Triple quadrupole tandem mass spectrometry of sesquiterpene lactones: a study of goyazensolide and its congeners.

Electrospray ionization tandem mass spectrometry (ESI-MS/MS) was used to investigate the fragmentation pattern of ten sesquiterpene lactones of the goyazensolide type under low-energy collision-induced dissociation (CID) using a triple quadrupole mass spectrometer. The analysis revealed that loss of CO(2)M + H - 44 is the predominant process for compounds that exhibit a hydroxyl at C-8. In contrast, compounds with different acyloxy groups at C-8 fragment by means of elimination of the corresponding carboxylic acids M + H - (R(2)CO(2)H) and consecutive losses of CO and H(2)O. Our results also demonstrate the influence of both the stereochemistry of the acyloxy group at C-8 on the relative abundances of product ions and the hydroxyl at C-15, which creates an additional pathway, resulting in highly diagnostic product ions. This work clearly demonstrates the utility of tandem quadrupole low-resolution mass spectrometry for studies on the rationalization of the fragmentation of a series of compounds with a highly conserved core structure, but differing in substituent groups.