| High-performance liquid chromatography combined with electrospray ion trap mass spectrometry possesses high separation efficiency and great capability in on-line structural characterization. With the advantages of high sensitivity, relatively short analysis time and low sample amount, HPLC/ESI-MS" has been widely used as a powerful tool in various medicinial plants online analysis. In this dissertation, the liquid chromatography/electrospray tandem mass spectrometry method was developed to identify the following natural compounds:polyoxypregnane glycosides in Marsdenia tenacissima, oleanane-type saponins in Stephanotis mucronata, polyphenol compounds in Parthenocissus laetevirens and compounds in Zingiber cassumunar. The details are listed in the following:Part I A method based on ESI-MS" was established to analyze of the fragmentation behaviors of polyoxypregnane glycosides. Eighteen polyoxypregnane glycosides from the stems of Marsdenia tenacissima were rapidly identified by HPLC/MS". Offline Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) was also performed to assign the accurate elemental compositions. Among these eighteen polyoxypregnane glycosides, five of them are identified as Marsdenoside K, Tencissoside A, B, C and D; two of them are confirmed as novel compounds; and the other eleven compounds’structures are tentatively suggested. Furthermore, five pairs of isomers were also distinguished from these eighteen compounds through breakdown curves.PartⅡThe relationship between the structural characteristics and MSn fragmentation pathways of oleanane-type saponins in the roots of Stephanotis mucronata were investigated by ESI-MS". We found that direct loss of terminal sugar residue from the [M+Na]+ ion was observed, when the substituent (except hydroxyl group) located at C21 position. However, the terminal sugar did not loss from the [M+Na]+ ion, when the substituent (except hydroxyl group) linked to C22 position. Based on these dissociation behaviors, twelve saponins were identified by HPLC/MS". Four of the; saponins were reported in this plant for the first time and four of the saponins were presumed to be new compounds. The structures of four proposed saponins have been identified by 1D and 2D NMR experiments.Part III The relationship between the structural characteristics and MS" fragmentations of polyphenols in the roots and stems of Parthenocissus laetevirens was investigated by ESI-MS". We found that the fragment C3O2 was presented when the compound possessed a 2,3-dihydro-lH-indene-4,6-diol moiety. Meanwhile, the C2H2O fragment (42 Da) was yielded from the resorcinol ring. Finally, fifteen polyphenol compounds were characterized by HPLC/MS". Eleven of them were identified as known compounds. Three polyphenol compounds were extracted from P. laetevirens for the first time. In addition, one compound was thought as a novel one. Furthermore, a pair of stereoisomers was distinguished by breakdown curves, and the trans-, cis-isomers were identified by HPLC/DAD-UV spectra.PartⅣCompounds extracted from rhizomes of Zingiber cassumunar were analyzed by HPLC/MS". In short, thirteen components were identified. Seven known compounds were qualitatively analysized by retention times of reference standards, and the other six compounds were characterized by MS". Two of the six compounds were identified as known compounds, but the other four were assigned as new compounds. Furthermore, breakdown curves were utilized to distinguish the the configurations of four compounds.In addition, the principle of LC/MSn technique and its recent progress in medicinal plants was reviewed in details. |
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