Abstract:
The Sceletium genus has been of medicinal importance in southern Africa for millennia
and Sceletium tortuosum (Aizoaceae), one of eight species in the genus has gained
pharmaceutical importance as an anxiolytic and anti-depressant due to the presence of
mesembrine alkaloids. S. tortuosum is used for the manufacture of herbal teas, dietary
supplements and other phytopharmaceutical products. This study aimed to provide a
metabolomic characterization of S. tortuosum and its sister species as these are not
easy to distinguish using morphology alone. Plant samples were thus collected from
various locations in the succulent Karoo (South Africa) and analyzed through liquid
chromatography-mass spectrometry (LC-MS), using MSE
fragmentation as a putative
tool for chemical identities. Metabolomics-based analyses in combination with molecular
networking were able to distinguish between the four species of Sceletium based on
the presence of 4-(3,4-dimethyoxyphenyl)-4-[2-acetylmethlamino)ethyl]cyclohexanone
(m/z 334.2020; RT 6.60 min), mesembrine (m/z 290.1757; RT 5.10 min) and
4’-O-demethylmesembrenol (m/z 276.1597; RT 4.17 min). Metabolomic profiles varied
according to the different localities and metabolites occurred at variable quantitative
levels in Sceletium ecotypes. Molecular networking provided the added advantage
of being able to observe mesembrine alkaloid isomers and coeluting metabolites
(from the joubertiamine group) that were difficult to discern without this application.
By combining high-throughput metabolomics together with global and feature basedmolecular networking, a powerful metabolite profiling platform that is able to discern
chemical patterns within and between populations was established. These techniques
were able to reveal chemotaxonomic relationships and allowed for the discovery
of chemical markers that may be used as part of monitoring protocols during the
manufacture of phytopharmaceutical and dietary products based on Sceletium.
