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Vieira TM, Orenha RP, Crevelin EJ, Furtado SSP, Vessecchi R, Parreira RLT, Crotti AEM. Electrospray ionization tandem mass spectrometry of monoketone curcuminoids. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2020; 34 Suppl 3:e8699. [PMID: 31845428 DOI: 10.1002/rcm.8699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Revised: 11/20/2019] [Accepted: 12/12/2019] [Indexed: 06/10/2023]
Abstract
RATIONALE Although monoketone curcuminoids (MKCs) have been largely investigated due to their biological activities, data on the gas-phase fragmentation reactions of protonated MKCs under collision-induced dissociation (CID) conditions are still scarce. Here, we combined electrospray ionization tandem mass spectrometry (ESI-MS/MS) data, multiple-stage mass spectrometry (MSn ), deuterium exchange experiments, accurate-mass data, and thermochemical data estimated by computational chemistry to elucidate and to rationalize the fragmentation pathways of eleven synthetic MKCs. METHODS The MKCs were synthesized by Claisen-Schmidt condensation under basic (1-9) or acidic (10-11) conditions. ESI-CID-MS/MS analyses and deuterium-exchange experiments were carried out on a triple quadrupole mass spectrometer. MSn analyses on an ion trap mass spectrometer helped to elucidate the fragmentation pathways. Accurate-mass data and thermochemical data, obtained at the B3LYP/6-31+G(d,p) level of theory, were used to support the ion structures. RESULTS The most intense product ions were the benzyl ions ([C7 H2 R1 R2 R3 R4 R5 ]+ ) and the acylium ions ([M + H - C8 H3 R1 R2 R3 R4 R5 ]+ ), which originated directly from the precursor ion as a result of two competitive hydrogen rearrangements. Product ions [M + H - H2 O]+ and [M + H - C6 HR1 R2 R3 R4 R5 ]+ , which are formed after Nazarov cyclization, were also common to all the analyzed compounds. In addition, •Br and •Cl eliminations were diagnostic for the presence of these halogen atoms at the aromatic ring, whereas •CH3 eliminations were useful to identify the methyl and methoxy groups attached to this same ring. Nazarov cyclization in the gas phase occurred for all the investigated MKCs and did not depend on the presence of the hydroxyl group at the aromatic ring. However, the presence and the position of a hydroxyl group at the aromatic rings played a key role in the Nazarov cyclization mechanism. CONCLUSIONS Our results reinforce some aspects of the fragmentation pathways previously published for 1,5-bis-(2-methoxyphenyl)-1,4-pentadien-3-one and 1,5-bis-(2-hydroxyphenyl)-1,4-pentadien-3-one. The alternative fragmentation mechanism proposed herein can explain the fragmentation of a wider diversity of monoketone curcuminoids.
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Affiliation(s)
- Tatiana M Vieira
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, Monte Alegre, CEP 14040-901, Ribeirão Preto, SP, Brazil
| | - Renato P Orenha
- Núcleo de Pesquisas em Ciências Exatas e Tecnológicas, Universidade de Franca, CEP 14404-600, Franca, SP, Brazil
| | - Eduardo J Crevelin
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, Monte Alegre, CEP 14040-901, Ribeirão Preto, SP, Brazil
| | - Saulo S P Furtado
- Núcleo de Pesquisas em Ciências Exatas e Tecnológicas, Universidade de Franca, CEP 14404-600, Franca, SP, Brazil
| | - Ricardo Vessecchi
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, Monte Alegre, CEP 14040-901, Ribeirão Preto, SP, Brazil
| | - Renato L T Parreira
- Núcleo de Pesquisas em Ciências Exatas e Tecnológicas, Universidade de Franca, CEP 14404-600, Franca, SP, Brazil
| | - Antônio E M Crotti
- Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, Monte Alegre, CEP 14040-901, Ribeirão Preto, SP, Brazil
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Cyriac J, Paulose J, George M, Srinivas R, Giblin D, Gross ML. Protonation of Curcumin Triggers Sequential Double Cyclization in the Gas-Phase: An Electrospray Mass Spectrometry and DFT Study. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2019; 438:107-114. [PMID: 31080356 PMCID: PMC6508607 DOI: 10.1016/j.ijms.2019.01.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
ESI-protonated natural curcumin (1) undergoes gas-phase cyclization and dissociates via competitive expulsions of 2-methoxy phenol and C4H4O2 (diketene or an isomer). Evidence from mechanistic mass spectrometry and from Density Functional Theory (DFT) reveals that a two-step sequential cyclization occurs for the protonated molecule prior to the unusual loss of the elements of 2-methoxy phenol. Furthermore, the presence of the methoxy group at postion-3 is essential for the second cyclization. The transformation of curcumin upon protonation in the gas phase may be predictive of its solution chemistry and explain how curcumin plays a protective role in biology.
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Affiliation(s)
- June Cyriac
- Department of Chemistry, Sacred Heart College, Thevara, Kochi, Kerala, India
| | - Justin Paulose
- Department of Chemistry, Sacred Heart College, Thevara, Kochi, Kerala, India
| | - M George
- Department of Chemistry, Sacred Heart College, Thevara, Kochi, Kerala, India
| | - R Srinivas
- National center for Mass Spectrometry, IICT, Hyderabad, India
| | - Daryl Giblin
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
| | - Michael L Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130
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Zhang X, Cheng S. Intramolecular Halogen Atom Coordinated H Transfer via Ion-Neutral Complex in the Gas Phase Dissociation of Protonated Dichlorvos Derivatives. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:2246-2254. [PMID: 28681359 DOI: 10.1007/s13361-017-1736-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Revised: 05/25/2017] [Accepted: 06/08/2017] [Indexed: 06/07/2023]
Abstract
Intramolecular halogen atom coordinated H transfer reaction in the gas phase dissociation of protonated dichlorvos derivatives has been explored by electrospray ionization tandem mass spectrometry. Upon collisional activation, protonated dichlorvos underwent dissociation reaction via cleavage of the P-O bond to give reactive ion-neutral complex (INC) intermediate, [dimethoxylphosphinoylium + dichloroacetaldehyde]. Besides direct dissociation of the complex, intramolecular chlorine atom coordinated H transfer reaction within the complex takes place, leading to the formation of protonated dimethyl chlorophosphate. To investigate the fragmentation mechanism, deuterium-labeled experiments and several other halogen-substituted (Br and F) analogs of dichlorvos were prepared and evaluated, which display a similar intramolecular halogen transfer. Density functional theory (DFT)-based calculations were performed and the computational results also support the mechanism. Graphical Abstract ᅟ.
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Affiliation(s)
- Xiaoping Zhang
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, People's Republic of China.
| | - Shuai Cheng
- Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang, 330013, People's Republic of China
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Allen AD, Tidwell TT. Structure and Mechanism in Ketene Chemistry. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 2014. [DOI: 10.1016/b978-0-12-800256-8.00004-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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