Assessment of Antimicrobial, Antimalarial, and Antitrypanosomal Activities of Crude Extracts and Fractions from Piliostigma thonningii Schum. Leaves in Vitro

Introduction: The plant Piliostigma thonningii (Milne-Redhead, Fabaceae) has been traditionally used as a medicinal remedy in several African countries. This study aimed to investigate and validate the antimalarial, antitrypanosomal, and antimicrobial potential of the crude methanolic extract and fractions of P. thonningii leaves through in vitro assays. Methods: Cold maceration of dried P. thonningii leaves in methanol produced crude extracts, which were then fractionated into dichloromethane (DCM), ethyl acetate (EtOAc), and butanol (BuOH) fractions. The extracts and fractions were subsequently tested for biological activity. In vitro antimalarial activity was assessed using the plasmodial lactate dehydrogenase culture sensitivity test, while antitrypanosomal activity was evaluated using Trypanosoma brucei promastigote cultures. Results: The crude methanolic extract did not exhibit observable antitrypanosomal activity. However, the EtOAc fraction demonstrated antitrypanosomal potential with an IC50 value of 13.35 µg/mL, and the BuOH fraction had an IC50 of 13.36 µg/mL. The EtOAc fraction also showed moderate antimalarial activity, with IC50 values of 33.45 µg/mL against Plasmodium falciparum D6 strain and 38.94 µg/mL against the W2 strain. Additionally, a sub-fraction of the EtOAc fraction, labeled PTE, exhibited enhanced antimalarial activity with IC50 values of 21.38 µg/mL against P. falciparum D6 and 23.21 µg/mL against P. falciparum W2. Conclusion: The findings suggest that certain fractions from P. thonningii leaf extract have potential use in the treatment of African trypanosomiasis and could be further developed into chemotherapeutic agents for treating malaria and other ailments.