<i>In vivo</i> antimalarial activity of methanol extracts and fractions of <i>Brachystegia eurycoma</i> and <i>Mondia whitei</i>on chloroquine-resistant <i>Plasmodium berghei</i>

Abstract

Malaria remains a major public health problem in the tropics. According to WHO estimates, sub-Saharan Africa continues to carry a   disproportionately high share of global malaria burden. Oxidative stress plays significant role in malaria pathogenesis. Recently, there is increasing  effort to develop more potent antimalarials from plant source. Brachystegia eurycoma and Mondia whitei are used locally for malaria treatment. Medicinal plants used in therapy quite often possess antioxidant activities as a result of its inherent phytoconstituents. The phytochemical composition of Brachystegia eurycoma and Mondia whitei were qualitatively examined. The antioxidant activities of the methanolic extracts of the leaves of two medicinal plants were determined using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant assay. The Brine shrimp lethality assay (BSLA) and Lorke‘s acute toxicity study were used to estimate their toxicities; while Peter‘s 4-day chemosuppresive test was employed to evaluate their antimalarial activities. The flavonoid and saponins content were particularly high in both plants. Using ascorbic acid as reference (IC₅₀ 9.26 μg/mL), the antioxidant IC₅₀ values of B. eurycoma and M. whitei were 11.14 μg/ mL and 19.81μg/mL respectively; the BSLA LC₅₀ were 1.8 mg/mL and 1.2 mg/mL; acute toxicity LD₅₀ were 5000 mg/kg and 4500 mg/kg. Brachystegia eurycoma showed stronger daily average antimalarial activity (62.0 %) than Mondia whitei (39.3%), the standard drug, chloroquine, was 85.4%. The chloroform fraction of Brachystegia eurycoma was the most active with (65%) daily average suppression. This suggests that the extracts of leaves of the plants have good antioxidant activities, are non-toxic and supports their antimalarial use in ethnomedicine.