Metabolomic investigation of the ethnopharmacological use of Artemisia afra with NMR spectroscopy and multivariate data analysis

Ethnopharmacological relevance: Artemisia afra has been used as an infusion to treat malaria throughout the southern parts of Africa, in much the same way as the antimalarial plant Artemisia annua in China. The antiplasmodial activity of purified components from an apolar fraction of Artemisia afra has been shown in the past. No data on the efficacy of the tea infusion prepared from Artemisia afra are however available. Objective: To investigate the antiplasmodial activity of various extracts of Artemisia afra including an ethnopharmacological prepared sample. To identify polar metabolites in Artemisia afra and Artemisia annua and by using multivariate data analysis investigate the metabolic differences between these species. Materials and methods: The antiplasmodial activity of Artemisia afra and Artemisia annua extracts were tested for activity against Plasmodiam falciparum 3D7 (chloroquine-sensitive strain) with chloroquine, quinine and artemisinin as positive controls. Hydrophilic metabolites in Artemisia afra and Artemisia annua were identified directly from the crude extracts through 1D- and 2D-NMR spectra. The NMR spectra were also used to differentiate between the two species using principal component analysis (PCA) for quality control purposes. Results: The apolar fractions of both Artemisia afra and Artemisia annua showed activity against P. falciparum while activity was only found in the tea infusion of Artemisia annua. Metabolomic studies using 1D- and 2D-NMR spectroscopy identified 24 semi-polar components in Artemisia afra including three new phenylpropanoids for this species: caffeic acid, chlorogenic acid and 3,5-dicaffeoyl quinic acid. PCA analysis conducted on the samples yielded good separation between the polar extracts of Artemisia afra and Artemisia annua. Conclusion: These findings shows that there are no in vitro activity in the tea infusion of Artemisia afra and lists the identified metabolites causing the metabolic differences between Artemisia afra and Artemisia annua for quality control purposes.

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