Synthesis, β-hematin inhibition studies and antimalarial evaluation of new dehydroxy isoquine derivatives against Plasmodium berghei: A promising antimalarial agent

Abstract Many people are affected by Malaria around the world, and the parasite is developing resistance against available drugs. Currently, isoquine and N-tert -butyl isoquine are some of the most promising antimalarial candidates that have already reached Phase I and II clinical trials, respectively. Nevertheless, pharmacodynamic studies have demonstrated that isoquine is highly sensitive to form O- glucuronide metabolite, which may affect its accumulation in tissues. To avoid the O -glucuronide formation and its negative influence in the accumulation process, a series of novel five dehydroxy isoquine derivatives were designed and prepared herein as potential antimalarial agents. By a simple three-step procedure, five dehydroxy isoquines were prepared and subsequently examined on the inhibition of haemozoin formation, the main target of the 4-aminoquinolines. Four derivatives displayed significant inhibitory activities at low IC 50 values from 1.66 to 1.86 μM comparable to CQ. On the basis of the results, these four compounds were subsequently tested against Plasmodium berghei ANKA model in mice, showing to be as active as CQ with significant curative responses and parasitemia suppression in mice infected. On the other hand, these four compounds showed an acceptable non specific cytotoxicity on murine peritoneal macrophague and human erythrocyte cells. Thus, the presented data indicate that the dehydroxy isoquines 4b, 4c and 4e constitute promising cost-effective leads for the development of new antiplasmodial targeted at blood-stage malaria parasites.