In-depth exploration of Strychnos alkaloids by molecular networking: Discovery of strychnine in new species

Due to their wide variety of traditional uses and promising activities against Plasmodium parasites, plants of the Strychnos genus have been very well studied. Moreover, different attempts to draw an intrageneric taxonomy were made, based on morphological (Duvigneaud) and genetic (Setubal) characters. Moreover, in the Setubal et al. (2021) study, the results concluded that the classification established by Duvigneau is currently the most appropriate.
In this context, my research project consists in exploring the chemodiversity of Strychnos alkaloids in order to identify new bioactive metabolites against malaria and cancer, but also to study the chemotaxonomy of Strychnos genus. To achieve these objectives, 44 extracts, from 28 species of Strychnos, were studied by LC-MS/MS and molecular networking. Furthermore, by comparison with MS/MS spectra databases, known and unknown metabolites were annotated. Among the known ones, strychnine was surprisingly detected in seven Strychnos species for the first time, namely in S. tricalysioides, S. camptoneura, S. congolana, S. boonei, S. densiflora, S. tchibangensis and S. usambarensis. The TLC, HPLC, NMR and UPLC-MS/MS analyses allowed to detect the presence of this compound.
This novel identification of strychnine, allowed by the sensitivity of the technique used, offers new insights in the chemotaxonomy of the Strychnos genus. The perspectives are, on the one hand, further delineation of indole monoterpene alkaloids distribution in Strychnos spp., in regard to their taxonomic organization and, on the other hand, the identification of original bioactive compounds in this series.