Structural analyses of protoberberine alkaloids in medicine herbs by using ESI-FT-ICR-MS and HPLC-ESI-MSn

The Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) using sustained off-resonance irradiation (SORI)/collision-induced dissociation (CID) method at high mass resolution has been first applied to investigate the characteristic fragment ions of four protoberberine alkaloids in medicine herbs. The ESI-FT-ICR SORI-CID experiment results demonstrate that the unambiguous elemental composition of fragment ions can be obtained at high mass resolution, then the logical fragmentation pathways of the protoberberine alkaloids has been proposed. The characteristic fragment ions of CID and MSn of protoberberine alkaloids have been discussed, which are specific and useful for the identification of some protoberberine alkaloid compounds. Then, the extracts of four kinds of medicine herbs have been analyzed by HPLC-ESI-MSn. According to these characteristic fragmentation pathways, the retention time (tR) of HPLC and mass spectra of product ion, the structures of six kinds of protoberberine alkaloids have been identified. And, in the present paper, the selected ion monitoring (SIM) method has been used to separate and identify the alkaloid isomers.