Synthesis and pharmacological evaluation of fluoro/chloro-substituted acetyl and benzoyl esters of quinine as antimalarial agents

After establishment of the pharmacokinetic and toxicological profile of quinine derivatives using in silico approaches, this study reports the synthesis of new acetyl and benzoyl esters of quinine bearing one or more fluorine or chlorine atoms on the acetyl/benzoyl moiety. The antimalarial activity of these compounds on Plasmodium falciparum 3D7 and K1 strains as well as the antiprotozoal activity on Trypanosoma brucei brucei and Trypanosoma cruzi were evaluated. Lastly, the cytotoxicity on MRC-5SV2 cells was established. The fluoroacetyl ester compounds were found to be more active in vitro against Plasmodium falciparum 3D7 strain than the reference compound quinine. All synthesized quinine derivatives were non-cytotoxic for MRC-5SV2 cells (CC50 > 64 µM). These results confirm that the introduction of one or more fluorine atoms into acetyl and benzoyl esters of quinine can sometimes improve the biological activity.