Fig. 1.

(a) 4-Methylsulphinylbutyl glucosinolate (glucoraphanin) derived from methionine and the precursor of isothiocyanate sulforaphane. (b) 3-Indolylmethyl glucosinolate derived from tryptophan. Tryptophan-derived glucosinolates do not form stable isothiocyanates upon hydrolysis. (c) S-Methylcysteine sulphoxide which is thermally degraded to several volatile sulphur-containing compounds upon cooking which are largely responsible for the ‘sulphurous’ odour of cooked Brassica vegetables.