Morroniside consists of two anomeric isomers, α-morroniside and β-morroniside. These two anomeric compounds have been separated by reversed-phase high-performance liquid chromatography(HPLC) using a gradient mobile phase of acetonitrile-water at 7 ℃, and verified to be anomers of morroniside by ESI-TOF-MS. The higher peak in the chromatogram was appointed to α-morroniside according to NMR data reported in previous literature. The molar ratio of α-morroniside to β-morroniside was found to be 2.855∶1 at 25 ℃. Temperature appeared to be an important factor, which affects the separation result, and a better separation was achieved at a lower temperature. The relative peak height of β-morroniside in the total ion current chromatogram measured with positive ion ESI-TOF mass spectrometer was only a half of that in UV chromatogram. This indicates that β-morroniside is less sensitive to positive ion electrospray ionization than the α-isomer.
Oligodeoxynucleotide from SARS virus was selected and synthesized. Its complexes with alkaloid compounds were investigated by electrospray mass spectrometry. We found that three alkaloid compounds could interact with the DNA target molecule in five alkaloids analyzed. With increasing molar ratio of the three alkaloid compounds, the complexes between alkaloids and DNA with different stoichiometric ratios were found in their MS spectra. The order of the alkalinity of their gas phase corresponds to that of liquid phase, that is: Palmatine>Jatrorrhizine>Berberin. The relative abundance of these complexes in mass spectra can assess the relative affinities of above three alkaloid compounds with the DNA target molecule. In this paper, the binding sites between jatrorrhizine and DNA was deduced from the interaction experiments of jatrorrhizine with three nucleosides.
