Molecular networking and ion mobility complementarity in metabolites identification of a Fagara heitzii extract
Résumé
Plants are an invaluable natural source of active compounds. Studying these secondary metabolites is of great interest for medicine and biotechnology. Nevertheless, the amount of data generated after a LC-MS/MS analysis induces an important work to target known metabolites and focus the efforts on unknown structures. Therefore, molecular networking has been developed to associate families of compounds based on their MS/MS fingerprint and to implement database searches. This tool considerably enhances metabolite search.[1,2] In addition, coupling liquid chromatography-ion mobility-mass spectrometry (LC-IM-MS) increases the efficiency of separation and brings an additional parameter of characterization. Indeed, collision cross section (CCS) is an intrinsic property of a given compound, it could increase reliability of compound annotation in metabolomics by comparing experimental CCS either with reference values in the case of known compounds, or with theoretical CCS values in the case of unknown compounds.[3,4]
We work on Zanthoxylum heitzii or Fagara heitzii, which is a tree from the Rutaceae family. This medicinal plant is widely used in central Africa for the treatment of many diseases such as cancers, syphilis and malaria but limited amount of chemical and pharmacological studies have been conducted. Previous phytochemical investigations reported compounds including amides, lignanes, alkaloids, steroids and terpenes and were realized by performing extraction, isolation steps followed by characterization of the purified compounds. [5,6] To gain in time and resources, our objective was to develop analytical tools to study different parts of the plant: root, leaf, bark and branch. We worked on the polar methanol extract of each part. Each extract was analyzed by ultra-high performance liquid chromatography coupled to tandem - mass spectrometry (MS-MS) or ion mobility - mass spectrometry (IM-MS), with a hybrid quadrupole-time of flight analyzer, equipped with an ion mobility cell.
On the one hand, MS-MS parameters were optimized in the objective to build molecular networks using the Global Natural Products Social Molecular Networking platform. These data analysis tools allowed us to compare fragmentation profiles of the different compounds in each extract and between the different extracts. On the other hand, IM-MS data were acquired to determine the collision cross sections (CCS) of each compound detected in the plant extracts. Thus, compounds could be annotated with different confidence levels, as described by the Metabolomics Standards Initiative, with CCS determination.
[1 ]Wang et al. Nature Biotechnology (2016) [2] F. Olivon et al. Analytical Chemsitry (2018) [3] Domalain et al. Chemical Science (2014) [4] Fernie et al. The Plant Cell (2011) [5] Moussavi et al. Parasites & Vectors (2015)