| Two simple and convenient analytical systems for structural elucidation of trace constituents in crude extracts from Tylophora Atrofolliculata Metc and Halenia Elliptica D. Don were established by using various mass spectrometric hyphenated techniques, such as direct infusion ESI-MS~n, LC-UV-MS and LC-MS~n. In order to find the relationship between the structural characterization and the mass spectrometric behavior, some natural products with different structural skeletons which belong to one kind were investigated in detail by positive and negative ion ESI-MS~n. Based on the characteristic fragmentation reactions and the structural features of these compounds, some bioactive crude extracts were analyzed by ESI-MS~n, LC-UV-MS and LC-MS~n techniques. Furthermore, the structures of some constituents were confirmed by FAB-HRMS and NMR techniques. By using the above method, seven crude extracts were analyzed and a total of 33 constituents including known and new compounds were identified rapidly. This analytical method has been established as a powerful tool for rapid analysis of trace constituents in crude extracts from natural plants.1. Fragmentation behavior of phenanthroindolizidine alkaloids and identification of the constituents in three extracts from Tylophora Atrofolliculata by ESI-MS~n and LC-MS~nThe mass spectrometric behavior of eight known phenanthroindolizidine alkaloids isolated from Tylophora Atrofolliculata were examined in detail by positive and negative ion ESI-MS~n. It was found that the fragmentation behavior was observed to vary markedly due to the different skeleton structures and the substituent types and positions. In general, the positive ion mode yielded more intense signals than did the negative mode. The fragmentation behavior in the two modes can provide a valuable aid for... |
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