Detection, characterization and identification of crucifer phytoalexins using high-performance liquid chromatography with diode array detection and electrospray ionization mass spectrometry

We have analyzed 23 crucifer phytoalexins (e.g. brassinin, dioxibrassinin, cyclobrassinin, brassicanals A and C) by HPLC with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD–ESI-MS) using both negative and positive ion modes. Positive ion mode ESI-MS appeared more sensitive than negative ion mode ESI-MS in detecting this group of compounds. A new HPLC separation method, new LC–MS and LC–MS2 data and proposed fragmentation pathways, LC retention times, and UV spectra for selected compounds are reported.