Comparative molecular networking analysis of a Rauwolfia plant powder and biological matrices in a fatal ingestion case

Abstract

Identifying xenobiotics involved in deaths remains a challenge in toxicology, especially when they are missing from the usual suspect databases. The tool development for the rapid processing of untargeted screening data is a valuable asset. In recent years, the molecular networking has been developed in various fields, including toxicology, because of its ability to graphically display and compare complex data acquired from tandem mass spectrometry. Here, we report a case of fatal poisoning by ingestion of an unknown powder (labelled as Tabernanthe iboga) and apply molecular networking to tentatively identify the plant involved in a woman’s death. The supposedly ingested powder, an authentic Tabernanthe iboga root powder and postmortemed biological samples (peripheral blood and bile) were extracted and analyzed according to a screening method using high resolution liquid chromatography hyphenated to tandem mass spectrometry (Q-Exactive®). Analysis of these four matrices by molecular networking revealed a cluster of nodes composed of indolomonoterpenic alkaloids, a characteristic of the Apocynaceae family (ibogaine, ibogamine, ajmaline, reserpiline, yohimbine). Analysis of the spectral annotations of the supposedly ingested powder also shows a majority of occurrences related to the genus Rauwolfia, which differed from the authentic Tabernanthe iboga root powder. Molecular networking allowed us to discard the Tabernanthe iboga identification hypothesis and suggest an alternate Apocynaceae species, most likely belonging to the Rauwolfia genus. In addition, eleven putative compounds could be detected by the molecular networking, many of which seemed to be metabolites of the major components in the Rauwolfia genus.