Constitution of a Lichen Metabolite Data Base (LDB) through HRLC-MS/MS analysis of 250 lichen compounds

Since W. Zopf’ pioneering works on lichen metabolite identification, physicochemical data of lichen compounds were accumulated during the twentieth century, culminating in the publication of S. Huneck & I. Yoshimura’s Identification of lichen substances in 1996 [1]. This compendium summarized analytical data for lichen molecules (TLC, NMR, LC, MS/MS and microcrystallization). Nowadays, over thousand lichen metabolites have been described [2] among which one hundred are highly frequently produced in large amounts by a variety of lichens species. While TLC is widely used in lichenology, mainly for chemotaxonomic purpose [3], the field remains underexplored in regards to the standards set in the era of metabolomics. Highly informative approaches through high resolution LC-MS and NMR are commonplace but their efficiency as a quick dereplication method for complex mixtures is highly reliant on databases. Consequently, with the aim to provide to the lichen chemist community a modern dereplication methodology using HRLC-MS/MS analysis, a database constituting of MS/MS spectra for lichen metabolites is under construction. A significant number of lichen molecules was collected, thanks to 300 pure compounds graciously donated by the Berlin Botanical Museum, completed by some molecules from the chemical library of University of Rennes. All molecules were then analysed by HRLC-MS/MS selecting the most appropriate ionization mode. In total 250 lichen compounds representing 8 main structural classes have been recorded. Data were converted to mzXML format using the ProteoWizard Toolkit [4] and manually curated to be treated using MZmine [5]. The resulting spectra are ready to be uploaded online and to serve as a public database for the community.

• References

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• 2 Elix JA. A Catalogue of Standardized Chromatographic Data and Biosynthetic Relationships for Lichen Substances. 2014 (3^rd Ed., Published by the Author, http://www.cpbr.gov.au/abrs/lichenlist/Chem%20Cat%203.pdf)
• 3 Huneck H, Yoshimura I. Identification of Lichen Substances. Springer-Verlag; 1996
• 4 Pluskal T, Castillo S, Villar-Briones A. et al. MZmine 2: Modular framework for processing, visualizing, and analyzing mass spectrometry based molecular profile data. BMC Bioinformatics 2010
• 5 Culberson CF, Kristinsson H, Standardized A. Method for the Identification of Lichen Products. J Chromatogr 1970; 46: 85-93.