The chemical profiling of complex mixtures of natural products (NPs) is a major challenge in analytical chemistry and generally addressed by liquid chromatography coupled to mass spectrometry (LC-MS). In recent years also matrix free laser desorption ionization-mass spectrometry (LDI-MS) has become a versatile and time efficient complement to LC-MS. However, the absence of chromatographic separation in LDI-MS does not permit the differentiation of isomers. Providing a potential solution to this problem, the current work presents a combined LDI-Ion mobility spectrometry-tandem mass spectrometry (LDI-IMS-MS2) approach, which facilitated the successful differentiation of four constitutional xanthone isomers namely butyraxanthone D, cratoxylone, garcinone D and parvixanthone G. In addition, the experimental collision cross section (CCS) distribution values of nine unreported xanthones are described. Based on these results, a proof of concept for the so far unexplored concept of a LDI-IMS-MS2 based molecular network is being presented.
This Data Descriptor announces the submission to public repositories of the monoterpene indole alkaloid database (MIADB), a cumulative collection of 172 tandem mass spectrometry (MS/MS) spectra from multiple research projects conducted in eight natural product chemistry laboratories since the 1960s. All data have been annotated and organized to promote reuse by the community. Being a unique collection of these complex natural products, these data can be used to guide the dereplication and targeting of new related monoterpene indole alkaloids within complex mixtures when applying computer-based approaches, such as molecular networking. Each spectrum has its own accession number from CCMSLIB00004679916 to CCMSLIB00004680087 on the GNPS. The MIADB is available for download from MetaboLights under the identifier: MTBLS142 ( https://www.ebi.ac.uk/metabolights/MTBLS142 ).