In vitro leishmanicidal activity of imidazole- or pyrazole-based benzo[g]phthalazine derivatives against Leishmania infantum and Leishmania braziliensis species

The repertoire of iron superoxide dismutases from Leishmania infantum as targets in the search for therapeutic agents against leishmaniasis

Species of Leishmania and Trypanosoma genera are the causative agents of relevant parasitic diseases. Survival inside their hosts requires the existence of a potent antioxidant enzymatic machinery. Four iron superoxide dismutases have been described in trypanosomatids (FeSODA, FeSODB1, FeSODB2, and FeSODC) that hold a potential as therapeutic targets. Nonetheless, very few studies have been developed that make use of the purified enzymes. Moreover, FeSODC remains uncharacterised in Leishmania. In this work, for the first time, we describe the purification and enzymatic activity of recombinant versions of the four Leishmania FeSOD isoforms and establish an improved strategy for developing inhibitors. We propose a novel parameter [(V*cyt. c - Vcyt. c)/Vcyt. c] which, in contrast to that used in the classical cytochrome c reduction assay, correlates linearly with enzyme concentration. As a proof of concept, we determine the IC50 values of two ruthenium carbosilane metallodendrimers against these isoforms.

Lactoperoxidase Inhibition of Celecoxib Derivatives Containing the Pyrazole Linked-Sulfonamide Moiety: Antioxidant Capacity, Antimicrobial Activity, and Molecular Docking Studies

Celecoxib derivatives that contain the pyrazole-linked sulfonamide moiety were synthesized, and the in vitro inhibitory impacts of the aforesaid compounds against the lactoperoxidase (LPO) enzyme were researched. To this end, LPO was purified using the affinity chromatography technique with a yield of 12.63% (319.23-fold). The results showed that the aromatic pyrazole compound (compound 1) containing 2,3-dimethoxyphenyl functional groups was the most effective LPO inhibitor with a Ki value of 3.2 ± 0.7 nM and noncompetitive inhibition type. The second section of the study tested the previously synthesized compounds to reveal their antioxidant and antimicrobial properties. The above-mentioned compound also displayed high activity levels compared to standard antibiotics and antifungals, while all other compounds also showed antibacterial activity. In the three antioxidant methods we used, the compound with 2,5-dimethoxy phenyl groups obtained from the reaction of the aromatic pyrazole compound with propionic anhydride in the presence of NEt3 displayed the highest activity. Furthermore, molecular docking and molecular mechanics studies were conducted to complement and validate the experimental findings. The results obtained from these computational analyses are highly consistent with the experimental data.

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.

Pyrazole-based and N,N-diethylcarbamate functionalized some novel aurone analogs: Design, synthesis, cytotoxic evaluation, docking and SAR studies, against AGS cancer cell line

The present study involves the design, synthesis, and biological evaluation of a series of thirty-three, pyrazole-based and N,N-diethylcarbamate functionalized, novel aurone analogs, against AGS cancer cell line. These novel aurone analogs are obtained from the reaction of pyrazole-based 6-hydroxyaurones with diethyl carbamoyl chloride using mild basic reagent. The cytotoxic activities of these compounds were evaluated against a human gastric adenocarcinoma cell line (AGS) and disclosed some potential outcomes as several analogs were found to have cytotoxicity better than the reference drugs Oxaliplatin and Leucovorin. The structure-activity relationship (SAR) study further unveiled the critical role of replacing the hydroxyl group in ring A with a carbamoyl group for cytotoxic activity. Among these aurone analogs, 8e and 8f, with IC50 values of 6.5 ± 0.024 μM and 6.6 ± 0.035 μM, respectively, are identified as the most active compounds. Molecular docking studies were conducted against HER2, a human epidermal growth factor involved in gastric and ovarian cancer, to investigate the binding interactions between the compounds and the protein HER2, where7e and 8e exhibited maximum interactions.

Vanadium compounds as antiparasitic agents: An approach to their mechanisms of action

BACKGROUND

Parasitic infections are a public health problem since they have high morbidity and mortality worldwide. In parasitosis such as malaria, leishmaniasis and trypanosomiasis it is necessary to develop new compounds for their treatment since an increase in drug resistance and toxic effects have been observed. Therefore, the use of different compounds that couple vanadium in their structure and that have a broad spectrum against different parasites have been proposed experimentally.

OBJECTIVE

Report the mechanisms of action exerted by vanadium in different parasites.

CONCLUSION

In this review, some of the targets that vanadium compounds have were identified and it was observed that they have a broad spectrum against different parasites, which represents an advance to continue investigating therapeutic options.

Synthesis of Fluorinated 1-(2-Benzyl)-phthalazinone, 1-Phthalazinamine, and 1-Alkoxy/Benzyloxy-Phthalazine Derivatives by Ultrasonication Method

Fluorinated heterocyclic compounds have been proven to exhibit interesting potential biological activities. Therefore, various fluorinated 1(2-(N)-benzyl) phthalazinones, 1-Phthalazinamine, and non-fluorinated 1-alkoxy/benzyloxy phthalazines derivatives have been synthesized by the ultrasonication method. This protocol is more efficient than the conventional method in terms of product yield and reaction handling and timelines.

Heterocyclic Diamines with Leishmanicidal Activity

Leishmaniasis is one of the world's most neglected diseases with a worldwide prevalence of 12 million people. There are no effective human vaccines for its prevention, and outdated drugs hamper treatment. Therefore, research aimed at developing new therapeutic tools to fight leishmaniasis remains a crucial goal today. With this purpose in mind, here, we present 10 new compounds made up by linking alkylated ethylenediamine units to pyridine or quinoline heterocycles with promising in vitro and in vivo efficacy against promastigote and amastigote forms of Leishmania infantum, Leishmania donovani, and Leishmania braziliensis species. Three compounds (2, 4, and 5) showed a selectivity index much higher in the amastigote form than the reference drug glucantime. These three derivatives affected the parasite infectivity rates; the result was lower parasite infectivity rates than glucantime tested at an IC₂₅ dose. In addition, these derivatives were substantially more active against the three Leishmania species tested than glucantime. The mechanism of action of these compounds has been studied, showing alterations in glucose catabolism and leading to greater levels of iron superoxide dismutase inhibition. These molecules could be potential candidates for leishmaniasis chemotherapy due to their effectiveness and their ready synthesis.

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.

New silver(I) phosphino complexes: Evaluation of their potential as prospective agents against Mycobacterium tuberculosis

Despite being a preventable and curable disease, Tuberculosis (TB) is the world's top infectious killer. Development of new drugs is urgently needed. In this work, the synthesis and characterization of new silver(I) complexes, that include N'-[(E)-(pyridine-2-ylmethylene)pyrazine-2-carbohydrazide, HPCPH, as main ligand and substituted aryl-phosphines as auxiliary ligands, is reported. HPCPH was synthesized from pyrazinoic acid, the active metabolite of the first-line antimycobacterial drug pyrazinamide. Complexes [Ag(HPCPH)(PPh₃)₂]OTf (1), [Ag(HPCPH)((P(p-tolyl)₃)₂]OTf (2) and [Ag(HPCPH)(P(p-anisyl)₃)₂]OTf (3) were characterized in solid state and in solution by elemental analysis and FTIR and NMR spectroscopies (OTftriflate). Crystal structures of (1,2) were determined by XRD. The Ag atom is coordinated to azomethine and pyridine nitrogen atoms of HPCPH ligand and to the phosphorous atom of each aryl-phosphine co-ligand. Although HPCPH did not show activity, the Ag(I) compounds demonstrated activity against Mycobacterium tuberculosis (MTB), H₃₇Rv strain, and multi-drug resistant clinical isolates (MDR-TB). Globally, results showed that the compounds are not only effective against the sensitive strain, but are more potent against MDR-TB than antimycobacterial drugs used in therapy. The compounds showed low to moderate selectivity index values (SI) towards the bacteria, using MRC-5 cells (ATCC CCL-171) as mammalian cell model. Interaction with DNA was explored to get insight into the potential mechanism of action against the pathogen. No significant interaction was detected, allowing to discard this biomolecule as a potential molecular target. Compound 1 was identified as a hit compound (MIC₉₀ 2.23 μM; SI 4.4) to develop further chemical modifications in the search for new drugs.

The antimicrobial and immunomodulatory effects of Ionophores for the treatment of human infection

Ionophores are a diverse class of synthetic and naturally occurring ion transporter compounds which demonstrate both direct and in-direct antimicrobial properties against a broad panel of bacterial, fungal, viral and parasitic pathogens. In addition, ionophores can regulate the host-immune response during communicable and non-communicable disease states. Although the clinical use of ionophores such as Amphotericin B, Bedaquiline and Ivermectin highlight the utility of ionophores in modern medicine, for many other ionophore compounds issues surrounding toxicity, bioavailability or lack of in vivo efficacy studies have hindered clinical development. The antimicrobial and immunomodulating properties of a range of compounds with characteristics of ionophores remain largely unexplored. As such, ionophores remain a latent therapeutic avenue to address both the global burden of antimicrobial resistance, and the unmet clinical need for new antimicrobial therapies. This review will provide an overview of the broad-spectrum antimicrobial and immunomodulatory properties of ionophores, and their potential uses in clinical medicine for combatting infection.

Axenic amastigotes of Leishmania species as a suitable model for in vitro studies

Leishmania spp. are etiological agents of infection diseases, which in some cases can be fatal. The main forms of their biological cycle, promastigotes and amastigotes, can be maintained in vitro. While promastigotes are easier to maintain, amastigotes are more complex and can be obtained through different ways, including infection assays of tissues or in vitro cells, and differentiation from promastigotes to axenic amastigotes. Several protocols have been proposed for in vitro differentiation for at least 12 Leishmania spp. of both subgenera, Leishmania and Viannia. In this review we propose a critical summary of axenic amastigotes induction, as well as the impact of these strategies on metabolic pathways and regulatory networks analyzed by omics approaches. The parameters used by different research groups show considerable variations in temperature, pH and induction stages, as highlighted here for Leishmania (Viannia) braziliensis. Therefore, a consensus on strategies for inducing amastigogenesis is necessary to improve accuracy and even define stage-specific biomarkers. In fact, the axenic amastigote model has contributed to elucidate several aspects of the parasite cycle, however, since it does not reproduce the intracellular environment, its use requires several precautions. In addition, we present a discussion about using axenic amastigotes for drug screening, suggesting the need of a more sensitive methodology to verify cell viability in these tests. Collectively, this review explores the advantages and limitations found in studies with axenic amastigotes, done for more than 30 years, and discuss the gaps that impair their use as a suitable model for in vitro studies.

Recent advancements in anti-leishmanial research: Synthetic strategies and structural activity relationships

Leishmaniasis is a parasitic neglected tropical disease caused by various species of Leishmania parasite. Despite tremendous advancements in the therapeutic sector and drug development strategies, still the existing anti-leishmanial agents are associated with some clinical issues like drug resistance, toxicity and selectivity. Therefore, several research groups are continuously working towards the development of new therapeutic candidates to overcome these issues. Many potential heterocyclic moieties have been explored for this purpose including triazoles, chalcones, chromone, thiazoles, thiosemicarbazones, indole, quinolines, etc. It is evident from the literature that the majority of anti-leishmanial agents act by interacting with key regulators including PTR-I, DHFR, LdMetAP1, MAPK, 14 α-demethylase and pteridine reductase-I, etc. Also, these tend to induce the production of ROS which causes damage to parasites. In the present compilation, authors have summarized various significant synthetic procedures for anti-leishmanial agents reported in recent years. A brief description of the pharmacological potentials of synthesized compounds along with important aspects related to structural activity relationship has been provided. Important docking outcomes highlighting the possible mode of interaction for the reported compounds have also been included. This review would be helpful to the scientific community to design newer strategies and also to develop novel therapeutic candidates against leishmaniasis.

Novel (+)-Neoisopulegol-Based O-Benzyl Derivatives as Antimicrobial Agents

Discovery of novel antibacterial agents with new structures, which combat pathogens is an urgent task. In this study, a new library of (+)-neoisopulegol-based O-benzyl derivatives of aminodiols and aminotriols was designed and synthesized, and their antimicrobial activity against different bacterial and fungal strains were evaluated. The results showed that this new series of synthetic O-benzyl compounds exhibit potent antimicrobial activity. Di-O-benzyl derivatives showed high activity against Gram-positive bacteria and fungi, but moderate activity against Gram-negative bacteria. Therefore, these compounds may serve a good basis for antibacterial and antifungal drug discovery. Structure-activity relationships were also studied from the aspects of stereochemistry of the O-benzyl group on cyclohexane ring and the substituent effects on the ring system.

Synthesis of novel pyrazole tagged pyridine derivatives; their antimicrobial activity

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Novel pyrazole tagged pyridine derivatives 5a-n synthesized starting from 3-cyano-4-trifluoromethyl-6- thiophenyl 2(1H) pyridone 1. Compound 1 on hydrolysis followed by decarboxylation resulted in 4-trifluoro-methyl-6- thiophenyl 2(1H)pyridone 2. Compound 2 treated with POCl3 to get 2- chloro-4-trifluoromethyl-6- thiophenyl pyridine 3 further reaction with hydrazine hydrate, which resulted in the formation of compound 4. Compound 4 on reaction with different substituted 1,3-diketones in ethanol reflux condition to afford pyrazole substituted pyridine derivatives 5a-n. All derivatives were tested against Gram-positive and Gram-negative bacterial strains and different Candida strains by well diffusion method, compounds 5k and 5l showed significant activity. The binding mode of 5k and 5l also studied by molecular docking studies.

Synthetic and medicinal chemistry of phthalazines: Recent developments, opportunities and challenges

Fused diaza-heterocycles constitute the core structure of numerous bioactive natural products and effective therapeutic drugs. Among them, phthalazines have been recognized as remarkable structural leads in medicinal chemistry due to their wide application in pharmaceutical and agrochemical industries. Accessing such challenging pharmaceutical agents/drug candidates with high chemical complexity through synthetically efficient approaches remains an attractive goal in the contemporary medicinal chemistry and drug discovery arena. In this review, we focus on the recent developments in the synthetic routes towards the generation of phthalazine-based active pharmaceutical ingredients and their biological potential against various targets. The general reaction scope of these innovative and easily accessible strategies was emphasized focusing on the functional group tolerance, substrate and coupling partner compatibility/limitation, the choice of catalyst, and product diversification. These processes were also accompanied by the mechanistic insights where deemed appropriate to demonstrate meaningful information. Moreover, the rapid examination of the structure-activity relationship analyses around the phthalazine core enabled by the pharmacophore replacement/integration revealed the generation of robust, efficient, and more selective compounds with pronounced biological effects. A large variety of in silico methods and ADME profiling tools were also employed to provide a global appraisal of the pharmacokinetics profile of diaza-heterocycles. Thus, the discovery of new structural leads offers the promise of improving treatments for various tropical diseases such as tuberculosis, leishmaniasis, malaria, Chagas disease, among many others including various cancers, atherosclerosis, HIV, inflammatory, and cardiovascular diseases. We hope this review would serve as an informative collection of structurally diverse molecules enabling the generation of mature, high-quality, and innovative routes to support the drug discovery endeavors.

Optimization of phthalazin-based aryl/heteroarylhydrazones to design new promising antileishmanicidal agents: synthesis and biological evaluation of 3-aryl-6-piperazin-1,2,4-triazolo[3,4-a]phthalazines

1-Monosubstituted and 1,4-substituted phthalazins based on aryl/heteroarylhydrazinyl have demonstrated attractive antileishmanial profiles against amastigote forms of the Leishmania braziliensis parasite.

Current Advances in the Synthesis and Biological Evaluation of Pharmacologically Relevant 1,2,4,5-Tetrasubstituted-1H-Imidazole Derivatives

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In recent years, the synthesis and evaluation of the biological properties of 1,2,4,5-tetrasubstituted-1H-imidazole derivatives have been the subject of a large number of studies by academia and industry. In these studies it has been shown that this large and highly differentiated class of heteroarene derivatives includes high valuable compounds having important biological and pharmacological properties such as antibacterial, antifungal, anthelmintic, anti-inflammatory, anticancer, antiviral, antihypertensive, cholesterol-lowering, antifibrotic, antiuricemic, antidiabetic, antileishmanial and antiulcer activities.

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The present review with 411 references, in which we focused on the literature data published mainly from 2011 to 2017, aims to update the readers on the recent developments on the synthesis and biological evaluation of pharmacologically relevant 1,2,4,5-tetrasubstituted-1H-imidazole derivatives with an emphasis on their different molecular targets and their potential use as drugs to treat various types of diseases. Reference was also made to substantial literature data acquired before 2011 in this burgeoning research area.

Acid–base behaviour and binding to double stranded DNA/RNA of benzo[g]phthalazine-based ligands

Benzo[g]phthalazine derivatives show different binding modes and base selectivity towards canonical DNA/RNA depending on the substitution of the aromatic moiety.

Effective Tetradentate Compound Complexes against Leishmania spp. that Act on Critical Enzymatic Pathways of These Parasites

The spectrum and efficacy of available antileishmanial drugs is limited. In the present work we evaluated in vitro the antiproliferative activity of 11 compounds based on tetradentate polyamines compounds against three Leishmania species (L. braziliensis, L. donovani and L. infantum) and the possible mechanism of action. We identified six compounds (3, 5, 6, 7, 8 and 10) effective against all three Leishmania spp both on extracellular and intracellular forms. These six most active leishmanicidal compounds also prevent the infection of host cells. Nevertheless, only compound 7 is targeted against the Leishmania SOD. Meanwhile, on the glucose metabolism the tested compounds have a species-specific effect on Leishmania spp.: L. braziliensis was affected mainly by 10 and 8, L. donovani by 7, and L. infantum by 5 and 3. Finally, the cellular ultrastructure was mainly damaged by 11 in the three Leishmania spp. studied. These identified antileishmania candidates constitute a good alternative treatment and will be further studied.

Current progress on antioxidants incorporating the pyrazole core

The search of new antioxidants, as drugs candidates, is an active field of medicinal chemistry. The synthesis of compounds with antioxidant potential has increased in recent years and a high number of structurally diverse compounds have been published. This review aims to show the current state-of-the-art on the development of antioxidant compounds incorporating the pyrazole pharmacophore. It is a well-timed review driven by the increasing number of papers, on this issue, that have been published since the beginning of the 21st century (from 2000 to 2017). The aim is to look deeper into the structures already published in the literature containing the pyrazole core as the unique pharmacophore or combined with other pharmacophores and see the relationship between the presence of this five-membered nitrogen heterocycle and the behaviour of the compounds as potential antioxidant agents. An attempt was made to whenever possible establish structure-activity relationships that could help the design of new and more potent antioxidant agents containing this important pharmacophore.

Molecular Cloning and Biochemical Characterization of Iron Superoxide Dismutase from Leishmania braziliensis

Leishmaniasis is one of the most important neglected tropical diseases, with a broad spectrum of clinical manifestations. Among the clinical manifestations of the disease, cutaneous leishmaniasis, caused by species of Leishmania braziliensis, presents wide distribution in Brazil. In this work, we performed the cloning, expression, and purification of the enzyme superoxide dismutase of Leishmania braziliensis (LbSOD-B2) considered a promising target for the search of new compounds against leishmaniasis. In vitro assays based on pyrogallol oxidation showed that LbSOD-B2 is most active around pH 8 and hydrogen peroxide is a LbSOD-B2 inhibitor at low millimolar range (IC₅₀ = 1 mM).

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.

Imidazoles as potential anticancer agents

Cancer is a black spot on the face of humanity in this era of science and technology. Presently, several classes of anticancer drugs are available in the market, but issues such as toxicity, low efficacy and solubility have decreased the overall therapeutic indices. Thus, the search for new promising anticancer agents continues, and the battle against cancer is far from over. Imidazole is an aromatic diazole and alkaloid with anticancer properties. There is considerable interest among scientists in developing imidazoles as safe alternatives to anticancer chemotherapy. The present article describes the structural, chemical, and biological features of imidazoles. Several classes of imidazoles as anticancer agents based on their mode of action have been critically discussed. A careful observation has been made into pharmacologically active imidazoles with better or equal therapeutic effects compared to well-known imidazole-based anticancer drugs, which are available on the market. A brief discussion of the toxicities of imidazoles has been made. Finally, the current challenges and future perspectives of imidazole based anticancer drug development are conferred.

In vitro antileishmanial activity and iron superoxide dismutase inhibition of arylamine Mannich base derivatives

Leishmaniasis is one of the world's most neglected diseases, and it has a worldwide prevalence of 12 million. There are no effective human vaccines for its prevention, and treatment is hampered by outdated drugs. Therefore, research aiming at the development of new therapeutic tools to fight leishmaniasis remains a crucial goal today. With this purpose in mind, we present 20 arylaminoketone derivatives with a very interesting in vitro and in vivo efficacy against Trypanosoma cruzi that have now been studied against promastigote and amastigote forms of Leishmania infantum, Leishmania donovani and Leishmania braziliensis strains. Six out of the 20 Mannich base-type derivatives showed Selectivity Index between 39 and 2337 times higher in the amastigote form than the reference drug glucantime. These six derivatives affected the parasite infectivity rates; the result was lower parasite infectivity rates than glucantime tested at an IC25 dose. In addition, these derivatives were substantially more active against the three Leishmania species tested than glucantime. The mechanism of action of these compounds has been studied, showing a greater alteration in glucose catabolism and leading to greater levels of iron superoxide dismutase inhibition. These molecules could be potential candidates for leishmaniasis chemotherapy.

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.

Effective anti-leishmanial activity of minimalist squaramide-based compounds

In order to evaluate the in vitro leishmanicidal activity of N,N'-Squaramides derivatives, compounds that feature both hydrogen bond donor and acceptor groups and are capable of multiple interactions with complementary sites, against Leishmania infantum, Leishmania braziliensis and Leishmania donovani a series of 18compounds was prepared and assayed on extracellular and intracellular parasite forms. Infectivity and cytotoxicity tests were performed on J774.2 macrophage cells using meglumine antimoniate (Glucantime) as the reference drug. Changes in metabolite excretion by ¹H-NMR and the ultrastructural alterations occurring in the parasites treated using transmission electron microscopy (TEM), was analyzed. Compounds 1, 7, 11, 14 and 17 were the more active and less toxic. Infection rates showed that the order of effectiveness was 17 > 11 > 14 > 7 for both L. infantum and L. braziliensis and in the same way, the compound 1 for L. donovani. All these compounds have altered the typical structure of the promastigotes, glycosomes and mitochondria. These severe modifications by the compounds are the ultimate reasons for the alterations observed in the excretion products. The Squaramide 17 (3-(butylamino)-4-((3-(dimetilamino)propyl)(methyl)amino)cyclobut-3-en-1,2-dione) was clearly the most efficient of all compounds. The data appear to confirm that the severe modifications generated in organelles such as glycosomes or mitochondria by the compounds are the ultimate reasons for the alterations observed in the excretion products of all species. The activity, stability, low cost of starting materials, and straightforward synthesis make amino squaramides appropriate molecules for the development of an affordable anti-leishmanial agent.

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.

In vitro leishmanicidal activity of 1,3-disubstituted 5-nitroindazoles

The antiprotozoal activity of some indazole-derived amines (2, 3, 5-8) as well as that of some simple structurally related 3-alkoxy-1-alkyl-5-nitroindazoles (1, 4) against promastigote and amastigote forms of Leishmania infantum and Leishmania braziliensis is reported. In some cases, these compounds showed in vitro activities against the different morphological forms of Leishmania similar to or higher than those of the reference drug glucantime; this fact, along with low unspecific cytotoxicities against macrophages shown by some of them, led to good selectivity indexes (SI). The high efficiency of some 5-nitroindazoles against the mentioned protozoa was confirmed by further in vitro studies on infection rates. Complementary analyses by (1)H NMR of the changes on the metabolites excreted by parasites after treatment with the more active indazole derivatives in many cases showed the decreased excretion of succinate and increased levels of acetate, lactate and alanine, as well as, in some cases, the appearance of glycine and pyruvate as new metabolites. Damage caused by indazoles at the glycosomal or mitochondrial level are consistent with these metabolic changes as well as with the huge ultrastructural alterations observed by transmission electron microscopy (TEM), especially affecting the mitochondria and other cytoplasmic organelles.

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.

Anti Leishmanial Effect of Zinc Sulphate on the Viability of Leishmania tropica and L. major Promastigotes

Background:

Cutaneous leishmaniasis (CL) is an endemic disease in developing countries. Although pentamidine orantimonite (Glucantime) has been recommended for cutaneous leishmaniasis treatment by the World Health Organization, there are some concerns too such as high cost, side effects, need for frequent injections, and restricted efficacy. Therefore, different methods have been used for CL treatment so far.

Objectives:

This study assessed the sensitivity of two parasite agents of cutaneous leishmaniasis: Leishmania major and L. tropica to zinc sulphate in vitro. In the present study, the zinc sulphate effect on urban and rural strains of cutaneous leishmaniasis, viability of old world, in vitro is under investigation.

Materials and Methods:

The design of the present study was experimental (laboratory-trial) based. Iranian endemic species of L. major and L.tropica were appropriately collected, proliferated, and maintained in the standard culture. Afterward, the proper concentrations of zinc sulphate were provided, sterilized, and added to the cultures containing parasites. In different intervals, parasites were counted by two methods: the slide and cell proliferation ELISA.

Results:

Both parasite species showed sensitivity to zinc sulphate in vitro and in comparison with the control group, their numbers were reduced. Zinc sulphate (in concentrations of 0.5, 1, 2, and 3 percent) was added to the cultures containing parasites, and the total number of the live parasites was counted through the slide method (Neubauer slide) every day up to the fifth day. The results were analyzed and found statistically significant (P < 0.05). In the second phase, the counting process was repeated with the addition of zinc sulphate compound with different concentrations (3, 4, 5, and 6 percent) and live parasite numbers were counted by ELISA method after 24 hours. The findings revealed that all the cultures containing zinc sulphate showed a slower growth in comparison to the control group. The mentioned difference was statistically significant (P < 0.05).

Conclusions:

Considering the safety of zinc sulphate compound in comparison with Glucantime, there is a possibility of using it in the treatment of CL caused by both species of L. major and L. tropica. It is obvious that more researches are mandatory both in vivo and in vitro to figure out its daily dosage, proper concentration, time and duration, and possible side effects.

Activity of melatonin against Leishmania infantum promastigotes by mitochondrial dependent pathway

Visceral leishmaniasis, a potentially fatal disease, remains a major international health problem. Only a limited number of effective antileishmanial agents are available for chemotherapy, and many of them are expensive with severe side effects or have a markedly reduced effectiveness due to the development of drug resistance. Hence, there is a genuine need to develop a novel effective and less toxic antileishmanial drug. Melatonin, a neurohormone found in animals, plants, and microbes, can participate in various biological and physiological functions. Several in vitro or in vivo studies have reported the inhibitory effect of melatonin against many parasites via various mechanisms, including modulation of intracellular concentrations of calcium in the parasite and/or any other suggested mechanism. Importantly, many of available antileishmanial drugs have been reported to exert their effects by disrupting calcium homeostasis in the parasite. The objective of the present study was to test the efficacy of exogenous melatonin against Leishmania infantum promastigotes in vitro. Interestingly, melatonin not only demonstrated a significant antileishmanial activity of against promastigote viability in tested cultures but was also accompanied by an alteration of the calcium homeostasis of parasite mitochondrion, represented by earlier mitochondrial permeability transition pore opening, and by changes in some mitochondrial parameters are critical to parasite survival. These pioneering findings suggest that melatonin may be a candidate for the development of novel effective antileishmanial agents either alone or in associations with other drugs.

In vivo anti-Trypanosoma cruzi activity of hydro-ethanolic extract and isolated active principles from Aristeguietia glutinosa and mechanism of action studies

The currently available treatments for Chagas disease show limited therapeutic potential and are associated with serious side effects. Attempting to find alternative drugs isolated from Nature as agents against Trypanosoma cruzi has been our goal. Recently, we have demonstrated the in vitro anti-T. cruzi activities of two secondary metabolites isolated from the hydro-ethanolic extract of the aerial parts of Aristeguietia glutinosa (Lam.), (family Asteraceae). These active principles displayed poor hemolytic activity, low toxicity against murine macrophages, and absence of mutagenicity. Herein, proof of concept in vivo studies of the whole hydro-ethanolic extract of the aerial parts of Aristeguietia glutinosa and of the most active component isolated from the hydro-ethanolic extract, i.e., (+)-15-hydroxy-7-labden-17-al, was done in a murine acute model of Chagas disease. Both treatments caused a decrease in the animals’ parasitemia. Metabolomic mechanism of action studies were done by ¹H-NMR, both on the extract and on the active compounds, examining the effects of the metabolites both on membrane sterol biosynthesis and mitochondrial dehydrogenases, whereby we found that one of the metabolites inhibited the activity of the parasite mitochondrial dehydrogenases and the other inhibited the biosynthesis of parasite membrane sterols. The results are interesting in the context of popular use of plants for the treatment of Chagas disease.

Alkyl galactofuranosides strongly interact with Leishmania donovani membrane and provide antileishmanial activity

We investigated the in vitro effects of four alkyl-galactofuranoside derivatives, i.e., octyl-β-D-galactofuranoside (compound 1), 6-amino-β-D-galactofuranoside (compound 2), 6-N-acetamido-β-D-galactofuranoside (compound 3), and 6-azido-β-D-galactofuranoside (compound 4), on Leishmania donovani. Their mechanism of action was explored using electron paramagnetic resonance spectroscopy (EPR) and nuclear magnetic resonance (NMR), and ultrastructural alterations were analyzed by transmission electron microscopy (TEM). Compound 1 showed the most promising effects by inhibiting promastigote growth at a 50% inhibitory concentration (IC50) of 8.96±2.5 μM. All compounds exhibit low toxicity toward human macrophages. Compound 1 had a higher selectivity index than the molecule used for comparison, i.e., miltefosine (159.7 versus 37.9, respectively). EPR showed that compound 1 significantly reduced membrane fluidity compared to control promastigotes and to compound 3. The furanose ring was shown to support this effect, since the isomer galactopyranose had no effect on parasite membrane fluidity or growth. NMR showed a direct interaction of all compounds (greatest with compound 1, followed by compounds 2, 3, and 4, in descending order) with the promastigote membrane and with octyl-galactopyranose and octanol, providing evidence that the n-octyl chain was primarily involved in anchoring with the parasite membrane, followed by the putative crucial role of the furanose ring in the antileishmanial activity. A morphological analysis of compound 1-treated promastigotes by TEM revealed profound alterations in the parasite membrane and organelles, but this was not the case with compound 3. Quantification of annexin V binding by flow cytometry confirmed that compound 1 induced apoptosis in >90% of promastigotes. The effect of compound 1 was also assessed on intramacrophagic amastigotes and showed a reduction in amastigote growth associated with an increase of reactive oxygen species (ROS) production, thus validating its promising effect.

Initial studies on mechanism of action and cell death of active N-oxide-containing heterocycles in Trypanosoma cruzi epimastigotes in vitro

Chagas disease, endemic in 21 countries across Latin America, kills more people in the region each year than any other parasite-borne disease. Therapeutic options have problems ranging from toxicity, poor efficacy, drug resistance and high cost. Thus, cheaper and less toxic treatments are necessary. From our in-house chemical library of agents against Trypanosoma cruzi the most relevant N-oxide-containing heterocycles were selected for mode of action and type of death studies. Also included in these studies were two active nitrofuranes. Epimastigotes of T. cruzi were used as the biological model in this study. The metabolic profile was studied by 1H NMR in association with the MTT assay. Excreted catabolites data, using 1H NMR spectroscopy, showed that most of the studied N-oxides were capable of decreasing both the release of succinate and acetate shedding, the compounds therefore possibly acting on mitochondria. Only quinoxalines and the nitrofurane Nf1 showed significant mitochondrial dehydrogenase inhibitions, but with different dose-time profiles. In the particular case of quinoxaline Qx2 the glucose uptake study revealed that the integrity of some pathways into the glycosome could be affected. Optic, fluorescence (TUNEL and propidium iodide) and transmission electron microscopy (TEM) were employed for type of death studies. These studies were complemented with 1H NMR to visualize mobile lipids. At low concentrations none of the selected compounds showed a positive TUNEL assay. However, both quinoxalines, one furoxan and one benzofuroxan showed a necrotic effect at high concentrations. Curiously, one furoxan, Fx1, one benzofuroxan, Bfx1, and one nitrofurane, Nf1, caused a particular phenotype, with a big cytoplasmatic vacuole being observed while the parasite was still alive. Studies of TEM and employing a protease inhibitor (3-methyladenine) suggested an autophagic phenotype for Bfx1 and Nf1 and a 'BigEye' phenotype for Fx1.

Synthesis and biological evaluation of N,N'-squaramides with high in vivo efficacy and low toxicity: toward a low-cost drug against Chagas disease

Access to basic drugs is a major issue in developing countries. Chagas disease caused by Trypanosoma cruzi is a paradigmatic example of a chronic disease without an effective treatment. Current treatments based on benznidazole and nifurtimox are expensive, ineffective, and toxic. N,N'-Squaramides are amide-type compounds that feature both hydrogen bond donor and acceptor groups and are capable of multiple interactions with complementary sites. When combined with amine and carboxylic groups, squaramide compounds have increased solubility and therefore make suitable therapeutic agents. In this work, we introduce a group of Lipinski's rule of five compliant squaramides as candidates for treating Chagas disease. The in vivo studies confirmed the positive expectations arising from the preliminary in vitro studies, revealing compound 17 to be the most effective for both acute and chronic phases. The activity, stability, low cost of starting materials, and straightforward synthesis make amino squaramides appropriate molecules for the development of an affordable anti-Chagasic agent.

Direct synthesis of C3-mono-functionalized oxindoles from N-unprotected 2-oxindole and their antileishmanial activity

A novel approach for the synthesis of unprecedented C3-mono-functionalized indolin-2-ones is reported, starting from 2-oxindole and chalcones. The reactions proceed regioselectively under mild conditions, without di- and tri-alkylated side products. The new compounds have been evaluated in vitro for their antiproliferative effects against the protozoan Leishmania infantum. Interestingly, they appear able to kill L. infantum promastigotes and amastigotes, without significant cytotoxic effects.