From this primary
fragment other characteristic fragments of vindoline could be
originated. The analogous fragment ions can also be observed for
bisindole alkaloids in the fragmentation of their vindoline parts analysis. The first EI-MS measurements of VLB [15,18] provided
confusing results regarding its molecular weight due to this lability.
In the beginning of the measurement, when the analyte started to
evaporate, an m/z 810 ion peak was detected in the mass spectrum
which corresponded to the actual molecular weight of VLB; however,
as the evaporation time was growing, ion peaks of m/z 824
and 838 appeared with increasing intensities