Gas‐phase dissociation study of erythrinian alkaloids by electrospray ionization mass spectrometry and computational methods

Gas‐phase dissociation study of erythrinian alkaloids by electrospray ionization mass spectrometry and computational methods

Alkaloids from plants of the genus Erythrina display important biological activities, including anxiolytic action. Characterization of these alkaloids by mass spectrometry (MS) has contributed to the construction of a spectral library, has improved understanding of their structures and has supported...

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Bibliographic Details
Published in:Journal of mass spectrometry. Vol. 52; no. 9; pp. 571 - 579
Main Authors: Guaratini, T., Feitosa, L. G. P., Silva, D. B., Lopes, N. P., Lopes, J. L. C., Vessecchi, R.
Format: Journal Article
Language:English
Published: England Wiley Subscription Services, Inc 01-09-2017
Subjects:
Alkaloids
Basicity
Biological properties
Biological samples
Charge transfer
Computer applications
Contraction
Dissociation
Drug development
Drugs
Electrostatic properties
Epoxy compounds
Fragmentation
High resolution
Ionization
Mass spectrometry
Mass spectroscopy
natural products
Oxygen
Oxygen atoms
Pharmacology
Plants (botany)
proton affinity
Protonation
protonation site
Resolution
Scientific imaging
Spectroscopy
spirocyclic alkaloid
natural products
proton affinity
spirocyclic alkaloid
protonation site
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Summary:Alkaloids from plants of the genus Erythrina display important biological activities, including anxiolytic action. Characterization of these alkaloids by mass spectrometry (MS) has contributed to the construction of a spectral library, has improved understanding of their structures and has supported the proposal of fragmentation mechanisms in light of density functional calculations. In this study, we have used low‐resolution and high‐resolution MSn analyses to investigate the fragmentation patterns of erythrinian alkaloids; we have employed the B3LYP/6‐31+G(d,p) model to obtain their reactive sites. To suggest the fragmentation mechanism of these alkaloids, we have studied their protonation sites by density functional calculation, and we have obtained their molecular electrostatic potential map and their gas‐phase basicity values. These analyses have indicated the most basic sites on the basis of the proton affinities of the nitrogen and oxygen atoms. The protonated molecules were generated by two major fragmentations, namely, neutral loss of CH3OH followed by elimination of H2O. High‐resolution analysis confirmed elimination of NH3 by comparison with the losses of H2 and •CH3. NH3 was eliminated from compounds that did not bear a substituent on ring C. The benzylic carbocation initiated the dissociation mechanism, and the first reaction involved charge transfer from a lone pair of electrons in the oxygen atoms. The second reaction consisted of ring contraction with loss of a CO molecule. The presence of hydroxy and epoxy groups could change the intensity or the occurrence of the fragmentation pathways. Given that erythrinian alkaloids are applied in therapeutics and are promising leads for the development of new drugs, the present results could aid identification of several analogues of these alkaloids in biological samples and advance pharmacokinetic studies of new plant derivatives based on MSn and MS/MS analyses. Copyright © 2017 John Wiley & Sons, Ltd.
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ISSN:1076-5174
1096-9888
DOI:10.1002/jms.3962