Quantification of Total Glucosinolates and Isothiocyanates for Common Brassicaceous Vegetables Consumed in the US Market Using Cyclocondensation and Thiocyanate Ion Measurement Methods

Abstract

Glucosinolates are a group of important sulfur and nitrogen containing plant secondary metabolites found in Brassicaceous vegetables that are associated with many health benefits. There is a growing interest in assessing dietary glucosinolates and their degradation products’ isothiocyanates exposure to humans. Determination of glucosinolates in plants is a very challenging task. In this study, the total glucosinolates from 22 commonly consumed Brassicaceous vegetables in the US market were determined by employing 1,2-benzenedithiol cyclocondensation for the determination of isothiocyanates (ITCs) from non-indole glucosinolates and a colorimetric method for the determination of thiocyanate ion (SCN−) from indole glucosinolates. The total glucosinolates were determined from the sum of these two methods. In the 22 investigated vegetables, the highest level of total ITCs was found in horse radish (5189.0 ± 544.8 nmol/g dry weight) and the highest level of total SCN− level was found in brussel sprouts (1294.0 ± 141.6 nmol/g dry weight). The total glucosinolates ranged from 18.6 ± 3.2 to 2271.2 ± 215.3 nmol/g dry weight. The total glucosinolate and ITC data are necessary for the USDA glucosinolates database and important for establishing the relationship of glucosinolates to human nutrition.