Planta Med 2014; 80 - P2O29
DOI: 10.1055/s-0034-1395021

The use of mass defect plots in phytochemical analysis

MM Rubner 1, D Intelmann 1
  • 1Bionorica research GmbH (subs. Bionorica SE), Mitterweg 24, A-6020 Innsbruck, Austria

High resolution MS scans enable a broad variety of analytical possibilities. Complex data sets are more and more used for chemometric projections besides the general use of structure elucidation and quantification. Well established multivariate data analysis, e.g. metabolomics, requires commercial software tools and profound knowledge to interpret the validity of the corresponding model. However, in the case of unknown chemical profiles a general overview on molecular subclasses is often the first step to focus the following evaluation. In this work we present a simple approach for the initial characterization and profiling of herbal drugs using mass defect plots. The mass defect, which is the result of the free binding energy of atoms, can either be calculated for any molecule of interest by their molecular formula or from high resolution m/z values from HR-MS scan profiles. In the first step we calculated a large number of common secondary plant metabolites that represent a varied mixture of molecular classes in polarity, glycosylation, alkylation etc. In addition, we validated the calculation with qualified reference substances measured with HR-ToF-MS (ESI neg. and pos.). The plot of the relative mass defect versus the m/z of the pseudo molecular ions is the basis for further analyses and represents a kind of “molecular map” (Fig. top). Subsequently, we analyzed a variety of herbal drugs with well described compositions to confirm our approach (Fig. bottom). The data processing includes automated peak detection, isotope filtering, solvent blank correction and elimination of adduct and fragment signals. The corresponding mass defect plots allow fast and detailed overviews of secondary plant metabolites detectable with MS.

Fig. 1: Top: Molecular map – theoretical mass defect plot of common secondary plant metabolites which can be calculated for any substance of interest. Bottom: Mass defect plot of a flavonoid rhich plant shows its typical composition (HR-MS data).

Keywords: High Resolution Mass Spectrometry – Analysis – Metabolites – Mass Defect Plot