Advances in MALDI-MS/MS: A new metabolomic protocol for Brazilian “Cerrado” plants

Plants show a very wide variety of secondary metabolites and in addition to their pharmaceutical interest, these compounds have also been used as taxonomic markers. The advances in analytical tools make it possible to work with a large range of metabolites and in the last decade the metabolomics research has emerged. Metabolomic studies mainly apply nuclear magnetic resonance or hyphenated mass spectrometry methods. From the mass spectrometry perspective the development of the electronspray ionization (ESI) allowed the investigation of polar and thermo instable compounds, but sample preparation make the range of analysis restrict to the solvent solubility. Matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS) might be an alternative to ESI in metabolomics studies, however it is not widespread yet. In this work we are proposing a first protocol for metabolic fingerprinting by MALDI-MS. Effects of matrices were analyzed using multivariate data analysis by in-house algorithms in the R environment. “Cerrado” plants (21 species) from the Asteraceae family (tribes Vernonieae, Eupatorieae and Heliantheae) and the Melastomataceae family (tribe Microlicieae) were investigated. With the MALDI-MS protocol, taxonomic classifications, which showed close similarity to the literature-based taxonomic classification, could be observed with a hit of more than 95%. The main advantage of MALDI-MS is less ion suppression effects, the extremely rapid data acquisition and the large range of metabolites analyzed in one experiment (from apolar to polar compounds). On the other hand, an important disadvantage is the necessity to use more than one matrix. In summary we present a new strategy for plant metabolomics and results emphasize the potential of applying MALDI-MS.

Acknowledgements: CAPES, FAPESP (Process: 2009/54098 – 6, 2012/18031 – 7, 2011/05215 – 0), INCT-if and CNPq.

Keywords: Asteraceae, Melastomataceae metabolomics, chemotaxonomy, Cerrado