Limonene, a monoterpene abundant in essential oils of citrus plants, exhibits well-documented activity against both promastigote and amastigote forms of Leishmania in vitro and in vivo. Leishmania (L.) amazonensis is one of the etiological agents of localized and diffuse cutaneous leishmaniasis in the Americas, clinical forms frequently associated with limited therapeutic efficacy and recurrent treatment failure. Here, we show that limonene inhibits the biosynthesis of key isoprenoids in L. amazonensis promastigotes, including ubiquinone, dolichol, and ergosterol. Mechanistically, limonene disrupts the mevalonate pathway, reducing mevalonate synthesis by 69 %. The consequent decrease in ubiquinone levels impairs mitochondrial redox homeostasis, leading to increased mitochondrial reactive oxygen species, with a marked rise in hydrogen peroxide production following limonene exposure. In contrast, superoxide levels decline and reach a significant reduction at the highest limonene concentration tested. These redox disturbances are accompanied by pronounced mitochondrial morphological alterations, including severe vacuolization and degranulation of cytosolic and nuclear contents. Together, these findings demonstrate that limonene exerts pleiotropic effects on parasite sterol and isoprenoid metabolism and induces mitochondrial dysfunction. Our data identify the mevalonate pathway as a critical molecular target underlying limonene's antileishmanial mechanism of action and highlight its potential as a scaffold for the development of new therapeutic strategies against cutaneous leishmaniasis caused by L. amazonensis.

Complexes are emerging as promising alternatives for the treatment of neglected parasitic and viral infections, which urgently require new therapeutic strategies due to limited effective drugs. In this study, a series of [Pt(II)(phpy)(PR 3 )Cl] complexes, where phpy is 2-phenylpyridine, and PR 3 represents triphenylphosphine (PPh 3 ), 1,3,5-triaza-7-phosphaadamantane (PTA), para-benzoic acid-diphenylphosphine (PPh 2 (Ph p -COOH), or tris(2-carboxyethyl)phosphine (TCEP), are synthesized and systematically evaluated for their chemical properties and in vitro biological activities. Chemical reactivity, including ligand exchange with L-histidine and N -acetylcysteine, hydrophilic/lipophilic balance, and interactions with bovine serum albumin (BSA) and DNA, was correlated with biological outcomes. The novel TCEP complex exhibited exceptional chloride stability and intrinsic fluorescence but lacked antiviral and antileishmanial activity. The PTA derivative showed selective antileishmanial activity, achieving a selectivity index (SI) of 10.8 and reducing the infectivity index by 40% at 12 µM. Also, PTA showed selective antitumor activity in ovarian cancer (SI 9.1). In contrast, the PPh 2 (Ph p -COOH) derivative demonstrated significant antiviral activity, inhibiting Mayaro virus and Zika virus replication by 94% and 78%, respectively, at 50 µM. These findings underscore the potential of coordination chemistry to fine-tune biological activity and support the rational design of metal-based therapeutics for neglected diseases.

Leishmaniasis is one of the most important neglected diseases, classically characterized by three clinical forms that if left untreated can lead to skin lesions, lifelong scarring, or death depending on the parasite species. Unfortunately, treatment is unsatisfactory and the search for an improved therapy has been a priority. Gold compounds have emerged as promising candidates and among them, Au(I)bis-N-heterocyclic carbene (Au (BzTMX)2) has stood out. We have shown that it alters the plasma membrane permeability of Leishmania amazonensis and L. braziliensis, with superior activity for L. amazonensis. Herein, we moved a step forward towards the elucidation of its mechanism of action in L. amazonensis axenic amastigotes in vitro and in vivo. After 24 h incubation, Au(BzTMX)2 induced changes in safranin O uptake, reflecting the ultrastructural changes observed in mitochondria, especially cristae swelling, and oxygen consumption rates. Besides mitochondrial alterations, plasma membrane blebbing and the formation of multilamellar structures were also observed suggesting an autophagy-like process induction. In vivo, Au(BzTMX)2 was capable of delaying lesion progression, decreasing the total ulcerated area and leading to a marked reduction in the parasite burden of infected BALB/c mice. Taking all into consideration, our results give support to the current knowledge of the importance of gold compounds in therapeutics and open new possibilities for leishmaniasis treatment.

Gold(i) N-heterocyclic carbenes have been explored for their therapeutic potential against several diseases. Neglected tropical diseases, including leishmaniasis, Chagas disease, and viral infections, such as zika, mayaro, and chikungunya, urgently require new treatment options. The emergent SARS-CoV-2 also demands significant attention. Gold complexes have shown promise as alternative treatments for these conditions. Previously, gold(i)(1,3-bis(mesityl)imidazole-2-ylidene)Cl (AuIMesCl) demonstrated significant leishmanicidal and anti-Chikungunya virus activities. In this study, we synthesized and fully characterized a series of gold(i)(1,3-bis(mesityl)imidazole-2-ylidene)(SR) complexes, where SR includes thiolate donor species such as 1,3-thiazolidine-2-thione, 1,3-benzothiazole-2-thione, 2-mercaptopyrimidine, and 2-thiouracil. These compounds were stable in solution, and ligand exchange reactions with N-acetyl-l-cysteine indicated that complexes with SR ligands are more labile than those with chloride. Although the reactions are rapid, they reach equilibrium at varying molar ratios depending on the SR ligand. The increased lability of these compounds results in higher cytotoxicity to host cells, such as Vero E6 and bone marrow-differentiated macrophages, compared to AuIMesCl. Despite this, the compounds effectively inhibited viral replication, achieving 95.5% inhibition of Zika virus replication at 2 mu M with 96% host cell viability. Although active at low concentrations (similar to 2 mu M) against Leishmania (L.) amazonensis and Trypanosoma cruzi, their high cytotoxicity for macrophages confirmed AuIMesCl as a better candidate with a higher selectivity index. This work correlates the coordination chemistry of pyrimidines and thiazolidines with their in vitro biological activities against significant diseases. Novel gold(i)(NHC) containing thiopyrimidines and thiazolidines with promising antiviral and antiparasitic activity.

Countless efforts have been made to prevent and suppress the formation and spread of melanoma. Natural astaxanthin (AST; extracted from the alga Haematococcus pluvialis) showed an antitumor effect on various cancer cell lines due to its interaction with the cell membrane. This study aimed to characterize the antitumor effect of AST against B16F10-Nex2 murine melanoma cells using cell viability assay and evaluate its mechanism of action using electron microscopy, western blotting analysis, terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) assay, and mitochondrial membrane potential determination. Astaxanthin exhibited a significant cytotoxic effect in murine melanoma cells with features of apoptosis and autophagy. Astaxanthin also decreased cell migration and invasion in vitro assays at subtoxic concentrations. In addition, assays were conducted in metastatic cancer models in mice where AST significantly decreased the development of pulmonary nodules. In conclusion, AST has cytotoxic effect in melanoma cells and inhibits cell migration and invasion, indicating a promising use in cancer treatment.

Leishmaniasis is a worldwide disease caused by more than 20 species of Leishmania parasites. Leishmania amazonensis and L. braziliensis are among the main causative agents of cutaneous leishmaniasis, presenting a broad spectrum of clinical forms. As these pathologies lead to unsatisfactory treatment outcomes, the discovery of alternative chemotherapeutic options is urgently required. In this investigation, a leishmanicidal bioassay-guided fractionation of the growth media extract produced by Aspergillus terreus P63 led to the isolation of the cyclic depsipeptide beauvericin (1). The viability of L. amazonensis, L. braziliensis and mammalian cells (macrophages and L929 fibroblasts) was assessed in 1 incubated cultures. Leishmania promastigotes were sensitive to 1, with EC50 values ranging from 0.7 to 1.3 μM. Microscopy analysis indicated that Leishmania spp. parasites showed morphological abnormalities in a dose-dependent manner in the presence of 1. L. amazonensis intracellular amastigotes were more sensitive to 1 than promastigotes (EC50 = 0.8 ± 0.1 μM), with a good selectivity index (22-30). 1 reduced the infectivity index at very low concentrations, maintaining the integrity of the primary murine host cell for up to the highest concentration tested for 1. In vivo assays of 1 conducted using BALB/c mice infected with stationary-phase promastigotes of L. amazonensis in the tail base presented a significant reduction in the lesion parasite load. A second round of in vivo assays was performed to assess the efficacy of the topical use of 1. The results demonstrated a significant decrease in the total ulcerated area of mice treated with 1 when compared with untreated animals. Our results present promising in vitro and in vivo leishmanicidal effects of beauvericin, emphasizing that systemic inoculation of 1 led to a decrease in the parasite load at the lesion site, whereas topical administration of 1 delayed the progression of leishmaniasis ulcers, a cure criterion established for cutaneous leishmaniasis management.

Acanthamoeba castellanii is a free-living amoeba capable of causing keratitis in humans, with most cases related to contact lens wearers and surgical procedures. In addition, A. castellanii may cause pneumonia, granulomatous encephalitis, and skin lesions in immunocompromised individuals. Considering the lack of adequate treatment for acanthamoebiasis, the aim of this review is to assess relevant original articles that covered the current arsenal of drugs and models of organisms used in the field of experimental A. castellanii infection that have been published within the last 5 years (2018–2023) in journals indexed by the following databases: Electronic Library Online (SciELO), PubMed, Medical Literature Analysis and Retrieval System Online (Medline), Latin American and Caribbean Literature in Health Sciences (Lilacs), Google Academic, and Capes Periodical Portal. Thirty articles were selected, and the main findings showed that the available therapeutics for acanthamoebiasis are still limited and nonspecific, and no innovations have occurred in the last few years. In terms of novel chemotherapeutic advances, the last findings have focused on the activity of natural products (plant-based extracts), nanoemulsions, coated particles, and photodynamic association against A. castellanii, without advancing from the bench to bedside perspective. The choice of a non-representative model system for acanthamoebiasis, as well as the limitations of studies in vivo, impairs the advancement of toxicity analyses. Efforts should be made to expand the model systems used, standardize tests for evaluating anti-A. castellanii drug candidates, and increase and support research groups focusing on the biology of A. castellanii and the pharmacology of acanthamoebiasis.

Lutzomyia longipalpis is the primary vector of Leishmania infantum in the Americas and a permissive vector for Leishmania amazonensis. Previous studies showed that Leishmania infantum-infected hosts can release different volatile organic compounds (VOCs) compared with uninfected hosts, presenting a higher attractiveness to vectors. In this study, we aimed to evaluate a possible effect of L. amazonensis infection of golden hamsters in three parameters: attractiveness to Lu. longipalpis females; blood volume ingested by sand fly females; and VOCs released by the animals.. Attractiveness was measured indirectly by the number of Lu. longipalpis females that blood fed in each L. amazonensis-infected and uninfected animal. For VOCs extraction, solid phase micro extraction fibers were used, which were analyzed by gas chromatography-mass spectrometry. Behavioral trials did not show any effect of L. amazonensis infection on the attraction of sand flies nor difference on blood meal rates of Lu. longipalpis fed in both goups of hamsters. Additionally, there was no difference between the VOCs profiles of L. amazonensis-infected or uninfected hamsters.

Pt(II) and Pd(II) coordinating N-donor ligands have been extensively studied as anticancer agents after the success of cisplatin. In this work, a novel bidentate N-donor ligand, the N-[[4-(phenylmethoxy)phenyl]methyl]-2-pyridinemethanamine, was designed to explore the antiparasitic, antiviral and antitumor activity of its Pt(II) and Pd(II) complexes. Chemical and spectroscopic characterization confirm the formation of [MLCl2] complexes, where M=Pt(II) and Pd(II). Single crystal X-ray diffraction confirmed a square-planar geometry for the Pd(II) complex. Spectroscopic characterization of the Pt(II) complex suggests a similar structure. 1H NMR, 195Pt NMR and HR-ESI-MS(+) analysis of DMSO solution of complexes indicated that both compounds exchange the chloride trans to the pyridine for a solvent molecule with different reaction rates. The ligand and the two complexes were tested for in vitro antitumoral, antileishmanial, and antiviral activity. The Pt(II) complex resulted in a GI50 of 10.5 mu M against the NCI/ADR-RES (multidrug-resistant ovarian carcinoma) cell line. The ligand and the Pd(II) complex showed good anti-SARS-CoV-2 activity with around 65 % reduction in viral replication at a concentration of 50 mu M. The novel N-[[4-(phenylmethoxy)phenyl]methyl]-2-pyridinemethanamine (L) coordinates Pt(II) and Pd(II) giving two complexes of formula [MLCl2]. The ligand and Pd(II) complex impaired 65 % and 59 %, respectively, of SARS-CoV-2 replication at the viable concentrations of 50 mu M. In the in vitro antitumor evaluation, Pt(II) complex showed significant cytotoxicity with a GI50 of 10 mu M, and no selectivity in the panel of tumor cells evaluated. image

The quest for new drug candidates targeting neglected parasitic diseases has become increasingly urgent over the past decades. Advancements in formulating and optimizing drug delivery systems begin with basic research, including direct assays to evaluate the activity of molecules against parasitic stages maintained in laboratories; i.e., promastigotes. In the context of leishmaniasis, an endemic disease worldwide, the cultivation of Leishmania parasites can vary significantly across different laboratories. Factors such as culture media composition, pH, supplementation, and temperature can lead to varied drug responses in in vitro activity assays. This study aims to compile the parameters used in Leishmania spp. promastigotes cultivation protocols described in scientific articles published in indexed journals over the past ten years. The data reveal a lack of uniformity among Leishmania culture protocols, suggesting a potential bottleneck in comparing the leishmanicidal potential of in vitro drug candidates reported by different research groups. This condition is crucial to consider, because viability/inhibition assays should begin with fully-grown, healthy promastigote cultures capable of homogeneous division, thereby producing more reproducible results.

Chalcones are chemical precursors of flavonoids and exhibit a variety of biological properties, including anti-cancer, anti-inflammatory, and anti-malarial activities. According to the literature, different transition metal complexes of chalcones exhibit antitumor and antibacterial properties. Herein we report the synthesis, characterization, and the in vitro evaluation of antileishmanial, antiproliferative, and antiviral activities of novel copper(II)-2 '-hydroxy-4-benzyloxychalcone complexes. Two of the complexes (1 and 2) had the formula [Cu(L)(2)], and the other two (3 and 4) were characterized as [Cu(L)(phen)Cl], where L is the deprotonated form of the 2 '-hydroxy-4-benzyloxychalcones (HL1, is a fluorine substituted analog of HL2) and phen is 1,10- phenanthroline. Structures resolved by single-crystal X-ray diffraction showed that complexes 3 and 4 had a distorted square pyramid geometry, with chloride at the apical position. The stability of the complexes in dimethyl sulfoxide showed a significant variation. A wide range of ligand exchange kinetics was observed in the solution, influenced by chalcone fluorination and the presence of phenanthroline. Potential pharmacological applications were evaluated using in vitro assays for anti-proliferative, leishmanicidal, and antiviral activities. Complexes 1 and 3 showed cytostatic effects against the human breast tumor cell line (MCF-7, GI(50) = 4.6 and 1.0 mu M, respectively) that could be attributed to the free ligand HL1 (MCF-7, GI(50) = 1.16 mu M). Moreover, complex 1 showed higher selectivity to MCF-7 cells in comparison to murine immortalized 3T3 cells (GI(50) > 100 mu M). Complex 2 was inactive and toxic while complex 4 showed an unspecific cytostatic effect. Despite a weak leishmanicidal activity, at 25 mu M, complex 3 inhibited (85,1 %) the SARS-CoV-2 replication at 2 mu M. As complex 4 also showed good antiviral activity against SARS-CoV-2 (84,7 %), the antiviral activity seems to be related to copper(II)-phenanthroline fragment. This work demonstrates how simple changes in the structure of the ligand affect ligand exchange reactions and, consequently biological activity. It also expands the biological applications of Cu(II) chalcone complexes.

Malaria, leishmaniasis and Chagas disease are vector-borne protozoal infections with a disproportionately high impact on the most fragile societies in the world, and despite malaria-focused research gained momentum in the past two decades, both trypanosomiases and leishmaniases remain neglected tropical diseases. Affordable effective drugs remain the mainstay of tackling this burden, but toxicicty, inneficiency against later stage disease, and drug resistance issues are serious shortcomings. One strategy to overcome these hurdles is to get new therapeutics or inspiration in nature. Indeed, snake venoms have been recognized as valuable sources of biomacromolecules, like peptides and proteins, with antiprotozoal activity. This review highlights major snake venom components active against at least one of the three aforementioned diseases, which include phospholipases A2, metalloproteases, L-amino acid oxidases, lectins, and oligopeptides. The relevance of this repertoire of biomacromolecules and the bottlenecks in their clinical translation are discussed considering approaches that should increase the success rate in this arduous task. Overall, this review underlines how venom-derived biomacromolecules could lead to pioneering antiprotozoal treatments and how the drug landscape for neglected diseases may be revolutionized by a closer look at venoms. Further investigations on poorly studied venoms is needed and could add new therapeutics to the pipeline.

Leishmania amazonensis and L. braziliensis are the main etiological agents of the American Tegumentary Leishmaniasis (ATL). Taking into account the limited effectiveness and high toxicity of the current drug arsenal to treat ATL, novel options are urgently needed. Inspired by the fact that gold-based compounds are promising candidates for antileishmanial drugs, we studied the biological action of a systematic series of six (1)-(6) symmetric Au(I) benzyl and aryl-N-heterocyclic carbenes. All compounds were active at low micromolar concentrations with 50% effective concentrations ranging from 1.57 to 8.30 μM against Leishmania promastigotes. The mesityl derivative (3) proved to be the best candidate from this series, with a selectivity index ~13 against both species. The results suggest an effect of the steric and electronic parameters of the N-substituent in the activity. Intracellular infections were drastically reduced after 24h of (2)-(5) incubation in terms of infection rate and amastigote burden. Further investigations showed that our compounds induced significant parasites' morphological alterations and membrane permeability. Also, (3) and (6) were able to reduce the residual activity of three Leishmania recombinant cysteine proteases, known as possible targets for Au(I) complexes. Our promising results open the possibility of exploring gold complexes as leishmanicidal molecules to be further screened in in vivo models of infection.

A growing number of studies have demonstrated the in vitro potential of an impressive number of antileishmanial candidates in the past years. However, the lack of uniformity regarding the choice of cell types for cytotoxicity assays may lead to uncomparable and inconclusive data. In vitro assays relying solely on non-phagocytic cell models may not represent a realistic result as the effect of an antileishmanial agent should ideally be presented based on its cytotoxicity profile against reticuloendothelial system cells. In the present review, we have assembled studies published in the scientific literature from 2015 to 2021 that explored leishmanicidal candidates, emphasising the main host cell models used for cytotoxicity assays. The pros and cons of different host cell types as well as primary cells and cell lines are discussed in order to draw attention to the need to establish standardised protocols for preclinical testing when assessing new antileishmanial candidates.

Although macrophages have long been considered key players in the course of Leishmania infections, other non-professional phagocytes have lately been shown to maintain low levels of the parasite in safe intracellular niches. Recently, it was demonstrated that the adipose tissue is capable of harboring Old World L. (L.) infantum in mice. However, there is no evidence of experimental adipocyte infection with New World Leishmania species so far. In addition, it was not known whether adipocytes would be permissive for formation of the unique, large and communal parasitophorous vacuoles that are typical of L. (L.) amazonensis in macrophages. Here we evaluated the ability of L. (L.) amazonensis and L. (V.) braziliensis promastigotes and amastigotes to infect 3T3-L1 fibroblast-derived adipocytes (3T3-Ad) using light and transmission electron microscopy. Our results indicate that amastigotes and promastigotes of both species were capable of infecting and surviving inside pre- and fully differentiated 3T3-Ad for up to 144 h. Importantly, L. (L.) amazonensis amastigotes resided in large communal parasitophorous vacuoles in pre-adipocytes, which appeared to be compressed between large lipid droplets in mature adipocytes. In parallel, individual L. (V.) braziliensis amastigotes were detected in single vacuoles 144 h post-infection. We conclude that 3T3-Ad may constitute an environment that supports low loads of viable parasites perhaps contributing to parasite maintenance, since amastigotes of both species recovered from these cells differentiated into replicative promastigotes. Our findings shed light on the potential of a new host cell model that can be relevant to the persistence of New World Leishmania species.

Neglected tropical diseases such as Leishmaniasis and Chikungunya fever are worldwide public health challenges mainly affecting tropical and subtropical countries. One cationic [Cu-(1)(NHC)(2)](+) (4) and two neutral [Cu(I)(NHC)CI] complexes, where NHC=1,3-bis(mesityl)imidazole-2-ylidene (IMes) (5) or 1,3-bis-(2,6-diisopropylphenyl)imidazole-2-ylidene (IPr) (6), had their in vitro activity evaluated towards Leishmonia ornozonensis and Chikungunya virus (CHIKV). The compound (6) inhibited 95% of L. omozonensis infection in RAW macrophages at 10 mu M and 90% of the CHIKV replication at 2 mu M in BHK-21 cells. Otherwise, the other compounds showed higher cytotoxicity in BHK-21 and RAW or lower antiparasitic or antiviral activities. The best activity of compound 6 can be explained by slower ligand exchange with solvent molecules measured by H-1 NMR technique and the best hydrophilic/lipophilic balance (log P= -0.684 +/- 0.055) in the series determined by shake flask method. Antioxidant activity measured by reduction of DPPH revealed a moderate redox ability of all complexes. The binding constant of (6) with bovine serum albumin (BSA) represents the weakest in the series (10(3)). The chemical and in vitro evaluation reported here represent a novel application and chemical insights for the design of [Cu(I)(NHC)L] metallodrugs for these infectious diseases.

Chagas disease (CD), caused by Trypanosoma cruzi, occurs in several countries in Latin America and non-endemic countries. Heterogeneity among T. cruzi population has been the Achilles' heel to find a better treatment for CD. In this study, we characterized the biochemical parameters and mitochondrial bioenergetics of epimastigotes differentiated from eight T. cruzi isolates (I1-I8) obtained from Brazilian CD patients. Molecular analysis of parasites DTUs grouped all of them as TcII. The profile of the growth curves in axenic cultures was distinct among them, except for I1 and I3 and I2 and I4. Doubling times, growth rates, cell body length, and resistance to benznidazole were also significantly different among them. All the isolates were more glucose-dependent than other T. cruzi strains adapted to grow in axenic culture. Mitochondrial bioenergetics analysis showed that each isolate behaved differently regarding oxygen consumption rates in non-permeabilized and in digitonin-permeabilized cells in the presence of a complex II-linked substrate. When complex IV-linked respiratory chain substrate was used to provide electrons to the mitochondrial respiratory chain (MRC), similarity among the isolates was higher. Our findings show that TcII epimastigotes derived from patients' trypomastigotes displayed their own characteristics in vitro, highlighting the intra-TcII diversity, especially regarding the functionality of mitochondrial respiratory complexes II and IV. Understanding T. cruzi intraspecific biological features help us to move a step further on our comprehension regarding parasite's survival and adaptability offering clues to improve the development of new therapies for CD.

Leishmaniasis is one of the most neglected parasitic infections of the world and current therapeutic options show several limitations. In the search for more effective drugs, plant compounds represent a powerful natural source. Artemisinin is a sesquiterpene lactone extracted from Artemisia annua L. leaves, from which dihydroartemisinin (DQHS) and artesunic acid (AA)/artesunate are examples of active derivatives. These lactones have been applied successfully on malaria therapy for decades. Herein, we investigated the sensitivity of Leishmania braziliensis, one of the most prevalent Leishmania species that cause cutaneous manifestations in the New World, to artemisinin, DQHS, and AA. L. braziliensis promastigotes and the stage that is targeted for therapy, intracelular amastigotes, were more sensitive to DQHS, showing EC50 of 62.3 ± 1.8 and 8.9 ± 0.9 μM, respectively. Cytotoxicity assays showed that 50% of bone marrow-derived macrophages cultures were inhibited with 292.8 ± 3.8 μM of artemisinin, 236.2 ± 4.0 μM of DQHS, and 396.8 ± 6.7 μM of AA. The control of intracellular infection may not be essentially attributed to the production of nitric oxide. However, direct effects on mitochondrial bioenergetics and H2O2 production appear to be associated with the leishmanicidal effect of DQHS. Our data provide support for further studies of artemisinin and derivatives repositioning for experimental leishmaniasis.

Here we highlight coinfections of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with ectoparasites, helminths, and protozoa, described in the literature, and the urgent need to understand the conditions of these associated pathologies. We emphasize the notion that such information is crucial for the continuity of measures that have been used for decades to control neglected parasitic diseases.