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da Silva Borges L, Batista JHC, Bozzini L, Lourenço CD, Lopes NP, Clososki GC, Vessecchi R. Are benzoylium and nitrilium ions produced from substituted 2-arene-2-oxazolines during mass spectrometry? A study based on density functional theory calculations, quantum theory of atoms in molecules, and electrospray ionization tandem mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2023; 37:e9449. [PMID: 36459945 DOI: 10.1002/rcm.9449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 11/25/2022] [Accepted: 11/27/2022] [Indexed: 06/17/2023]
Abstract
RATIONALE Oxazolines are important compounds for drug development, synthesis, and pharmaceutical applications. Interest in analyzing and developing methods to characterize reaction products from these small heterocyclics has led us to study the gas-phase reactivity and fragmentation of seven 2-arene-2-oxazolines compounds using computational chemistry combined with mass spectrometry. METHOD Protonation sites were investigated using computed proton affinity, gas-phase basicity, and some quantum chemistry descriptors of reactivity; the B3LYP/6-31+G(d,p) computational model was used. Fragmentation mechanisms were suggested by employing data from collision-induced dissociation (CID), energy-resolved plots from MS/MS spectra, multiple-stage experiments, and survival-yield method. RESULTS Protonation studies based on quantum theory of atoms in molecules (QTAIM) and computational thermochemistry were useful to describe the reactivity of the investigated 2-arene-2-oxazolines, which can be protonated at the nitrogen atom. Three major fragmentation pathways were identified for the protonated molecules: formation of (a) benzoylium or (b) nitrilium ions through elimination of 71 and 72 u from the protonated molecules, respectively, and (c) elimination of 54 u from [M+H]+ . These pathways were exploited by the density functional theory calculations combined with QTAIM studies. CONCLUSIONS Our results can help in identifying 2-arene-2-oxazoline derivatives using electrospray ionization tandem mass spectrometry (ESI-MS/MS), which can be applied for monitoring reactions through the identified diagnostic ions (product ions). Also, we can suggest that benzoylium and nitrilium ions emerge during fragmentation under CID conditions.
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Affiliation(s)
- Letícia da Silva Borges
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brasil
| | - João Henrique Carvalho Batista
- Núcleo de Pesquisa em Produtos Naturais e Sintéticos (NPPNS), Departamento Ciências Moleculares, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brasil
| | - Leandro Bozzini
- Núcleo de Pesquisa em Produtos Naturais e Sintéticos (NPPNS), Departamento Ciências Moleculares, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brasil
| | - Celso Donizete Lourenço
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brasil
| | - Norberto Peporine Lopes
- Núcleo de Pesquisa em Produtos Naturais e Sintéticos (NPPNS), Departamento Ciências Moleculares, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brasil
| | - Giuliano Cesar Clososki
- Núcleo de Pesquisa em Produtos Naturais e Sintéticos (NPPNS), Departamento Ciências Moleculares, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brasil
| | - Ricardo Vessecchi
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brasil
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Wan X, Lan Z, Yang S, Yang S, Zhu Y, Wang F, Yang W, Chen J. Investigation of fragmentation pathways of norpimarane diterpenoids by mass spectrometry combined with computational chemistry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2022; 36:e9269. [PMID: 35156244 DOI: 10.1002/rcm.9269] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 11/20/2021] [Accepted: 11/22/2021] [Indexed: 06/14/2023]
Abstract
RATIONALE Norpimarane diterpenes possess plentiful bioactivities and are widely distributed in herbs, such as Flickingeria fimbriata. Rapid characterization of these natural products in complicated plant extracts is of great importance, and electrospray ionization tandem mass spectrometry is a powerful tool for chemical constituent profiling. However, limited researches on their fragmentation mechanisms seriously hinder identification via mass spectrometry. METHODS Three norpimarane diterpenes isolated from F. fimbriata via multiple types of column chromatography served as reference compounds, and collision-induced dissociation experiments were performed on them with a series of variable collision energies. Plausible fragmentation pathways were proposed based on product ions. To further validate the fragmentation mechanisms, the proton affinity and product ion energy were simulated by density functional theory at the B3LYP/6-31+G(d, p) level. RESULTS Three main cleavage reactions induced skeleton breakage and resulted in characteristic ions, methyl (CH3 -20) migration, hydrogen arrangement and Retro-Diels-Alder reaction, among which methyl migration was firstly proposed for pimarane diterpenes. A series of common diagnostic ions were identified, such as m/z 133.1012, 121.1012, 119.0805 and 107.0855. Additionally, the constructed fragmentation mechanisms were successfully applied for fragment ion rationalization of previously reported isopimarane diterpenes. CONCLUSIONS Fragmentation mechanisms of norpimarane diterpenes have been uncovered. Carbocation located at the C ring tends to result in methyl (CH3 -20) migration which has been rarely reported before. This characteristic dissociation reaction allows multiple diagnostic ions to be rationalized and aids in rationalizing fragmentation patterns of other diterpenes. The uncovered mechanisms also shed light on rapid identification of norpimarane diterpenes.
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Affiliation(s)
- Xunda Wan
- School of Resources Environmental & Chemical Engineering, Nanchang University, Nanchang, Jiangxi, China
| | - Ziqiang Lan
- Paediatrics College, Nanchang University, Nanchang, Jiangxi, China
| | - Shushu Yang
- School of Resources Environmental & Chemical Engineering, Nanchang University, Nanchang, Jiangxi, China
| | - Shanzheng Yang
- Jiangxi Medical College, Nanchang University, Nanchang, Jiangxi, China
| | - Yangjian Zhu
- School of Resources Environmental & Chemical Engineering, Nanchang University, Nanchang, Jiangxi, China
| | - Feng Wang
- CSPC Jiangxi Jinfurong Pharmaceutical Co. Ltd, Jiujiang, Jiangxi, China
| | - Weiran Yang
- School of Resources Environmental & Chemical Engineering, Nanchang University, Nanchang, Jiangxi, China
| | - Jinlong Chen
- School of Resources Environmental & Chemical Engineering, Nanchang University, Nanchang, Jiangxi, China
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Chu YY, Lolinco A, Eedugurala N, Ellern A, Windus TL, Sadow AD. Reversible Ligand Protonation in Noninnocent Constrained-Geometry-Like Group 4 Complexes. Organometallics 2022. [DOI: 10.1021/acs.organomet.1c00612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yang-Yun Chu
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, 2415 Osborn Drive, Ames, Iowa 50011, United States
- Ames Laboratory, 2416 Pammel Drive, Spedding Hall Dock, Ames, Iowa 50011, United States
| | - Annabelle Lolinco
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, 2415 Osborn Drive, Ames, Iowa 50011, United States
- Ames Laboratory, 2416 Pammel Drive, Spedding Hall Dock, Ames, Iowa 50011, United States
| | - Naresh Eedugurala
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, 2415 Osborn Drive, Ames, Iowa 50011, United States
- Ames Laboratory, 2416 Pammel Drive, Spedding Hall Dock, Ames, Iowa 50011, United States
| | - Arkady Ellern
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, 2415 Osborn Drive, Ames, Iowa 50011, United States
| | - Theresa L. Windus
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, 2415 Osborn Drive, Ames, Iowa 50011, United States
- Ames Laboratory, 2416 Pammel Drive, Spedding Hall Dock, Ames, Iowa 50011, United States
| | - Aaron D. Sadow
- Department of Chemistry, Iowa State University, 1605 Gilman Hall, 2415 Osborn Drive, Ames, Iowa 50011, United States
- Ames Laboratory, 2416 Pammel Drive, Spedding Hall Dock, Ames, Iowa 50011, United States
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Guo Y, Li S, Chen H, Wang Y, Cao S, Zhao Y. Gas-phase fragmentation of protonated 3-phenoxy imidazo[1,2-a] pyridines using tandem mass spectrometry and computational chemistry. JOURNAL OF MASS SPECTROMETRY : JMS 2021; 56:e4794. [PMID: 34881486 DOI: 10.1002/jms.4794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 10/12/2021] [Accepted: 11/02/2021] [Indexed: 06/13/2023]
Abstract
Imidazo[1,2-a] pyridine is one of the pharmaceutically important scaffolds and has been widely studied due to its extensive biological activities. In this work, electrospray ionization tandem mass spectrometry (ESI-MS/MS) in positive mode was used to study the gas-phase fragmentation behavior of a series of 3-phenoxy imidazo[1,2-a] pyridines. Proposed fragmentation pathways were supported by ESI-MS/MS data and computational thermochemistry. Homolytic cleavage of the 3-phenoxy C-O bond was the characteristic fragmentation of 3-phenoxy imidazo [1,2-a] pyridines. The eliminations of the one substituted phenoxy radical and CO produced other diagnostic ions for 3-phenoxy imidazo [1,2-a] pyridines, which were useful to identify the 3-phenoxy group and imidazo [1,2-a] pyridine scaffold. The results contribute to the further understanding of the gas-phase fragmentation of 3-phenoxy imidazo [1,2-a] pyridines and the identification of other analogs using tandem mass spectrometry techniques.
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Affiliation(s)
- Yanchun Guo
- College of Chemistry, The Key Laboratory of Chemical Biology and Organic Chemistry of Henan Province, Zhengzhou University, Zhengzhou, China
| | - Shigai Li
- College of Chemistry, The Key Laboratory of Chemical Biology and Organic Chemistry of Henan Province, Zhengzhou University, Zhengzhou, China
| | - Hong Chen
- College of Chemistry, The Key Laboratory of Chemical Biology and Organic Chemistry of Henan Province, Zhengzhou University, Zhengzhou, China
| | - Yuexiu Wang
- College of Chemistry, The Key Laboratory of Chemical Biology and Organic Chemistry of Henan Province, Zhengzhou University, Zhengzhou, China
| | - Shuxia Cao
- College of Chemistry, The Key Laboratory of Chemical Biology and Organic Chemistry of Henan Province, Zhengzhou University, Zhengzhou, China
| | - Yufen Zhao
- College of Chemistry, The Key Laboratory of Chemical Biology and Organic Chemistry of Henan Province, Zhengzhou University, Zhengzhou, China
- Institute of Drug Discovery Technology, Ningbo University, Ningbo, China
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Ieritano C, Hopkins WS. "Thermometer" Ions Can Fragment Through an Unexpected Intramolecular Elimination: These Are Not the Fragments You Are Looking For. J Phys Chem Lett 2021; 12:5994-5999. [PMID: 34161734 DOI: 10.1021/acs.jpclett.1c01538] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Benzylpyridinium analogs are effective thermometer ions since monitoring the formation of the benzylium fragment produced from heterolytic cleavage of the C-N bond can be linked to the ion's internal energy. In this study, three para-substituted benzylpyridinium ions containing ethoxy (OEt), isopropoxy (OiPr) and tert-butoxy (OtBu) substitutents were synthesized and evaluated as chemical thermometers. Intriguingly, the product ion spectra of the three benzylpyridinium ions were dominated by m/z 107 instead of the anticipated benzylium species. Deuterium labeling suggested that the m/z 107 fragment resulted from an intramolecular elimination (Ei), which formed via a four-membered transition state (TS). The fragmentation pathway appears to be an anomaly within the mass spectrometry literature, as four-membered pericyclic TSs are usually accompanied by the formation of an exceptionally stable neutral molecule (e.g., CO2). Quantum-chemical calculations confirmed our hypothesis that stabilization of the strained TS is afforded by hyperconjugation (ΔG‡ tert-butoxy < isopropyoxy < ethoxy).
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Affiliation(s)
- Christian Ieritano
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- Watermine Innovation, Waterloo, Ontario N0B 2T0, Canada
| | - W Scott Hopkins
- Department of Chemistry, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1, Canada
- Watermine Innovation, Waterloo, Ontario N0B 2T0, Canada
- Centre for Eye and Vision Research, Hong Kong Science Park, New Territories, 999077, Hong Kong
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Dias HJ, Baguenard M, Crevelin EJ, Palaretti V, Gates PJ, Vessecchi R, Crotti AEM. Gas-phase fragmentation reactions of protonated benzofuran- and dihydrobenzofuran-type neolignans investigated by accurate-mass electrospray ionization tandem mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2019; 54:35-46. [PMID: 30362641 DOI: 10.1002/jms.4304] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 09/12/2018] [Accepted: 10/17/2018] [Indexed: 06/08/2023]
Abstract
We have investigated gas-phase fragmentation reactions of protonated benzofuran neolignans (BNs) and dihydrobenzofuran neolignans (DBNs) by accurate-mass electrospray ionization tandem and multiple-stage (MSn ) mass spectrometry combined with thermochemical data estimated by Computational Chemistry. Most of the protonated compounds fragment into product ions B ([M + H-MeOH]+ ), C ([B-MeOH]+ ), D ([C-CO]+ ), and E ([D-CO]+ ) upon collision-induced dissociation (CID). However, we identified a series of diagnostic ions and associated them with specific structural features. In the case of compounds displaying an acetoxy group at C-4, product ion C produces diagnostic ions K ([C-C2 H2 O]+ ), L ([K-CO]+ ), and P ([L-CO]+ ). Formation of product ions H ([D-H2 O]+ ) and M ([H-CO]+ ) is associated with the hydroxyl group at C-3 and C-3', whereas product ions N ([D-MeOH]+ ) and O ([N-MeOH]+ ) indicate a methoxyl group at the same positions. Finally, product ions F ([A-C2 H2 O]+ ), Q ([A-C3 H6 O2 ]+ ), I ([A-C6 H6 O]+ ), and J ([I-MeOH]+ ) for DBNs and product ion G ([B-C2 H2 O]+ ) for BNs diagnose a saturated bond between C-7' and C-8'. We used these structure-fragmentation relationships in combination with deuterium exchange experiments, MSn data, and Computational Chemistry to elucidate the gas-phase fragmentation pathways of these compounds. These results could help to elucidate DBN and BN metabolites in in vivo and in vitro studies on the basis of electrospray ionization ESI-CID-MS/MS data only.
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Affiliation(s)
- Herbert J Dias
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Manon Baguenard
- Institut de Chimie, Université de Poitiers, Poitiers, France
| | - Eduardo J Crevelin
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Vinicius Palaretti
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Paul J Gates
- School of Chemistry, University of Bristol, Bristol, UK
| | - Ricardo Vessecchi
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
| | - Antônio E M Crotti
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, Brazil
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Dias HJ, Stefani R, Tomaz JC, Vessecchi R, Crotti AEM. Differentiation between 3,4- and 4,15-Epoxyeudesmanolides by Electrospray Ionization Tandem Mass Spectrometry. JOURNAL OF ANALYTICAL METHODS IN CHEMISTRY 2017; 2017:7921867. [PMID: 29234552 PMCID: PMC5695018 DOI: 10.1155/2017/7921867] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 10/03/2017] [Indexed: 06/07/2023]
Abstract
We investigated the fragmentation of the eudesmanolide-type sesquiterpene lactones 1α-(4-hydroxymethacryloyloxy)-3α,4α-epoxy-8α-hydroxyeudesm-11(13)-6α,12-olide (1) and 1α-(2,3-epoxyangeloyloxy)-4α,15-epoxy-8α-hydroxyeudesm-11(13)-6α,12-olide (2) by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The elimination of the different ester substituent at C(1) directly from protonated 1 and 2 (A) led to the formation of two regioisomer product ions B (A - RCO2H). Further fragmentation of B resulted from consecutive eliminations of H2O and CO molecules. However, we identified four product ions that allowed for the differentiation between 3,4- and 4,15-epoxyeudesmanolides. The formation of these diagnostic ions was associated with the C(3)-O bond of compound 1, which propitiates the participation of the lone pair of the oxygen epoxide in the formation of B through a Grob-Wharton-type fragmentation, then resulting in an alternative fragmentation pathway. These data can be useful for the fast differentiation between epoxyeudesmanolide regioisomers directly from Dimerostemma extracts by liquid chromatography-tandem mass spectrometry (LC-MS/MS), as an alternative to NMR, or even for quantitation studies of these compounds using multiple reaction monitoring (MRM) scan.
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Affiliation(s)
- Herbert Júnior Dias
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Ricardo Stefani
- Instituto de Ciências Exatas e da Terra, Universidade Federal do Mato Grosso, Campus Universitário do Araguaia, Araguaia, MT, Brazil
| | - José Carlos Tomaz
- Departamento de Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Ricardo Vessecchi
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - Antônio Eduardo Miller Crotti
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
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da Silva-Junior EA, Paludo CR, Gouvea DR, Kato MJ, Furtado NAJC, Lopes NP, Vessecchi R, Pupo MT. Gas-phase fragmentation of protonated piplartine and its fungal metabolites using tandem mass spectrometry and computational chemistry. JOURNAL OF MASS SPECTROMETRY : JMS 2017; 52:517-525. [PMID: 28581151 DOI: 10.1002/jms.3955] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Revised: 05/29/2017] [Accepted: 05/31/2017] [Indexed: 06/07/2023]
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 © 2017 John Wiley & Sons, Ltd.
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Affiliation(s)
- E A da Silva-Junior
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, S/N, Ribeirão Preto, SP, 14040-903, Brazil
| | - C R Paludo
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, S/N, Ribeirão Preto, SP, 14040-903, Brazil
| | - D R Gouvea
- Núcleo de Pesquisa em Produtos Naturais e Sintéticos (NPPNS), Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, S/N, Ribeirão Preto, SP, 14040-903, Brazil
| | - M J Kato
- Instituto de Química, Universidade de São Paulo, Av. Professor Lineu Prestes, São Paulo, SP, 05508-000, Brazil
| | - N A J C Furtado
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, S/N, Ribeirão Preto, SP, 14040-903, Brazil
| | - N P Lopes
- Núcleo de Pesquisa em Produtos Naturais e Sintéticos (NPPNS), Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, S/N, Ribeirão Preto, SP, 14040-903, Brazil
| | - R Vessecchi
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, Ribeirão Preto, SP, 14040-901, Brazil
| | - M T Pupo
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, S/N, Ribeirão Preto, SP, 14040-903, Brazil
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da Cunha Pinto A, Vessecchi R, da Silva CG, Amorim ACL, dos Santos Júnior HM, Rezende MJC, Gates PJ, Rezende CM, Lopes NP. Electrospray ionization tandem mass spectrometry analysis of isopimarane diterpenes from Velloziaceae. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:61-68. [PMID: 26661971 DOI: 10.1002/rcm.7411] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/24/2015] [Accepted: 09/25/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE The study of natural products by electrospray ionization tandem mass spectrometry (ESI-MS/MS) is an important strategy for the characterization of the major fragmentation reactions which can then help to determine the composition of complex mixtures. Application of ESI-MS/MS to a series of isopimarane diterpenes from Velloziaceae allowed the rationalization of their fragmentation mechanisms. METHODS Velloziaceae diterpenes were isolated by silica gel column chromatography and investigated by ESI-MS/MS analysis. The fragmentation studies were performed on a quadrupole-time-of-flight instrument using N2 as the collision gas. To help rationalize the fragmentation pathways observed, the geometry and sites of reactivity of the diterpenes were obtained by theoretical calculations using the B3LYP/6-31 + G(d,p) model. Fragmentation mechanisms were proposed on the basis of the calculated protonation sites and product ions energies using density functional theory (DFT) methods. RESULTS The presence of hydroxyl and carbonyl groups on the terpene core influences the protonation site observed. One compound showed a radical cation as the base peak. MS/MS spectra exhibit water elimination as the major fragmentation pathway (via two ways), either when protonation takes place on the oxygen atom, or through elimination after activation from hydrogen migration. After the elimination of water, the formation of an endocyclic double bond induces a sequential retro-Diels-Alder (RDA) reaction as the major fragmentation step. CONCLUSIONS A thorough rational analysis of the fragmentation mechanisms of protonated Velloziaceae diterpenes was used to propose the dissociation mechanisms in ESI-MS/MS. The presence of esters in the side chain also influenced the intensity or occurrence of the observed protonated or cationized molecules in ESI-MS. These results will aid the identification of analogues in sample extracts in future metabolomics studies.
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Affiliation(s)
- Angelo da Cunha Pinto
- Departamento de Química Orgânica, Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, CT, Bloco A, sala 626A, CEP 21941-909, Rio de Janeiro, RJ, Brazil
| | - Ricardo Vessecchi
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901, Ribeirão Preto, SP, Brazil
| | - Carmelita Gomes da Silva
- Instituto Federal de Educação, Ciência e Tecnologia. Campus Nilópolis, R. LúcioTaváres, 1045, CEP 26530-060, Centro, Nilópolis, RJ, Brazil
| | - Ana Carolina Lourenço Amorim
- Departamento de Química Orgânica, Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, CT, Bloco A, sala 626A, CEP 21941-909, Rio de Janeiro, RJ, Brazil
| | - Helvécio Martins dos Santos Júnior
- Departamento de Química Orgânica, Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, CT, Bloco A, sala 626A, CEP 21941-909, Rio de Janeiro, RJ, Brazil
| | - Michelle Jakeline Cunha Rezende
- Departamento de Química Orgânica, Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, CT, Bloco A, sala 626A, CEP 21941-909, Rio de Janeiro, RJ, Brazil
| | - Paul J Gates
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
| | - Claudia Moraes Rezende
- Departamento de Química Orgânica, Instituto de Química, Universidade Federal do Rio de Janeiro, Cidade Universitária, CT, Bloco A, sala 626A, CEP 21941-909, Rio de Janeiro, RJ, Brazil
| | - Norberto Peporine Lopes
- Núcleo de Pesquisas em Produtos Naturais e Sintéticos (NPPNS) - Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café, s/n, CEP 14040-903, Ribeirão Preto, SP, Brazil
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