Total glucosinolates content was determined according to Heaney, Spinks, and Fenwick (1988). The method was based on the measurement of enzymically released glucose, which was hydrolysed by the enzyme myrosinase (thioglcose glycohydrolase, EC 3.2.3.1). The content of glucose was determined by the method of phenol–sulfuric acid, to assay the absorbance at 490 nm, and then the amount of glucosinolate can be calculated from the glucose content.