Division of Biophysics, Johns Hopkins School of Hygiene, for the 300 MHz NMR spectra; and C. Abeygunawardana and A. S. Mild-van for the 600 MHz NMR spectra and their interpretation. We have also received valuable advice from C. H. Robinson and T. Prestera, Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, and from L. Xue, Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, The University of Illinois at Chicago. We thank Gale Doremus for preparing the manuscript and the illustrations.
PY - 1992/8/15
Y1 - 1992/8/15
N2 - Organic isothiocyanates are widely distributed in plants and are responsible for a variety of beneficial and toxic biological effects. No direct and generic method for quantitating isothiocyanates has been described. Under mild conditions nearly all organic isothiocyanates (R-NCS) react quantitatively with an excess of vicinal dithiols to give rise to five-membered cyclic condensation products with release of the corresponding free amines (R-NH2). The products of the condensation of propyl-NCS with 1,2-ethanedithiol, 2,3-dimercaptopropanol, and 1,2-benzenedithiol have been isolated and identified as 1,3-dithiolane-2-thione, 4-hydroxymethyl-1,3-dithiolane-2-thione, and 1,3-benzodithiole-2-thione, respectively. Since 1,3-benzodithiole-2-thione (λmax 365 nm and αm 23,000 m-1 cm-) can be sensitively measured spectroscopically, the reaction of organic isothiocyanates with 1,2-benzenedithiol has been developed for analytical purposes. All aliphatic and aromatic isothiocyanates tested (except tert-butyl and other tertiary isothiocyanates) reacted quantitatively with an excess of 1,2-benzenedithiol. Thiocyanates, cyanates, isocyanates, cyanides, or related compounds did not interfere with this reaction under assay conditions. The method can be used to measure 1 nmol or less of pure isothiocyanates or isothiocyanates in crude mixtures. It can also be used to measure isothiocyanates in chromatographic fractions obtained from plant extracts and for the assay of the rate of cleavage of glucosinolates by myrosinase (thioglucoside glucohydrolase; EC 3.2.3.1.).
AB - Organic isothiocyanates are widely distributed in plants and are responsible for a variety of beneficial and toxic biological effects. No direct and generic method for quantitating isothiocyanates has been described. Under mild conditions nearly all organic isothiocyanates (R-NCS) react quantitatively with an excess of vicinal dithiols to give rise to five-membered cyclic condensation products with release of the corresponding free amines (R-NH2). The products of the condensation of propyl-NCS with 1,2-ethanedithiol, 2,3-dimercaptopropanol, and 1,2-benzenedithiol have been isolated and identified as 1,3-dithiolane-2-thione, 4-hydroxymethyl-1,3-dithiolane-2-thione, and 1,3-benzodithiole-2-thione, respectively. Since 1,3-benzodithiole-2-thione (λmax 365 nm and αm 23,000 m-1 cm-) can be sensitively measured spectroscopically, the reaction of organic isothiocyanates with 1,2-benzenedithiol has been developed for analytical purposes. All aliphatic and aromatic isothiocyanates tested (except tert-butyl and other tertiary isothiocyanates) reacted quantitatively with an excess of 1,2-benzenedithiol. Thiocyanates, cyanates, isocyanates, cyanides, or related compounds did not interfere with this reaction under assay conditions. The method can be used to measure 1 nmol or less of pure isothiocyanates or isothiocyanates in crude mixtures. It can also be used to measure isothiocyanates in chromatographic fractions obtained from plant extracts and for the assay of the rate of cleavage of glucosinolates by myrosinase (thioglucoside glucohydrolase; EC 3.2.3.1.).
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U2 - 10.1016/0003-2697(92)90585-U
DO - 10.1016/0003-2697(92)90585-U
M3 - Article
C2 - 1443546
AN - SCOPUS:0026783989
SN - 0003-2697
VL - 205
SP - 100
EP - 107
JO - Analytical biochemistry
JF - Analytical biochemistry
IS - 1
ER -