Modulation of the biosynthesis of specific glucosinolates is a major goal in Brassica breeding. The glucosinolates are a class of secondary metabolites found in fifteen botanical families of dicotyledonous plants. These families are the Akaniaceae, Bataceae, Brassicaceae, Bretschneideraceae, Capparaceae, Caricaceae, Euphorbiaceae, Gyrostemonaceae, Limnanthaceae, Moringaceae, Pentadiplantdraceae, Resedaceae, Salvodoraceae, Tropaeolaceae and Tovariaceae. At the present time over 100 glucosinolates have been reported. Glucosinolates are found in all parts of the plant and up to fifteen different glucosinolates have been found in the same plant.
Concentrations differ according to tissue type, physiological age, plant health and nutrition.
Studies have shown that myrosinases are localised in vacuoles of specialised plant cells, called myrosin cells. Thus the two components of the system are separated until autolysis or tissue damage brings them into contact. The precise localization of glucosinolates is not known, but they have been reported to be stored in vacuoles. The skeleton of glucosinolates consists of a thioglucosidic link to the carbon of a sulphonated oxime. The R group is derived from amino acids and is highly variable.