1. Introduction
Chinese kale , an original Chinese vegetable belonging to the family of Brassicaceae , is widespread in southern China and Southeast Asia. Bolting stems are generally the edible part of Chinese kale, but, in recent years, the sprouts of Chinese kale are also popularly consumed owing to the good flavor, vivid colours and abundance in bioactive compounds, including glucosinolates, vitamin C and polyphenols. Glucosinolates are a group of nitrogen- and sulfur-containing secondary metabolites, mainly existing in the order Capparales. Isothiocyanates and indoles, two major groups of hydrolysis products of glucosinolates, have been well characterized in the prevention against cancers. In addition, it has also been reported that glucosinolates can behave as indirect antioxidants, by induction of phase II enzymes . In contrast to glucosinolates, vitamin C and polyphenols, the major antioxidants inBrassicavegetables, protect cells against oxidative damage by directly scavenging free radicals, and therefore bring benefits to human health .