Chemoprotection against cancer by isothiocyanates and glucosinolates.

Introduction Organic isothiocyanates (R-N=C=S) and glucosinolates, their biosynthetic precursors in plants, are attracting increasing attention as chemical and dietary protectors against cancer. More than 20 natural and synthetic isothiocyanates and several glucosinolates have been shown to block chemical carcinogenesis in animal models (see reviews in [1,2]); moreover, these substances are widely and often abundantly distributed in edible plants. The human consumption of isothiocyanates and glucosinolates is estimated at milligram quantities daily [3,4]. Nevertheless, it remains unclear to what extent these phytochemicals contribute to the wellrecognized observations that individuals who consume large amounts of vegetables have lower risks of developing cancer (see review [5]). More than 100 isothiocyanates and glucosinolates have been isolated from plants, many of which belong to the family Cruciferae and more specifically to the genus Brassica (e.g. Brassica oleracea sp.: cabbage, cauliflower, Brussels sprouts, broccoli, kale) and the genus Raphanus (radishes and daikons) [3]. In addition, a large number of isothiocyanates have been synthesized for cancer chemoprotection studies [6,7]. Isothiocyanates are biosynthesized and stored in plants as relatively stable precursors known as glucosinolates (P-thioglucoside N -