Synthesis and in vitro antiprotozoal activities of water-soluble, inexpensive phenothiazinium chlorides

Tropical diseases are serious infectious diseases caused by protozoan parasites in tropical and subtropical regions. Novel, effective, safe, and inexpensive drugs are required to treat the parasites and contribute to the global goal of eradication. A series of phenothiazinium chlorides were synthesized and evaluated for in vitro activities against Plasmodium falciparum, Trypanosoma cruzi, Trypanosoma brucei rhodesiense, and Leishmania donovani. Notably, 3,7-bis(piperidinyl)phenothiazinium chloride showed IC50 of 0.097 μmol L−1 against T. cruzi and 3,7-bis(benzyl(methyl)amino)phenothiazinium chloride exhibited IC50 of 0.081 μmol L−1 against L. donovani, although the cytotoxicities of these compounds against L-6 cells were observed at low concentration.