Interaction of oxidized glutathione with allyl isothiocyanate

Isothiocyanates formed from glucosinolates in Brassica species have a strong affinity for amino acids and proteins, especially for their thiol, sulphide and terminal amino groups. To investigate the action of isothiocyanate on cystine residues in proteins and peptides, the present study on the interaction between allyl isothiocyanate and oxidized glutathione under physiological conditions was undertaken. Oxidized glutathione was oxidatively cleaved to some modified glutathiones by the attack of allyl isothiocyanate on its disulphide bond. Two new modified products were isolated from the reaction mixture by gel chromatography and HPLC, and their structures were determined by NMR and mass spectral analyses as glutathionyl N-allyldithiocarbaramate and its allyl thiohydantoin derivative. The formation of these products indicated oxidative cleavage of the disulphide bond in the cystine residue; the electrophilic attack of the isothiocyanate on the sulphur atom must cleave the disulphide bond oxidatively to dithiocarbamate and sulphenate, as in the case of cystine.