Chemometric study of Strychnos species by molecular networking: example of the occurrence of strychnine

In the last 150 years, different attempts to establish the taxonomy of the Strychnos L. genus (family of Loganiaceae) have been carried out, but the results were not conclusive. The classification that has been most used to this date is from Leeuwenberg which divides the genus into 12 sections. However, in the article from Setubal, R. B. et al (2021), the results led rather to a return to the classification of Duvigneaud. Because of its complexity, the taxonomy of Strychnos is constantly changing. In this context, using new innovative techniques, the various studies of Strychnos carried out within the framework of my project will make it possible to bring new chemical information essential to the elucidation of the taxonomy of the Strychnos genus. This is notably the case of the strychnine study conducted here. During the study of 44 crude extracts of different species (28) and plant parts by LC-MS/MS and by molecular networking, it was found that strychnine is present in species in which it has never been described in the literature. These species are: trunk barks of S. tricalysioides, S. camptoneura, S. congolana, S. boonei, S. densiflora, S. tchibangensis and leaves of S. usambarensis. To confirm this identification, additional analyses by TLC, NMR, HPLC and LC-MS/MS were performed. Moreover, based on MS/MS data, a dereplication software (SIRIUS) was used. In view of the results obtained, it could be confirmed that the quantities of strychnine are very low. Thus, in order to have an estimate of the amount of strychnine contained in these samples, the limit of detection of strychnine using a UV detector was determined. Finally, it was confirmed that strychnine is present in these species, which is a significant contribution to the chemotaxonomic study of Strychnos that still holds many surprises.