Antimalarial potential and phytochemical composition of fractions of Lippia kituiensis Vatke (Verbenaceae) growing in Northern Tanzania

A Dissertation Submitted in Partial Fulfilment of Requirements for Award of a Degree of Master’s in Life Sciences of Nelson Mandela African Institution of Science and TechnologyDespite past decades of steady advances in reducing severity of Malaria, statistics show that the disease continues to pose a serious threat to human health. Previous successes in development of antimalarial drugs from medicinal plants have fuelled research in this area. However, antimalarial studies to fractionate extracts from such plants have progressed slowly. This study reports antimalarial potential of fractions from Lippia kituiensis Vatke, for the first time. Column chromatography was used during fractionation. Antiplasmodial assays against chloroquine-sensitive (D6) and resistant (W2) Plasmodium strains was done using hypoxanthine incorporation assay. A colorimetric assay was done to assess cytotoxicity of fractions against the Vero cell line. Obtained fractions exhibited varied inhibitory concentrations (IC 50 ); with the most efficacious being, Lk-5 (19.45 ± 6.20 μg/ml), Lk-3 (30.43 ± 0.68 μg/ml), Lk-4 (30.82 ± 18.01 μg/ml), and Lk-6 (36.53 ± 14.42 μg/ml) against D6. Generally, lower activity against W2 was obtained with the most active being Lk-4 (24.18±2.50 μg/ml), and Lk-5 (24.42±5.95 μg/ml), while chloroquine (positive control) exerted IC 50 of 77.86±4.09 ng/ml (W2) and 15.71±6.49 ng/ml (D6) respectively. Fraction LK-4 was the most cytotoxic showing cytotoxic concentration of 46.26 μg/ml. When tested in mice, fractions suppressed Plasmodium berghei significantly compared to the negative control with Lk-3 being the most efficacious (80.01±1). Due to substantive efficacy, GC-MS was done on Lk-3 revealing 8 compounds where three have previously been ascribed to antimalarial activity and other pharmacological effects. This study adds to present knowledge of antimalarial efficacy of L. kituiensis and provides basis for further work to be done on isolation of compounds from its extracts