Design, synthesis, and biological evaluation of eugenol-isoxazoline hybrid derivatives as potential anti-leishmanial agents

Abstract

Leishmaniasis is a group of protozoan parasitic diseases caused by various Leishmania species. The clinical manifestations range from skin abrasions to lethal infection in the visceral organs such as the liver and spleen. The emergence of drug resistance, long hospitalization periods, and various adverse effects of the current therapeutic regimen have incited the quest for exploring novel molecules as efficient treatment regimens. Eugenol is the major component of clove essential oil and has significant biological potential with anti-microbial properties. Moreover, natural product derivatives having the isoxazoline group have shown promising pharmacological applications. Thus, various analogs were synthesized and characterized to explore the anti-leishmanial potency of eugenol and isoxazoline hybrid. Results from the in vitro assay against Leishmania donovani parasites identified three potent derivatives (7e, 8a, and 8b) with IC50 values in the range of 7–17 µM. Cytotoxicity analysis against the J774A.1 macrophage cell line confirmed the satisfactory safety index of these potent hits and ex vivo infectivity assay established the role of these hits in reducing intracellular amastigote burden. Next, various mechanistic studies, including SEM analysis, higher ROS production, reduced intracellular ATP levels, mitochondrial dysfunction, formation of intracellular lipid bodies, and acidic vesicular organelles, confirmed the role of these potent hits in parasite cell death. According to the molecular docking analysis results, the most potent derivative, 8b, had strong binding interactions with residues Ile296, Pro299, and Phe354 of sterol 14α-demethylase protein of the Leishmania parasite. Entirely the study highlights the role of eugenol-isoxazoline hybrid derivatives as potential leishmanicidal agents.