Antikinetoplastid Agents Research Articles

Investigation of Novel Isatinylhydantoin Derivatives as Potential Anti-kinetoplastid Agents.

Neglected tropical diseases are a group of infectious diseases with a high endemicity in developing countries of Africa, Asia, and the Americas. Treatment for these diseases depends solely on chemotherapy, which is associated with severe side effects, toxicity, and the development of parasitic resistance. This highlights a critical need to develop new and effective drugs to curb these diseases. As a result, a series of novel isatinylhydantoin derivatives were synthesized and evaluated for in vitro anti-kinetoplastid activity against seven human- or animal-infective Trypanosoma and two human-infective Leishmania species. The synthesized derivatives were tested for potential cytotoxicity against human, animal, and parasite host-related cell lines. The isatinylhydantoin hybrid 4b bearing 5-chloroisatin and p-bromobenzyl moieties, showed strong trypanocidal activity against blood-stage T. congolense parasites; however, the promising in vitro trypanocidal potency of 4b could not be translated to in vivo treatment efficacy in a preliminary animal study. Compounds 5, 2b, and 5b, were the most active against amastigotes of L. donovani, showing higher leishmanicidal activity than the reference drug, amphotericin B. These compounds were identified as early antileishmanicidal leads, and future investigations will focus on confirming their antileishmanial potential through in vivo efficacy evaluation as well as their exact mechanism of action.

Salvadoran Celastraceae Species as a Source of Antikinetoplastid Quinonemethide Triterpenoids

Chagas disease and leishmaniasis are among the most widespread neglected tropical diseases, and their current therapies have limited efficacy and several toxic side effects. The present study reports the chemical and antikinetoplastid profiles of extracts from five Salvadoran Celastraceae species against theTrypanosoma cruzi epimastigotes stage and Leishmania amazonensis and Leishmania donovani promastigote forms. The phytochemical profile evinced the presence of flavonoids, tannins, sterols, and triterpenes as the main components in all plant species, whereas quinonemethide triterpenoids (QMTs) were restricted to the root bark of the studied species. Antikinetoplastid evaluation highlights the root bark extracts from Zinowewia integerrima, Maytenus segoviarum, and Quetzalia ilicina as the most promising ones, exhibiting higher potency against T. cruzi (IC50 0.71–1.58 µg/mL) and L. amazonensis (IC50 0.38–2.05 µg/mL) than the reference drugs, benznidazole (IC50 1.81 µg/mL) and miltefosine (IC50 2.64 µg/mL), respectively. This potent activity was connected with an excellent selectivity index on the murine macrophage J774A.1 cell line. These findings reinforce the potential of QMTs as antikinetoplastid agents for the development of innovative phytopharmaceuticals and the plant species under study as a source of these promising lead compounds.

Design and synthesis of imidazo[1,2-a]pyridine-chalcone conjugates as antikinetoplastid agents.

A library of imidazo[1,2-a]pyridine-appended chalcones were synthesized and characterized using 1 H NMR, 13 C NMR and HRMS. The synthesized analogues were screened for their antikinetoplastid activity against Trypanosoma cruzi, Trypanosoma brucei brucei, Trypanosoma brucei rhodesiense and Leishmania infantum. The analogues were also tested for their cytotoxicity activity against human lung fibroblasts and primary mouse macrophages. Among all screened derivatives, 7f was found to be the most active against T. cruzi and T. b. brucei exhibiting IC50 values of 8.5 and 1.35 μM, respectively. Against T. b. rhodesiense, 7e was found to be the most active with an IC50 value of 1.13 μM. All synthesized active analogues were found to be non-cytotoxic against MRC-5 and PMM with selectivity indices of up to more than 50.

Multi-target withaferin-A analogues as promising anti-kinetoplastid agents through the programmed cell death

Leishmaniasis and Chagas disease, two of the most prevalent neglected tropical diseases, are a world health problem. The harsh reality of these infective diseases is the absence of effective and safe therapies. In this framework, natural products play an important role in overcoming the current need to development new antiparasitic agents. The present study reports the synthesis, antikinetoplastid screening, mechanism study of fourteen withaferin A derivatives (2-15). Nine of them (2-6, 8-10 and 12) showed a potent dose-dependent inhibitory effect on the proliferation of Leishmania amazonensis and L. donovani promastigotes and Trypanosoma cruzi epimastigotes with IC50 values ranging from 0.19 to 24.01 µM. Outstandingly, the fully acetylated derivative 10 (4,27-diacetylwithaferin A) was the most potent compound showing IC50 values of 0.36, 2.82 and 0.19 µM against L. amazonensis, L. donovani and T. cruzi, respectively. Furthermore, analogue 10 exhibited approximately 18 and 36-fold greater antikinetoplastid activity, on L. amazonensis and T. cruzi, than the reference drugs. The activity was accompanied by significantly lower cytotoxicity on the murine macrophage cell line. Moreover, compounds 2, 3, 5-7, 9 and 10 showed more potent activity than the reference drug against the intracellular amastigotes forms of L. amazonensis and T.cruzi, with a good selectivity index on a mammalian cell line. In addition, withaferin A analogues 3, 5-7, 9 and 10 induce programmed cell death through a process of apoptosis-like and autophagy. These results strengthen the anti-parasitic potential of withaferin A-related steroids against neglected tropical diseases caused by Leishmania spp. and T. cruzi parasites.

Withaferin A-silyl ether analogs as potential anti-kinetoplastid agents targeting the programmed cell death

Current therapies of leishmaniasis and Chagas disease, two of the most widespread neglected tropical diseases, have limited efficacy and toxic side effects. In this regard, natural products play an important role in overcoming the current need for new antiparasitic agents. The present study reports the leishmanicidal and trypanocidal activities of twenty-four known silyl-ether derivatives of withaferin A. Eleven compounds from this series (4, 7, 8, 10, 12, 15, 17, 18, 20, 22 and 25) showed a potent dose-dependent inhibitory effect on the proliferation of Leishmania amazonensis promastigotes and Trypanosoma cruzi epimastigotes respectively, even higher than the references drugs, miltefosine and benznidazole. Among them, the most promising compound, derivative 10, exhibited approximately 34-fold higher leishmanicidal activity and 49-fold higher trypanocidal activity compared to the reference drugs, as well as lower cytotoxicity. Moreover, compounds 4, 7, 10, 12 and 15 were more active than the reference drugs against the amastigote forms of L. amazonensis, presenting a high selectivity index. Assays performed to study the ATP levels, mitochondrial membrane potential, plasma membrane permeability, chromatin condensation, reactive oxygen species and autophagy indicated that these withaferin A-silyl analogs appear to induce events characteristic of apoptosis-like and also autophagy leading to programmed cell death. These findings support the therapeutic potential of withaferin A-related steroids as anti-Leishmania and Trypanosoma agents.

Green, zero-waste pathway to fabricate supported nanocatalysts and anti-kinetoplastid agents from sugarcane bagasse

The conversion processes of sugarcane into direct-consumption sugar and juice are generating a tremendous amount of waste, the so-called sugarcane bagasse (SCB). Biochar preparation is among the practical solutions aiming to manage and valorize SCB into high added-value functional material (FM).Herein, we propose a novel zero-waste pathway to fabricate two FMs from one biomass. The SCB was first macerated and ultrasonicated to obtain the natural extract that served as bio-reducing medium. Then, the H2O/EtOH-extracted SCB was in-situ impregnated with a bimetallic solution of copper and silver nitrates. The process produced an intermediate composite (FM0), Ag/Cu-Ag+/Cu2+-loaded SCB which was carbonized to elaborate Ag/Cu-Biochar (FM1), free Ag/Cu nanoparticles (FM2) were obtained by microwaving the residual liquid waste.FM1 exhibited high catalytic activity for the total Fenton-like degradation of methylene blue. The experimental data followed the pseudo-first and the pseudo-second order rate laws with apparent degradation rate constants K1 45 10−3 min−1 and K2 0.115 g.mg−1.min−1, respectively. FM0, FM1 and FM2 were tested as new anti-kinetoplastid materials against two flagellated protozoans namely the Leishmania spp and the Trypanosoma cruzi. Notably, Ag/Cu (FM2) showed exceptional leishmanicidal and trypanocidal effects with IC50 values of 2.909 ± 0.051, 3.580 ± 0.016 and 3.020 ± 0.372 ppm for L.donovani, L. amazonensis and Trypanosoma cruzi, respectively.In this way, we combine green chemistry and agrowaste valorization in a full zero-waste process, to address the 3rd (indicator 3.3.5) and 6th (indicator 6.3.1) United Nations sustainable development goals, ″Good Health and Well-Being″ and ″Clean Water and Sanitation″.

6-Methyl-7-deazapurine nucleoside analogues as broad-spectrum antikinetoplastid agents

Kinetoplastid parasites are the causative agents of Chagas disease (CD), leishmaniasis and human African trypanosomiasis (HAT). Despite a sustained decrease in the number of HAT cases, more efforts are needed to discover safe and effective therapies against CD and leishmaniasis. Kinetoplastid parasites lack the capability to biosynthesize purines de novo and thus critically depend on uptake and processing of purines from host cells. As such, modified purine nucleoside analogues may act as broad-spectrum antikinetoplastid agents. This study assessed the in vitro activity profile of 7-modified 6-methyl tubercidin derivatives against Trypanosoma cruzi, Leishmania infantum, Trypanosoma brucei brucei and T. b. rhodesiense, and led to the identification of analogues that display activity against all these species, such as 7-ethyl (13) and 7-chloro (7) analogues. These selected analogues also proved sufficiently stable in liver microsomes to warrant in vivo follow-up evaluation.

Synthesis and evaluation of 3'-fluorinated 7-deazapurine nucleosides as antikinetoplastid agents.

Kinetoplastid parasites are the causative agents of neglected tropical diseases with an unmet medical need. These parasites are unable to synthesize the purine ring de novo, and therefore rely on purine salvage to meet their purine demand. Evaluating purine nucleoside analogs is therefore an attractive strategy to identify antikinetoplastid agents. Several anti-Trypanosoma cruzi and anti-Trypanosoma brucei 7-deazapurine nucleosides were previously discovered, with the removal of the 3'-hydroxyl group resulting in a significant boost in activity. In this work we therefore decided to assess the effect of the introduction of a 3'-fluoro substituent in 7-deazapurine nucleosides on the anti-kinetoplastid activities. Hence, we synthesized two series of 3'-deoxy-3'-fluororibofuranosyl and 3'-deoxy-3'-fluoroxylofuranosyl nucleosides comprising 7-deazaadenine and -hypoxanthine bases and assayed these for antiparasitic activity. Several analogs with potent activity against T.cruzi and T.brucei were discovered, indicating that a fluorine atom in the 3'-position is a promising modification for the discovery of antiparasitic nucleosides.

Synthesis and evaluation of a collection of purine-like C-nucleosides as antikinetoplastid agents.

The kinetoplastid parasites Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp. are the causative agents of neglected tropical diseases with a serious burden in several parts of the world. These parasites are incapable of synthesizing purines de novo, and therefore rely on ingenious purine salvage pathways to acquire and process purines from their host. Purine nucleoside analogs that may interfere with these pathways therefore constitute a privileged source of new antikinetoplastid agents. In this study, we synthetized a collection of C-nucleosides employing five different heterocyclic nucleobase surrogates. C-nucleosides are chemically and enzymatically stable and allow for extensive structural modification. Inspired by earlier 7-deazaadenosine nucleosides and known antileishmanial C-nucleosides, we introduced different modifications tailored towards antikinetoplastid activity. Both adenosine and inosine analogs were synthesized with the aim of discovering new antikinetoplastid hits and expanding knowledge of structure-activity relationships. Several promising hits with potent activity against Trypanosoma brucei, Trypanosoma cruzi and Leishmania infantum were discovered, and the nature of the nucleobase surrogate was found to have a profound influence on the selectivity profile of the compounds.

Sesquiterpenoids and flavonoids from Inula viscosa induce programmed cell death in kinetoplastids

Neglected tropical diseases such as leishmaniasis and American trypanosomiasis represent an increasing health problem. Current treatments are not satisfactory which remains an urgent need for novel, cheap and safe chemotherapies. In the course of our ongoing search for new potential anti-protozoal agents, this study aimed to perform a bio-guided fractionation of Inula viscosa (Asteraceae) using in vitro assays against three strains of Leishmania and Trypanosma genus. Eight known compounds were identified from the ethanolic extract of leaves, sesquiterpenoids (3 and 4) and flavonoids (5 and 6) were characterized as the main bioactive constituents. Sesquiterpene lactones 3 and 4 (IC50 values between 4.99 and 14.26 μM) showed promising antiparasitic activity against promastigotes of L. donovani, L. amazonensis and epimastigotes of T. cruzi. Their structures were successfully characterized by spectroscopic techniques including 1D and 2D NMR experiments. Furthermore, the main bioactive compounds 4, 5 and 6 displayed higher potency (IC50 values between 0.64 and 2.13 μM) against amastigotes of L. amazonensis than miltefosine (IC50 3.11 μM), and a low toxicity on macrophages cell line (SI > 45). The analysis of structure-activity relationship (SAR) of the anti-protozoal activity revealed that lactonization or oxidation enhanced the biological profile, suggesting that the hydrophobic moiety was presumably involved in the activity by increasing the affinity and/or cell membrane permeability. In order to get an insight into the mechanism of action of these compounds, programmed cell death (PCD) experiments were performed, and the obtained results suggest that the reported compounds induced PCD in the treated parasites. These results highlight that sesquiterpenoids and flavonoids from I. viscosa could constitute an interesting scaffold for the development of novel antikinetoplastid agents.

Synthesis and in vitro evaluation of new 5-substituted 6-nitroimidazooxazoles as antikinetoplastid agents

In continuation of our pharmacomodulation work on the nitroimidazooxazole series, we report the synthesis of new 5-substituted 6-nitroimidazooxazole derivatives. Our aim was to evaluate how functionalization of the 5-position of the 6-nitroimidazooxazole scaffold affects antileishmanial and antitrypanosomal in vitro activities. Twenty-one original compounds were synthesized and evaluated for their in vitro antileishmanial (L. donovani) and antitrypanosomal (T. cruzi) properties. Pallado-catalyzed cross-coupling reactions were used to introduce an aryl or ethynyl aryl substituent in 5-position from a 5-brominated-6-nitroimidazooxazole starting product. Unfortunately, the first series of compounds bearing an aryl group in 5-position presented limited in vitro activities against L. donovani and T. cruzi, with IC50 > 10 μM (vs 0.18 μM and 2.31 μM for the reference drugs amphotericin B and benznidazole respectively). Interestingly, the second series of compounds bearing an ethynyl aryl substituent in 5-position showed more promising, particularly against T. cruzi. Compounds 6a, 6b, 6c, 6g and 6h had better activity than the reference drug benznidazole (0.92 μM ≤ IC50 ≤ 2.18 μM vs IC50 = 2.31 μM), whereas the non-functionalized 2-methyl-6-nitro-2,3-dihydroimidazo [2,1-b]oxazole 2 was not active against T. cruzi (IC50 > 10 μM).

Recent synthetic efforts in the preparation of 2-(3,4)-alkenyl (aryl) quinoline molecules towards anti-kinetoplastid agents.

Leishmaniasis, Chagas disease and African sleeping sickness have been considered some of the most important tropical protozoan afflictions. As the number of drugs currently available to treat these human illnesses is severely limited and the majority has poor safety profiles and complicated administration schedules, actually there is an urgent need to develop new effective, safe and cost-effective drugs. Because quinoline alkaloids with antiprotozoal activity (quinine, chimanine, cryptolepine or huperzine groups) were historically and are still essential models for drug research to combat these parasitic infections, synthetic or semi-synthetic quinoline-based molecules are important for anti-kinetoplastid drug design approaches and synthetic methods of their preparation become a key task that is the central subject of this review. Its goal is to highlight the advances in the conventional and current syntheses of new 2-(3,4)-alkenyl (aryl) quinoline derivatives, which kill the most important kinetoplastid protozoa, – Leishmania and Trypanosoma and could be useful models for antileishmanial and antitrypanosomal research. An attempt has been made to present and discuss the more recent contributions in this field over the period 2015–2019, paying special attention to molecular design, synthetic efforts to new green reaction conditions for classical methods such as Skraup synthesis, Friedländer synthesis, Conrad–Limpach, Doebner–Miller, as well as contemporary methods like Gould–Jacobs, Meth–Cohn and Povarov reactions. This review includes brief general information on these neglected tropical diseases, their current chemotherapies, and primary natural models (quinoline alkaloids), suitable for development of anti-kinetoplastid quinoline-based agents. The main part of the review comprises critical discussion on the synthesis and chemistry of new quinolines diversely substituted by alkyl (alkenyl, aryl) fragments on the pyridine part of the quinoline skeleton, which could be considered interesting analogues of chimanine alkaloids. The methods described in this review were developed with the aim of overcoming the drawbacks of the traditional protocols using revolutionary precursors and strategies.

Withanolides from Withania aristata as Antikinetoplastid Agents through Induction of Programmed Cell Death.

Leishmaniasis and American trypanosomiasis are parasitic diseases that cause significant clinical, social and economic impact on the population of tropical and subtropical countries. Their current treatment is limited and presents multiple drawbacks, including high toxicity, high cost, lengthy treatment plans, as well as the emergence of resistant species. Therefore, there is a need to find new lead compounds with high potency against parasites and low toxicity in patients. In the present work, the bioguided fractionation of an endemic plant from the Canary Islands, Withania aristata, led to the identification of withanolide-type metabolites (1–3) with leishmanicidal and trypanocidal activities. Compounds 1 and 3 showed a significant dose-dependent inhibition effect on the proliferation of L. amazonensis promastigotes and T. cruzi epimastigotes, higher than the reference drugs, miltefosine and benznidazole, respectively. Moreover, compounds 1–3 were more potent (IC50 0.055–0.663 µM) than the reference drug against the intracellular amastigote stage of L. amazonensis, with a high selectivity index on murine macrophage cells (SI 58.66–216.73). Studies on the mechanism of death showed that the compounds induced programmed cell death or that which was apoptosis-like. The present findings underline the potential of withanolides as novel therapeutic antikinetoplastid agents.

Synthesis and in vitro antikinetoplastid activity of polyamine–hydroxybenzotriazole conjugates

Thirteen new polyamine derivatives coupled to hydroxybenzotriazole have been synthesized and evaluated for their in vitro antikinetoplastid activity. Trypanosoma Trypanothione reductase (TryR) was envisioned as a potential target. Among all tested molecules, only one compound, a N3-spermidine–benzotriazole derivative, displayed relevant inhibitory activity on this enzyme but was not active on parasites. The corresponding Boc-protected spermidine–benzotriazole was however trypanocidal against Trypanosoma brucei gambiense with an IC50 value of 1μM and was completely devoid of cytotoxicity. On the intramacrophage amastigotes of Leishmania donovani, a N2-spermidine conjugate of this series, exhibited an interesting IC50 value of 3μM associated with both low cytotoxicity against axenic Leishmania donovani. These new compounds are promising leads for the development of antikinetoplastid agents and their targets have to be deciphered.

Novel compounds to combat trypanosomatid infections: a medicinal chemical perspective

Introduction: The current therapeutic arsenal against the kinetoplastids Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp. is clearly inadequate and underscores the urgent need to develop new effective, safe and cost-effective drugs.Areas covered: Accordingly, this review of patented products and processes using anti-kinetoplastid agents provides insight into the identification of novel or more refined drugs. In this review, we describe products developed in recent years for the treatment of human African trypanosomiasis, American trypanosomiasis and leishmaniasis from a medicinal chemical perspective.Expert opinion: Applications so far have looked only superficially for candidate anti-trypanosomatid drugs and are deficient in the final stages of drug development studies, i.e., tolerance/safety, selectivity, drug-resistance, scaling-up, pharmacokinetic and pharmacodynamic assays. The ultimate goal for production of agents with anti-HAT activity has been the development of dicationic agents with parasite DNA-binding activity. Another goal for control of human African trypanosomiasis as well as for Chagas disease and leishmaniasis is the development of protease inhibitors. It should also be noted that several recent studies describing promising targets and compounds have not yet been patented. An effort should be made by foundations, international health organizations and pharmaceutical corporations to support analysis and development of promising new chemotherapeutic agents for controlling the trypanosomiasis and leishmaniasis.

Synthesis and antitubulin activity of N1- and N4-substituted 3,5-dinitro sulfanilamides against African trypanosomes and Leishmania.

Thirty analogues of N(1)-phenyl-3,5-dinitro-N(4),N(4)-di-n-propylsulfanilamide (GB-II-5, compound 3), a new antikinetoplastid antimitotic agent, have been synthesized and evaluated. The addition of simple functional groups to the N1 aromatic ring generally decreases antiparasitic and antimitotic potency, but placement of a dibutyl substituent at the N4 nitrogen to give N(1)-phenyl-3,5-dinitro-N(4),N(4)-di-n-butylsulfanilamide (compound 35) augments antitrypanosomal and antileishmanial activity. Compound 35 possesses IC(50) values of 0.12 and 2.6 microM against cultured T. brucei and L. donovani amastigote-like forms, surpassing the activity of compound 3 against these parasites by 3.4- and 1.9-fold, respectively. Compound 35 inhibits the assembly of leishmanial tubulin with an IC(50) of 6.9 microM and displays antimitotic effects in cultured T. brucei as assessed by flow cytometry, but shows little effect on purified mammalian tubulin, and displays 100-fold selectivity for trypanosomes over two mammalian cell lines. Although 3 and 35 were not effective in initial in vivo antitrypanosomal assays, the in vitro potency and selectivity of these compounds make N(1)-aryl-3,5-dinitro-N(4),N(4)-dialkylsulfanilamides a promising new class of antikinetoplastid agents that act on parasite tubulin.