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MALDI‐MS of flavonoids: a systematic investigation of ionization and in‐source dissociation mechanisms
Author(s) -
Silva Denise B.,
Lopes Norberto P.
Publication year - 2015
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/jms.3516
Subject(s) - chemistry , flavonols , dissociation (chemistry) , flavones , mass spectrometry , radical , molecule , ionization , flavonoid , ion , photochemistry , organic chemistry , chromatography , antioxidant
Matrix assisted laser desorption ionization (MALDI) is a technique widely employed in the analysis of proteins and peptides, and nowadays it has also been applied to small molecules. There is little significant information regarding the in‐source dissociation processes on MALDI for natural products. Twenty‐six flavonoids (flavanones, flavones and flavonols) were analyzed by MALDI using different methods (with different matrices) and without matrix to comprehend the in‐source reactions and establish good analysis methods for these compounds. Depending on the class, structure and the laser intensity applied, methoxylated flavonoid aglycones can eliminate methyl radicals (˙CH 3 ) in the source, such as flavonols, but lithium 2,4‐dihydroxybenzoate matrix suppresses the ˙CH 3 eliminations and retro‐Diels–Alder cleavages in the source. All of the flavonoid O ‐glycosides evaluated herein eliminated the sugar in source, even in the presence of the matrix, and its product radical ions ([M‐H‐sugar] − ˙) were observed in the negative mode. The flavone C ‐glycosides suffered intense dissociation, which was reduced by the addition of a matrix and the application of low laser intensity, mainly in the negative mode. Depending on the hydroxyl substituents, the [M‐H‐H] − ˙ ion was observed with variable relative intensity in the spectra. Copyright © 2015 John Wiley & Sons, Ltd.