Phytochemical analysis and in vitro anti-plasmodial activity of selected ethnomedicinal plants used to treat malaria associated symptoms in northern Namibia

The search for biologically active compounds from plants is of importance for discovery of novel medicine against infectious diseases such as malaria. The aims of this study were to identify ethno-medicinal plants that are used to treat malaria-associated symptoms in traditional settings in northern Namibia; to detect and quantify the presence of major anti-plasmodial phytochemicals to evaluate the anti-plasmodial activity against Plasmodium falciparum 3D7A strain of the extracts of lead plants. Ten plants were identified through a survey conducted by the Multidisciplinary Research Centre at the University of Namibia. Nineteen methanolic extracts from 10 selected ethnomedicinal plants were prepared and analyzed using Thin Layer Chromatography (TLC) to detect classes of anti-plasmodial phytochemical compounds. Furthermore, total phenolic and alkaloids were also quantified. Furthermore, in vitro anti-plasmodial activity of crude methanol and aqueous extracts at 5, 10 and 50 mg/ml was evaluated against P. falciparum 3D7A strain at 1% parasitaemia and 2% hematocrit after 48 hours. The study revealed the presence of at least one of the major anti-plasmodial classes of compounds such as terpenoids, alkaloids, anthraquinones, flavonoids and coumarins in all the plant extracts analyzed. Out of 10 plant species, Mundulea sericea’s shoots indicated the presence of all five major anti-plasmodial phytochemical. The plants species studied show a high estimate of total alkaloids (0.37- 21.21 mg/1g of extracts) and phenolics (99. 58 - 444.07 GA/E mg/ml). Methanol extracts of M. sericea, D. mespiliformis and Cyphostemma spp showed the best anti-plasmodial activity with range of IC50 values from 3.179 to 3.523 mg/ml. The presence of anti-plasmodial phytochemical classes of compounds and high in vitro anti-plasmodial activity of selected plants extracts support the further investigation of these plants, as potential sources of novel anti-plasmodial compounds for malaria drug discovery.