Anti-malarial and repellent activities of Tithonia diversifolia (Hemsl.) leaf extracts.
Extracts from the leaf of Tithonia diversifolia used in folk medicine for treatment of various ailments were tested for antimalaria and mosquito repellency properties in experimental animals and human volunteers, under the laboratory conditions. Comparison of the effectiveness of Chloroquine with the aqueous and methanolic extracts from the plant (T. diversifolia) showed that Chloroquine was 100% effective in clearing the parasite while the aqueous and methanolic extracts were 50 and 74% effective in clearing the parasites respectively. Both aqueous and methanolic extracts were more effective when administered before the onset of the infection, probably indicating the time-dependency of the antimalaria effects. Earlier application of the extracts at the onset of the malaria symptoms was more effective in reducing the parasitemia within a few days. The administration of the plant extracts during the malaria episode was also effective with longer period of administration. The LC50 of the aqueous extract in mice was 1.2 ml/100 g body weight while the Maximum Tolerated Dose (MTD) was found to be 1.0 ml/g. The repellent activity of volatile oil at different concentrations was measured by protection period against the bites of Anopheles gambiae, Aedes aegypti and Culex quinquefasciatus. The volatile oil extract showed higher repellent effect on A. gambiae at higher concentrations however its repellent and protective effects at various concentrations on all other species of mosquito tested can not be underestimated.