Abstract:
Plants from the Sceletium genus (Aizoaceae) have been traditionally used for
millennia by the Khoe and Khoen people in southern Africa, as an appetite
suppressant as well as a mood elevator. In more recent times, this moodelevating activity has been commercialised in the South African natural
products industry for the treatment of anxiety and depression, with several
products available both locally and abroad. Research on this species has seen
rapid growth with advancements in analytical and pharmacological tools, in an
effort to understand the composition and biological activity. The Web of Science
(WoS) database was searched for articles related to ‘Sceletium’ and ‘Mesembrine’.
These data were additionally analysed by bibliometric software (VOSviewer) to
generate term maps and author associations. The thematic areas with the most
citations were South African Traditional Medicine for mental health (110) and
anxiolytic agents (75). Pioneer studies in the genus focused on chemical
structural isolation, purification, and characterisation and techniques such as
thin layer chromatography, liquid chromatography (HPLC, UPLC, and more
recently, LC-MS), gas chromatography mass spectrometry (GC-MS), and
nuclear magnetic resonance (NMR) to study mesembrine alkaloids. Different
laboratories have used a diverse range of extraction and preanalytical methods
that became routinely favoured in the analysis of the main metabolites
(mesembrine, mesembranol, mesembranone, and Sceletium A4) in their
respective experimental settings. In contrast with previous reviews, this paper
identified gaps in the research field, being a lack of toxicology assays, a deficit of
clinical assessments, too few bioavailability studies, and little to no investigation
into the minor alkaloid groups found in Sceletium. Future studies are likely to see
innovations in analytical techniques like leaf spray mass spectrometry and direct
analysis in real-time ionisation coupled with high-resolution time-of-flight mass
spectrometry (DART-HR-TOF-MS) for rapid alkaloid identification and quality
control purposes. While S. tortuosum has been the primary focus, studying other
Sceletium species may aid in establishing chemotaxonomic relationships and
addressing challenges with species misidentification. This research can benefit
the nutraceutical industry and conservation efforts for the entire genus. At present, little to no pharmacological information is available in terms of the
molecular physiological effects of mesembrine alkaloids in medical clinical
settings. Research in these fields is expected to increase due to the growing
interest in S. tortuosum as a herbal supplement and the potential development of
mesembrine alkaloids into pharmaceutical drugs.
