Evaluation of antiprotozoal and plasmodial enoyl-ACP reductase inhibition potential of Turkish medicinal plants

A total of 58 extracts of different polarity were prepared from various organs of 16 species of Turkish plants and screened for their antitrypanosomal, antileishmanial and antiplasmodial activities. No significant activity was observed against Trypanosoma cruzi, whereas many extracts showed appreciable trypanocidal potential against T. brucei rhodesiense, with the CHCl ₃-soluble portion of Phlomis kurdica being the most active (IC ₅₀ 2.7 μg/mL). Almost all extracts, particularly the CHCl ₃ phases, exhibited growth inhibition activity against Leishmania donovani amastigotes. The CHCl₃-solubles of Putoria calabrica roots (IC₅₀ 1.9 μg/mL), Wendlandia ligustroides leaves (IC₅₀ 2.1 μg/mL) and Rhododendron luteum leaves (IC₅₀ 2.3 μ/mL) displayed the highest leishmanicidal potential. The majority of the extracts also possessed antiplasmodial activity against the multidrug resistant K1l Plasmodium falciparum strain. The most potent antiplasmodial activity was observed with the CHCl₃ extracts of Phlomis kurdica (IC₅₀ 1.5 μ/mL), P. leucophracta (IC₅₀ 1.6 μg/mL), Scrophularia cryptophila (IC₅₀ 1.8 μg/mL), Marina persica (IC₅₀ 1.9 μg/mL) and the aqueous root extract of Asperula nitida subsp. subcapitellata (IC₅₀ 1.6 μg/mL). Twenty-one extracts with significant antimalarial activity (IC₅₀ < 5 μg/mL) were also tested for their ability to inhibit the purified enoyl-ACP reductase (FabI), a crucial enzyme in the fatty acid biosynthesis of P. falciparum. The CHCl₃ extract of Rhododendron ungernii leaves (IC₅₀ 10 μg/mL) and the H₂O-soluble portion of Rhododendron smirnovii leaves (IC₅₀ 0.4 μg/mL) strongly inhibited the FabI enzyme. The preliminary data indicate that some (poly)phenolic compounds are responsible for the FabI inhibition potential of these extracts. The presented work reports for the first time the antiprotozoal activity of nine different genera as well as a target specific antimalarial screening for the identification of P. falciparum FabI inhibitors from medicinal plant extracts.