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Makunga, Nokwanda [1].

Through the looking glass: exploratory metabolomics of the medicinal South African succulent Sceletium tortuosum (L.) N.E. Br.

The South African indigenous, medicinal succulent Sceletium tortuosum (L.) N.E. Br. has human health applications associated with anxiolytic and antidepressant effects of mesembrine alkaloids that are produced by the species. Although chemotypic differences amongst populations of this species found in various semi-arid locations are known, greater insights into the fundamental endogenous and exogenous environmental triggers determining mesembrine alkaloid signatures in planta is still needed. Using an eco-metabolomics approach, seasonal variation of mesembrine and related alkaloids was monitored using a single geographically isolated S. tortuosum population via high resolution liquid chromatography-mass spectrometry. Added to this, in vitro plants were subjected to different microenvironmental stresses to decipher their impacts on metabolome-proteome signatures. Mesembrine alkaloid expression patterns were strongly correlated to seasonality. During summer, the major alkaloids mesembrine (4.01 ±5.62 mg/kg DW), mesembrenol (2.49 ±2.85 mg/kg DW) and mesembranol (52.79 ±51.29 mg/kg DW) and the isomers 6-epimesembrenol (2.10 ±2.19 mg/kg DW) and 6-epimesembranol (1.45 ±1.41 mg/kg DW) exhibited maximal tissue accumulation. This season, of extreme high temperatures and water scarcity, coincided with greatly curtailed plant growth. A spatiotemporal study of the chemotypic variation in developing leaves of tunnel grown plants indicated specific leaf age and developmental stages as key regulators of mesembrine alkaloid accumulation. Mesembrine was associated with actively growing leaves, whereas Δ4-mesembrenone, mesembranol and 6-epimesembranol were present at highest levels with the onset and progression of senescent aging of leaves. Proteomic analyses under stressed conditions provided new insights into the regulatory controls that possibly govern mesembrine alkaloid production. This new information linked to improved understanding of the developmental and spatial accumulation of these alkaloids, serves to inform on biosynthetic routes and metabolite transformations that define possible ecological and/or biological functional significance of the accumulation patterns associated with mesembrine and its isomers.

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1 - Stellenbosch University, Department Of Botany And Zoology, Private Bag X1, Matieland, Stellenbosch, WC, 7600, South Africa

Plant Specialized Metabolism
Metabolite profiling
Medicinal Plants.

Presentation Type: Oral Paper
Session: PHYT1, Phytochemistry I
Location: /
Date: Tuesday, July 20th, 2021
Time: 10:30 AM(EDT)
Number: PHYT1003
Abstract ID:706
Candidate for Awards:None

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