In Europe, the cabbage stem flea beetle (Psylliodes chrysocephala) is a specialized insect feeding on Brassicaceae plants. The plants use the glucosinolate-myrosinase defense system, but P. chrysocephala can overcome this chemical defense by detoxification of the emerging ITCs by conjugation with glutathione (mercapturic acid pathway). In addition to known products of the mercapturic acid pathway, previously unreported metabolites were isolated, and their structures were elucidated by means of high resolution mass spectroscopy (HR-ESITOFMS) and nuclear magnetic resonance (NMR). The products found may represent general detoxification products of the mercapturic acid pathway.