Structural characterization of secoiridoid glycosides by high-performance liquid chromatography/electrospray ionization mass spectrometry.

The fragmentation behavior of seven secoiridoid glycosides (SIGs) isolated from Gentiana triflora Pall., a traditional Chinese medicine, was investigated by electrospray ionization ion trap mass spectrometry (ESI-IT-MS). Multistage electrospray ionization mass spectrometry (ESI-MS(n)) experiments both in positive- and negative-ion mode were used to elucidate the main fragmentation pathways of these compounds. In full scan mass spectra, different deprotonated or protonated molecules were observed for compounds with different basic structure. Ring cleavages of the aglycon moiety were observed in MS(2) spectra and the characteristic ions provided valuable information on the basic structural skeletons. Their fragmentation pathways and fragment ion structures were proposed. The established fragmentation patterns have been successfully used to identify eleven SIGs in the extract of Gentiana triflora Pall.