S-METHYL-L-CYSTEINE SULFOXIDE AS THE PRECURSOR OF METHYL METHANETHIOLSULFINATE, THE PRINCIPAL ANTIBACTERIAL COMPOUND IN CABBAGE

S-Methyl-L-cysteine sulfoxide (SMCSO) was present in several cultivars of cabbage (Brassica oleracea) at 690-1,120 ppm. SMCSO was not inhibitory to Leuconostoc mesenteroides, but its hydrolysis product, methyl methanethiolsulfinate (MMTSO), was inhibitory. MMTSO was formed in fresh cabbage juice (CJ) and in a model system containing SMCSO and fresh cabbage (pH 4.0) precipitate, perhaps by cysteine sulfoxide lyase. Growth inhibition by 1 mM MMTSO was reversed by 5 mM dithiothreitol, cysteine, or reduced glutathione, but not by oxidized glutathione or thiamine.