Antioxidant, Cysteine Protease and Beta Hematin Inhibitory Activities of Methanol Stem bark Extract and Fractions of Uapaca togoensis (Pax)

Malaria ranks among the most severe diseases affecting tropical and subtropical countries worldwide. The increasing prevalence of drug-resistant Plasmodium strains has led to a reduction in the efficacy of currently used antimalarial drugs. The development of innovative drugs targeting biochemical mechanisms is urgently needed to address the disease. The methanol extract and fractions of Uapaca togoensis have been previously confirmed to exhibit antimalarial activity. Nonetheless, there is a paucity of information regarding the mechanism of antimalarial action. In this study, the crude methanol stem bark extract (MUT), ethyl acetate (EUT), n-butanol (BUT), and residual aqueous (RUT) fractions of Uapaca togoensis was screened for antioxidant, cysteine protease, and beta hematin inhibitory activities. Phytochemical screening was conducted using the standard protocol. The 2,2-di-phenyl-1-picrylhydrazyl (DPPH) radical scavenging assay was used to examine antioxidant activity. Cysteine protease and beta hematin inhibitory activities were evaluated by papain and hematin polymerization inhibition assays respectively. Following the measurement of percentage inhibition, IC₅₀ values were calculated for the various samples. In the DPPH assay, ascorbic acid (standard) showed the lowest IC₅₀ at 0.023 mg/mL, followed by MUT (0.032 mg/mL), BUT (0.031 mg/mL), RUT (0.040 mg/mL), and EUT (0.054 mg/mL). Among the fractions tested, the n-butanol fraction (BUT) showed significant antimalarial activity, recording IC₅₀ values of 0.43 ± 0.19 mg/mL for cysteine protease inhibition and 1.67 ± 0.12 mg/mL in the β-hematin assay. The results indicate that Uapaca togoensis may serve as a viable source for developing novel antimalarial pharmaceuticals.