In vitro leishmanicidal activity of pyrazole-containing polyamine macrocycles which inhibit the Fe-SOD enzyme of Leishmania infantum and Leishmania braziliensis species

Compounds with potentialities as novel chemotherapeutic agents in leishmaniasis at preclinical level

Leishmaniasis are neglected infectious diseases caused by kinetoplastid protozoan parasites from the genus Leishmania. These sicknesses are present mainly in tropical regions and almost 1 million new cases are reported each year. The absence of vaccines, as well as the high cost, toxicity or resistance to the current drugs determines the necessity of new treatments against these pathologies. In this review, several compounds with potentialities as new antileishmanial drugs are presented. The discussion is restricted to the preclinical level and molecules are organized according to their chemical nature, source and molecular targets. In this manner, we present antimicrobial peptides, flavonoids, withanolides, 8-aminoquinolines, compounds from Leish-Box, pyrazolopyrimidines, and inhibitors of tubulin polymerization/depolymerization, topoisomerase IB, proteases, pteridine reductase, N-myristoyltransferase, as well as enzymes involved in polyamine metabolism, response against oxidative stress, signaling pathways, and sterol biosynthesis. This work is a contribution to the general knowledge of these compounds as antileishmanial agents.

The Bioactivity of Xylene, Pyridine, and Pyrazole Aza Macrocycles against Three Representative Leishmania Species

Due to the urgent need for finding effective and free of secondary effect treatments for every clinical form of Leishmaniasis, a series of synthetic xylene, pyridine and, pyrazole azamacrocycles were tested against three Leishmania species. A total of 14 compounds were tested against J774.2 macrophage cells which were models for host cells, and against promastigote and amastigote forms of each studied Leishmania parasite. Amongst these polyamines, one proved effective against L. donovani, another one for L. braziliensis and L. infantum, and another one was selective solely for L. infantum. These compounds showed leishmanicidal activity and reduced parasite infectivity and dividing ability. Action mechanism studies gave a hint that compounds were active against Leishmania due to their ability to alter parasite metabolic pathways and reduce (except Py33333) parasitic Fe-SOD activity.

Insights on the Synthesis of N-Heterocycles Containing Macrocycles and Their Complexion and Biological Properties

Macrocyclic chemistry has been extensively developed over the past several decades. In fact, the architecture of new macrocyclic models has undergone exponential growth to offer molecules with specific properties. In this context, an attempt is made in this study to provide an overview of some synthetic methods allowing the elaboration of N-heterocycles containing macrocycles (imidazole, triazole, tetrazole, and pyrazole), as well as their applications in the complexation of metal cations or as pharmacological agents.

In vitro Leishmanicidal and Trypanosomicidal Properties of Imidazole-Containing Azine and Benzoazine Derivatives

Leishmaniasis and Chagas diseases are two of the most important parasitic diseases in the world. Both belong to the category of Neglected Tropical Diseases, and they cannot be prevented by vaccination. Their treatments are founded in outdated drugs that possess many pernicious side-effects and they're not easy to administer. With the aim of discovering new compounds that could serve as anti-trypanosomal drugs, an antiparasitic study of a synthetic compound family has been conducted. A series of new 1,4-bis(alkylamino)- and 1-alkylamino-4-chloroazine and benzoazine derivatives 1-4 containing imidazole rings have been synthesized and identified. Their structures showed a possible interest based on previous work. Their in vitro anti-Leishmania infantum, anti-L. braziliensis, anti-L. donovani and anti-T. cruzi activity were tested, as well as the inhibition of Fe-SOD enzymes. It was found that some of them exhibited quite relevant values indicative of being worthy of future more detailed studies, as most of them showed activity to more than only one parasite species, especially compound 3 c was active for the three studied Leishmania species and also for T. cruzi, which is a very interesting trait as it covers a wide spectrum.

Molecular cages for biological applications

Artificial receptors able to recognise biologically relevant molecules or ions have gained interest in the chemical community because they offer a plethora of posibilities. Molecular cage compounds are polycyclic compounds with a cavity designed for the encapsulation of guest species. Once inside the host cavity, the substrate can be transported through membranes and protected from the action of enzymes or other reactive species, thus offering the possibility of interfering with biological systems. Commonly, enzymes have been an inspiration for chemists in the search and design of defined cavities for different purposes. However, the chemical preparation of molecular cages has struggled with many synthetic challenges but this effort is worthwhile as they are a very promising tool for many applications ranging from sensing, delivery, purification or even promotion of/prevention from chemical modifications. Since the early reports at the end of the 60s, this field has experienced a growing interest; this review summarises the progress in the preparation and study of cage-like compounds highlighting their importance in biological applications.

First Example of Antiparasitic Activity Influenced by Thermochromism: Leishmanicidal Evaluation of 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine Metal Complexes

BACKGROUND

The World Health Organization catalogues illnesses such as Leishmaniasis as neglected diseases, due to low investment in new drugs to fight them. The search of novel and non-side effects anti-parasitic compounds is one of the urgent needs for the Third World. The use of triazolopyrimidines and their metallic complexes has demonstrated hopeful results in this field.

OBJECTIVE

This work studies the antiparasitic efficacy of a series of 5,7-dimethyl-1,2,4- triazolo[1,5-a]pyrimidine first row transition metal complexes against three leishmania spp. strains.

METHODS

The in vitro antiproliferation of promastigote forms of different strains of leishmania spp. (L. infantum, L. braziliensis and L donovani) and the cytotoxicity in macrophage host cells are reported here. The antiparasitic assays have been complemented with enzymatic tests to elucidate the mechanisms of action. New crystal structure description, thermal analysis, magnetic susceptibility and magnetization experiments have also been carried out in order to present a whole characterization of the studied compounds and interesting physical properties besides the biological tests.

RESULTS

The results of antiproliferation screening and cytotoxicity show great antiparasitic efficacy in the studied complexes. The superoxide dismutase enzymatic assays exhibit a different behaviour according to the thermochromic triazolopyrimidine form tested.

CONCLUSION

Antiproliferative assays and enzymatic tests corroborate the synergetic leishmanicidal effect present in coordination triazolopyrimidine complexes. The changes in coordination sphere derived from thermochromism affect the physical properties as well as the biological efficacy.

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.

Simple dialkyl pyrazole-3,5-dicarboxylates show in vitro and in vivo activity against disease-causing trypanosomatids

The synthesis and antiprotozoal activity of some simple dialkyl pyrazole-3,5-dicarboxylates (compounds 2-6) and their sodium salts (pyrazolates) (compounds 7-9) against Trypanosoma cruzi, Leishmania infantum and Leishmania braziliensis are reported. In most cases the studied compounds showed, especially against the clinically significant amastigote forms, in vitro activities higher than those of the reference drugs (benznidazole for T. cruzi and glucantime for Leishmania spp.); furthermore, the low non-specific cytotoxicities against Vero cells and macrophages shown by these compounds led to good selectivity indexes, which are 8-72 times higher for T. cruzi amastigotes and 15-113 times higher for Leishmania spp. amastigotes than those of the respective reference drugs. The high efficiency of diethyl ester 3 and its sodium salt 8 against the mentioned protozoa was confirmed by further in vitro assays on infection rates and by an additional in vivo study in a murine model of acute and chronic Chagas disease. The inhibitory capacity of compounds 3 and 8 on the essential iron superoxide dismutase of the aforementioned parasites may be related to the observed anti-trypanosomatid activity. The low acute toxicity of compounds 3 and 8 in mice is also reported in this article.

In vitro antileishmanial activity of aza-scorpiand macrocycles. Inhibition of the antioxidant enzyme iron superoxide dismutase

Aza-scorpiand-like macrocycles candidates for the development of affordable anti-leishmanicidal agents.

Imidazole-containing phthalazine derivatives inhibit Fe-SOD performance in Leishmania species and are active in vitro against visceral and mucosal leishmaniasis

The in vitro leishmanicidal activity of a series of imidazole-containing phthalazine derivatives 1–4 was tested on Leishmania infantum, Leishmania braziliensis and Leishmania donovani parasites, and their cytotoxicity on J774·2 macrophage cells was also measured. All compounds tested showed selectivity indexes higher than that of the reference drug glucantime for the three Leishmania species, and the less bulky monoalkylamino substituted derivatives 2 and 4 were clearly more effective than their bisalkylamino substituted counterparts 1 and 3. Both infection rate measures and ultrastructural alterations studies confirmed that 2 and 4 were highly leishmanicidal and induced extensive parasite cell damage. Modifications to the excretion products of parasites treated with 2 and 4 were also consistent with substantial cytoplasmic alterations. On the other hand, the most active compounds 2 and 4 were potent inhibitors of iron superoxide dismutase enzyme (Fe-SOD) in the three species considered, whereas their impact on human CuZn-SOD was low. Molecular modelling suggests that 2 and 4 could deactivate Fe-SOD due to a sterically favoured enhanced ability to interact with the H-bonding net that supports the antioxidant features of the enzyme.