Analysis Of Phytochemicals And Anti-Plasmodial Activities Of Extracts From Harrisonia Abyssinica, Leucas Calostachys And Rubia Cordifolia Against Plasmodium Falciparum

ABSTRACT

Malaria is the commonest parasitic disease that continues to cause considerable number of deaths despite the fact that it is treatable and preventable. In 2016, nearly 3.2 billion persons were at risk of malaria and a total of 216 million cases occurred occasioning deaths of approximately 445 thousand people worldwide with majority of the affected being children below five years of age. These numbers are high for a disease which is treatable and preventable. Plasmodium falciparum, the deadliest human malaria parasite has become resistant to nearly all antimalarials previously used and its drug resistant strains have shown rapid extension thus complicating the fight against malaria. As such there is need for continuous search for new medicines. Studies on plants traditionally used for the treatment of malaria presents one of the most viable strategies of developing new and effective antimalarial drugs. This study evaluated the in vitro effects of crude extracts obtained from Harrisonia abyssinica Oliv., Leucas calostachys Oliv. and Rubia cordifolia L. frequently used in the herbal management of malaria and other infections among the Maasai community in Transmara West sub-county. Aqueous, methanol and hexane extracts were assessed against two Plasmodium falciparum strains namely, Plasmodium falciparum W2, (Chloroquine resistant) and Plasmodium falciparum 3D7, Chloroquine sensitive. The parasite strains were cultured in malaria laboratory at the Institute of Primate Research (IPR). The in vitro effects of the extracts on the parasite strains were evaluated in 12x8 flat bottom wells and sterile microtitre plates. All bioassays were performed in triplicate at eight concentrations ranging between 50μg/ml and 0.4μg/ml. The set-up were then kept in an incubator maintained at 37ºC for 48 hours before harvesting and parasitaemia determined microscopically from thin Giemsa-stained slides. IC50 values for the crude plant extracts were graphically determined from dose-response curves. Data was analyzed by ANOVA, student t-test and correlation analysis using Graph pad prism version 5.0. All p < 0.05 values were considered significant. All the three plants were shown to have antimalarial activity with Rubia cordifolia L. Hexane extract being the most active (IC50 =0.5517 μg/ml) against chloroquine resistant Plasmodium falciparum, W2. This same extract was effective against CQ-sensitive strain with IC50 value of 2.747μg/ml. Qualitative phytochemistry on the extracts revealed bioactive compounds being present including Alkaloids, Terpenoids and Flavonoids among others. These results indicate that the plant extracts possess antiplasmodial activity. It therefore confirms the antimalarial properties of the three medicinal plants. The study recommended isolation, identification and characterization of compounds and toxicity studies on extracts from the plants to act as lead molecules in the manufacture of effective antimalarial drugs.