The role and effects of glucosinolates of Brassica species - a review

Glucosinolates are the substituted esters of thio amino acids and their synthesis is based on the corresponding amino acids. Methionine and cysteine are the natural donors in the case of the Brassica plants and L-tryptophane in the indole glucosinolates, respectively. In Brassica genus, alkenyl glucosinolates are mostly present and their content and composition differ as far as the development stage and the part of the plant are concerned. The indole glucosinolates are present in a minority level. Their role of sulphur supply is questioned by their very low content between 2% in the beginning of vegetation and 0.1% in its end. Glucosinolates are discussed mostly from the aspect of their anti-nutrition, anti-microbial, anti-fungicidal, and anti-bacterial effects and as being natural bio-fumigants. Their decomposition products have the mentioned properties. The products originate by prepared passive protection by the two-component system. From the aspect of these properties, it is useful to divide them into the following three groups according to the characters of their decomposition products. The first group (I.), whose hydrolysis in the neutral and alkaline environment creates iso-thio-cyanates. These bioactive compounds form the natural protection of the plant with bio-fumigatory effects particularly. Their anti-nutritive effects can be compensated by iodine, contrary to the second group (II.). This group is created by hydroxy-glucosinolates, whose decomposition products - iso-thio-cyanates - are not stable and they cycle while producing substituted 2-oxazolidinethione (goitrine - VTO). These glucosinolates represent a serious problem in feed industry since the VTO has a strong goitrogenic property. The third group (III.) - glucosinolates containing the indole group or the benzene ring (Sinalbin), create thio-cyanates during their hydrolysis. The role of indole glucosinolates has not been completely clarified so far. Their anti-carcinogenic effects are studied and they fulfil the role of an active protection.