Myrosinase Compatible Simultaneous Determination of Glucosinolates and Allyl Isothiocyanate by Capillary Electrophoresis Micellar Electrokinetic Chromatography (CE-MEKC)

Gonda, Sándor and Kiss-Szikszai, Attila and Szűcs, Zsolt and Nguyen, Nhat Minh and Vasas, Gábor (2016) Myrosinase Compatible Simultaneous Determination of Glucosinolates and Allyl Isothiocyanate by Capillary Electrophoresis Micellar Electrokinetic Chromatography (CE-MEKC). PHYTOCHEMICAL ANALYSIS, 27 (3-4). pp. 191-198. ISSN 0958-0344

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Abstract

Introduction. The functional food Cruciferous vegetables contain glucosinolates which are decomposed by the myrosinase enzyme upon tissue damage. The isothiocyanates are the most frequent decomposition products. Because of their various bioactivities, these compounds and the myrosinase is of high interest to many scientific fields. Objective. Development of a capillary electrophoresis method capable of myrosinase- compatible, simultaneous quantification of glucosinolates and isothiocyanates. Methods. Capillary electrochromatography parameters were optimized, followed by optimization of a myrosinase-compatible derivatization procedure for isothiocyanates. Vegetable extracts (Brussels sprouts, horseradish, radish and watercress) were tested for myrosinase activity, glucosinolate content and isothiocyanate conversion rate. Allyl isothiocyanate was quantified in some food products. Results. The method allows quantification of sinigrin, gluonasturtiin and allyl isothiocyanate after myrosinase compatible derivatization in-vial by mercaptoacetic acid. The chromatograhpic separation takes 2.5 minutes (short end injection) or 15 minutes (long end injection). For the tested vegetables, measured myrosinase activity was between 0.960 – 27.694 and 0.461 – 26.322 μmol min-1 mg-1 protein, glucosinolate content was between 0 – 2291.8 and 0 – 248.5 μg g-1 fresh weight for sinigrin and gluconastrutiin, respectively. The possible specificity of plants to different glucosinolates was also shown. Allyl isothiocyanate release rate was different in different vegetables (73.13 to 102.13 %). The method could also be used for quantification of allyl isothiocyanate from food products. Conclusions. The presented capillary electrophoresis method requires a minimal amount of sample and contains only a few sample preparation steps, and can be used in several applications (glucosinolate determination, myrosinase activity measurement, isothiocyanate release estimation).

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