Characterizing some gossypol and gossypolone Schiff's bases by studying their fragmentation patterns with electrospray ionization tandem mass spectra

To investigate the structural form of gossypol and gossypolone Schiff's bases, seven relevant Schiff's bases were synthesized and the electrospray ionization–tandem mass spectrometry (ESI–MS/MS) with low-energy collision-induced dissociation was used to analyze their fragmentations. A common fragmentation pathway with the loss of RNH2 from those schiff's bases quasi-molecular ions was observed and proposed on the basis of their MS/MS spectra data. This common pathway indicated that those Schiff's bases existed mainly as the enamine form not the imine form previously showed in most reports.