Synthesis and evaluation of in vitro and in vivo trypanocidal properties of a new imidazole-containing nitrophthalazine derivative

Synthesis of Antiprotozoal 2-(4-Alkyloxyphenyl)-Imidazolines and Imidazoles and Their Evaluation on Leishmania mexicana and Trypanosoma cruzi

Twenty 2-(4-alkyloxyphenyl)-imidazolines and 2-(4-alkyloxyphenyl)-imidazoles were synthesized, with the former being synthesized in two steps by using MW and ultrasonication energy, resulting in good to excellent yields. Imidazoles were obtained in moderate yields by oxidizing imidazolines with MnO2 and MW energy. In response to the urgent need to treat neglected tropical diseases, a set of 2-(4-alkyloxyphenyl)- imidazolines and imidazoles was tested in vitro on Leishmania mexicana and Trypanosoma cruzi. The leishmanicidal activity of ten compounds was evaluated, showing an IC50 < 10 µg/mL. Among these compounds, 27-31 were the most active, with IC50 values < 1 µg/mL (similar to the reference drugs). In the evaluation on epimastigotes of T. cruzi, only 30 and 36 reached an IC50 < 1 µg/mL, showing better inhibition than both reference drugs. However, compounds 29, 33, and 35 also demonstrated attractive trypanocidal activities, with IC50 values < 10 µg/mL, similar to the values for benznidazole and nifurtimox.

Nitro compounds against trypanosomatidae parasites: Heroes or villains?

Chagas disease and Human African trypanosomiasis (HAT) are caused by Trypanosoma cruzi, T. brucei rhodesiense or T. b. gambiense parasites, respectively; while Leishmania is caused by parasites from the Leishmania genus. In recent years, many efforts have been addressed to develop inhibitors against these parasites, especially nitro-containing derivatives, which can interfere with essential enzymes from the protozoa. In this review, all anti-trypanosomatidae nitrocompounds reported so far are shown herein, highlighting their activities and SAR analyses, providing all the benefits and problems associated with this ambiguous chemical group. Finally, this review paper will be useful for many research teams around the world, which are searching for novel trypanocidal and leishmanicidal agents.

Antiparasitary and antiproliferative activities in vitro of a 1,2,4-oxadiazole derivative on Trypanosoma cruzi

Chagas disease (CD) is a neglected disease, prevalent and endemic in Latin America, but also present in Europe and North America. The main treatment used for this disease is benznidazole, but its efficacy is variable in the chronic phase and presents high toxicity. So, there is a need for the development of new therapeutic agents. The five-membered heterocyclic 1,2,4-oxadiazole ring has received attention for its unique properties and a broad spectrum of biological activities and is therefore a potential candidate for the development of new drugs. Thus, the aim of this study was to evaluate the activity of the N-cyclohexyl-3-(3-methylphenyl)-1,2,4-oxadiazol-5-amine (2) on the evolutionary forms of Trypanosoma cruzi strain Y, as well as its mechanisms of action and in silico theoretical approach. The results by computational method showed an interaction of the 1,2,4-oxadiazole (2) with TcGAPDH, cruzain, and trypanothione reductase, showing good charge distribution and affinity in those three targets. Furthermore, cytotoxicity in LLC-MK₂ cells was performed by the MTT method. In the assays with different parasite forms, the tested compound showed similar time-dependent concentration effect. The evaluation of the antiamastigote effect between the two concentrations tested showed a reduction in the number of infected cells and also in the number of amastigotes per infected cell. By flow cytometry, the compound (2) displayed alterations suggestive of necrotic events. Finally, in scanning electron microscopy structural alterations were present, characteristic of necrosisin the epimastigote forms. Overall, the 1,2,4-oxadiazole derivative (2) here evaluated opens perspectives to the development of new antichagasic agents.

Antioxidant defence system as a rational target for Chagas disease and Leishmaniasis chemotherapy

Chagas disease and leishmaniasis are neglected tropical diseases caused by the protozoan parasites Trypanosoma cruzi and Leishmania spp., respectively. They are among the most important parasitic diseases, affecting millions of people worldwide, being a considerable global challenge. However, there is no human vaccine available against T. cruzi and Leishmania infections, and their control is based mainly on chemotherapy. Treatments for Chagas disease and leishmaniasis have multiple limitations, mainly due to the high toxicity of the available drugs, long-term treatment protocols, and the occurrence of drug-resistant parasite strains. In the case of Chagas disease, there is still the problem of low cure rates in the chronic stage of the disease. Therefore, new therapeutic agents and novel targets for drug development are urgently needed. Antioxidant defence in Trypanosomatidae is a potential target for chemotherapy because the organisms present a unique mechanism for trypanothione-dependent detoxification of peroxides, which differs from that found in vertebrates. Cellular thiol redox homeostasis is maintained by the biosynthesis and reduction of trypanothione, involving different enzymes that act in concert. This study provides an overview of the antioxidant defence focusing on iron superoxide dismutase A, tryparedoxin peroxidase, and ascorbate peroxidase and how the enzymes play an important role in the defence against oxidative stress and their involvement in drug resistance mechanisms in T. cruzi and Leishmania spp.

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.

Assessing the effectiveness of AS-48 in experimental mice models of Chagas' disease

OBJECTIVES

We report the in vivo trypanocidal activity of the bacteriocin AS-48 (lacking toxicity), which is produced by Enterococcus faecalis, against the flagellated protozoan Trypanosoma cruzi, the aetiological agent of Chagas' disease.

METHODS

We determined the in vivo activity of AS-48 against the T. cruzi Arequipa strain in BALB/c mice (in both acute and chronic phases of Chagas' disease). We evaluated the parasitaemia, the reactivation of parasitaemia after immunosuppression and the nested parasites in the chronic phase by PCR in target tissues.

RESULTS

AS-48 reduced the parasitaemia profile in acute infection and showed a noteworthy reduction in the parasitic load in chronic infection after immunosuppression according to the results obtained by PCR (double-checking to demonstrate cure).

CONCLUSIONS

AS-48 is a promising alternative that provides a step forward in the development of a new therapy against Chagas' disease.

The role of imidazole and benzimidazole heterocycles in Chagas disease: A review

The haemoflagellate protozoan Trypanosoma cruzi (T. cruzi) is the causative agent of Chagas disease (CD), a potentially life-threatening disease. Little by little, remarkable progress has been achieved against CD, although it is still not enough. In the absence of effective chemotherapy, many research groups, organizations and pharmaceutical companies have focused their efforts on the search for compounds that could become viable drugs against CD. Within the wide variety of reported derivatives, this review summarizes and provides a global vision of the situation of those compounds that include broadly studied heterocycles in their structures due to their applications in medicinal chemistry: imidazole and benzimidazole rings. Therefore, the intention of this work is to present a compilation, as much as possible, of all the reported information, regarding these imidazole and benzimidazole derivatives against T. cruzi, as a starting point for future researchers in this field.

Current and Future Prospects of Nitro-compounds as Drugs for Trypanosomiasis and Leishmaniasis

Interest in nitroheterocyclic drugs for the treatment of infectious diseases has undergone a resurgence in recent years. Here we review the current status of monocyclic and bicyclic nitroheterocyclic compounds as existing or potential new treatments for visceral leishmaniasis, Chagas' disease and human African trypanosomiasis. Both monocyclic (nifurtimox, benznidazole and fexinidazole) and bicyclic (pretomanid (PA-824) and delamanid (OPC-67683)) nitro-compounds are prodrugs, requiring enzymatic activation to exert their parasite toxicity. Current understanding of the nitroreductases involved in activation and possible mechanisms by which parasites develop resistance is discussed along with a description of the pharmacokinetic / pharmacodynamic behaviour and chemical structure-activity relationships of drugs and experimental compounds.

Tropical and Subtropical Parasitic Diseases: Targets for a New Approach to Virtual Screening

Computational techniques are widely used to reduce costs associated with new drug development with the ability to bind a specific molecular target. These studies need a Brookhaven protein data bank structure sample of the enzyme interaction with an inhibitor of adequate size. In this context, a new computational methodology is postulated to be used when there are no published samples fulfilling this requirements. In this study, 7 compounds, which showed anti-T. cruzi, L. donovani and L. infantum properties, and proved to be inhibitors of their Fe-SOD enzymes, have been theoretically evaluated against related parasites Fe-SOD enzymes, which have been proposed as targets for antiparasitic drugs. This methodology may be applied to similar cases and also to generate starting structures to be used with different CADD methods.

Synthesis and biological evaluation of new long-chain squaramides as anti-chagasic agents in the BALB/c mouse model

Chagas Disease is caused by infection with the insect-transmitted protozoan Trypanosoma cruzi and affects more than 10 million people. It is a paradigmatic example of a chronic disease without an effective treatment in Latin America where the current therapies, based on Benznidazole and Nifurtimox, are characterised by limited efficacy, toxic side-effects and frequent failures in the treatment. We present a series of new long-chain squaramides, identified based on their ¹H and ¹³C NMR spectra, and their trypanocidal activity and cytotoxicity were tested in vitro through the determination of IC₅₀ values. Compounds 4 and 7 were more active and less toxic than the reference drug Benznidazole, and these results were the basis of promoting in vivo assays, where parasitaemia levels, assignment of cure, reactivation of parasitaemia and others parameters were determined in mice treated in both the acute and chronic phases. Finally, the mechanisms of action were elucidated at metabolic and mitochondrial levels and superoxide dismutase inhibition. The experiments allowed us to select compound 7 as a promising candidate for treating Chagas Disease, where the activity, stability and low cost make long-chain squaramides appropriate molecules for the development of an affordable anti-chagasic agent versus current treatments.

New polyamine drugs as more effective antichagas agents than benznidazole in both the acute and chronic phases

Despite the continuous research effort that has been made in recent years to find ways to treat the potentially life threatening Chagas disease (CD), this remains the third most important infectious disease in Latin America. CD is an important public health problem affecting 6-7 million people. Since the need to search for new drugs for the treatment of DC persists, in this article we present a panel of new polyamines based on the tripodal structure of tris(2-aminomethyl)amine (tren) that can be prepared at low cost with high yields. Moreover, these polyamines present the characteristic of being water-soluble and resistant to the acidic pH values of stomach, which would allow their potential oral administration. In vitro and in vivo assays permitted to identify the compound with the tren moiety functionalized with one fluorene unit (7) as a potential antichagas agent. Compound 7 has broader spectrum of action, improved efficacy in acute and chronic phases of the disease and lower toxicity than the reference drug benznidazole. Finally, the action mechanisms studied at metabolic and mitochondrial levels shows that the trypanocidal activity of compound 7 could be related to its effect at the glycosomal level. Therefore, this work allowed us to select compound 7 as a promising candidate to perform preclinical evaluation studies.

Experimental models in Chagas disease: a review of the methodologies applied for screening compounds against Trypanosoma cruzi

One of the main problems of Chagas disease (CD), the parasitic infection caused by Trypanosoma cruzi, is the lack of a completely satisfactory treatment, which is currently based on two old nitroheterocyclic drugs (i.e., nifurtimox and benznidazole) that show important limitations for treating patients. In this context, many laboratories look for alternative therapies potentially applicable to the treatment, and therefore, research in CD chemotherapy works in the design of experimental protocols for detecting molecules with activity against T. cruzi. Phenotypic assays are considered the most valuable strategy for screening these antiparasitic compounds. Among them, in vitro experiments are the first step to test potential anti-T. cruzi drugs directly on the different parasite forms (i.e., epimastigotes, trypomastigotes, and amastigotes) and to detect cytotoxicity. Once the putative trypanocidal drug has been identified in vitro, it must be moved to in vivo models of T. cruzi infection, to explore (i) acute toxicity, (ii) efficacy during the acute infection, and (iii) efficacy in the chronic disease. Moreover, in silico approaches for predicting activity have emerged as a supporting tool for drug screening procedures. Accordingly, this work reviews those in vitro, in vivo, and in silico methods that have been routinely applied during the last decades, aiming to discover trypanocidal compounds that contribute to developing more effective CD treatments.

Synthesis of Xylitan Derivatives and Preliminary Evaluation of in Vitro Trypanocidal Activity

A series of novel xylitan derivatives derived from xylitol were synthesized using operationally simple procedures. A xylitan acetonide was the key intermediate used to prepare benzoate, arylsulfonate esters and 1,2,3-triazole derivatives of xylitan. These compounds were evaluated for their in vitro anti-Trypanosoma cruzi activity against trypomastigote and amastigote forms of the parasite in T. cruzi-infected cell lineages. Benznidazole was used as positive control against T. cruzi and cytotoxicity was determined in mammalian L929 cells. The arylsulfonate xylitan derivative bearing a nitro group displayed the best activity of all the compounds tested, and was slightly more potent than the reference drug benznidazole. The importance of the isopropylidene ketal moiety was established and the greater lipophilicity of these compounds suggests enhancement in cell penetration.