Antiparasitic potential of plants used in folk medicine in Brazil

Context: Neglected Tropical Diseases (NTDs) face growing challenges due to parasite resistance and the declining efficacy of available treatments. For diseases such as Chagas and malaria, limited private sector investment further hinders therapeutic innovation, reinforcing the urgent need for more effective interventions. Aims: To analyze the antiprotozoal potential of known medicinal species by providing novel insights into their biological activities. Methods: Five ethnomedicinal plant species were selected based on their limited documentation regarding antiprotozoal activity. Twenty crude extracts were obtained by maceration with solvents of increasing polarity from the branches of Anchietea salutaris A. St.-Hil. and Davilla rugosa Poir., and the aerial parts of Banisteriopsis argyrophylla A. Juss., Grindelia robusta Nutt. and Pyrostegia venusta (Ker Gawl.) Miers. The extracts were tested in vitro against Trypanosoma cruzi, Leishmania amazonensis, and Plasmodium falciparum and evaluated for cytotoxicity to determine selectivity indexes (SI). Results: In the preliminary screening at 25 µg/mL, all species exhibited some antiprotozoal activity. None of the extracts were considered active against T. cruzi. Hexane and dichloromethane extracts from A. salutaris, B. argyrophylla, and D. rugosa demonstrated potent antiplasmodial effects (IC50  9.2 g/mL; SI ≥ 22). Additionally, the dichloromethane extract of G. robusta showed strong activity against L. amazonensis (IC50 = 2.2 g/mL; SI = 78). Conclusions: These findings highlight the potential of underexplored medicinal plant species as sources of bioactive compounds for developing treatments for NTDs.