RESUMO
INTRODUCTION: The persistent increase of resistance to existing antimalarials underscores the needs for new drugs. Historically, most of the successful antimalarial are derived from plants. The leaves of the S. cymosum is one of the plant materials used by traditional healers in malaria-endemic areas in Bangladesh for treatment of malaria. Here, we investigated the crude extract and its fractions against chloroquine (CQ)-sensitive 3D7, CQ-resistant Dd2, and artemisinin (ART)-resistant IPC 4912 Mondulkiri strains of Plasmodium falciparum. METHODOLOGY: The antimalarial activities were tested using HRP II based in-vitro antimalarial drug sensitivity ELISA described by WWARN and half inhibitory concentrations (IC50) were calculated by non-linear regression analysis using GraphaPad Prism. The cytotoxicity of the crude methanolic extract was assessed using the MTT assay on Vero cell line. RESULTS: The methanolic crude extract revealed promising activity against 3D7 (IC50 6.28 µg/mL), Dd2 (IC50 13.42 µg/mL), and moderate activity against IPC 4912 Mondulkiri (IC50 17.47 µg/mL). Among the fractionated portions, the chloroform fraction revealed highest activity against IPC 4912 Mondulkiri (IC50 1.65 µg/mL) followed by Dd2 (1.73 µg/mL) and 3D7 (2.39 µg/mL). The crude methanolic extract also demonstrated good selectivity with the selectivity indices of > 15.92, > 7.45, and > 6.91 against 3D7, Dd2, and IPC 4912, respectively when tested against Vero cell line. CONCLUSIONS: This is the first report on S. cymosum for its putative antimalarial activity, and is imperative to go for further phytochemical analyses in order to investigate possible novel antimalarial drug compound(s).