Gas-phase fragmentation of protonated piplartine and its fungal metabolites using tandem mass spectrometry and computational chemistry

Author(s)

da Silva-Junior, E. A. ; Paludo, C. R. ; Gouvea, D. R. ; Kato, M. J. ; Furtado, N. A. J. C. ; Lopes, N. P. ; Vessecchi, R. ; Pupo, M. T.

• Document type: Journal article
• Source: Journal of Mass Spectrometry; v. 52, n. 8, p. 517-525, AUG 2017.
• Web of Science Citations: 3

Abstract

Piplartine, an alkaloid produced by plants in the genus Piper, displays promising anticancer activity. Understanding the gas-phase fragmentation of piplartine by electrospray ionization tandem mass spectrometry can be a useful tool to characterize biotransformed compounds produced by in vitro and in vivo metabolism studies. As part of our efforts to understand natural product fragmentation in electrospray ionization tandem mass spectrometry, the gas-phase fragmentation of piplartine and its two metabolites 3,4-dihydropiplartine and 8,9-dihydropiplartine, produced by the endophytic fungus Penicillium crustosum VR4 biotransformation, were systematically investigated. Proposed fragmentation reactions were supported by ESI-MS/MS data and computational thermochemistry. Cleavage of the C-7 and N-amide bond, followed by the formation of an acylium ion, were characteristic fragmentation reactions of piplartine and its analogs. The production of the acylium ion was followed by three consecutive and competitive reactions that involved methyl and methoxyl radical eliminations and neutral CO elimination, followed by the formation of a four-member ring with a stabilized tertiary carbocation. The absence of a double bond between carbons C-8 and C-9 in 8,9-dihydropiplartine destabilized the acylium ion and resulted in a fragmentation pathway not observed for piplartine and 3,4-dihydropiplartine. These results contribute to the further understanding of alkaloid gas-phase fragmentation and the future identification of piplartine metabolites and analogs using tandem mass spectrometry techniques. Copyright (C) 2017 John Wiley \& Sons, Ltd. (AU)

• FAPESP's process: 11/01404-2 - In vitro metabolism studies of natural products: microbial biotransformation of piplartine
• Grantee: Eduardo Afonso da Silva Junior
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 09/51812-0 - Development of a platform for the study of in vitro and in vivo metabolism of natural products, a need for pre-clinical testing system
• Grantee: Norberto Peporine Lopes
• Support Opportunities: BIOTA-FAPESP Program - Thematic Grants
• FAPESP's process: 14/23604-1 - Computational chemistry: a tool to studies of mass spectrometry, reactivity and fragmentation/reaction mechanisms of organic compounds
• Grantee: Ricardo Vessecchi Lourenço
• Support Opportunities: Regular Research Grants