Trifluoromethylcinnamanilides – Effective dual inhibitors of Mycobacterium smegmatis and Plasmodium falciparum

Abstract

A series of eighteen new 2-trifluoromethylcinnamanilides (1a–r) were synthesized by microwave synthesis and investigated for their antimycobacterial and antimalarial activities, along with the complementary (2E)-3-[3-(trifluoromethyl)phenyl]-N-arylprop-2-enanilides (2a–r) and (2E)-3-[4-(trifluoromethyl)phenyl]-N-arylprop-2-enanilides (3a–r) prepared earlier. All the compounds were evaluated in vitro against Mycobacterium smegmatis ATCC 700084 and a chloroquine-sensitive strain of Plasmodium falciparum 3D7/MRA-102. The most active compounds against M. smegmatis (MIC values in the range of 1.17–11.1 µM, more effective than rifampicin) were anilides substituted by 3,5-CF3 (1q, 2q, 3q), 4-OCF3 (1k), and 4-CF3 (1j, 2j). The most effective agents against P. falciparum (IC50 values in the range of 0.32–4.5 µM, comparable to chloroquine) were anilides substituted by 3,5-CF3 (1q, 2q, 3q), 2-Br-4-OCF3 (1r), 4-CF3 (1j, 3j), 4-F (2d), 4-Cl (2g), 2-Cl (1e, 2e). A preliminary in vitro cytotoxicity screening was assessed using human leukemic cell lines and human dermal fibroblasts, revealing the toxic effect of 3,5-CF3 substituted anilides. On the other hand, the other investigated agents showed insignificant cytotoxic effects. Stability assays using rat liver microsomes demonstrated that compounds 1r (R = 2-Br-4-OCF3) and 1q (R = 3,5-CF3) are neither metabolized nor affect cytochrome P450 metabolizing capacity in vitro. Furthermore, complex in silico studies were performed – a combined approach (docking/MD simulations/QTAIM calculations) helped to define the molecular interactions that were applied during the binding of active agents and the subsequent inhibition of their molecular targets – InhA (activity against M. smegmatis) and arginase (activity against P. falciparum). In conclusion, promising active agents with dual antimycobacterial and antimalarial effects were identified.