Authors:
Danuello, Amanda [1, 2] ; de Castro, Rogerio Cardoso [3, 4] ; Pilon, Alan Cesar [5, 6, 7] ; Pires Bueno, Paula Carolina [1] ; Pivatto, Marcos [2] ; Vieira Junior, Gerardo Magela [8] ; Carvalho, Flavio Alexandre [9] ; Oda, Fernando Bombarda [9] ; Perez, Consuelo Javiera [4] ; Lopes, Norberto Peporine [1] ; Dos Santos, Andre Gonzaga [1] ; Ifa, Demian Rocha [4] ; Cavalheiro, Alberto Jose [6]
Abstract:
Rationale Clerodane-type diterpenes from Casearia species show important pharmacological activites such as antitumor, antimicrobial and anti-inflamatory. There are several mass spectrometry (MS)-based methods for identification of diterpenes; however, there is still a lack of MS procedures capable of providing characteristic fragmentation pathways for a rapid and unambiguous elucidation of casearin-like compounds. Methods Casearin-like compounds were investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The fragmentation studies were carried out by tandem mass spectrometry in space (quadrupole time-of-flight (QTOF)) using different collision energies and also by tandem mass spectrometry in time (QIT) by selective isolation of product ions. Results Casearin-like compounds presented a predominance of sodium- and potassium-cationized precursor ions. Both QIT and QTOF techniques provided sequential neutral losses of esters related to the R-1 to R-5 substituents linked to the nucleus of the clerodane diterpenes. The fragmentation pathway is initiated with a cleavage of the ester moieties R-2 followed by the elimination of the ester groups R-3, both losing neutral carboxylic acids. Using QIT, it was also possible to observe the cleavage of the ester groups R-1 or R-5 by MS4 experiments. Conclusions Through a rational analysis of the fragmentation mechanisms of Casearia diterpenes it was possible to suggest an annotation strategy based on the sequential cleavages of the ester groups related to the R-2, R-3 and R-5 substituents. These results will assist studies of the dereplication and metabolomics involving casearin-like compounds present in complex extracts of Casearia species.
1 Ribeirão Preto School of Pharmaceutical Science, University of Sao Paulo, Ribeirão Preto, São Paulo, Brazil
2 Institute of Chemistry, Federal University of Uberlândia, Uberlândia, Minas Gerais, Brazil
3 Laboratory of Pharmacognosy, School of Pharmaceutical Sciences, São Paulo State University, Araraquara, São Paulo, Brazil
4 Centre for Research in Mass Spectrometry, Department of Chemistry, York University, Toronto, Ontario, Canada
5 Ribeirão Preto School of Pharmaceutical Science, University of Sao Paulo, Ribeirão Preto, São Paulo, Brazil
6 Institute of Chemistry, São Paulo State University, Araraquara, São Paulo, Brazil
7 Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, UK
8 Chemistry Department, Federal University of Piauí, Teresina, Piauí, Brazil
9 Laboratory of Pharmacognosy, School of Pharmaceutical Sciences, São Paulo State University, Araraquara, São Paulo, Brazil
Link to article: https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/full/10.1002/rcm.8781
