Investigation of Synergistic Antimalarial Activity of Corymbia citriodora, Maytenus senegalensis and Warbugia ugandensis Used in Traditional Medicine in Kenya

Abstract

Malaria is majorly caused by Plasmodium falciparum in Kenya where 30% of the population relies on traditional medicine for treatment due to cost and accessible medical facilities especially in the rural areas. W. ugandensis (W), M. senegalensis (M) and C. citriodora (C) are plants used in herbal medicine for treating malaria. However, their combined antimalarial efficacy and safety is yet to be determined. The negative control and solvent used was water and chloroquine as positive control. Cytotoxic properties (CC50) of the plants were carried out against Vero cell-lines in vitro via MTT assay. Acute oral toxicity (LD50) was conducted according to OECD protocol. Antimalarial properties (ED50) of aqueous plant extracts were analyzed against Plasmodium berghei in vivo. The combinations of C: M: W (1:1:1) used in the study exhibited no cytotoxicity, (CC50) of 101.47±3.17 µg/ml. All the plant extracts demonstrated LD50 above 2000 mg/kg with no adverse effects hence recognized as safe. The result indicated that the combination of M:W (1:1) had the highest antimalarial activity, ED50 of 1.05mg/kg and C:M:W (1:1:1) (ED50 of 2.26 mg/kg). Phytochemical profile of plant extracts not conducted but activity attributed to individual plant tannins, flavonoids, sesquiterpenes, and saponins. The SFIC determines the interaction between two or more drug compounds. Two-plant extracts exhibited synergistic effect whereas C.M.W in the ratio 1:1:1 showed antagonism with SFIC 1.92. Non-linear analysis was used to determine CC50, ED50 and LD50, one- way ANOVA for means between treatment groups and Tukey’s post hoc for pairwise control of means. From a molecular medicine perspective, this study elucidates the potential of combination therapy at the molecular level by evaluating the interactions between plant-derived compounds through the Synergistic Fractional Inhibitory Concentration (SFIC) index. The determination of cytotoxicity and effective concentrations provides critical insights into the molecular mechanisms underlying the safety and efficacy of these herbal extracts, paving the way for their optimization as targeted antimalarial therapies.