Evaluation of the In Vitro Antiplasmodial, Antileishmanial, and Antitrypanosomal Activity of Medicinal Plants Used in Saudi and Yemeni Traditional Medicine

The antiplasmodial, antileishmanial, and antitrypanosomal activity of twenty-five medicinal plants distributed in Saudi Arabia and Yemen was evaluated. The plants were extracted with methanol and screened in vitro against erythrocytic schizonts of Plasmodium falciparum, intracellular amastigotes of Leishmania infantum and Trypanosoma cruzi, and free trypomastigotes of T. brucei. To assess selectivity, cytotoxicity was determined on MRC-5 cells. Criteria for activity were an IC(50) < 10 μg/mL and high selectivity (SI). Seven plants showed interesting antiprotozoal activity in one or more models. Extracts of Caralluma penicillata and Acalypha ciliata showed fairly good activity against P. falciparum with IC(50) of 6.7 and 10.8 μg/mL and adequate selectivity (SI > 9.6 and >5.9). Interesting activity against L. infantum was obtained with Verbascum bottae (IC(50) of 3.2 μg/mL, SI 10.2) and Solanum glabratum (IC(50) 8.1 μg/mL, SI 3.4). The extracts of C. penicillata, Leucas virgata, Loranthus regularis, and V. bottae exhibited moderate activity against T. brucei (IC(50) 8.5, 8.1, 8.3, and 2.3 μg/mL; SI > 7.6, 7.7, 4.3, and >14.1). These results partly support the traditional use of some of the selected medicinal plants and warrant further investigations into the putative active constituents.