Evaluation Of Antimalarial Properties Of Indigenous Plants Used By Traditional Healers In Namibia

ABSTRACT

Malaria is on the decline in Namibia and the country is moving towards pre-elimination of the disease. However, some communities preferring traditional medicines and not accepting allopathic medicine may prevent elimination. Ethnomedicines need to be integrated into mainstream malaria case management to achieve malaria elimination by 2020. To do so, they need to be documented and validated to allow their safe and effective use. Seven indigenous plants were investigated for antiplasmodia properties on the basis of their indigenous uses to treat malaria-like ailments. Extracts of Vahlia capensis, Nicolasia costata, Rhigozum brevispinosum, Dicerocarym eriocarpum, Senna occidentalis, Lophiocarpus sp. and Crotalaria flavicarinata were prepared using aqueous and organic solvents. Phytochemical screening was performed to detect the presence of selected antiplasmodial compounds. Growth inhibition studies using cellular infection models of Plasmodium falciparum 3D7 and D10 were carried out to determine anti-plasmodial effects of extracts from Vahlia capensis, Nicolasia costata and Dicerocarym eriocarpum. Mechanistic studies were also conducted to determine the mode of action of the three plants. Phytochemical screening revealed the presence of alkaloids, anthraquinones, flavonoids, terpenoids, steroids, coumarins and glycosides in the plant extracts with each plant possessing at least 3 classes of the antimalarial compounds. Organic extracts of V. capensis, N. costata and D. eriocarpum showed antiplasmodial activity at concentrations ranging from 50-250 μg/mL. Extracts from

D. eriocarpum showed the highest activity with an IC50 of 63.17μg/mL followed by

V. capensis and N. costata at 93.29μg/mL and 86.63μg/mL, respectively. All the plant extracts inhibited haemazoin accumulation with D. eriocarpum exhibiting the highest inhibition. The extracts also inhibited protease activity at the early ring stage where infection of red blood cells was being established and at the trophozoite stage where metabolism of the parasites was increased. These results support the ethno-medicinal uses for these plants as complementary medicine for malaria