Neglected tropical diseases such as Leishmaniasis and Chikungunya fever are worldwide public health challenges mainly affecting tropical and subtropical countries. One cationic [Cu-(I)(NHC) 2 ] + (4) and two neutral [Cu(I)(NHC)Cl] complexes, where NHC = 1,3-bis(mesityl)imidazole-2-ylidene (IMes) (5) or 1,3-bis-(2,6-diisopropylphenyl)imidazole-2-ylidene (IPr) (6), had their in vitro activity evaluated towards Leishmania amazonensis and Chikungunya virus (CHIKV). The compound (6) inhibited 95 % of L. amazonensis infection in RAW macrophages at 10 μM and 90 % of the CHIKV replication at 2 μM in BHK-21 cells. Otherwise, the other compounds showed higher cytotoxicity in BHK-21 and RAW or lower antiparasitic or antiviral activities.The best activity of compound 6 can be explained by slower ligand exchange with solvent molecules measured by 1 H NMR technique and the best hydrophilic/lipophilic balance (log P = À 0.684 � 0.055) in the series determined by shake flask method. Antioxidant activity measured by reduction of DPPH revealed a moderate redox ability of all complexes. The binding constant of ( 6) with bovine serum albumin (BSA) represents the weakest in the series (10 3 ). The chemical and in vitro evaluation reported here represent a novel application and chemical insights for the design of [Cu(I)(NHC)L] metallodrugs for these infectious diseases.
Leishmaniasis is one of the most neglected diseases worldwide and is considered a serious public health issue. The current therapeutic options have several disadvantages that make the search for new therapeutics urgent. Gold compounds are emerging as promising candidates based on encouraging in vitro and limited in vivo results for several AuI and AuIII complexes. The antiparasitic mechanisms of these molecules remain only partially understood. However, a few studies have proposed the trypanothione redox system as a target, similar to the mammalian thioredoxin system, pointed out as the main target for several gold compounds with significant antitumor activity. In this review, we present the current status of the investigation and design of gold compounds directed at treating leishmaniasis. In addition, we explore potential targets in Leishmania parasites beyond the trypanothione system, taking into account previous studies and structure modulation performed for gold‐based compounds.
Herein a systematic series of four [AuLL’]n+ n = 0, +1 complexes, where L = 1,3-bis(mesityl)imidazole-2-ylidene (IMes), or triphenylphosphine (PPh3), and L’ = chloride, or 4-dimethylaminopyridine (DMAP), had their in vitro antiviral activity assessed against Chikungunya virus (CHIKV). The PPh3 derivatives inhibited viral replication by 99%, whereas the IMes derivatives about 50%. The lipophilicity of the PPh3 derivatives is higher than the IMes-bearing compounds, which can be related to their more prominent antiviral activities. The dissociation of DMAP is faster than chloride in solution for both IMes and PPh3 derivatives; however, it does not significantly affect their in vitro activities, showing a higher dependence on the nature of L rather than L’ towards their antiviral effects. All complexes bind to N-acetyl-L-cysteine, with the Ph3P-bearing complexes coordinating at a faster rate to this amino acid. The binding constants to bovine serum albumin (BSA) are in the order of 104, slightly higher for the DMAP complexes in both PPh3 and IMes derivatives. Mechanistic investigations of the PPh3 complexes showed a ubiquitous protective effect of the compounds in the pre-treatment, early stages, and post-entry assays. The most significant inhibition was observed in post-entry activity, in which the complexes blocked viral replication in 99%, followed by up to 95% inhibition of the early stages of infection. Pre-treatment assays showed a 92% and 80% replication decrease for the chloride and DMAP derivatives, respectively. dsRNA binding assays showed a significant interaction of the compounds with dsRNA, an essential biomolecule to viral replication.
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