Revisiting the fermentation of Sceletium tortuosum

• The natural fermentation of Sceletium tortuosum were monitored. • UHPLC-MS was used for chemical profiling. • The partial internal transcribed spacer (ITS) and beta-tubulin regions of the gDNA of the microbiome were observed over time. • The mesembrine alkaloids profile started changing after 5 days. • Fusarium species were identified as contributing to the changes in the alkaloid levels during fermentation. Sceletium tortuosum, a medicinal plant used as natural antidepressant, has been fermented traditionally to yield what is believed by its users to be a stronger more potent product. The question persists if fermenting is changing the actives (mesembrine alkaloids) in the plant material or if it is just a natural way of concentrating it and increasing its bioavailability. In this study the plant material was macerated and incubated over a period of 9 days with regular sampling to monitor any chemical and metagenomic changes over time. Ultra-high pressure liquid chromatography-mass spectrometry (UHPLC-MS) analysis showed that the first significant changes in the chemical composition occurred after 5 days when Fusarium species became the predominant species in the microflora. To confirm whether fusaroid taxa do play a role in the alkaloid production and/or changes in the alkaloid profile, the sterilized plant biomass was inoculated with three Fusarium species as monocultures and the fermentation monitored. The alkaloid profile in the control did not change over time, but similarly to the natural fermentation, one of the Fusarium species yielded an increase in epimesembranol and decreases in some of the other alkaloids which indicates that the microbiome indeed plays a role.