Psilostachyin C: a natural compound with trypanocidal activity

In silico toxicologic profile and in vivo trypanocidal activity of estafietin, a sesquiterpene lactone isolated from Stevia alpina Griseb

Chagas disease is an infection caused by the protozoan Trypanosoma cruzi, affecting 6-8 million people worldwide. Only two drugs are available for its treatment, having a limited efficacy and adverse side-effects. Estafietin is a sesquiterpene lactone isolated from Stevia alpina with in vitro activity against T. cruzi and low cytotoxicity against mammalian cells. The aim of this work was to predict the toxicologic profile of estafietin by in silico methods and assess its in vivo activity on a murine model of Chagas disease. Estafietin showed low toxicity according to pkCSM web tool and passed the PAINS filter from PAINS-remover web server. The treatment of infected mice with 1 mg/Kg/day of estafietin for five consecutive days administrated by intraperitoneal route significatively decreased parasitemia levels and reduced inflammatory infiltrates and myocyte damage on muscle tissue. These results suggest that estafietin had effect both on acute and chronic stages of the infection.

Identification of potential biological target for trypanocidal sesquiterpene lactones derivatives

Sesquiterpene lactones are natural products of the Asteraceae family that have shown trypanocidal activity against Trypanosoma cruzi, even exceeding the effectiveness of drugs used in the treatment of American trypanosomiasis. However, there is no agreement on their mechanism of action and their specificity to interact with parasite proteins. For this reason, we aimed to find biological targets that can interact with these compounds by reverse virtual screening with ligand pharmacophores and putative binding sites and the use of bioinformatic databases. Therefore, 41 possible biological targets were found, and four of them (with crystallized proteins), interfering directly or indirectly in the trypanosomatid redox system, were studied in detail. As a first approach, we focused on the study of trypanothione reductase, and protein-ligand interaction fingerprint analyses were performed to find binding site determinants that promote a possible inhibition of the enzyme. This study contributes to the understanding of one of the putative mechanisms of action of sesquiterpene lactones on one of the numerous suggested targets.Communicated by Ramaswamy H. Sarma.

Sesquiterpenoids from the Inflorescence of Ambrosia artemisiifolia

The successful invasion of Ambrosia artemisiifolia is largely due to allelopathy. As an invasive alien plant, A. artemisiifolia has spread rapidly in Asia and Europe. Studies have shown that sesquiterpenoids play an important role in plant allelopathy. However, it is unclear whether the inflorescence of A. artemisiifolia also contains allelopathic components. In this paper, our phytochemical research focuses on the inflorescence of A. artemisiifolia. Twenty sesquiterpenoids, including four new ones (1–4) were isolated through successive chromatographic columns and identified by spectroscopic methods. At a concentration of 200 μg/mL, all the compounds tested were evaluated for their allelopathic activities on seedling growth of wheat. Our results indicate that nine compounds inhibited both the root and shoot growth of seedlings. Compounds 14, 15, 17, and 20 significantly inhibited root length, which was more than 50% shorter than the control. This study identified the chemical profile of the sesquiterpenoids occurring in the inflorescence of A. artemisiifolia. The bioactivity screening results provide further understanding of the chemical basis of allelopathy in A. artemisiifolia.

Psilostachyins as trypanocidal compounds: Bioguided fractionation of Ambrosia tenuifolia chemically modified extract

This work focusses on the chemical diversification of an Ambrosia tenuifolia extract and its bioguided fractionation, aiming to unveil the chemical entity responsible for the trypanocidal activity. Besides, a revision of the phytochemical study of this species, based on previous reports of the antiparasitic psilostachyins A and C as main compounds, was conducted. To improve the biological properties of a plant extract through a simple chemical reaction, the oxidative diversification of the dichloromethane extract of this plant species was carried out. A bioguided fractionation of a chemically modified extract was performed by evaluating the inhibitory activity against Trypanosoma cruzi trypomastigotes. This experiment led to the isolation of one of the most active compounds. In general terms, epoxidized metabolites were obtained as a result of the oxidation of the major metabolite of the species. The trypanocidal activity of some tested metabolites overperformed the reference drug, benznidazole, displaying no cytotoxicity at trypanocidal concentrations. Key structure-activity relationships were obtained for designing previously undescribed antiparasitic sesquiterpene lactones.

In Vitro, In Vivo, and In Silico Studies of Cumanin Diacetate as a Potential Drug against Trypanosoma cruzi Infection

The sesquiterpene lactones cumanin, helenalin, and hymenin and their semisynthetic derivatives were evaluated against Trypanosoma cruzi epimastigotes. The cytotoxicity of the compounds was evaluated on murine splenocytes. Cumanin diacetate was one of the most active and selective compounds [IC₅₀ = 3.20 ± 0.52 μg/mL, selectivity index (SI) = 26.0]. This sesquiterpene lactone was selected for its evaluation on trypomastigote and amastigote forms of the parasite. The diacetylated derivative of cumanin showed moderate activity on trypomastigotes (IC₅₀ = 32.4 ± 5.8 μg/mL). However, this compound was able to efficiently inhibit parasite replication with an IC₅₀ value of 2.2 ± 0.05 μg/mL against the amastigote forms. Cumanin diacetate showed selectivity against the intracellular forms of Trypanosoma cruzi with an SI value of 52.7. This cumanin analogue was also active on an in vivo model of Chagas disease, leading to a reduction in the parasitemia levels in comparison with nontreated animals. Histopathological analysis of skeletal muscular tissues from treated mice showed only focal interstitial lymphocyte inflammatory infiltrates with slight myocyte necrosis; in contrast, nontreated animals showed severe lymphocyte inflammatory infiltrates with necrosis of the myocytes. A molecular docking study of cumanin and its derivatives on trypanothione reductase from T. cruzi (TcTR) was performed. The results of ΔG docking achieved let the identification of diacetylated and O-alkylated derivatives of cumanin as good inhibitors of TcTR. Cumanin diacetate could be considered a potential candidate for further studies for the development of new therapies against Chagas disease.

Natural-Product-Based Solutions for Tropical Infectious Diseases

About half of the world's population and 80% of the world's biodiversity can be found in the tropics. Many diseases are specific to the tropics, with at least 41 diseases caused by endemic bacteria, viruses, parasites, and fungi. Such diseases are of increasing concern, as the geographic range of tropical diseases is expanding due to climate change, urbanization, change in agricultural practices, deforestation, and loss of biodiversity. While traditional medicines have been used for centuries in the treatment of tropical diseases, the active natural compounds within these medicines remain largely unknown. In this review, we describe infectious diseases specific to the tropics, including their causative pathogens, modes of transmission, recent major outbreaks, and geographic locations. We further review current treatments for these tropical diseases, carefully consider the biodiscovery potential of the tropical biome, and discuss a range of technologies being used for drug development from natural resources. We provide a list of natural products with antimicrobial activity, detailing the source organisms and their effectiveness as treatment. We discuss how technological advancements, such as next-generation sequencing, are driving high-throughput natural product screening pipelines to identify compounds with therapeutic properties. This review demonstrates the impact natural products from the vast tropical biome have in the treatment of tropical infectious diseases and how high-throughput technical capacity will accelerate this discovery process.

Lychnopholide in Poly(d,l-Lactide)-Block-Polyethylene Glycol Nanocapsules Cures Infection with a Drug-Resistant Trypanosoma cruzi Strain at Acute and Chronic Phases

Chagas disease remains neglected, and current chemotherapeutics present severe limitations. Lychnopholide (LYC) at low doses loaded in polymeric poly(d,l-lactide)-block-polyethylene glycol (PLA-PEG) nanocapsules (LYC-PLA-PEG-NC) exhibits anti-Trypanosoma cruzi efficacy in mice infected with a partially drug-resistant strain. This study reports the efficacy of LYC-PLA-PEG-NC at higher doses in mice infected with a T. cruzi strain resistant to benznidazole (BZ) and nifurtimox (NF) treated at both the acute phase (AP) and the chronic phase (CP) of infection by the oral route. Mice infected with the T. cruzi VL-10 strain were treated by the oral route with free LYC (12 mg/kg of body weight/day), LYC-PLA-PEG-NC (8 or 12 mg/kg/day), or BZ at 100 mg/kg/day or were not treated (controls). Treatment efficacy was assessed by hemoculture (HC), PCR, enzyme-linked immunosorbent assay (ELISA), heart tissue quantitative PCR (qPCR), and histopathology. According to classical cure criteria, treatment with LYC-PLA-PEG-NC at 12 mg/kg/day cured 75% (AP) and 88% (CP) of the animals, while at a dose of 8 mg/kg/day, 43% (AP) and 43% (CP) were cured, showing dose-dependent efficacy. The negative qPCR results for heart tissue and the absence of inflammation/fibrosis agreed with the negative results obtained by HC and PCR. Thus, the mice treated with the highest dose could be considered 100% cured, in spite of a low ELISA reactivity in some animals. No cure was observed in animals treated with free LYC or BZ or the controls. These results are exceptional in terms of experimental Chagas disease chemotherapy and provide evidence of the outstanding contribution of nanotechnology in mice infected with a T. cruzi strain totally resistant to BZ and NF at both phases of infection. Therefore, LYC-PLA-PEG-NC has great potential as a new treatment for Chagas disease and deserves further investigations in clinical trials.

Asteraceae Plants as Sources of Compounds Against Leishmaniasis and Chagas Disease

Leishmaniasis and Chagas disease cause great impact on social and economic aspects of people living in developing countries. The treatments for these diseases are based on the same regimen for over 40 years, thus, there is an urgent need for the development of new drugs. In this scenario, Asteraceae plants (a family widely used in folk medicine worldwide) are emerging as an interesting source for new trypanocidal and leishmanicidal compounds. Herein, we provide a non-exhaustive review about the activity of plant-derived products from Asteraceae with inhibitory action toward Leishmania spp. and T. cruzi. Special attention was given to those studies aiming the isolation (or identification) of the bioactive compounds. Ferulic acid, rosmarinic acid, and ursolic acid (Baccharis uncinella DC.) were efficient to treat experimental leishmaniasis; while deoxymikanolide (Mikania micrantha) and (+)-15-hydroxy-labd-7-en-17-al (Aristeguietia glutinosa Lam.) showed in vivo anti-T. cruzi action. It is also important to highlight that several plant-derived products (compounds, essential oils) from Artemisia plants have shown high inhibitory potential against Leishmania spp., such as artemisinin and its derivatives. In summary, these compounds may help the development of new effective agents against these neglected diseases.

Activity of Estafietin and Analogues on Trypanosoma cruzi and Leishmania braziliensis

Sesquiterpene lactones are naturally occurring compounds mainly found in the Asteraceae family. These types of plant metabolites display a wide range of biological activities, including antiprotozoal activity and are considered interesting structures for drug discovery. Four derivatives were synthesized from estafietin (1), isolated from Stevia alpina (Asteraceae): 11βH,13-dihydroestafietin (2), epoxyestafietin (3a and 3b), 11βH,13-methoxyestafietin, (4) and 11βH,13-cianoestafietin. The antiprotozoal activity against Trypanosoma cruzi and Leishmania braziliensis of these compounds was evaluated. Epoxyestafietin was the most active compound against T. cruzi trypomastigotes and amastigotes (IC₅₀ values of 18.7 and 2.0 µg/mL, respectively). Estafietin (1) and 11βH,13-dihydroestafietin (2) were the most active and selective compounds on L. braziliensis promastigotes (IC₅₀ values of 1.0 and 1.3 μg/mL, respectively). The antiparasitic activity demonstrated by estafietin and some of its derivatives make them promising candidates for the development of effective compounds for the treatment of Chagas disease and leihsmaniasis.

Primary targets of the sesquiterpene lactone deoxymikanolide on Trypanosoma cruzi

BACKGROUND

Deoxymikanolide is a sesquiterpene lactone isolated from Mikania micrantha and M. variifolia which, has previously demonstrated in vitro activity on Trypanosoma cruzi and in vivo activity on an infected mouse model.

PURPOSE

Based on these promising findings, the aim of this study was to investigate the mechanism of action of this compound on different parasite targets.

METHODS

The interaction of deoxymikanolide with hemin was examined under reducing and non- reducing conditions by measuring modifications in the Soret absorption band of hemin; the thiol interaction was determined spectrophotometrically through its reaction with 5,5'-dithiobis-2-nitrobenzoate in the presence of glutathione; activity on the parasite antioxidant system was evaluated by measuring the activity of the superoxide dismutase and trypanothione reductase enzymes, together with the intracellular oxidative state by flow cytometry. Superoxide dismutase and trypanothione reductase activities were spectrophotometrically tested. Cell viability, phosphatidylserine exposure and mitochondrial membrane potential were assessed by means of propidium iodide, annexin-V and rhodamine 123 staining, respectively; sterols were qualitatively and quantitatively tested by TLC; ultrastructural changes were analyzed by transmission electron microscopy. Autophagic cells were detected by staining with monodansylcadaverine.

RESULTS

Deoxymikanolide decreased the number of reduced thiol groups within the parasites, which led to their subsequent vulnerability to oxidative stress. Treatment of the parasites with the compound produced a depolarization of the mitochondrial membrane even though the plasma membrane permeabilization was not affected. Deoxymikanolide did not affect the intracellular redox state and so the mitochondrial dysfunction produced by this compound could not be attributed to ROS generation. The antioxidant defense system was affected by deoxymikanolide at twenty four hours of treatment, when both an increased oxidative stress and decreased activity of superoxide dismutase and trypanothione reductase (40 and 60% respectively) were observed. Both the oxidative stress and mitochondrial dysfunction induce parasite death by apoptosis and autophagy.

CONCLUSION

Based on our results, deoxymikanolide would exert its anti-T cruzi activity as a strong thiol blocking agent and by producing mitochondrial dysfunction.

Bioassay-Guided Isolation and Structure Elucidation of Fungicidal and Herbicidal Compounds from Ambrosia salsola (Asteraceae)

The discovery of potent natural and ecofriendly pesticides is one of the focuses of the agrochemical industry, and plant species are a source of many potentially active compounds. We describe the bioassay-guided isolation of antifungal and phytotoxic compounds from the ethyl acetate extract of Ambrosia salsola twigs and leaves. With this methodology, we isolated and identified twelve compounds (four chalcones, six flavonols and two pseudoguaianolide sesquiterpene lactones). Three new chalcones were elucidated as (S)-β-Hydroxy-2',3,4,6'-tetrahydroxy-5-methoxydihydrochalcone (salsolol A), (S)-β-Hydroxy-2',4,4',6'-tetrahydroxy-3-methoxydihydrochalcone (salsolol B), and (R)-α, (R)-β-Dihydroxy-2',3,4,4',6'- pentahydroxydihydrochalcone (salsolol C) together with nine known compounds: balanochalcone, six quercetin derivatives, confertin, and neoambrosin. Chemical structures were determined based on comprehensive direct analysis in real time-high resolution mass spectrometry (HR-DART-MS), as well as 1D and 2D NMR experiments: Cosy Double Quantum Filter (DQFCOSY), Heteronuclear Multiple Quantum Coherence (HMQC) and Heteronuclear Multiple Bond Coherence (HMBC), and the absolute configurations of the chalcones were confirmed by CD spectra analysis. Crystal structure of confertin was determined by X-ray diffraction. The phytotoxicity of purified compounds was evaluated, and neoambrosim was active against Agrostis stolonifera at 1 mM, while confertin was active against both, Lactuca sativa and A. stolonifera at 1 mM and 100 µM, respectively. Confertin and salsolol A and B had IC50 values of 261, 275, and 251 µM, respectively, against Lemna pausicotata (duckweed). The antifungal activity was also tested against Colletotrichum fragariae Brooks using a thin layer chromatography bioautography assay. Both confertin and neoambrosin were antifungal at 100 µM, with a higher confertin activity than that of neoambrosin at this concentration.

Active Natural Product Scaffolds against Trypanosomatid Parasites: A Review

Neglected tropical diseases caused by trypanosomatid parasites are a continuing and escalating problem, which devastate the less economically developed cultures in countries in which they are endemic by impairing both human and animal health. Current drugs for these diseases are regarded as out-of-date and expensive, with unacceptable side-effects and mounting parasite resistance, meaning there is an urgent need for new therapeutics. Natural products have long been a source of potent, structurally diverse bioactive molecules. Herein are reviewed natural products with reported trypanocidal activity, which have been clustered based on core structural similarities, to aid the future discovery of new trypanocidal core motifs with potential routes to synthetically accessible natural product cores suggested.

In Silico Studies Designed to Select Sesquiterpene Lactones with Potential Antichagasic Activity from an In-House Asteraceae Database

Chagas disease is an endemic disease caused by Trypanosoma cruzi, which affects more than eight million people, mostly in the Americas. A search for new treatments is necessary to control and eliminate this disease. Sesquiterpene lactones (SLs) are an interesting group of secondary metabolites characteristic of the Asteraceae family that have presented a wide range of biological activities. From the ChEMBL database, we selected a diverse set of 4452, 1635, and 1322 structures with tested activity against the three T. cruzi parasitic forms: amastigote, trypomastigote, and epimastigote, respectively, to create random forest (RF) models with an accuracy of greater than 74 % for cross-validation and test sets. Afterward, a ligand-based virtual screen of the entire SLs of the Asteraceae database stored in SistematX (1306 structures) was performed. In addition, a structure-based virtual screen was also performed for the same set of SLs using molecular docking. Finally, using an approach combining ligand-based and structure-based virtual screening along with the equations proposed in this study to normalize the probability scores, we verified potentially active compounds and established a possible mechanism of action.

Germacranolide-type sesquiterpene lactones from Smallanthus sonchifolius with promising activity against Leishmania mexicana and Trypanosoma cruzi

Background

Leishmaniasis and Chagas disease are life-threatening illnesses caused by the protozoan parasites Leishmania spp. and Trypanosoma cruzi, respectively. They are known as “neglected diseases” due to the lack of effective drug treatments and the scarcity of research work devoted to them. Therefore, the development of novel and effective drugs is an important and urgent need. Natural products are an important source of bioactive molecules for the development of new drugs. In this study, we evaluated the activity of enhydrin, uvedalin and polymatin B, three sesquiterpene lactones (STLs) isolated from Smallanthus sonchifolius, on Leishmania mexicana (MNYC/BZ/62/M) and Trypanosoma cruzi (Dm28c). In addition, the in vivo trypanocidal activity of enhydrin and uvedalin and the effects of these STLs on parasites’ ultrastructure were evaluated.

Methods

The inhibitory effect of the three STLs on the growth of L. mexicana amastigotes and promastigotes as well as T. cruzi epimastigotes was evaluated in vitro. The changes produced by the STLs on the ultrastructure of parasites were examined by transmission electron microscopy (TEM). Enhydrin and uvedalin were also studied in a murine model of acute T. cruzi infection (RA strain). Serum activities of the hepatic enzymes alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase were used as biochemical markers of hepatotoxicity.

Results

The three compounds exhibited leishmanicidal activity on both parasite forms with IC₅₀ values of 0.42–0.54 μg/ml for promastigotes and 0.85–1.64 μg/ml for intracellular amastigotes. Similar results were observed on T. cruzi epimastigotes (IC₅₀ 0.35–0.60 μg/ml). The TEM evaluation showed marked ultrastructural alterations, such as an intense vacuolization and mitochondrial swelling in both L. mexicana promastigotes and T. cruzi epimastigotes exposed to the STLs. In the in vivo study, enhydrin and uvedalin displayed a significant decrease in circulating parasites (50–71%) and no signs of hepatotoxicity were detected.

Conclusions

Enhydrin, uvedalin and polymatin B possess significant leishmanicidal and trypanocidal activity on different parasite stages. These results show that these compounds may provide valuable leads for the development of new drugs against these neglected parasitic diseases.

Applicability of plant-based products in the treatment ofTrypanosoma cruziandTrypanosoma bruceiinfections: a systematic review of preclinicalin vivoevidence

Chagas disease and sleeping sickness are neglected tropical diseases closely related to poverty, for which the development of plant-derived treatments has not been a promising prospect. Thus, we systematicaly review the preclinicalin vivoevidence on the applicability of plant-based products in the treatment ofTrypanosoma cruziandTrypanosoma bruceiinfections. Characteristics such as disease models, treatments, toxicological safety and methodological bias were analysed. We recovered 66 full text articles from 16 countries investigating 91 plant species. The disease models and treatments were highly variable. Most studies used native (n= 36, 54·54%) or exotic (n= 30, 45·46%) plants with ethnodirected indication (n= 45, 68·18%) for trypanosomiasis treatment. Complete phytochemical screening and toxicity assays were reported in only 15 (22·73%) and 32 (48·49%) studies, respectively. The currently available preclinical evidence is at high risk of bias. The absence of or incomplete characterization of animal models, treatment protocols, and phytochemical/toxicity analyses impaired the internal validity of the individual studies. Contradictory results of a same plant species compromise the external validity of the evidence, making it difficult determine the effectiveness, safety and biotechnological potential of plant-derived products in the development of new anti-infective agents to treatT. cruziandT. bruceiinfections.

Repeated-dose toxicity of common ragweed on rats

Ambrosia artemisiifolia L. is an invasive species with highly allergenic pollens. Ragweed originates from North America, but it also occurs and is spreading in Europe, causing seasonal allergic rhinitis for millions of people. Recently, the herb of A. artemisiifolia has gained popularity as medicinal plant and food. The effects of its long-term intake are unknown; there are no toxicological data to support the safe use of this plant. The aim of our study was to assess the repeated dose toxicity of A. artemisiifolia on animals. Ragweed puree was administered in low dose (500 mg/kg b. w.) and high dose (1000 mg/kg b. w.) to male Wistar rats according to 407 OECD Guidelines for the Testing of Chemicals. Clinical symptoms, various blood chemical parameters, body weight and organ weights of the rats were measured. Reduced liver function enzymes (AST, ALT), reduced triglyceride level in the low dose and increased carbamide level in the high dose group were observed. The weight of the liver relative to body weight was significantly reduced in both groups, while the brain weight relative to body weight was significantly elevated in both groups. According to our results, the repeated use of ragweed resulted in toxic effects in rats and these results question the safety of long-term human consumption of common ragweed.

Natural Sesquiterpene Lactones as Potential Trypanocidal Therapeutic Agents: A Review

Chagas’ disease and Human African Trypanosomiasis are parasitic diseases that remain major health problems, mainly among the poorest and the most marginalized communities from Latin America and Africa. The scarcity of effective chemotherapy, due to the low investment in the research and development (R&D) of new drugs, together with a high incidence of side effects, and the emergence of drug resistance phenomena emphasize the urgent need for new prophylactic and therapeutic agents. Over the ages, humans have employed natural products to treat a wide spectrum of diseases. Recently, the pharmaceutical industry has focused on plant research and a large body of evidence has been collected to demonstrate the immense potential of medicinal plants as a source of bioactive compounds and lead molecules. In the field of parasitic diseases, drug development from plants has been successful for the sesquiterpene lactone (STL) artemisinin, which is employed as an antimalarial agent. STLs are a large group of naturally occurring terpenoids derived from plants that mostly belong to the Asteraceae family which exhibit a variety of skeletal arrangements and are the largest and most diverse category of natural products with an α-methylene-λ-lactone motif. STLs display a broad spectrum of biological activities such as antitumor, cytotoxic, antibacterial, anthelmintic, uterus contracting, antimalarial, neurotoxic, antiprotozoal and allergic (contact dermatitis) activities. In this context, the purpose of the present review is to provide an overview of the trypanocidal activity reported for STLs against Trypanosoma cruzi and T. brucei rhodesiense over the period 1993–2015.

Trypanocidal and leishmanicidal activities of flavonoids isolated from Stevia satureiifolia var. satureiifolia

Context Chagas' disease and leishmaniasis produce significant disability and mortality with great social and economic impact. The genus Stevia (Asteraceae) is a potential source of antiprotozoal compounds. Objective Aerial parts of four Stevia species were screened on Trypanosoma cruzi. Stevia satureiifolia (Lam.) Sch. Bip. var. satureiifolia (Asteraceae) dichloromethane extract was selected for a bioassay-guided fractionation in order to isolate its active compounds. Additionally, the antileishmanial activity and the cytotoxicity of these compounds on mammalian cells were assessed. Materials and methods The dichloromethane extract was fractionated by column chromatography. The isolated compounds were evaluated using concentrations of 0-100 μg/mL on T. cruzi epimastigotes and on Leishmania braziliensis promastigotes for 72 h, on trypomastigotes and amastigotes of T. cruzi for 24 h and 120 h, respectively. The compounds' cytotoxicity (12.5-500 μg/mL) was assessed on Vero cells by the MTT assay. The structure elucidation of each compound was performed by spectroscopic methods and HPLC analysis. Results The dichloromethane extracts of Stevia species showed significant activity on T. cruzi epimastigotes. The flavonoids eupatorin (1.3%), cirsimaritin (1.9%) and 5-desmethylsinensetin (1.5%) were isolated from S. satureiifolia var. satureiifolia extract. Eupatorin and 5-desmethylsinensetin showed IC50 values of 0.2 and 0.4 μg/mL on T. cruzi epimastigotes and 61.8 and 75.1 μg/mL on trypomastigotes, respectively. The flavonoid 5-desmethylsinensetin showed moderate activity against T. cruzi amastigotes (IC50  value = 78.7 μg/mL) and was the most active compound on L. braziliensis promastigotes (IC50  value = 37.0 μg/mL). Neither of the flavonoids showed cytotoxicity on Vero cells, up to a concentration of 500 μg/mL.

Efficacy of Lychnopholide Polymeric Nanocapsules after Oral and Intravenous Administration in Murine Experimental Chagas Disease

The etiological treatment of Chagas disease remains neglected. The compounds available show several limitations, mainly during the chronic phase. Lychnopholide encapsulated in polymeric nanocapsules (LYC-NC) was efficacious in mice infected with Trypanosoma cruzi and treated by intravenous administration during the acute phase (AP). As the oral route is preferred for treatment of chronic infections, such as Chagas disease, this study evaluated the use of oral LYC-NC in the AP and also compared it with LYC-NC administered to mice by the oral and intravenous routes during the chronic phase (CP). The therapeutic efficacy was evaluated by fresh blood examination, hemoculture, PCR, and enzyme-linked immunosorbent assay (ELISA). The cure rates in the AP and CP were 62.5% and 55.6%, respectively, upon oral administration of LYC-poly(d,l-lactide)-polyethylene glycol nanocapsules (LYC-PLA-PEG-NC) and 57.0% and 30.0%, respectively, with LYC-poly-ε-caprolactone nanocapsules (LYC-PCL-NC). These cure rates were significantly higher than that of free LYC, which did not cure any animals. LYC-NC formulations administered orally during the AP showed cure rates similar to that of benznidazole, but only LYC-NC cured mice in the CP. Similar results were achieved with intravenous treatment during the CP. The higher cure rates obtained with LYC loaded in PLA-PEG-NC may be due to the smaller particle size of these NC and the presence of PEG, which influence tissue diffusion and the controlled release of LYC. Furthermore, PLA-PEG-NC may improve the stability of the drug in the gastrointestinal tract. This work is the first report of cure of experimental Chagas disease via oral administration during the CP. These findings represent a new and important perspective for oral treatment of Chagas disease.

Mode of Action of the Sesquiterpene Lactones Psilostachyin and Psilostachyin C on Trypanosoma cruzi

Trypanosoma cruzi is the causative agent of Chagas' disease, which is a major endemic disease in Latin America and is recognized by the WHO as one of the 17 neglected tropical diseases in the world. Psilostachyin and psilostachyin C, two sesquiterpene lactones isolated from Ambrosia spp., have been demonstrated to have trypanocidal activity. Considering both the potential therapeutic targets present in the parasite, and the several mechanisms of action proposed for sesquiterpene lactones, the aim of this work was to characterize the mode of action of psilostachyin and psilostachyin C on Trypanosoma cruzi and to identify the possible targets for these molecules. Psilostachyin and psilostachyin C were isolated from Ambrosia tenuifolia and Ambrosia scabra, respectively. Interaction of sesquiterpene lactones with hemin, the induction of oxidative stress, the inhibition of cruzipain and trypanothione reductase and their ability to inhibit sterol biosynthesis were evaluated. The induction of cell death by apoptosis was also evaluated by analyzing phosphatidylserine exposure detected using annexin-V/propidium iodide, decreased mitochondrial membrane potential, assessed with Rhodamine 123 and nuclear DNA fragmentation evaluated by the TUNEL assay. Both STLs were capable of interacting with hemin. Psilostachyin increased about 5 times the generation of reactive oxygen species in Trypanosoma cruzi after a 4h treatment, unlike psilostachyin C which induced an increase in reactive oxygen species levels of only 1.5 times. Only psilostachyin C was able to inhibit the biosynthesis of ergosterol, causing an accumulation of squalene. Both sesquiterpene lactones induced parasite death by apoptosis. Upon evaluating the combination of both compounds, and additive trypanocidal effect was observed. Despite their structural similarity, both sesquiterpene lactones exerted their anti-T. cruzi activity through interaction with different targets. Psilostachyin accomplished its antiparasitic effect by interacting with hemin, while psilostachyin C interfered with sterol synthesis.

Sesquiterpene lactones from Ambrosia spp. are active against a murine lymphoma cell line by inducing apoptosis and cell cycle arrest

Sesquiterpene lactones (STLs) are natural terpenoid compounds. They have been recognized as antitumor agents. The purpose of this investigation was to explore the antiproliferative effects of psilostachyin, psilostachyin C, peruvin and cumanin on the murine lymphoma cell line BW5147. Cells were treated with the STLs at different concentrations. Tritiated thymidine uptake was employed to determine cell proliferation. MTT assay was used to analyze cell viability. Flow cytometry assay with annexin V-FITC and propidium iodide was employed to evaluate cell death. Reactive oxygen species (ROS), mitochondrial membrane potential and cell cycle analysis were also evaluated by flow cytometry. Antioxidant enzymes activities were determined spectrophotometrically by kinetic assays. Results showed that these STLs inhibited cell proliferation in a concentration-dependent manner by exerting cytotoxicity through apoptosis. Psilostachyin C was the most active and the less toxic compound. This STL induced apoptosis with an impairment in mitochondrial membrane potential. Psilostachyin C was able to induce ROS generation, related to a modulation of the antioxidant enzymes activity. In addition, it induced cell cycle arrest in S phase. In conclusion, psilostachyin C was found to be active against lymphoma cells exerting both cytostatic and cytotoxic effects. These findings may provide a novel approach for lymphoma treatment.

Natural terpenoids from Ambrosia species are active in vitro and in vivo against human pathogenic trypanosomatids

Among the natural compounds, terpenoids play an important role in the drug discovery process for tropical diseases. The aim of the present work was to isolate antiprotozoal compounds from Ambrosia elatior and A. scabra. The sesquiterpene lactone (STL) cumanin was isolated from A. elatior whereas two other STLs, psilostachyin and cordilin, and one sterol glycoside, daucosterol, were isolated from A. scabra. Cumanin and cordilin were active against Trypanosoma cruzi epimastigotes showing 50% inhibition concentrations (IC50) values of 12 µM and 26 µM, respectively. Moreover, these compounds are active against bloodstream trypomastigotes, regardless of the T. cruzi strain tested. Psilostachyin and cumanin were also active against amastigote forms with IC50 values of 21 µM and 8 µM, respectively. By contrast, daucosterol showed moderate activity on epimastigotes and trypomastigotes and was inactive against amastigote forms. We also found that cumanin and psilostachyin exhibited an additive effect in their trypanocidal activity when these two drugs were tested together. Cumanin has leishmanicidal activity with growth inhibition values greater than 80% at a concentration of 5 µg/ml (19 µM), against both L. braziliensis and L. amazonensis promastigotes. In an in vivo model of T. cruzi infection, cumanin was more active than benznidazole, producing an 8-fold reduction in parasitemia levels during the acute phase of the infection compared with the control group, and more importantly, a reduction in mortality with 66% of the animals surviving, in comparison with 100% mortality in the control group. Cumanin also showed nontoxic effects at the doses assayed in vivo, as determined using markers of hepatic damage.

Effect of the sesquiterpene lactone incomptine A in the energy metabolism of Entamoeba histolytica

Entamoeba histolytica is the causative agent of human amoebiasis, which mainly affects developing countries. Although several drugs are effective against E. histolytica trophozoites, the control of amoebiasis requires the development of new and better alternative therapies. Medicinal plants have been the source of new molecules with remarkable antiprotozoal activity. Incomptine A isolated from Decachaeta incompta leaves, is a sesquiterpene lactone of the heliangolide type which has the major in vitro activity against E. histolytica trophozoites. However the molecular mechanisms involved in its antiprotozoal activity are still unknown. Using a proteomic approach based on two-dimensional gel electrophoresis and mass spectrometry (ESI-MS/MS) analysis, we evidenced that 21 E. histolytica proteins were differentially expressed in response to incomptine A treatment. Notably, three glycolytic enzymes, namely enolase, pyruvate:ferredoxin oxidoreductase and fructose-1,6-biphosphate aldolase, were down-regulated. Moreover, ultrastructural analysis of trophozoites through electronic microscopy showed an increased number of glycogen granules. Taken together, our data suggested that incomptine A could affect E. histolytica growth through alteration of its energy metabolism.

Trypanocidal Activity of Smallanthus sonchifolius: Identification of Active Sesquiterpene Lactones by Bioassay-Guided Fractionation

In order to find novel plant-derived biologically active compounds against Trypanosoma cruzi, we isolated, from the organic extract of Smallanthus sonchifolius, the sesquiterpene lactones enhydrin (1), uvedalin (2), and polymatin B (3) by bioassay-guided fractionation technique. These compounds showed a significant trypanocidal activity against the epimastigote forms of the parasite with IC50 values of 0.84  μ M (1), 1.09  μ M (2), and 4.90  μ M (3). After a 24 h treatment with 10  μ g/mL of enhydrin or uvedalin, parasites were not able to recover their replication rate. Compounds 1 and 2 showed IC50 values of 33.4  μ M and 25.0  μ M against T. cruzi trypomastigotes, while polymatin B was not active. When the three compounds were tested against the intracellular forms of T. cruzi, they were able to inhibit the amastigote replication with IC50 of 5.17  μ M, 3.34  μ M, and 9.02  μ M for 1, 2, and 3, respectively. The cytotoxicity of the compounds was evaluated in Vero cells obtaining CC50 values of 46.5  μ M (1), 46.8  μ M (2), and 147.3  μ M (3) and the selectivity index calculated. According to these results, enhydrin and uvedalin might have potentials as agents against Chagas disease and could serve as lead molecules to develop new drugs.

Natural Sesquiterpene Lactones Induce Oxidative Stress in Leishmania mexicana

Leishmaniasis is a worldwide parasitic disease, caused by monoflagellate parasites of the genus Leishmania. In the search for more effective agents against these parasites, the identification of molecular targets has been attempted to ensure the efficiency of drugs and to avoid collateral damages on the host's cells. In this work, we have investigated some of the mechanisms of action of a group of natural sesquiterpene lactones that are effective against Leishmania mexicana mexicana promastigotes. We first observed that the antiproliferative effect of mexicanin I (Mxc), dehydroleucodine (DhL), psilostachyin (Psi), and, at lesser extent, psilostachyin C (Psi C) is blocked by 1.5 mM reduced glutathione. The reducing agent was also able to reverse the early effect of the compounds, suggesting that lactones may react with intracellular sulfhydryl groups. Moreover, we have shown that all the sesquiterpene lactones, except Psi C, significantly decreased the endogenous concentration of glutathione within the parasite. Consistent with these findings, the active sesquiterpene lactones increased between 2.7 and 5.4 times the generation of ROS by parasites. These results indicate that the induction of oxidative stress is at least one of the mechanisms of action of DhL, Mxc, and Psi on parasites while Psi C would act by another mechanism.

Biogenic trypanocidal sesquiterpenes: lead compounds to design future trypanocidal drugs - a mini review

Human trypanosomiasis is a parasitic disease among poor people in Africa and Latin America. Therapy against African and American trypanosomiasis is based on a few drugs that often cause severe side-effects. Therefore, it is essential to develop drug discovery especially from natural origins. Sesquiterpenes, a diverse group of natural terpenoids, are found in essential oils of many plants and show a broad range of bioactivities. They act through multiple mechanisms in the chemotherapy of trypanosomiasis. Some of these active compounds contain hydroperoxides, aldehydes, alcohols, α,β-unsaturated γ-lactone and even halogenated moieties. Among the compounds reported, sesquiterpene lactones showed a potent anti-trypanosoma effect comparable with commercial trypanocidal drugs. Trypanocidal activity of sesquiterpene lactones mostly depends on the reaction between γ-lactone moieties and nucleophile groups of trypanithione, which is essential for Trypanosoma defense against the oxidative stresses. Elatol is a sesquiterpenoid from marine algae, with a different structure and considerable trypanocidal activity which could be an interesting candidate for further antiprotozoal investigations. To develop novel drugs with higher efficacy and lower toxicity from natural products, this review summarizes the more recent information on trypanocidal activities of various sesquiterpenes.

Antiparasitic Effect of Vitamin B12 on Trypanosoma cruzi

A nutritional characteristic of trypanosomatid protozoa is that they need a heme compound as a growth factor. Because of the cytotoxic activity of heme and its structural similarity to cobalamins, we have investigated the in vitro and in vivo effect of vitamin B(12) (or cyanocobalamin) on the different forms of Trypanosoma cruzi. Cyanocobalamin showed a marked antiparasitic activity against epimastigotes (50% inhibitory concentration [IC(50)], 2.42 μM), amastigotes (IC(50), 10.69 μM), and trypomastigotes (IC(50), 9.46 μM). Anti-epimastigote and -trypomastigote values were 1.7 to 4 times lower than those obtained with the reference drug benznidazole (Bnz). We also found that B(12) and hemin do not interact with each other in their modes of action. Our results show that B(12) increases intracellular oxidative activity and stimulates both superoxide dismutase (50%) and ascorbate peroxidase (20%) activities, while the activity of trypanothione reductase was not modified. In addition, we found that the antioxidants dithiothreitol and ascorbic acid increase the susceptibility of the parasite to the cytotoxic action of B(12). We propose that vitamin B(12) exerts its growth-inhibitory effect through the generation of reactive oxygen species. In an in vivo assay, a significant reduction in the number of circulating parasites was found in T. cruzi-infected mice treated with cyanocobalamin and ascorbic acid. The reduction of parasitemia in benznidazole-treated mice was improved by the addition of these vitamins. According to our results, a combination of B(12) and Bnz should be further investigated due to its potential as a new therapeutic modality for the treatment of Chagas' disease.

Conventional therapy and promising plant-derived compounds against trypanosomatid parasites

Leishmaniasis and trypanosomiasis are two neglected and potentially lethal diseases that affect mostly the poor and marginal populations of developing countries around the world and consequently have an important impact on public health. Clinical manifestations such as cutaneous, mucocutaneous, and visceral disorders are the most frequent forms of leishmaniasis, a group of diseases caused by several Leishmania spp. American trypanosomiasis, or Chagas disease, is caused by Trypanosoma cruzi, a parasite that causes progressive damage to different organs, particularly the heart, esophagus, and lower intestine. African trypanosomiasis, or sleeping sickness, is caused by Trypanosoma brucei and is characterized by first presenting as an acute form that affects blood clotting and then becoming a chronic meningoencephalitis. The limited number, low efficacy, and side effects of conventional anti-leishmania and anti-trypanosomal drugs and the resistance developed by parasites are the major factors responsible for the growth in mortality rates. Recent research focused on plants has shown an ingenious way to obtain a solid and potentially rich source of drug candidates against various infectious diseases. Bioactive phytocompounds present in the crude extracts and essential oils of medicinal plants are components of an important strategy linked to the discovery of new medicines. These compounds have proven to be a good source of therapeutic agents for the treatment of leishmaniasis and trypanosomiasis. This work highlights some chemotherapeutic agents while emphasizing the importance of plants as a source of new and powerful drugs against these widespread diseases.

In vitro evaluation of antiprotozoal and antiviral activities of extracts from Argentinean Mikania species

The aim of this study was to investigate the antiprotozoal and antiviral activities of four Argentinean Mikania species. The organic and aqueous extracts of Mikania micrantha, M. parodii, M. periplocifolia, and M. cordifolia were tested on Trypanosoma cruzi epimastigotes, Leishmania braziliensis promastigotes, and dengue virus type 2. The organic extract of M. micrantha was the most active against T. cruzi and L. braziliensis exhibiting a growth inhibition of 77.6 ± 4.5% and 84.9 ± 6.1%, respectively, at a concentration of 10 μg/ml. The bioguided fractionation of M. micrantha organic extract led to the identification of two active fractions. The chromatographic profile and infrared analysis of these fractions revealed the presence of sesquiterpene lactones. None of the tested extracts were active against dengue virus type 2.

Synthesis, trypanocidal activity and molecular modeling studies of 2-alkylaminomethylquinoline derivatives

Research and development of new drugs effective in the treatment of Trypanosoma cruzi infections are a real need for the 16 million people infected in the Americas. In a previous work, a quinoline derivative substituted by a 2-piperidylmethyl moiety showed to be active against Chagas disease and was considered a lead compound for further optimization. A series of ten analogous derivatives were tested against epimastigotes as a first approach. In view of their promising results, six of them were evaluated against the blood and intracellular replicative forms of the parasite in humans. Among them, compound 12 which possesses a 6-acetamidohexylamino substituent showed remarkable improvement in activity against epimastigotes, trypomastigotes and amastigotes compared with the structure lead, as well as a good selectivity index for the two parasite stages present in humans. In addition, treatment of infected mice with compound 12 induced a significant reduction in parasitemia compared with non-treated mice. Molecular modeling studies were performed by computational methods in order to elucidate the factors determining these experimental bioactivities.