Analogues of Marine Guanidine Alkaloids Are in Vitro Effective against Trypanosoma cruzi and Selectively Eliminate Leishmania (L.) infantum Intracellular Amastigotes

Guanidines Conjugated with Cell-Penetrating Peptides: A New Approach for the Development of Antileishmanial Molecules

Leishmaniasis is a neglected tropical disease caused by a protozoan of the genus Leishmania, which has visceral and cutaneous forms. The symptoms of leishmaniasis include high fever and weakness, and the cutaneous infection also causes lesions under the skin. The drugs used to treat leishmaniasis have become less effective due to the resistance mechanisms of the protozoa. In addition, the current compounds have low selectivity for the pathogen, leading to various side effects, which results in lower adherence to treatment. Various strategies were developed to solve this problem. The bioconjugation between natural compounds with antimicrobial activity and cell-penetrating peptides could alleviate the resistance and toxicity of current treatments. This work aims to conjugate the cell penetration peptide TAT to the guanidine GVL1. The GVL1-TAT bioconjugate exhibited leishmanicidal activity against Leishmania amazonensis and Leishmania infantum with a high selectivity index. In addition, the bioconjugate was more active against the intracellular enzyme CPP than the individual compounds. This target is very important for the viability and virulence of the parasite within the host cell. Docking studies confirmed the higher interaction of the conjugate with CPP and suggested that other proteins, such as trypanothione reductase, could be targeted. Thus, the data indicated that guanidines conjugated with cell-penetrating peptides could be a good approach for developing antileishmanial molecules.

Selective Activity Against Amastigote Forms of Trypanosoma cruzi and Leishmania infantum of Diastereomeric Dicentrine N-oxides

As part of our continuous research for the discovery of bioactive compounds against Trypanosoma cruzi and Leishmania infantum, the alkaloid (6aS)-dicentrine (1) was oxidized to afford (6aS,6S)- (2) and (6aS,6R)- (3) dicentrine-N-oxides. Evaluation of the cytotoxicity against NCTC cells indicated that 2 and 3 are non-toxic (CC50>200 μM) whereas 1 demonstrated CC50 of 52.0 μM. Concerning T. cruzi activity against amastigotes, derivatives 2 and 3 exhibited EC50 values of 9.9 μM (SI>20.2) and 27.5 μM (SI>7.3), respectively, but 1 is inactive (EC50>100 μM). Otherwise, when tested against L. infantum amastigotes, 1 and 3 exhibited EC50 values of 10.3 μM (SI=5.0) and 12.7 μM (SI>15.7), respectively, being 2 inactive (EC50>100 μM). Comparing the effects of positive controls benznidazol (EC50=6.5 μM and SI>30.7) and miltefosine (EC50=10.2 μM and SI=15.2), it was observed a selective antiparasitic activity to diastereomers 2 and 3 against T. cruzi and L. infantum. Considering stereochemical aspects, it was suggested that the configuration of the new stereocenter formed after oxidation of 1 played an important role in the bioactivity against amastigotes of both tested parasites.

Synthesis and Evaluation of (Bis)benzyltetrahydroisoquinoline Alkaloids as Antiparasitic Agents

Visceral leishmaniasis and Chagas disease are neglected tropical diseases (NTDs) that severely impact the developing world. With current therapies suffering from poor efficacy and safety profiles as well as emerging resistance, new drug leads are direly needed. In this work, 26 alkaloids (9 natural and 17 synthetic) belonging to the benzyltetrahydroisoquinoline (BI) family were evaluated against both the pro/trypomastigote and amastigote forms of the parasites Leishmania infantum and Trypanosoma cruzi, the causative agents of these diseases. These alkaloids were synthesized via an efficient and modular enantioselective approach based on Bischler-Napieralski cyclization/Noyori asymmetric transfer hydrogenation to build the tetrahydroisoquinoline core. The bis-benzyltetrahydroisoquinoline (BBI) alkaloids were prepared using an Ullmann coupling of two BI units to form the biaryl ether linkage, which enabled a comprehensive survey of the influence of BI stereochemistry on bioactivity. Preliminary studies into the mechanism of action against Leishmania mexicana demonstrate that these compounds interfere with the cell cycle, potentially through inhibition of kinetoplast division, which may offer opportunities to identify a new target/mechanism of action. Three of the synthesized alkaloids showed promising druglike potential, meeting the Drugs for Neglected Disease initiative (DNDi) criteria for a hit against Chagas disease.

Synthetic and natural guanidine derivatives as antitumor and antimicrobial agents: A review

Guanidines are fascinating small nitrogen-rich organic compounds, which have been frequently associated with a wide range of biological activities. This is mainly due to their interesting chemical features. For these reasons, for the past decades, researchers have been synthesizing and evaluating guanidine derivatives. In fact, there are currently on the market several guanidine-bearing drugs. Given the broad panoply of pharmacological activities displayed by guanidine compounds, in this review, we chose to focus on antitumor, antibacterial, antiviral, antifungal, and antiprotozoal activities presented by several natural and synthetic guanidine derivatives, which are undergoing preclinical and clinical studies from January 2010 to January 2023. Moreover, we also present guanidine-containing drugs currently in the market for the treatment of cancer and several infectious diseases. In the preclinical and clinical setting, most of the synthesized and natural guanidine derivatives are being evaluated as antitumor and antibacterial agents. Even though DNA is the most known target of this type of compounds, their cytotoxicity also involves several other different mechanisms, such as interference with bacterial cell membranes, reactive oxygen species (ROS) formation, mitochondrial-mediated apoptosis, mediated-Rac1 inhibition, among others. As for the compounds already used as pharmacological drugs, their main application is in the treatment of different types of cancer, such as breast, lung, prostate, and leukemia. Guanidine-containing drugs are also being used for the treatment of bacterial, antiprotozoal, antiviral infections and, recently, have been proposed for the treatment of COVID-19. To conclude, the guanidine group is a privileged scaffold in drug design. Its remarkable cytotoxic activities, especially in the field of oncology, still make it suitable for a deeper investigation to afford more efficient and target-specific drugs.

Leishmanicidal Activity of Guanidine Derivatives against Leishmania infantum

Leishmaniasis is a neglected tropical infectious disease with thousands of cases annually; it is of great concern to global health, particularly the most severe form, visceral leishmaniasis. Visceral leishmaniasis treatments are minimal and have severe adverse effects. As guanidine-bearing compounds have shown antimicrobial activity, we analyzed the cytotoxic effects of several guanidine-bearing compounds on Leishmania infantum in their promastigote and amastigote forms in vitro, their cytotoxicity in human cells, and their impact on reactive nitrogen species production. LQOFG-2, LQOFG-6, and LQOFG-7 had IC50 values of 12.7, 24.4, and 23.6 µM, respectively, in promastigotes. These compounds exhibited cytotoxicity in axenic amastigotes at 26.1, 21.1, and 18.6 µM, respectively. The compounds showed no apparent cytotoxicity in cells from healthy donors. To identify mechanisms of action, we evaluated cell death processes by annexin V and propidium iodide staining and nitrite production. Guanidine-containing compounds caused a significant percentage of death by apoptosis in amastigotes. Independent of L. infantum infection, LQOFG-7 increased nitrite production in peripheral blood mononuclear cells, which suggests a potential mechanism of action for this compound. Therefore, these data suggest that guanidine derivatives are potential anti-microbial molecules, and further research is needed to fully understand their mechanism of action, especially in anti-leishmanial studies.

Exploring the antileishmanial activity of N1,N2-disubstituted-benzoylguanidines: synthesis and molecular modeling studies

In this report, we describe the synthesis and evaluation of nine N¹,N²-disubstituted-benzoylguanidines against promastigotes and amastigotes forms of Leishmania amazonensis. The derivatives 2g and 2i showed low IC₅₀ values against promastigote form (90.8 ± 0.05 µM and 68.4 ± 0.03 µM, respectively), low cytotoxicity profile (CC₅₀ 396 ± 0.02 µM and 857.9 ± 0.06 µM) for peritoneal macrophages cells and SI of 5.5 and 12.5, respectively. Investigations about the mechanism of action of 2g and 2i showed that both compounds cause mitochondrial depolarization, increase in ROS levels, and generation of autophagic vacuoles on free promastigotes forms. These compounds were also capable of reducing the number of infected macrophages with amastigotes forms (59.5% ± 0.08% and 98.1% ± 0.46%) and the number of amastigotes/macrophages (79.80% ± 0.05% and 96.0% ± 0.16%), through increasing induction of microbicide molecule NO. Additionally, ADMET-Tox in silico predictions showed drug-like features and free of toxicological risks. The molecular docking studies with arginase and gp63 showed that relevant intermolecular interactions could explain the experimental results. Therefore, these results reinforce that benzoylguanidines could be a starting scaffold for the search for new antileishmanial drugs.Communicated by Ramaswamy H. Sarma.

Mitochondrial Imbalance of Trypanosoma cruzi Induced by the Marine Alkaloid 6-Bromo-2'-de-N-Methylaplysinopsin

Chagas disease, caused by Trypanosoma cruzi, affects seven million people worldwide and lacks effective treatments. Using bioactivity-guided fractionation, NMR, and electrospray ionization-high resolution mass spectrometry (ESI-HRMS) spectral analysis, the indole alkaloid 6-bromo-2'-de-N-methylaplysinopsin (BMA) was isolated and chemically characterized from the marine coral Tubastraea tagusensis. BMA was tested against trypomastigotes and intracellular amastigotes of T. cruzi, resulting in IC₅₀ values of 62 and 5.7 μM, respectively, with no mammalian cytotoxicity. The mechanism of action studies showed that BMA induced no alterations in the plasma membrane permeability but caused depolarization of the mitochondrial membrane potential, reducing ATP levels. Intracellular calcium levels were also reduced after the treatment, which was associated with pH alteration of acidocalcisomes. Using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF)/MS analysis, alterations of mass spectral signals were observed after treatment with BMA, suggesting a different mechanism from benznidazole. In silico pharmacokinetic-pharmacodynamic (PKPD) parameters suggested a drug-likeness property, supporting the promising usefulness of this compound as a new hit for optimizations.

Marine alkaloids as bioactive agents against protozoal neglected tropical diseases and malaria

Covering: 2000 up to 2021Natural products are an important resource in drug discovery, directly or indirectly delivering numerous small molecules for potential development as human medicines. Among the many classes of natural products, alkaloids have a rich history of therapeutic applications. The extensive chemodiversity of alkaloids found in the marine environment has attracted considerable attention for such uses, while the scarcity of these natural materials has stimulated efforts towards their total synthesis. This review focuses on the biological activity of marine alkaloids (covering 2000 to up to 2021) towards Neglected Tropical Diseases (NTDs) caused by protozoan parasites, and malaria. Chemotherapy represents the only form of treatment for Chagas disease, human African trypanosomiasis, leishmaniasis and malaria, but there is currently a restricted arsenal of drugs, which often elicit severe adverse effects, show variable efficacy or resistance, or are costly. Natural product scaffolds have re-emerged as a focus of academic drug discovery programmes, offering a different resource to discover new chemical entities with new modes of action. In this review, the potential of a range of marine alkaloids is analyzed, accompanied by coverage of synthetic efforts that enable further studies of key antiprotozoal natural product scaffolds.

Simplified Derivatives of Dibenzylbutyrolactone Lignans from Hydrocotyle bonariensis as Antitrypanosomal Candidates

The search for the pharmacophore of a bioactive compound, crucial for drug discovery studies, involves the adequate arrangement of different atoms in the molecule. As part of a continuous work aiming discovery of new drug candidates against the protozoan parasite Trypanosoma cruzi, the hexane extract of Hydrocotyle bonariensis was subjected to a bioactivity-guided fractionation to afford two chemically related dibenzylbutyrolactone lignans - hinokinin (1) and hibalactone (2). Compounds 1 and 2 showed activity against trypomastigote with EC₅₀ values of 17.0 and 69.4 μM, respectively. Compound 1 was also active against the clinically relevant form of the parasite, amastigotes, displaying an EC₅₀ value of 34.4 μM. The structure-activity relationship (SAR) indicated that the absence of the double bond at C-7 is a crucial feature for the increment of the antiparasitic activity. The lethal action of the most potent compound 1 was investigated in the trypomastigotes. The fluorescent-based assay with SYTOX Green demonstrated a significant alteration of the plasma membrane permeability of the parasite. Additionally, compound 1 demonstrated no significant hemolytic activity in mice erythrocytes at 200 μM. To search the pharmacophore, three different simplified compounds - 3,4-methylenedioxydihydrocinnamic acid (3), 3,4-methylenedioxydihydrocinnamic alcohol (4) and 3,4-methylenedioxycinnamic acid (5) - were prepared and tested against T. cruzi. These derivatives displayed EC₅₀ values of 37.2 (3), 25.8 (4) and 73.5 (5) μM against trypomastigotes, and 41.3 (3) and 48.2 (4) μM against amastigotes, whereas compound 5 was inactive. Except for compound 2, which resulted in a CC₅₀ value of 114.5 μM, all compounds showed no mammalian cytotoxicity at 200 μM. An in silico ADMET study was performed and predicted values demonstrated an acceptable drug-likeness profile for compounds 1-5. Despite the minor reduction in the potency, the simplified derivatives retained the antitrypanosomal activity against the intracellular amastigotes, even with 95 % reduction of their molecular weight. Additionally, in silico studies suggested them as more soluble compounds, making these simplified structures promising scaffolds for optimization studies in Chagas disease.

Photoresponsive supramolecular strategy for controlled assembly in light-inert double-chain surfactant system

HYPOTHESIS

One of the main advances in double-chain surfactant systems has been their progress from the construction of assemblies to the transformation application in medicine and material science, especially to the drug delivery systems. Thus, it is critical to develop stimuli-responsive assemblies based on double-chain surfactants. We predicted that reversible assembly switching can be achieved by manipulation of the ternary host-guest competitive complexation among β-cyclodextrin (β-CD), surfactants, and designed azobenzene (Azo).

EXPERIMENTS

In this work, Azo was introduced into vesicles using supramolecular assembly strategy. Vesicles are formed only when Azo moieties are in trans-form. UV switching of Azo groups led to fast disruption of the Azo@β-CD complexes and relatively slow disintegration of the vesicles. With the alterative irradiation of UV and Vis light, the photoisomerization of azo group provokes the reversible disassembly and reassembly of vesicles.

FINDINGS

This photo-responsive supramolecular strategy offered a controllable way to prepare responsive vesicles assembled from complex double-chain surfactants, such as phospholipids, which could be further used in drug delivery systems. This new perspective is instructive for the design and functional use of complex surfactants assembly. Importantly, the study results paved the way for the development of novel light-responsive assembly materials operating in aqueous media and biological field.

Chemical Constituents from Aerial Parts of Baccharis sphenophylla and Effects against Intracellular Forms of Trypanosoma cruzi

The hexane extract from aerial parts Baccharis sphenophylla Dusén ex Malme (Asteraceae) displayed activity against amastigote forms of Trypanossoma cruzi and was subjected to chromatographic steps to afford one unreported - 7α-hydroxy-ent-abieta-8(14),13(15)-dien-16,12β-olide (1) and three known diterpenes - ent-kaur-16-en-19-oic acid, (2), grandifloric acid (3), and 15β-tiglinoyloxy-ent-kaur-16-en-19-oic acid (4), two sesquiterpenes - spathulenol (5) and oplopanone (6) - as well as hexacosyl p-coumarate (7). Isolated compounds were characterized by NMR and ESI-HR-MS spectra and were evaluated in vitro for activity against amastigote forms of the parasite T. cruzi - the relevant clinical form in the chronic phase of Chagas disease. In addition, the activity of compounds 1-7 against NCTC cells was evaluated. Compounds 1 and 7 showed effectiveness with EC₅₀ values of 21.3 and 16.9 μM, respectively. Both compounds also exhibited reduced toxicity against NCTC cells (CC₅₀ >200 μM) with SI values higher than 9.4 and 11.9. Obtained results suggest that the new ent-abietane diterpene 1 and alkyl coumarate 7 could be used as prototypes for the development of novel and selective semisynthetic derivatives against intracellular forms of T. cruzi.

Antitrypanosomal Lactones from Nectandra barbellata

Twigs of Nectandra barbellata were extracted using a solution of the ionic liquid 1-butyl-3-methylimidazolium bromide (BMImBr) in H₂O, assisted by microwave (MAE). After successive chromatographic steps, one sesquiterpene, costic acid, and three new related lactones, (R)-3(7)-Z-3-hexadec-21-enylidene-5-(hydroxymethyl)tetrahydrofuran-2-one (1), (R)-3(7)-Z-3-hexadecylidene-5-(hydroxymethyl)tetrahydrofuran-2-one (2), and (R)-3(7)-Z-3-docosylidene-5-(hydroxymethyl)tetrahydrofuran-2-one (3), were isolated. After structural elucidation using IR, UV, HRESIMS, NMR, ECD, and VCD, compounds 1-3 were tested against trypomastigote forms of Trypanosoma cruzi. The mechanism of action of bioactive isolated compounds was studied using different fluorescent-based approaches to investigate alterations of the plasma membrane, permeability/electric potential (ΔΨ_p), reactive oxygen species levels, mitochondria (electric membrane potential, ΔΨ_m/ATP levels), Ca²⁺ levels, and pH of the acidocalcisomes. In addition, in silico studies predicted no resemblance to pan assay interference compounds (PAINS).

Marine Bioactive Compounds against Aspergillus fumigatus: Challenges and Future Prospects

With the mortality rate of invasive aspergillosis caused by Aspergillus fumigatus reaching almost 100% among some groups of patients, and with the rapidly increasing resistance of A. fumigatus to available antifungal drugs, new antifungal agents have never been more desirable than now. Numerous bioactive compounds were isolated and characterized from marine resources. However, only a few exhibited a potent activity against A. fumigatus when compared to the multitude that did against some other pathogens. Here, we review the marine bioactive compounds that display a bioactivity against A. fumigatus. The challenges hampering the discovery of antifungal agents from this rich habitat are also critically analyzed. Further, we propose strategies that could speed up an efficient discovery and broaden the dimensions of screening in order to obtain promising in vivo antifungal agents with new modes of action.

Synthesis and Structure-Activity Relationship of Dehydrodieugenol B Neolignans against Trypanosoma cruzi

Trypanosoma cruzi is the etiologic agent of Chagas disease, which affects over seven million people, especially in developing countries. Undesirable side effects are frequently associated with current therapies, which are typically ineffective in the treatment of all stages of the disease. Here, we report the first synthesis of the neolignan dehydrodieugenol B, a natural product recently shown to exhibit activity against T. cruzi. Using this strategy, a series of synthetic analogues were prepared to explore structure-activity relationships. The in vitro antiparasitic activities of these analogues revealed a wide tolerance of modifications and substituent deletions, with maintained or improved bioactivities against the amastigote forms of the parasite (50% inhibitory concentration (IC₅₀) of 4-63 μM) and no mammalian toxicity (50% cytotoxic concentration (CC₅₀) of >200 μM). Five of these analogues meet the Drugs for Neglected Disease Initiative (DNDi) "hit criteria" for Chagas disease. This work has enabled the identification of key structural features of the natural product and sites where scaffold modification is tolerated.

Antifungal compounds with anticancer potential from Trichoderma sp. P8BDA1F1, an endophytic fungus from Begonia venosa

Fungi in the genus Trichoderma are notorious producers of secondary metabolites with diverse applications, such as antibacterial, antifungal, and plant growth-promoting properties. Peptaibols are linear peptides produced by such fungi, with more than 440 compounds described to date, including tricholongins, longibrachins, trichobrachins, and trichovirins. Peptaibols are synthesized by non-ribosomal peptide synthetases and they have several biological activities. Our research group isolated four peptaibols (6DP2, 6DP3, 6DP4, and 6DP5) with antifungal activity against the plant pathogen Colletotrichum gloeosporioides and the proteasome (a cancer chemotherapy target) from Trichoderma sp. P8BDA1F1, an endophytic fungus from Begonia venosa. The ethyl acetate extract of this endophyte showed activity of 6.01% and 75% against C. gloeosporioides and the proteasome, respectively. The isolated compounds were identified by MS/MS and compared to literature data, suggesting the presence of trilongins BI, BII, BIII, and BIV, which are peptaibols containing 20 amino acid residues. The minimum inhibitory concentration against C. gloeosporioides was 40 μM for trilongin BI, 320 μM for trilongin BII, 160 μM for trilongin BIII, and 310 μM for trilongin BIV. BI-BIV trilongins inhibited proteasome ChTL activity, with IC₅₀ values of 6.5 ± 2.7; 4.7 ± 1.8; 6.3 ± 2.2; and 2.7 ± 0.5 μM, respectively. The compounds were tested ex vivo against the intracellular amastigotes of Leishmania (L.) infantum but showed no selectivity. It is the first report of trilongins BI-BIV with antifungal activity against C. gloeosporioides and the proteasome target.

Marine Alkaloids with Anti-Inflammatory Activity: Current Knowledge and Future Perspectives

Alkaloids are nitrogenous compounds with various biological activities. Alkaloids with anti-inflammatory activity are commonly found in terrestrial plants, but there are few records of the identification and characterization of the activity of these compounds in marine organisms such as fungi, bacteria, sponges, ascidians, and cnidarians. Seaweed are a source of several already elucidated bioactive compounds, but few studies have described and characterized the activity of seaweed alkaloids with anti-inflammatory properties. In this review, we have gathered the current knowledge about marine alkaloids with anti-inflammatory activity and suggest future perspectives for the study and bioprospecting of these compounds.

Emerging Marine Immunomodulatory Small-molecules (2010- Present)

Background:

Immunomodulation-based therapy has achieved a breakthrough in the last decade, which stimulates the passion of searching for potential immunomodulatory substances in recent years.

Objective:

Marine natural products are a unique source of immunomodulatory substances. This paper summarized the emerging marine natural small-molecules and related synthesized derivatives with immunomodulatory activities to provide readers an overview of these bioactive molecules and their potential in immunomodulation therapy.

Conclusion:

An increasing number of immunomodulatory marine small-molecules with diverse intriguing structure-skeletons were discovered. They may serve as a basis for further studies of marine natural products for their chemistry, related mechanism of action and structure- activity relationships.

Dibenzylbutane neolignans from Saururus cernuus L. (Saururaceae) displayed anti-Trypanosoma cruzi activity via alterations in the mitochondrial membrane potential

The MeOH extract from leaves of Saururus cernuus L. (Saururaceae) displayed in vitro activity against trypomastigote forms of T. cruzi (100% of parasite death at 200 μg/mL), suggesting the presence of bioactive compounds. Thus, the bioactivity-guided fractionation was carried out, leading to the isolation of three related neolignan derivatives, identified as threo-austrobailignan-5 (1), threo-austrobailignan-6 (2), and threo-dihydroguaiaretic acid (3). Anti-T. cruzi activity of compounds 1-3 was performed against cell-derived trypomastigotes and intracellular amastigotes. Additionally, the mammalian cytotoxicity was investigated using NCTC cells. Compound 2 was the most effective against extracellular trypomastigotes with IC₅₀ of 3.7 μM, while compound 3 showed activity in both clinically relevant forms of the parasite, trypomastigotes and amastigotes, with IC₅₀ values of 7.0 and 16.2 μM, respectively. However, the structurally related compound 1 was inactive. Based on these results, compounds 2 and 3 were selected to evaluate the mechanism of cellular death. Compound 2 induced alteration in the plasma membrane permeability and consequently in the ROS levels after 120 min of incubation. By using flow cytometry and fluorescence microscopy, compound 3 showed alterations in the mitochondrial membrane potential (ΔΨ_m) of trypomastigotes. Considering the promising chemical and biological properties of neolignans 2 and 3, these compounds could be used as starting points to develop new lead compounds for Chagas disease.

Evaluation of the antitrypanosoma activity and SAR study of novel LINS03 derivatives

Chagas' disease is a parasitic infection caused by Trypanosoma cruzi that is still treated by old and toxic drugs. In the search for novel alternatives, natural sources are an important source for new drug prototypes against T. cruzi to further structural exploitation. A set of natural-based compounds (LINS03) was designed, showing promising antitrypanosoma activity and low cytotoxicity to host cells. In this paper, nine novel LINS03 derivatives were evaluated against T. cruzi trypomastigotes and amastigotes. The selectivity was assessed through cytotoxicity assays using NCTC mammalian cells and calculating the CC₅₀/IC₅₀ ratio. The results showed that compounds 2d and 4c are noteworthy, due their high activity against amastigotes (IC₅₀ 13.9 and 5.8 µM) and low cytotoxicity (CC₅₀ 107.7 µM and >200 µM, respectively). These compounds did not showed alteration on plasma membrane permeability in a Sytox green model. SAR analysis suggested an ideal balance between hydrosolubility and lipophilicity is necessary to improve the activity, and that insertion of a meta-substituent is detrimental to the activity of the amine derivatives but not to the neutral derivatives, suggesting different mechanisms of actions. The results presented herein are valuable for designing novel compounds with improved activity and selectivity to be applied in future studies.

A semi-synthetic neolignan derivative from dihydrodieugenol B selectively affects the bioenergetic system of Leishmania infantum and inhibits cell division

Leishmaniasis is a neglected disease that affects more than 12 million people, with a limited therapy. Plant-derived natural products represent a useful source of anti-protozoan prototypes. In this work, four derivatives were prepared from neolignans isolated from the Brazilian plant Nectandra leucantha, and their effects against intracellular amastigotes of Leishmania (L.) infantum evaluated in vitro. IC₅₀ values between 6 and 35 µM were observed and in silico predictions suggested good oral bioavailability, no PAINS similarities, and ADMET risks typical of lipophilic compounds. The most selective (SI > 32) compound was chosen for lethal action and immunomodulatory studies. This compound caused a transient depolarization of the plasma membrane potential and induced an imbalance of intracellular Ca²⁺, possibly resulting in a mitochondrial impairment and leading to a strong depolarization of the membrane potential and decrease of ATP levels. The derivative also interfered with the cell cycle of Leishmania, inducing a programmed cell death-like mechanism and affecting DNA replication. Further immunomodulatory studies demonstrated that the compound eliminates amastigotes via an independent activation of the host cell, with decrease levels of IL-10, TNF and MCP-1. Additionally, this derivative caused no hemolytic effects in murine erythrocytes and could be considered promising for future lead studies.

N, N', N″-trisubstituted guanidines: Synthesis, characterization and evaluation of their leishmanicidal activity

Leishmaniasis is a group of diseases caused by protozoan parasites from the genus Leishmania. There are estimated 1.3 million new cases annually with a mortality of 20,000-30,000 per year, when patients are left untreated. Current chemotherapeutic drugs available present high toxicity and low efficacy, the latter mainly due to the emergence of drug-resistant parasites, which makes discovery of novel, safe, and efficacious antileishmanial drugs mandatory. The present work reports the synthesis, characterization by ESI-MS, ¹H and ¹³C NMR, and FTIR techniques as well as in vitro and in vivo evaluation of leishmanicidal activity of guanidines derivatives presenting lower toxicity. Among ten investigated compounds, all being guanidines containing a benzoyl, a benzyl, and a substituted phenyl moiety, LQOF-G2 (IC_50-ama 5.6 μM; SI = 131.8) and LQOF-G7 (IC_50-ama 7.1 μM; SI = 87.1) were the most active against L. amazonensis intracellular amastigote, showing low cytotoxicity to the host cells according to their selectivity index. The most promising compound, LQOF-G2, was further evaluated in an in vivo model and was able to decrease 60% of the parasite load in foot lesions at a dose of 0.25 mg/kg/day. Moreover, this guanidine derivative demonstrated reduced hepatotoxicity compared to other leishmanicidal compounds and did not show nephrotoxicity, as determined by the analyses of biomarkers of hepatic damage and renal function, which make this compound a potential new hit for therapy against leishmaniasis.

Butenolides from Nectandra oppositifolia (Lauraceae) displayed anti-Trypanosoma cruzi activity via deregulation of mitochondria

BACKGROUND

From a previous screening of Brazilian biodiversity for antitrypanosomal activity, the n-hexane extract from twigs of Nectandra oppositifolia (Lauraceae) demonstrated in vitro activity against Trypanosoma cruzi.

PURPOSE

To perform the isolation and chemical characterization of bioactive compounds from n-hexane extract from twigs of N. oppositifolia and evaluate their therapeutical potential as well as to elucidate their mechanism of action against T. cruzi.

METHODS/STUDY DESIGN

Bioactivity-guided fractionation of the n-hexane extract from twigs of N. oppositifolia afforded three related butenolides: isolinderanolide D (1), isolinderanolide E (2) and secosubamolide A (3). These compounds were evaluated in vitro against T. cruzi (trypomastigote and amastigote forms) and against NCTC (L929) cells for mammalian cytotoxicity. Additionally, phenotypic analyzes of compounds-treated parasites were performed: alterations in the plasma membrane permeability, plasma membrane electric potential (ΔΨ_p), mitochondrial membrane potential (ΔΨ_m) and induction of ROS.

RESULTS

Compounds 1-3 were effective against T. cruzi, with IC₅₀ values of 12.9, 29.9 and 12.5 µM for trypomastigotes and 25.3, 10.1 and 12.3 µM for intracellular amastigotes. Furthermore, it was observed alteration in the mitochondrial membrane potential (ΔΨ_m) of parasites treated with butenolides 1-3. These compounds caused no alteration to the parasite plasma membrane, and the deregulation of the mitochondria might be an early event to cell death. In addition, in silico studies showed that all butenolides were predicted to be non-mutagenic, non-carcinogenic, non hERG blockers, with acceptable human intestinal absorption, low inhibitory promiscuity with the main five CYP isoforms, and with high metabolic stability. Otherwise, tested butenolides showed unfavorable blood-brain barrier penetration (BBB+).

CONCLUSION

Our results demonstrated the anti-T. cruzi effects of compounds 1-3 isolated from N. oppositifolia and indicated that the lethal effect of these compounds in trypomastigotes of T. cruzi could be associated to the alteration in the mitochondrial membrane potential (ΔΨ_m).

Efficacy of sertraline against Trypanosoma cruzi: an in vitro and in silico study

Background

Drug repurposing has been an interesting and cost-effective approach, especially for neglected diseases, such as Chagas disease.

Methods

In this work, we studied the activity of the antidepressant drug sertraline against Trypanosoma cruzi trypomastigotes and intracellular amastigotes of the Y and Tulahuen strains, and investigated its action mode using cell biology and in silico approaches.

Results

Sertraline demonstrated in vitro efficacy against intracellular amastigotes of both T. cruzi strains inside different host cells, including cardiomyocytes, with IC₅₀ values between 1 to 10 μM, and activity against bloodstream trypomastigotes, with IC₅₀ of 14 μM. Considering the mammalian cytotoxicity, the drug resulted in a selectivity index of 17.8. Sertraline induced a change in the mitochondrial integrity of T. cruzi, resulting in a decrease in ATP levels, but not affecting reactive oxygen levels or plasma membrane permeability. In silico approaches using chemogenomic target fishing, homology modeling and molecular docking suggested the enzyme isocitrate dehydrogenase 2 of T. cruzi (TcIDH2) as a potential target for sertraline.

Conclusions

The present study demonstrated that sertraline had a lethal effect on different forms and strains of T. cruzi, by affecting the bioenergetic metabolism of the parasite. These findings provide a starting point for future experimental assays and may contribute to the development of new compounds.

Electronic supplementary material

The online version of this article (10.1186/s40409-018-0165-8) contains supplementary material, which is available to authorized users.

Antiparasitic activity of new gibbilimbol analogues and SAR analysis through efficiency and statistical methods

Chagas' disease and leishmaniasis are parasitic infections enrolled among the neglected tropical diseases, which urge for new treatments. In the search for new chemical entities as prototypes, gibbilimbols A/B have shown antiparasitic activity against Trypanosoma cruzi and Leishmania infantum, and then a set of analogues (LINS03 series) of this natural product were synthesized and evaluated in vitro against the parasites. In the present paper we reported five new compounds with activity against these protozoan parasites, and quite low cytotoxicity. Moreover, the interference of plasma membrane permeability of these analogues were also evaluated. We found that [(4-methoxyphenyl)methyl]octylamine (4) was noteworthy due to its high activity against the amastigote form of both parasites (IC₅₀ 1.3-5.8 μM) and good selectivity index. In order to unveil the SAR for this chemotype, we also presented a group efficiency analysis and PCA and HCA study, which indicated that the methoxyl provides good activity with lower cytotoxicity to mammalian cells. The results from SAR analyses suggest different mechanisms of action between the neutral and basic compounds. In summary, the analogues represent important activity against these parasites and must be prototypes for further exploitation.

The effect of different parameters under ultrasound irradiation for synthesis of new nanostructured Fe3O4@bio-MOF as an efficient anti-leishmanial in vitro and in vivo conditions

In this work, a magnetic bio-metal-organic framework (MBMOF) nanocomposite with porous-layer open morphology is synthesized through a simple sonochemical approach and its effects on Leishmania major (MRHO/IR/75/ER) under both in vitro and in vivo conditions are investigated. The effects of sonication time, initial concentration of reagents and sonication power on size and morphology of MBMOF nanocomposites have been investigated and optimized. A comparison was then made between the structural information of the nanostructures and that of the bio-metal-organic framework crystals. Using the powder X-ray diffraction (PXRD), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), energy dispersive analysis of X-ray (EDAX), vibrating sample magnetometer (VSM), thermogravimetric analysis (TGA), and Brunauer-Emmet-Teller (BET) techniques, the prepared MBMOF nanocomposites were characterized. The mean numbers of promastigotes (cell/ml) in different MBMOF concentrations (3.12, 6.25, 12.5, 25, 50, 100, 200 and 400 µg mL^-1) were determined by direct counting after 24, 48 and 72 h. Using MTT assays, the cytotoxic impacts of the MBMOF nanocomposites on promastigotes, intracellular amastigotes, and J774 macrophages were estimated. In order to investigate their therapeutic effects, the prepared MBMOF nanocomposites (25 and 12.5 µg mL^-1) were used as ointment three times a week to treat Leishmania major in BALB/c mice. The lesion size and weight of mice were assessed before and during the treatment. The parasitic loads were measured in spleen and liver through the culture. After 72 h, the INF-γ and IL-4 cytokines levels in the supernatant of the spleen culture were measured. To the best of the authors' knowledge, this study is the first to attempt to synthesize the bio-MOFs through an in-situ sonosynthesis route under ultrasound irradiation and examine their cytotoxicity effects on Leishmania major under in vitro and in vivo conditions.

Acetylenic fatty acids from Porcelia macrocarpa (Annonaceae) against trypomastigotes of Trypanosoma cruzi: Effect of octadec-9-ynoic acid in plasma membrane electric potential

Porcelia macrocarpa (Warm.) R. E. Fries (Annonaceae) is an endemic plant in Brazil where its tasty pulp has been eaten fresh. The hexane extract from its flowers was subjected to chromatographic procedures to afford four acetylene derivatives identified as octadec-9-ynoic (stearolic acid - 1), (11E)-octadec-11-en-9-ynoic (santalbic acid - 2), 8-hydroxyoctadec-9,11-diynoic (3) and 8-hydroxyoctadec-17-en-9,11-diynoic (isanolic acid - 4) acids by NMR and HRESIMS. Among tested compounds against trypomastigote forms of T. cruzi, octadec-9-ynoic acid (1) displayed higher potential with IC₅₀ = 27.6 µM and a selectivity index (SI) higher than 7. Compounds 2 and 3 showed IC₅₀ of approximately 60 µM while compound 4 was inactive. The lethal action of the compound 1 was investigated using spectrofluorometric techniques to detect ROS content, plasma membrane permeability and plasma membrane potential by flow cytometry. Compound 1 showed no alteration in the production of ROS of treated trypomastigotes and no alteration of the plasma membrane permeability was observed as detected by the fluorescent probe SYTOX-green after 120 min of incubation. However, by using the potential-sensitive fluorescent probe DiSBAC₂(3), compound 1 caused depolarization of the plasma membrane potential when compared to untreated parasites. Our results demonstrated the anti-T. cruzi effects of compounds 1-3 isolated from flowers of P. macrocarpa and indicated that the lethal effect of compound 1 in T. cruzi could be associated to the plasma membrane disturbance of the parasite.

Batzella, Crambe and Monanchora: Highly Prolific Marine Sponge Genera Yielding Compounds with Potential Applications for Cancer and Other Therapeutic Areas

Pyrroloquinoline and guanidine-derived alkaloids present distinct groups of marine secondary metabolites with structural diversity that displayed potentialities in biological research. A considerable number of these molecular architectures had been recorded from marine sponges belonging to different marine genera, including Batzella, Crambe, Monanchora, Clathria, Ptilocaulis and New Caledonian starfishes Fromia monilis and Celerina heffernani. In this review, we aim to comprehensively cover the chemodiversity and the bioactivities landmarks centered around the chemical constituents exclusively isolated from these three marine genera including Batzella, Crambe and Monanchora over the period 1981-2017, paying a special attention to the polycyclic guanidinic compounds and their proposed biomimetic landmarks. It is concluded that these marine sponge genera represent a rich source of novel compounds with potential applications for cancer and other therapeutic areas.

Portable and power-free serodiagnosis of Chagas disease using magnetic levitating microbeads

Magnetic levitating microbeads enable the point-of-care detection of Chagas antibodies in blood solutions using a portable magnetic stage requiring no electricity.

Efficacy of a series of alpha-pyrone derivatives against Leishmania (L.) infantum and Trypanosoma cruzi

The neglected tropical diseases Chagas disease and leishmaniasis affect together more than 20 million people living mainly in developing countries. The mainstay of treatment is chemotherapy, however the drugs of choice, which include benznidazole and miltefosine, are toxic and have numerous side effects. Safe and effective therapies are urgently needed. Marine alpha-pyrones have been previously identified as scaffolds with potential antiprotozoan activities. In this work, using a phenotypic screen, twenty-seven examples of 3-substituted 4-hydroxy-6-methyl alpha-pyrones were synthesized and their antiparasitic efficacy evaluated against Leishmania (L.) infantum and Trypanosoma cruzi in order to evaluate structure-activity relationships within the series. The mechanism of action and the in vivo efficacy of the most selective compound against T. cruzi were evaluated using different techniques. In vitro data indicated that compounds 8, 15, 25, 26 and 28 presented IC₅₀ values in the range between 13 and 54 μM against L. infantum intracellular amastigotes. Among them, hexanoyl substituted pyrone 8 was the most selective and potent, with a Selectivity Index (SI) > 14. Fifteen of the alpha-pyrones were effective against T. cruzi trypomastigotes, with 3-undecanoyl (11) and 3-tetradecanoyl (12) substituted pyrones being the most potent against trypomastigotes, with IC₅₀ values of 1 and 2 μM, respectively, and SI higher than 70. Using flow cytometry and fluorescent-based assays, pyrone 12 was found to induce hyperpolarization of the mitochondrial membrane potential of T. cruzi, without affecting plasma membrane permeability. An experimental acute phase-murine model, demonstrated that in vivo dosing of 12 (30 mg/kg/day; 5 days), had no efficacy at the first parasitemia onset of T. cruzi, but reduced the second onset by 55% (p < 0.05), suggesting a delayed action in BALB/c mice. Additionally, a histopathology study demonstrated no toxic effects to the treated mice. The finding that several 3-substituted alpha-pyrones have in vitro efficacy against both L. infantum and T. cruzi, and that one analogue exhibited moderate and non-toxic in vivo efficacy against T. cruzi is encouraging, and suggests that this compound class should be explored as long-term treatments in experimental Chagas disease.

Neolignans from leaves of Nectandra leucantha (Lauraceae) display in vitro antitrypanosomal activity via plasma membrane and mitochondrial damages

Chagas disease is a neglected tropical disease, caused by the protozoan parasite Trypanosoma cruzi, which affects more than eight million people in Tropical and Subtropical countries especially in Latin America. Current treatment is limited to nifurtimox and benznidazole, both with reduced effectiveness and high toxicity. In this work, the n-hexane extract from leaves of Nectandra leucantha (Lauraceae) displayed in vitro antitrypanosomal activity against T. cruzi. Using several chromatographic steps, four related neolignans were isolated and chemically characterized as dehydrodieugenol B (1), 1-(8-propenyl)-3-[3'-methoxy-1'-(8-propenyl)-phenoxy]-4,5-dimethoxybenzene (2), 1-[(7S)-hydroxy-8-propenyl]-3-[3'-methoxy-1'-(8'-propenyl)-phenoxy]-4-hydroxy-5-methoxybenzene (3), and 1-[(7S)-hydroxy-8-propenyl]-3-[3'-methoxy-1'-(8'-propenyl)-phenoxy]-4,5-dimethoxybenzene (4). These compounds were tested against intracellular amastigotes and extracellular trypomastigotes of T. cruzi and for mammalian cytotoxicity. Neolignan 4 showed the higher selectivity index (SI) against trypomastigotes (>5) and amastigotes (>13) of T. cruzi. The investigation of the mechanism of action demonstrated that neolignan 4 caused substantial alteration of the plasma membrane permeability, together with mitochondrial dysfunctions in trypomastigote forms. In silico studies of pharmacokinetics and toxicity (ADMET) properties predicted that all compounds were non-mutagenic, non-carcinogenic, non-genotoxic, weak hERG blockers, with acceptable volume of distribution (1.66-3.32 L/kg), and low rodent oral toxicity (LD₅₀ 810-2200 mg/kg). Considering some clinical events of cerebral Chagas disease, the compounds also demonstrated favorable properties, such as blood-brain barrier penetration. Unfavorable properties were also predicted as high promiscuity for P450 isoforms, high plasma protein binding affinity (>91%), and moderate-to-low oral bioavailability. Finally, none of the isolated neolignans was predicted as interference compounds (PAINS). Considering the promising chemical and biological properties of the isolated neolignans, these compounds could be used as starting points to develop new lead compounds for Chagas disease.

The chemistry and biology of guanidine natural products

The chemistry and biology of natural guanidines isolated from microbial culture media, from marine invertebrates, as well as from terrestrial plants and animals, are reviewed.