Resolving the polycistronic aftermath: Essential role of topoisomerase IA in preventing R-loops in Leishmania.

Kinetoplastid parasites are "living bridges" in the evolution from prokaryotes to higher eukaryotes. The near-intronless genome of the kinetoplastid Leishmania exhibits polycistronic transcription which can facilitate R-loop formation. Therefore, to prevent such DNA-RNA hybrids, Leishmania has retained prokaryotic-like DNA Topoisomerase IA (LdTOPIA) in the course of evolution. LdTOPIA is an essential enzyme that is expressed ubiquitously and is adapted for the compartmentalized eukaryotic form in harboring functional bipartite nuclear localization signals. Although exhibiting greater homology to mycobacterial TOPIA, LdTOPIA could functionally complement the growth lethality of Escherichia coli TOPIA null GyrB ts strain at non-permissive temperatures. Purified LdTOPIA exhibits Mg2+-dependent relaxation of only negatively supercoiled DNA and preference towards single-stranded DNA substrates. LdTOPIA prevents nuclear R-loops as conditional LdTOPIA downregulated parasites exhibit R-loop formation and thereby parasite killing. The clinically used tricyclic antidepressant, norclomipramine could specifically inhibit LdTOPIA and lead to R-loop formation and parasite elimination. This comprehensive study therefore paves an avenue for drug repurposing against Leishmania.

Benznidazole treatment leads to DNA damage in Trypanosoma cruzi and the persistence of rare widely dispersed non-replicative amastigotes in mice.

Benznidazole is the front-line drug used to treat infections with Trypanosoma cruzi, the causative agent of Chagas disease. However, for reasons that are unknown, treatment failures are common. When we examined parasites that survived benznidazole treatment in mice using highly sensitive in vivo and ex vivo bioluminescence imaging, we found that recrudescence is not due to persistence of parasites in a specific organ or tissue that preferentially protects them from drug activity. Surviving parasites are widely distributed and located in host cells where the vast majority contained only one or two amastigotes. Therefore, infection relapse does not arise from a small number of intact large nests. Rather, persisters are either survivors of intracellular populations where co-located parasites have been killed, or amastigotes in single/low-level infected cells exist in a state where they are less susceptible to benznidazole. To better assess the nature of parasite persisters, we exposed infected mammalian cell monolayers to a benznidazole regimen that reduces the intracellular amastigote population to <1% of the pre-treatment level. Of host cells that remained infected, as with the situation in vivo, the vast majority contained only one or two surviving intracellular amastigotes. Analysis, based on non-incorporation of the thymidine analogue EdU, revealed these surviving parasites to be in a transient non-replicative state. Furthermore, treatment with benznidazole led to widespread parasite DNA damage. When the small number of parasites which survive in mice after non-curative treatment were assessed using EdU labelling, this revealed that these persisters were also initially non-replicative. A possible explanation could be that triggering of the T. cruzi DNA damage response pathway by the activity of benznidazole metabolites results in exit from the cell cycle as parasites attempt DNA repair, and that metabolic changes associated with non-proliferation act to reduce drug susceptibility. Alternatively, a small percentage of the parasite population may pre-exist in this non-replicative state prior to treatment.

Predicting anti-trypanosome effect of carbazole-derived compounds by powerful SVM with novel kernel function and comprehensive learning PSO.

In order to predict the anti-trypanosome effect of carbazole-derived compounds by quantitative structure-activity relationship, five models were established by the linear method, random forest, radial basis kernel function support vector machine, linear combination mix-kernel function support vector machine, and nonlinear combination mix-kernel function support vector machine (NLMIX-SVM). The heuristic method and optimized CatBoost were used to select two different key descriptor sets for building linear and nonlinear models, respectively. Hyperparameters in all nonlinear models were optimized by comprehensive learning particle swarm optimization with low complexity and fast convergence. Furthermore, the models' robustness and reliability underwent rigorous assessment using fivefold and leave-one-out cross-validation, y-randomization, and statistics including concordance correlation coefficient (CCC), [Formula: see text] , [Formula: see text] , and [Formula: see text] . Among all the models, the NLMIX-SVM model, which was established by support vector regression using a nonlinear combination of radial basis kernel function, sigmoid kernel function, and linear kernel function as a new kernel function, demonstrated excellent learning and generalization abilities as well as robustness: [Formula: see text] = 0.9581, mean square error (MSE) = 0.0199 for the training set and [Formula: see text] = 0.9528, MSE = 0.0174 for the test set. [Formula: see text] , [Formula: see text] , CCC, [Formula: see text] , [Formula: see text], and [Formula: see text] are 0.9539, 0.8908, 0.9752, 0.9529, 0.9528, and 0.9633, respectively. The NLMIX-SVM method proved to be a promising way in quantitative structure-activity relationship research. In addition, molecular docking experiments were conducted to analyze the properties of new derivatives, and a new potential candidate drug molecule was ultimately found. In summary, this study will provide help for the design and screening of novel anti-trypanosome drugs.

Venturicidin A affects the mitochondrial membrane potential and induces kDNA loss in Trypanosoma brucei.

Neglected tropical diseases caused by trypanosomatid parasites have devastating health and economic consequences, especially in tropical areas. New drugs or new combination therapies to fight these parasites are urgently needed. Venturicidin A, a macrolide extracted from Streptomyces, inhibits the ATP synthase complex of fungi and bacteria. However, its effect on trypanosomatids is not fully understood. In this study, we tested venturicidin A on a panel of trypanosomatid parasites using Alamar Blue assays and found it to be highly active against Trypanosoma brucei and Leishmania donovani, but much less so against Trypanosoma evansi. Using fluorescence microscopy, we observed a rapid loss of the mitochondrial membrane potential in T. brucei bloodstream forms upon venturicidin A treatment. Additionally, we report the loss of mitochondrial DNA in approximately 40%-50% of the treated parasites. We conclude that venturicidin A targets the ATP synthase of T. brucei, and we suggest that this macrolide could be a candidate for anti-trypanosomatid drug repurposing, drug combinations, or medicinal chemistry programs.

Novel 4-[4-(4-methylpiperazin-1-yl)phenyl]-6-arylpyrimidine derivatives and their antitrypanosomal activities against T.brucei.

Human African trypanosomiasis, or sleeping sickness, is a neglected tropical disease caused by Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense and is invariably fatal unless treated. Current therapies present limitations in their application, parasite resistance, or require further clinical investigation for wider use. Our work, informed by previous findings, presents novel 4-[4-(4-methylpiperazin-1-yl)phenyl]-6-arylpyrimidine derivatives with promising antitrypanosomal activity. In particular, 32 exhibits an in vitro EC50 value of 0.5 µM against Trypanosoma brucei rhodesiense, and analogues 29, 30 and 33 show antitrypanosomal activities in the <1 µM range. We have demonstrated that substituted 4-[4-(4-methylpiperazin-1-yl)phenyl]-6-arylpyrimidines present promising antitrypanosomal hit molecules with potential for further preclinical development.

Multifunctional Organometallic Compounds Active against Infective Trypanosomes: Ru(II) Ferrocenyl Derivatives with Two Different Bioactive Ligands.

Human African trypanosomiasis (HAT, sleeping sickness) and American trypanosomiasis (Chagas disease) are endemic zoonotic diseases caused by genomically related trypanosomatid protozoan parasites (Trypanosoma brucei and Trypanosoma cruzi, respectively). Just a few old drugs are available for their treatment, with most of them sharing poor safety, efficacy, and pharmacokinetic profiles. Only fexinidazole has been recently incorporated into the arsenal for the treatment of HAT. In this work, new multifunctional Ru(II) ferrocenyl compounds were rationally designed as potential agents against these pathogens by including in a single molecule 1,1'-bis(diphenylphosphino)ferrocene (dppf) and two bioactive bidentate ligands: pyridine-2-thiolato-1-oxide ligand (mpo) and polypyridyl ligands (NN). Three [Ru(mpo)(dppf)(NN)](PF6) compounds and their derivatives with chloride as a counterion were synthesized and fully characterized in solid state and solution. They showed in vitro activity on bloodstream T. brucei (EC50 = 31-160 nM) and on T. cruzi trypomastigotes (EC50 = 190-410 nM). Compounds showed the lowest EC50 values on T. brucei when compared to the whole set of metal-based compounds previously developed by us. In addition, several of the Ru compounds showed good selectivity toward the parasites, particularly against the highly proliferative bloodstream form of T. brucei. Interaction with DNA and generation of reactive oxygen species (ROS) were ruled out as potential targets and modes of action of the Ru compounds. Biochemical assays and in silico analysis led to the insight that they are able to inhibit the NADH-dependent fumarate reductase from T. cruzi. One representative hit induced a mild oxidation of low molecular weight thiols in T. brucei. The compounds were stable for at least 72 h in two different media and more lipophilic than both bioactive ligands, mpo and NN. An initial assessment of the therapeutic efficacy of one of the most potent and selective candidates, [Ru(mpo)(dppf)(bipy)]Cl, was performed using a murine infection model of acute African trypanosomiasis. This hit compound lacks acute toxicity when applied to animals in the dose/regimen described, but was unable to control parasite proliferation in vivo, probably because of its rapid clearance or low biodistribution in the extracellular fluids. Future studies should investigate the pharmacokinetics of this compound in vivo and involve further research to gain deeper insight into the mechanism of action of the compounds.

Synthesis and biological evaluation of orally active anti-Trypanosoma agents.

In previous studies, we developed anti-trypanosome tubulin inhibitors with promising in vitro selectivity and activity against Human African Trypanosomiasis (HAT). However, for such agents, oral activity is crucial. This study focused on further optimizing these compounds to enhance their ligand efficiency, aiming to reduce bulkiness and hydrophobicity, which should improve solubility and, consequently, oral bioavailability. Using Trypanosoma brucei brucei cells as the parasite model and human normal kidney cells and mouse macrophage cells as the host model, we evaluated 30 new analogs synthesized through combinatorial chemistry. These analogs have fewer aromatic moieties and lower molecular weights than their predecessors. Several new analogs demonstrated IC50s in the low micromolar range, effectively inhibiting trypanosome cell growth without harming mammalian cells at the same concentration. We conducted a detailed structure-activity relationship (SAR) analysis and a docking study to assess the compounds' binding affinity to trypanosome tubulin homolog. The results revealed a correlation between binding energy and anti-Trypanosoma activity. Importantly, compound 7 displayed significant oral activity, effectively inhibiting trypanosome cell proliferation in mice.

Optimization of benzenesulfonyl derivatives as anti-Trypanosomatidae agents: Structural design, synthesis, and pharmacological assessment against Trypanosoma cruzi and Leishmania infantum.

Leishmaniasis and Chagas disease are neglected tropical diseases caused by Trypanosomatidae parasites. Given the numerous limitations associated with current treatments, such as extended treatment duration, variable efficacy, and severe side effects, there is an urgent imperative to explore novel therapeutic options. This study details the early stages of hit-to-lead optimization for a benzenesulfonyl derivative, denoted as initial hit, against Trypanossoma cruzi (T. cruzi), Leishmania infantum (L. infantum) and Leishmania braziliensis (L. braziliensis). We investigated structure - activity relationships using a series of 26 newly designed derivatives, ultimately yielding potential lead candidates with potent low-micromolar and sub-micromolar activities against T. cruzi and Leishmania spp, respectively, and low in vitro cytotoxicity against mammalian cells. These discoveries emphasize the significant promise of this chemical class in the fight against Chagas disease and leishmaniasis.

Anti-trypanosomal Lignans Isolated from Salvadoran Peperomia pseudopereskiifolia.

A search for anti-trypanosomal natural compounds from plants collected in El Salvador, a country particularly endemic for Chagas disease, resulted in the isolation of five lignan-type compounds (1-5) from Peperomia pseudopereskiifolia. The lignan derivatives 1, 2, and 4 are new. Their absolute configuration was determined by chemical derivatization. Compounds 1, 5, 6, and 8 exhibited anti-trypanosomal activity against the amastigote form of T. cruzi comparable to that of the existing drug benznidazole.

Synthesis of new trypanocidal agents from the hybridisation of metronidazole and eugenol analogues.

Nitroimidazole compounds are well-known bioactive substances, and the structural activity relationship has been reported whereby the position of the nitro group within the imidazole ring has a large influence on the activity. This study focuses on synthesising new trypanocidal agents from the hybridisation of metronidazole with different natural phenols (eugenol, dihydroeugenol and guaiacol). Two different coupling methodologies have been explored in order to analyse the influence of the connector on bioactivity: i) classic direct esterification (AD compounds) and ii) "click" chemistry using a triazole connector (AC compounds). The in vitro trypanocidal tests show good results for both AC and AD hybrid compounds against both epimastigote and trypomastigote forms of T. cruzi. In silico studies showed positive data for most of the synthesised compounds and, in general present low toxicological risks. The AC compounds present lower ClogP (lipophilicity) values than those found for the AD series and higher TPSA (topological polar surface area) values, suggesting lower lipophilicity may be related to the presence of the triazole connector. The AD series compounds have higher Drug Score values than the AC series derivatives, suggesting better general properties for a pharmacological action.

In vitro and in vivo antitrypanosomal activity of the fresh leaves of Ranunculus Multifidus Forsk and its major compound anemonin against Trypanosoma congolense field isolate.

BACKGROUND: Animal trypanosomiasis is a major livestock problem due to its socioeconomic impacts in tropical countries. Currently used trypanocides are toxic, expensive, and the parasites have developed resistance to the existing drugs, which calls for an urgent need of new effective and safe chemotherapeutic agents from alternative sources such as medicinal plants. In Ethiopian traditional medicine fresh leaves of Ranunculus multifidus Forsk, are used for the treatment of animal trypanosomiasis. The present study aimed to evaluate the antitrypanosomal activity of the fresh leaves of R. multifidus and its major compound anemonin against Trypanosoma congolense field isolate. METHODS: Fresh leaves of R. multifidus were extracted by maceration with 80% methanol and hydro-distillation to obtain the corresponding extracts. Anemonin was isolated from the hydro-distilled extract by preparative TLC. For the in vitro assay, 0.1, 0.4, 2 and 4 mg/ml of the test substances were incubated with parasites and cessation or drop in motility of the parasites was monitored for a total duration of 1 h. In the in vivo assay, the test substances were administered intraperitoneally daily for 7 days to mice infected with Trypanosoma congolense. Diminazene aceturate and 1% dimethylsulfoxide (DMSO) were used as positive and negative controls, respectively. RESULTS: Both extracts showed antitrypanosomal activity although the hydro-distilled extract demonstrated superior activity compared to the hydroalcoholic extract. At a concentration of 4 mg/ml, the hydro-distilled extract drastically reduced motility of trypanosomes within 20 min. Similarly, anemonin at the same concentration completely immobilized trypanosomes within 5 min of incubation, while diminazene aceturate (28.00 mg/kg/day) immobilized the parasites within 10 min. In the in vivo antitrypanosomal assay, anemonin eliminates parasites at all the tested doses (8.75, 17.00 and 35.00 mg/kg/day) and prevented relapse, while in diminazene aceturate-treated mice the parasites reappeared on days 12 to 14. CONCLUSIONS: The current study demonstrated that the fresh leaves of R. multifidus possess genuine antitrypanosomal activity supporting the use of the plant for the treatment of animal trypanosomiasis in traditional medicine. Furthermore, anemonin appears to be responsible for the activity suggesting its potential as a scaffold for the development of safe and cost effective antitrypanosomal agent.

Activity of pyridyl-pyrazolone derivatives against Trypanosoma cruzi.

New affordable drugs are needed for the treatment of infection with the protozoan parasite Trypanosoma cruzi responsible for the Chagas disease (CD). Only two old drugs are currently available, nifurtimox and benznidazole (Bz) but they exhibit unwanted side effects and display a weak activity in the late chronic phase of the disease. In this context, we evaluated the activity of a series of aryl-pyrazolone derivatives against T cruzi, using both bloodstream trypomastigote and intracellular amastigote forms of the parasite. The test compounds originate from a series of anticancer agents targeting the immune checkpoint ligand PD-L1 and bear an analogy with known anti-trypanosomal pyrazolones. A first group of 6 phenyl-pyrazolones was tested, revealing the activity of a single pyridyl-pyrazolone derivative. Then a second group of 8 compounds with a common pyridyl-pyrazolone core was evaluated. The in vitro testing process led to the identification of two non-cytotoxic and highly potent molecules against the intracellular form of T. cruzi, with an activity comparable to Bz. Moreover, one compound revealed an activity largely superior to that of Bz against bloodstream trypomastigotes, while being non-cytotoxic (selectivity index >1000). Unfortunately, the compound showed little activity in vivo, most likely due to its very limited plasma stability. However, the study opens novel perspectives for the design of new anti-trypanosomal products and the mechanism of action of the compounds is discussed.

Trypanosoma cruzi killing and immune response boosting by novel phenoxyhydrazine-thiazole against Chagas disease.

Trypanosoma cruzi (T. cruzi) causes Chagas, which is a neglected tropical disease (NTD). WHO estimates that 6 to 7 million people are infected worldwide. Current treatment is done with benznidazole (BZN), which is very toxic and effective only in the acute phase of the disease. In this work, we designed, synthesized, and characterized thirteen new phenoxyhydrazine-thiazole compounds and applied molecular docking and in vitro methods to investigate cell cytotoxicity, trypanocide activity, nitric oxide (NO) production, cell death, and immunomodulation. We observed a higher predicted affinity of the compounds for the squalene synthase and 14-alpha demethylase enzymes of T. cruzi. Moreover, the compounds displayed a higher predicted affinity for human TLR2 and TLR4, were mildly toxic in vitro for most mammalian cell types tested, and LIZ531 (IC50 2.8 µM) was highly toxic for epimastigotes, LIZ311 (IC50 8.6 µM) for trypomastigotes, and LIZ331 (IC50 1.9 µM) for amastigotes. We observed that LIZ311 (IC50 2.5 µM), LIZ431 (IC50 4.1 µM) and LIZ531 (IC50 5 µM) induced 200 µg/mL of NO and JM14 induced NO production in three different concentrations tested. The compound LIZ331 induced the production of TNF and IL-6. LIZ311 induced the secretion of TNF, IFNγ, IL-2, IL-4, IL-10, and IL-17, cell death by apoptosis, decreased acidic compartment formation, and induced changes in the mitochondrial membrane potential. Taken together, LIZ311 is a promising anti-T. cruzi compound is not toxic to mammalian cells and has increased antiparasitic activity and immunomodulatory properties.

Suramin: Effectiveness of analogues reveals structural features that are important for the potent trypanocidal activity of the drug.

Suramin was the first effective drug for the treatment of human African sleeping sickness. Structural analogues of the trypanocide have previously been shown to be potent inhibitors of several enzymes. Therefore, four suramin analogues lacking the methyl group on the intermediate rings and with different regiochemistry of the naphthalenetrisulphonic acid groups and the phenyl rings were tested to establish whether they exhibited improved antiproliferative activity against bloodstream forms of Trypanosomes brucei compared to the parent compound. The four analogues exhibited low trypanocidal activity and weak inhibition of the antitrypanosomal activity of suramin in competition experiments. This indicates that the strong trypanocidal activity of suramin is most likely due to the presence of methyl groups on its intermediate rings and to the specific regiochemistry of naphthalenetrisulphonic acid groups. These two structural features are also likely to be important for the inhibition mechanism of suramin because DNA distribution and nucleus/kinetoplast configuration analyses suggest that the analogues inhibit mitosis while suramin inhibits cytokinesis.

Drug screening and development cascade for Chagas disease: an update of in vitro and in vivo experimental models.

Chagas disease is a tropical neglected disease that affects millions of people worldwide, still demanding a more effective and safer therapy, especially in its chronic phase which lacks a treatment that promotes substantial parasitological cure. The technical note of Romanha and collaborators published in 2010 aimed establish a guideline with the set of minimum criteria and decision gates for the development of new agents against Trypanosoma cruzi with the focus on developing new antichagasic drugs. In this sense, the present review aims to update this technical note, bringing the state of the art and new advances on this topic in recent years.

Improving in vitro screening compounds anti-Trypanosoma cruzi by GFP-expressing parasites.

BACKGROUND: Conventional microscopic counting is a widely utilised method for evaluating the trypanocidal effects of drugs on intracellular amastigotes. This is a low-cost approach, but it is time-consuming and reliant on the expertise of the microscopist. So, there is a pressing need for developing technologies to enhance the efficiency of low-cost anti-Trypanosoma cruzi drug screening. OBJECTIVES: In our laboratory, we aimed to expedite the screening of anti-T. cruzi drugs by implementing a fluorescent method that correlates emitted fluorescence from green fluorescent protein (GFP)-expressing T. cruzi (Tc-GFP) with cellular viability. METHODS: Epimastigotes (Y strain) were transfected with the pROCKGFPNeo plasmid, resulting in robust and sustained GFP expression across epimastigotes, trypomastigotes, and intracellular amastigotes. Tc-GFP epimastigotes and intracellular amastigotes were exposed to a serial dilution of benznidazole (Bz). Cell viability was assessed through a combination of microscopic counting, MTT, and fluorimetry. FINDINGS: The fluorescence data indicated an underestimation of the activity of Bz against epimastigotes (IC50 75 µM x 14 µM). Conversely, for intracellular GFP-amastigotes, both fluorimetry and microscopy yielded identical IC50 values. Factors influencing the fluorimetry approach are discussed. MAIN CONCLUSIONS: Our proposed fluorometric assessment is effective and can serve as a viable substitute for the time-consuming microscopic counting of intracellular amastigotes.

Listen to what the animals say: a systematic review and meta-analysis of sterol 14-demethylase inhibitor efficacy for in vivo models of Trypanosoma cruzi infection.

Sterol 14-demethylase (CYP51) inhibitors, encompassing new chemical entities and repurposed drugs, have emerged as promising candidates for Chagas disease treatment, based on preclinical studies reporting anti-Trypanosoma cruzi activity. Triazoles like ravuconazole (RAV) and posaconazole (POS) progressed to clinical trials. Unexpectedly, their efficacy was transient in chronic Chagas disease patients, and their activity was not superior to benznidazole (BZ) treatment. This paper aims to summarize evidence on the global activity of CYP51 inhibitors against T. cruzi by applying systematic review strategies, risk of bias assessment, and meta-analysis from in vivo studies. PubMed and Embase databases were searched for original articles, obtaining fifty-six relevant papers meeting inclusion criteria. Characteristics of animal models, parasite strain, treatment schemes, and cure rates were extracted. Primary outcomes such as maximum parasitaemia values, survival, and parasitological cure were recorded for meta-analysis, when possible. The risk of bias was uncertain in most studies. Animals treated with itraconazole, RAV, or POS survived significantly longer than the infected non-treated groups (RR = 4.85 [3.62, 6.49], P < 0.00001), and they showed no differences with animals treated with positive control drugs (RR = 1.01 [0.98, 1.04], P = 0.54). Furthermore, the overall analysis showed that RAV or POS was not likely to achieve parasitological cure when compared with BZ or NFX treatment (OD = 0.49 [0.31, 0.77], P = 0.002). This systematic review contributes to understanding why the azoles had failed in clinical trials and, more importantly, how to improve the animal models of T. cruzi infection by filling the gaps between basic, translational, and clinical research.

Design, synthesis and identification of novel molecular hybrids based on naphthoquinone aromatic hydrazides as potential trypanocide and leishmanicidal agents.

In pursuit of potential agents to treat Chagas disease and leishmaniasis, we report the design, synthesis, and identification novel naphthoquinone hydrazide-based molecular hybrids. The compounds were subjected to in vitro trypanocide and leishmanicidal activities. N'-(1,4-Dioxo-1,4-dihydronaphthalen-2-yl)-3,5-dimethoxybenzohydrazide (13) showed the best performance against Trypanosoma cruzi (IC50 1.83 µM) and Leishmania amazonensis (IC50 9.65 µM). 4-Bromo-N'-(1,4-dioxo-1,4-dihydronaphthalen-2-yl)benzohydrazide (16) exhibited leishmanicidal activity (IC50 12.16 µM). Regarding trypanocide activity, compound 13 was low cytotoxic to LLC-MK2 cells (SI = 95.28). Furthermore, through molecular modeling studies, the cysteine proteases cruzain, rhodesain and CPB2.8 were identified as the potential biological targets.

In Vitro and in Vivo Study of a Photostable Quinone Compound with Enhanced Therapeutic Efficacy against Chagas Disease.

Chagas disease, a neglected tropical disease caused by the protozoan Trypanosoma cruzi poses a significant health challenge in rural areas of Latin America. The current pharmacological options exhibit notable side effects, demand prolonged administration, and display limited efficacy. Consequently, there is an urgent need to develop drugs that are safe and clinically effective. Previously, we identified a quinone compound (designated as compound 2) with potent antiprotozoal activity, based on the chemical structure of komaroviquinone, a natural product renowned for its antitrypanosomal effects. However, compound 2 was demonstrated considerably unstable to light. In this study, we elucidated the structure of the light-induced degradation products of compound 2 and probed the correlation between the quinone ring's substituents and its susceptibility to light. Our findings led to the discovery of quinones with significantly enhanced light stability, some of which exhibiting antitrypanosomal activity. The most promising compound was evaluated for drug efficacy in a mouse model of Chagas disease, revealing where a notable reduction in blood parasitemia.

Lignans Isolated from Piper truncatum Act as New Potent Antitrypanosomal Compounds.

The hexane extract from twigs of Piper truncatum Vell (Piperaceae) displayed activity against Trypanosoma cruzi and was subjected to chromatographic steps to afford six dibenzylbutyrolactolic lignans, being four knowns: cubebin (1), (-)-9α-O-methylcubebin (2), (+)-9ß-O-methylcubebinin (3) and 3,4-dimethoxy-3,4-demethylenedioxycubebin (4) as well as two new, named truncatin A (5) and B (6). Initially, in vitro activity against trypomastigotes was evaluated and compounds 1, 4 and 6 exhibited EC50 values of 41.6, 21.0 and 39.6 µM, respectively. However, when tested against amastigotes, the relevant clinical form in the chronic phase of Chagas disease, compounds 1-6 displayed activities with EC50 values ranging from 1.6 to 13.7 µM. In addition, the mammalian cytotoxicity of compounds 1-6 was evaluated against murine fibroblasts (NCTC). Compounds 2, 3 and 4 exhibited reduced toxicity against NCTC cells (CC50>200 µM), resulting in SI values of>21.9,>14.5 and>121.9, respectively. Compound 4 showed the highest potency with an SI value twice superior to that determined by the standard drug benznidazole (SI>54.6) against the intracellular amastigotes. These data suggest that lignan 4 can be considered a possible scaffold for designing a new drug candidate for Chagas disease.