Structural speculation and identification of alkaloids in Macleaya cordata fruits by high‐performance liquid chromatography/quadrupole‐time‐of‐flight mass spectrometry combined with a screening procedure

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Abstract
RATIONALE: Alkaloids with significant therapeutic effects are the main active constituents of Macleaya cordata , which is a perennial herb plant in the Papaveraceae family. A systematic and novel method for speculating and identifying the structures of alkaloids in M. cordata fruits by high‐performance liquid chromatography/quadrupole‐time‐of‐flight mass spectrometry (HPLC/Q‐TOF‐MS) with a screening procedure was reported. METHODS: Investigation of mass spectral fragmentation of alkaloids was carried out based on the tandem mass spectrometry (MS/MS) data analyses of eight reference substances. The skeletons of alkaloids were determined by their ultraviolet spectra (UV) and MS/MS data. The substituent groups of the alkaloids were acquired through a screening procedure developed in our laboratory and MS/MS data. The substituent linkage sites were deduced by MS/MS fragmentation behavior, as well as biosynthetic pathways of related alkaloids. RESULTS: The structures of 21 alkaloids were speculated in this study, 10 of which were reported for the first time in M. cordata. Furthermore, benzyltetrahydroisoquinoline and N ‐methyltetrahydroprotoberberine‐type alkaloids were discovered, which indirectly proved that the biosynthetic pathways of benzophenanthridine alkaloids reported in Eschscholtzia california existed in M. cordata as well . CONCLUSIONS: HPLC/Q‐TOF‐MS combined with a screening procedure was a systematic and reliable method for speculating and elucidating the structures of alkaloids. This study might be useful for the identification of other compounds in herbal medicines. Copyright © 2014 John Wiley & Sons, Ltd.

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