Antimalarial Activity and Safety of Conyza pyrrhopappa Sch. Bip. ex A. Rich

Abstract

Background
Malaria continues to pose a significant global health challenge, particularly in developing countries including Tanzania. The rising resistance to existing antimalarial drugs has intensified the need for alternative therapeutic options.
Objective: This study aimed to evaluate the in-vivo antimalarial activity and safety profile of Conyza pyrrhopappa.
Methodology: Plant materials were collected from Mbulu District in Manyara Region, Tanzania. Extraction was performed using 80% ethanol-water. Fractionation was carried out via liquid-liquid partitioning with solvents of varying polarity, starting with petroleum ether, dichloromethane, and ethyl acetate. The in-vivo antimalarial activity was evaluated using a 4-day suppressive assay. Mice were infected with 2×107 erythrocytes infected with Plasmodium berghei ANKA. Chloroquine was used as a positive control, and extracts were administered orally. The crude extract’s effects on peripheral blood mononuclear cells (PBMCs) and brine shrimps were assessed. The oral acute toxicity was tested in mice.
Results: Conyza pyrrhopappa extracts demonstrated significant in-vivo antimalarial activity compared with the negative control group. The highest average percentage suppression of parasitaemia (65.7%) was observed with the leaf extract at a dose of 800 mg/kg body weight. The ethyl acetate leaf fraction exhibited the highest parasitaemia suppression compared with the negative control (P≤.001). In PBMCs, growth inhibition was found to be concentration-dependent, with an IC₅₀ (95% CI) of 94.56 (45.82-196.8) μg/ml. In the brine shrimp lethality assay, the leaf extract exhibited an LC₅₀ of 144.2 μg/ml (95% CI, 110.9 to 187.5). The oral acute toxicity test indicated that the leaf crude extract is safe, with an LD₅₀>2000 mg/kg body weight in mice.
Conclusion: Conyza pyrrhopappa leaf and root extracts demonstrated safety and in-vivo antimalarial activity. These findings support the traditional use of the plant in malaria treatment. Further research focusing on the ethyl acetate leaf fraction could lead to the identification of potent antimalarial compounds.