Fragmentation investigation of brassinosteroid compounds by ion trap and quadrupole time-of-flight mass spectrometry.

The fragmentation mechanisms of three types of brassinosteroids (BRs), 23,24-tris-epicastasterone, epicastasterone, tris-epicastasterone, 24-epibrassinolide and 6-deoxo-24-epicastasterone, have been extensively investigated by tandem mass spectrometry (MS(n), n = 1, 2, 3, 4, 5) with the assistance of high mass accuracy quadrupole time-of-flight mass spectrometry (QToF MS). The electrospray ionization (ESI) mass spectrometric fragmentation pathways of these five BRs were comprehensively elucidated for the first time. Cleavages of side chains, neutral losses of water or other molecules and opening of a ring induce the main fragmentation patterns. The results from the present study can potentially afford important guidance for the structural elucidation of different BRs and provide some fundamental data for metabolomic analysis of BRs.