Antileishmanial 2-substituted quinolines: in vitro behaviour towards biological components

The Potential of 2-Substituted Quinolines as Antileishmanial Drug Candidates

There is a need for new, cost-effective drugs to treat leishmaniasis. A strategy based on traditional medicine practiced in Bolivia led to the discovery of the 2-substituted quinoline series as a source of molecules with antileishmanial activity and low toxicity. This review documents the development of the series from the first isolated natural compounds through several hundred synthetized molecules to an optimized compound exhibiting an in vitro IC₅₀ value of 0.2 µM against Leishmania donovani, and a selectivity index value of 187, together with in vivo activity on the L. donovani/hamster model. Attempts to establish structure–activity relationships are described, as well as studies that have attempted to determine the mechanism of action. For the latter, it appears that molecules of this series act on multiple targets, possibly including the immune system, which could explain the observed lack of drug resistance after in vitro drug pressure. We also show how nanotechnology strategies could valorize these drugs through adapted formulations and how a mechanistic targeting approach could generate new compounds with increased activity.

Recent advances in research of natural and synthetic bioactive quinolines

Many natural products that consist of quinoline core are found to be bioactive and the versatility of quinoline and its derivatives have attracted great attention in the field of drug development. As a result, in recent years, many green and sustainable synthetic approaches for the synthesis of structurally diverse quinolines have been developed. This review covers four main aspects, namely bioactive quinoline alkaloids, the biological activity and mechanism of action of quinoline-based compounds as well as various quinoline syntheses.

Structures, targets and recent approaches in anti-leishmanial drug discovery and development

Recent years have seen a significant improvement in available treatment options for leishmaniasis. Two new drugs, miltefosine and paromomycin, have been registered for the treatment of visceral leishmaniasis (VL) in India since 2002. Combination therapy is now explored in clinical trials as a new treatment approach for VL to reduce the length of treatment and potentially prevent selection of resistant parasites. However there is still a need for new drugs due to safety, resistance, stability and cost issues with existing therapies. The search for topical treatments for cutaneous leishmaniasis (CL) is ongoing. This review gives a brief overview of recent developments and approaches in anti-leishmanial drug discovery and development.

Synthesis, antimicrobial, and mosquito larvicidal activity of 1-aryl-4-methyl-3,6-bis-(5-methylisoxazol-3-yl)-2-thioxo-2,3,6,10b-tetrahydro-1H-pyrimido[5,4-c]quinolin-5-ones

A series of 1-aryl-4-methyl-3,6-bis-(5-methylisoxazol-3-yl)-2-thioxo-2,3,6,10b-tetrahydro-1H-pyrimido[5,4-c]quinolin-5-ones (6a-h) have been synthesized by cyclization of ethyl-3-aryl-4-(2-chlorophenyl)-6-methyl-1-(5-methylisoxazol-3-yl)-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates 4a-h with 3-amino-5-methylisoxazole 5. Compounds 4a-h were obtained by Biginelli reaction, by condensation of aromatic aldehyde 1, ethyl acetoacetate 2, and isoxazolyl thioureas 3 in a one-pot reaction catalyzed by ceric ammonium nitrite (CAN). Compounds 6a-h were tested for their antibacterial and antifungal activities against various bacterial and fungal strains. The results showed that these compounds exhibited good antibacterial and antifungal activity compared with that of standard antibiotics. Mosquito larvicidal activity of the newly synthesized compounds 6a-h is also studied against fourth instar larvae Culex quinquefasciatus. Some of the compounds are proved to be lethal for mosquito larvae.