Southern Africa flora: a source of potential antimalarial compounds

Southern Africa has a diverse botanical flora with numerous plants being used traditionally as phytomedicines. Only a minuscule number of these plants have been scientifically validated for their therapeutic potential as antimalarials and even fewer have had the active chemical compound/s isolated from them. In an attempt to evaluate our plant flora, numerous plants have been assessed for their in vitro antimalarial activity. As such plants were collected from diverse areas of southern Africa and extracts and isolated compounds prepared. The antimalarial properties of the extracts/compounds were screened against Plasmodium falciparum using the tritiated hypoxanthine incorporation assay. The compounds were evaluated for their haemolytic and cytotoxic properties, and ability to chelate iron and inhibit haemozoin formation. Collation of several years of research reveals that Crinum bulbispermum (Burm.) Milne-Redh. & Schweick., Rosmarinus officinalis L., Leonotis leonorus (L.) R. Br., Syzygium cordatum Hochst. ex C.Krauss, Breonadia salicina (Vahl) Hepper & J.R.I.Wood, Agathosma and Menispermaceae species are highly active against P. falciparum, with minimal haemolysis. A. parva and A. purgens possessed the best safety index against the erythroleukaemia and kidney epithelial cells; while A. ovata was the most effective in chelating iron and inhibiting haemozoin formation. Numerous interactions have been investigated, including the synergistic interaction between Hermannia muricata Eckl. & Zeyh. and Hermannia trifurca L.; indicating a decreased risk of therapeutic failure when clinically combined to eradicate an infection. Plant-derived antimalarial agents have lead the way in the therapy of this disease and the next antimalarial agent or template may be within our flora awaiting discovery to successfully treat drug-resistant strains of P. falciparum malaria.

Keywords: malaria, phytomedicines, Agathosma, pharmacology, haemozoin, iron

Acknowledgement: The South African NRF Thuthuka Women in Research grant for financial support, all collaborators and postgraduate students who have contributed to the collated research.