Malaria caused by protozoa of the genus Plasmodium, because of its prevalence, virulence, and drug resistance, is the most serious and widespread parasitic disease encountered by mankind. The inadequate armory of drugs in widespread use for the treatment of malaria, development of strains resistant to commonly used drugs such as chloroquine, and the lack of affordable new drugs are the limiting factors in the fight against malaria. These factors underscore the continuing need of research for new classes of antimalarial agents, and a re-examination of the existing antimalarial drugs that may be effective against resistant strains. This review provides an in-depth look at the most significant progress made during the past 10 years in antimalarial drug development.
We report the synthesis, in vitro antiprotozoal (against Plasmodium and Leishmania), antimicrobial, cytotoxicity (Vero and MetHb-producing properties) and in vivo antimalarial activities of two series of 8-quinolinamines. -[4-(4-ethyl-6methoxy-5-pentyloxy-8-quinolylamino)pentyl]-(2S/2R)-2-aminosubstitutedamides (51-63) were synthesized in six steps from 6-methoxy-8-nitroquinoline and 4-methoxy-2-nitro-5-pentyloxyaniline, respectively. Several analogs displayed promising antimalarial activity in vitro against P. falciparum D6 (chloroquine-sensitive) and W2 (chloroquine-resistant) clones with high selectivity indices vs. mammalian cells. The most promising analogs (21-24) also displayed potent antimalarial activity in vivo in a P. berghei-infected mouse model. Most interestingly, many analogs exhibited promising in vitro antileishmanial activity against L. donovani promastigotes, and antimicrobial activities against a panel of pathogenic bacteria and fungi. Several analogs, notably 21-24, 26-32 and 60, showed less MetHb formation compared to primaquine indicating the potential of these compounds in 8-quinolinamine-based antimalarial drug development.
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