Malaria: the importance of phytochemicals as sources of alternative medicines

Malaria is a zoonotic disease caused by parasites from the Plasmodium genus. This parasite is transmitted to humans when bitten by female Anopheles mosquitos. Five species of Plasmodium are known to infect humans: P. malariae, P. ovale, P. knowlesi, P. falciparum, and P. vivax. Of these, P. falciparum is associated with the highest probability of severe infection. This parasite's lifecycle involves a sexual stage and an asexual stage. The first takes place in the mosquito and the second in humans. The diagnosis of malaria can be done by microscopy, rapid diagnostic tests or molecular methods, the latter being the most accurate. As for the treatment of this disease, artemisinin, chloroquine, primaquine, and tafenoquine are the principal components used in today's available treatments. Vaccination is also an important factor in the fight against malaria, and, presently, there are two available vaccines, RTS, S/AS01 and R21/Matrix-M. Several phytochemicals effective against malaria are also found in plant species used in traditional medicine. Examples are Azadirachta indica, Gossypium barbadense, Toddalia asiatica, Alstonia scholaris, Carica papaya, Andrographis paniculata, and Strychnos ligustrina. Furthermore, compounds from three wild nutmeg species have also been proven effective against P. falciparum. The medicinal properties of phytochemicals like alkaloids, phenolic compounds and terpenes have even allowed the investigation of drug-resistant malaria strains. When it comes to preventing malaria transmission, insecticide treated nests and indoor residual spraying have been proven to reduce transmission rates. For pregnant women, intermittent preventive treatment of malaria is also recommended. The need for the development of innovative treatment and prevention strategies is urgent due to the emergence of resistant strains. Hence, we present an overview of the available treatment and prevention strategies currently approved and employed while focusing on the potential of phytochemicals as targets for further studies that can lead to the development of new medicines.