MALDI-MS of flavonoids: a systematic investigation of ionization and in-source dissociation mechanisms

Author(s)

Silva, Denise B. ^[1] ; Lopes, Norberto P. ^[1]

Affiliation

^[1] Univ Sao Paulo, Fac Pharmaceut Sci Ribeirao Preto, Dept Chem & Phys, Nucleo Pesquisas Prod Nat & Sintet, BR-14040903 Ribeirao Preto, SP - Brazil

• Document type: Journal article
• Source: Journal of Mass Spectrometry; v. 50, n. 1, p. 182-190, JAN 2015.
• Web of Science Citations: 7

Abstract

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 (CH3) in the source, such as flavonols, but lithium 2,4-dihydroxybenzoate matrix suppresses the CH3 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 (c) 2015 John Wiley \& Sons, Ltd. (AU)

• FAPESP's process: 12/18031-7 - Application of MALDI-MS/MS in the vicenin-2 and derivatives analyses: Understanding the ionization processes to production of the images
• Grantee: Denise Brentan da Silva
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 09/54098-6 - Acquisition of a mass spectrometer for the generation of images at the Mass Spectrometry Center of the University of São Paulo Ribeirão Preto School of Pharmaceutical Sciences: studies of molecular localization of biologically active substances
• Grantee: Norberto Peporine Lopes
• Support Opportunities: Multi-user Equipment Program