In Vitro and in Vivo Trypanocidal Evaluation of Nickel Complexes with an Azapurine Derivative against Trypanosoma cruzi

Strategies for overcoming tropical disease by ruthenium complexes with purine analog: Application against Leishmania spp. and Trypanosoma cruzi

Tropical diseases currently constitute a major health problem and thus a challenge in the field of drug discovery. The current treatments show serious disadvantages due to cost, toxicity, long therapy duration and resistance, and the use of metal complexes as chemotherapeutic agents against these ailments appears to be a very attractive alternative. Herein, we describe three newly synthesized ruthenium complexes with a bioactive molecule, the purine analogue 5,6,7-trimethyl-1,2,4-triazolo[1,5-a]pyrimidine (tmtp): cis,fac-[RuCl₂(dmso)₃(tmtp)] (1), mer-[RuCl₃(dmso)(H₂O)(tmtp)]·2H₂O (2) and fac,cis-[RuCl₃(H₂O)(tmtp)₂] (3). Their structures were characterized using X-ray and spectroscopic methods (IR, NMR or EPR). The stability of the synthesized complexes 1-3 in various buffered solutions (pH=3-7.4) was monitored using conventional and stopped-flow techniques. The in vitro antiproliferative activity of all ruthenium complexes against promastigote forms of Leishmania spp. (L. infantum, L. braziliensis, and L. donovani) and epimastigote forms of Trypanosoma cruzi was investigated. Notably, the results showed that the activity of 1 against L. brasiliensis was more than three-fold higher than that of glucantime, and 1 showed no appreciable toxicity towards J774.2 macrophages. Additionally, 2 displayed even 141-fold lower toxicity against host cells than glucantime, demonstrating significantly higher selectivity than the reference drug. Therefore, 1 and 2 appear to be excellent candidates for further development as potential drugs for the effective treatment of leishmaniasis and Chagas disease. All novel complexes were also shown to be potent inhibitors of Fe-SOD in the studied species, while their effects on human CuZn-SOD were very low.

Glycosylated metal chelators as anti-parasitic agents with tunable selectivity

Metal complexation imparts selective anti-parasitic activity to aminopyridyl ligands: Zn(ii) and Cu(ii) complexes show potent activity and remarkable selectivity indexes.

Triazolopyrimidine compounds containing first-row transition metals and their activity against the neglected infectious Chagas disease and leishmaniasis

Leishmaniasis and Chagas disease remain a significant global problem. Current treatments have serious disadvantage due to cost, toxicity, long therapy duration and resistance. In the last years increasing interest has arisen in drug development to fight both diseases. Recently, metal-based drugs have revealed as promising drugs in a variety of therapeutic areas. Herein we describe six newly synthesized transition metal complexes with a bioactive molecule 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp). All of them have been characterized by X-ray, spectroscopic and thermal methods. In vitro and in vivo studies (murine model) on the antiproliferative activity of these complexes against Leishmania spp. (Leishmania infantum, Leishmania braziliensis) and Trypanosoma cruzi have been carried out. Our results reveal a strong potential of three of the assayed compounds as antiparasitic agents against the above-mentioned infectious diseases.

DPDS–DPS in situ transformation at room temperature via a 1,2-nucleophilic addition mechanism

A cleavage–reorganization reaction at room temperature has been detected in three metal organic coordination compounds synthesized from a DPDS [di(4-pyridyl)disulphide] ligand: Mn(NCS)₂(DPS)₄ (1), [Fe(NCS)₂(DPS)₂]·2H₂O (2) and Zn(NCO)₂(DPS) (3), [DPS = di(4-pyridyl)sulphide].

Comprehensive review in current developments of imidazole-based medicinal chemistry

Imidazole ring is an important five-membered aromatic heterocycle widely present in natural products and synthetic molecules. The unique structural feature of imidazole ring with desirable electron-rich characteristic is beneficial for imidazole derivatives to readily bind with a variety of enzymes and receptors in biological systems through diverse weak interactions, thereby exhibiting broad bioactivities. The related research and developments of imidazole-based medicinal chemistry have become a rapidly developing and increasingly active topic. Particularly, numerous imidazole-based compounds as clinical drugs have been extensively used in the clinic to treat various types of diseases with high therapeutic potency, which have shown the enormous development value. This work systematically gives a comprehensive review in current developments of imidazole-based compounds in the whole range of medicinal chemistry as anticancer, antifungal, antibacterial, antitubercular, anti-inflammatory, antineuropathic, antihypertensive, antihistaminic, antiparasitic, antiobesity, antiviral, and other medicinal agents, together with their potential applications in diagnostics and pathology. It is hoped that this review will be helpful for new thoughts in the quest for rational designs of more active and less toxic imidazole-based medicinal drugs, as well as more effective diagnostic agents and pathologic probes.

In vitro and in vivo studies of the trypanocidal activity of four terpenoid derivatives against Trypanosoma cruzi

Four terpenoid derivatives were examined for their activity against Trypanosoma cruzi. Our results show that two compounds were very active in vitro against both extra- and intracellular forms. These compounds, non-toxic for the host cells, are more effective than the reference drug benznidazole. The capacity to infect cells was negatively affected and the number of amastigotes and trypomastigotes was reduced. A wide range of ultrastructural alterations was found in the epimastigote forms treated with these compounds. Some metabolic changes occurred presumably at the level of succinate and acetate production, perhaps caused by the disturbance of the enzymes involved in sugar metabolism inside the mitochondria. In vivo results were consistent with those observed in vitro. The parasitic load was significantly lower than in the control assay with benznidazole. The effects of these products showed the reduction of the anti-T. cruzi antibodies level during the chronic stage.

Optimization of anti-Trypanosoma cruzi oxadiazoles leads to identification of compounds with efficacy in infected mice

We recently showed that oxadiazoles have anti-Trypanosoma cruzi activity at micromolar concentrations. These compounds are easy to synthesize and show a number of clear and interpretable structure-activity relationships (SAR), features that make them attractive to pursue potency enhancement. We present here the structural design, synthesis, and anti-T. cruzi evaluation of new oxadiazoles denoted 5a-h and 6a-h. The design of these compounds was based on a previous model of computational docking of oxadiazoles on the T. cruzi protease cruzain. We tested the ability of these compounds to inhibit catalytic activity of cruzain, but we found no correlation between the enzyme inhibition and the antiparasitic activity of the compounds. However, we found reliable SAR data when we tested these compounds against the whole parasite. While none of these oxadiazoles showed toxicity for mammalian cells, oxadiazoles 6c (fluorine), 6d (chlorine), and 6e (bromine) reduced epimastigote proliferation and were cidal for trypomastigotes of T. cruzi Y strain. Oxadiazoles 6c and 6d have IC(50) of 9.5 ± 2.8 and 3.5 ± 1.8 μM for trypomastigotes, while Benznidazole, which is the currently used drug for Chagas disease treatment, showed an IC(50) of 11.3 ± 2.8 μM. Compounds 6c and 6d impair trypomastigote development and invasion in macrophages, and also induce ultrastructural alterations in trypomastigotes. Finally, compound 6d given orally at 50mg/kg substantially reduces the parasitemia in T. cruzi-infected BALB/c mice. Our drug design resulted in potency enhancement of oxadiazoles as anti-Chagas disease agents, and culminated with the identification of oxadiazole 6d, a trypanosomicidal compound in an animal model of infection.

In vitro anti-leishmania evaluation of nickel complexes with a triazolopyrimidine derivative against Leishmania infantum and Leishmania braziliensis

Studies on the anti-proliferative activity in vitro of seven ternary nickel (II) complexes with a triazolopyrimidine derivative and different aliphatic or aromatic amines as auxiliary ligands against promastigote and amastigote forms of Leishmania infantum and Leishmania braziliensis have been carried out. These compounds are not toxic for the host cells and two of them are effective at lower concentrations than the reference drug used in the present study (Glucantime). In general, the in vitro growth rate of Leishmania spp. was reduced, its capacity to infect cells was negatively affected and the multiplication of the amastigotes decreased. Ultrastructural analysis and metabolism excretion studies were executed in order to propose a possible mechanism for the action of the assayed compounds. Our results show that the potential mechanism is at the level of organelles membranes, either by direct action on the microtubules or by their disorganization, leading to vacuolization, degradation and ultimately cell death.

In vitro and in vivo antiparasital activity against Trypanosoma cruzi of three novel 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one-based complexes

Conventional reactions of the versatile multidentate ligand 5-methyl-1,2,4-triazolo[1,5-a] pyrimidin-7(4H)-one (HmtpO) with metallic(II) perchlorate salts lead to three novel multidimensional complexes [Cu(HmtpO)(2)(H(2)O)(3)](ClO(4))(2)·H(2)O (1), {[Cu(HmtpO)(2)(H(2)O)(2)](ClO(4))(2) ·2HmtpO}(n) (2) and {[Co(HmtpO)(H(2)O)(3)](ClO(4))(2)·2H(2)O}(n) (3). We have tested the antiparasital activity in vitro and in vivo of the three new complexes against Trypanosoma cruzi showing very promising results and overcoming clearly the reference drug commonly used for the Chagas disease treatment, benznidazole.