Identification of structurally diverse alkaloids in Corydalis species by liquid chromatography/electrospray ionization tandem mass spectrometry

Abstract

RATIONALE Alkaloids with significant therapeutic effects are the main active constituents of Corydalis (C.) species. There are several kinds of alkaloids in C. species associated with diverse alkaloid metabolism in plants, but they are rarely identified. This study aimed to identify diverse alkaloids in C. species by liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS). METHODS Several types of alkaloids were extracted from C. species using ultrasonication with 70% CH3OH, and the extract was partitioned at pH 2 and 12. Separation of alkaloids was achieved by C18 high‐performance liquid chromatography (HPLC), and MS/MS analysis was conducted by electrospray ionization triple‐quadrupole mass spectrometry. For further confirmation, LC/Fourier transform ion cyclotron resonance (FTICR)‐MS was used to obtain accurate mass data and gas chromatography (GC)/MS combined with trimethylsilyl derivatization was applied for identification of the minor alkaloids. RESULTS Thirty‐three alkaloids among three different C. species were successfully separated and identified by LC/ESI‐MS/MS and LC/FTICR‐MS. Structural assignment of individual alkaloids was performed according to MS/MS spectral patterns. For further confirmation, accurate mass data of alkaloids by LC/FTICR‐MS were obtained within 5 ppm and the GC/MS data for the trimethylsilyl alkaloids were also obtained. Among 33 alkaloids identified from this study, 13 alkaloids were reported for the first time in the investigated C. species. CONCLUSIONS The LC/ESI‐MS/MS technique was effective in obtaining structural information and yielded diagnostic ions for diverse alkaloids. Based on the identified 33 alkaloids, marker compounds were suggested for the three C. species with different geographic origins. This study may also be useful for elucidating unknown alkaloids in herbal medicines. Copyright © 2012 John Wiley & Sons, Ltd.

UHPLC Separation of Structurally Diverse Markers in Fangchi Species

“…For magnoflorine with a quaternary amine group, its partial charge on nitrogen atom might be slightly decreased as pH decreases, resulting in increasing its hydrophobicity. In contrast, in our previous studies, 19,20 the HPLC retention behavior of quaternary protoberberine alkaloids did not greatly influence in acidic and neutral media due to intact cation on their nitrogen atoms. The retention time of syringaresinol did not change with respect to pH variations due to its less ionizability.…”

A Fragmentation Study on Four Unusual Secoiridoid Trimers, Swerilactones H–K, by Electrospray Tandem Mass Spectrometry

“…When [M–H] − ( 1a ) was selected as the precursor ion to perform MS 2 experiment, multiple product ions ( 1b – 1k ) were observed. Among them, the ions at m/z 549 ( 1b ) and 535 ( 1c ) were deduced to be generated by the neutral losses of H 2 O and CH 4 O from 1a due to the presence of vicinal hydroxyl and methoxy groups [18, 19]. The product ions at m/z 519 ( 1d ) and 505 ( 1e ) were assigned to be the elimination of CH 2 O and the retro-Diels–Alder (RDA) cleavage of C 2 H 4 O from 1b [20].…”

General Fragmentations of Alkaloids in Electrospray Ionization Tandem Mass Spectrometry

“…A plausible fragmentation mechanism for the dehydration of protopine alkaloids has been suggested in our previous literature. 16 The characteristic b-and c-type ions were produced through iminolization and RDA fragmentation. The MS/MS spectra of protopine and allocryptopine as protopinetype alkaloids are shown in Fig.…”