8-Aminoquinolines as anticoccidials-I

Synthesis, antimalarial, antileishmanial, antimicrobial, cytotoxicity, and methemoglobin (MetHB) formation activities of new 8-quinolinamines

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. N1-{4-[2-(tert-Butyl)-6-methoxy-8-quinolylamino]pentyl}-(2S/2R)-2-aminosubstitutedamides (21-33) and N1-[4-(4-ethyl-6-methoxy-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 Plasmodium falciparum D6 (chloroquine-sensitive) and W2 (chloroquine-resistant) clones with high selectivity indices versus mammalian cells. The most promising analogs (21-24) also displayed potent antimalarial activity in vivo in a Plasmodium berghei-infected mouse model. Most interestingly, many analogs exhibited promising in vitro antileishmanial activity against Leishmania 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.

Synthesis, antimalarial, antileishmanial, and antimicrobial activities of some 8-quinolinamine analogues

In the present communication, newly synthesized 8-quinolinamines (25-27) related to previously reported 2-tert-butylprimaquine (2) were evaluated for their in vitro antimalarial activity against chloroquine sensitive and resistant Plasmodium falciparum strains, in vivo antimalarial activity against P. berghei infected mice, in vitro antileishmanial activity against Leishmania donovani, in vitro antimicrobial activity against various fungi and bacteria, and cytotoxicity in a panel of mammalian cell lines. No promising cytotoxicities were observed for compounds reported herein. Analogue 25 was found to exhibit curative antimalarial activity at a dose of 25 mg/kg/dayx4 in a P. berghei infected mice model, and produced suppressive activity at a lower dose of 10 mg/kg/dayx4. In vitro antileishmanial activities (IC50 and IC90) comparable to standard drug pentamidine were exhibited by all synthesized 8-quinolinamines 25-27. At the same time, promising antibacterial and antifungal activities were also observed for synthesized compounds against a panel consisting of several bacteria and fungi.

8-aminoquinolines as anticoccidials - Part III

Analogues of the antimalarial pentaquine, 1, in which the nature of the side-chain on the 8-amino position was varied, were prepared and evaluated for anticoccidial activity both in vitro and in vivo. Specifically, both the inter-nitrogen distance and the nature of the terminal amino group were investigated. Novel analogues of equal or improved efficacy in vitro and in vivo to pentaquine were discovered.

8-Aminoquinolines as anticoccidials--II

During a chemistry program aimed at finding a novel analogue of pentaquine with improved in vivo activity, a number of hypotheses concerning the way this drug acts in the chicken were investigated. Consideration of the products of monoamine oxidase metabolism of pentaquine suggested that pentaquine aldehyde is the likely active metabolite. Although isolation of this unstable compound was not possible, oxime and cyclic acetal and ketal derivatives were obtained and shown to possess in vitro anticoccidial activity.