Efficacy of Lophira alata Leaf Extract and its Combination with Artesunate in Mice Prior Exposed to Plasmodium berghei

Abstract

Enhanced antimalarial activity of plant extracts used for treat- ment of malaria in endemic areas is attributed to partial im- munity gained by prior infection. This suggests synergy be- tween immunity and extract activity in treatment. Testing this hypothesis, rodent malaria was used to determine efficacy of Lophira alata leaf extracts in treating malaria in prior infected mice. One round of P. berghei infection and Pyrimethamine drug-cure was used to establish partial immunity in mice. Pre- viously Exposed Mice (PEM) and Previously Unexposed Mice (PUM) mice challenged with P. berghei were used to determine influence of partial antimalarial immunity on efficacy of L. ala- ta leaf extracts, administered alone or in combination with Artesunate (ART) in malaria treatment. There was a significant reduction in parasitemia in PEM when compared to PUM ani- mals (P < 0.001) irrespective of treatment regimen. Administra- tion of L. alata combined with ART significantly reduced para- sitemia (P < 0.0032) and prolonged (P = 0.0109) survival than when L. alata was administered alone in infected mice. These findings suggest that the action of L. alata in treating malaria infections in a murine model is enhanced by prior exposure to the malaria parasite. Thus the requirements of using plants in treating malaria in endemic populations may differ for those used in western systems, where trials are carried out with non- immune cohorts. Combining artemisinin derivatives and me- dicinal plants in malaria exposed populations may provide an alternative control measure in endemic regions and may jus- tify the continued use of these plants by indigenous popula- tions in treating malaria.