Amphotericin B loaded nanoemulsion: Optimization, characterization and in-vitro activity against L. donovani promastigotes

The present work aimed to develop and evaluate AmB-loaded nano-emulsion (AmB-NE) which will augment the solubility of AmB and lead to enhanced anti-leishmanial activity. The composition of AmB-NE was optimized by systematic screening followed by DoE-extreme vertices mixture design. The optimized NE revealed mean droplet size and PDI of 44.19 ± 5.5 nm, 0.265 ± 0.0723, respectively. The NE could efficiently encapsulate AmB with drug content and efficiency 83.509 ± 0.369% and 81.659 ± 0.013%, respectively. The presence of cholesterol and stearyl amine retarded the release (P < 0.0001) of AmB significantly compared to AmB suspension. The AmB-NE and pure AmB suspension demonstrated the IC50 of 0.06309 μg/mL and 0.3309 μg/mL against L.donovani promastigotes after 48 h incubation. The formulation was robust at all exaggerated stability conditions such as freeze-thaw and centrifugation. These findings indicate that AmB-NE is an attractive approach to treat visceral leishmaniasis with improved activity.

Spiro-Acridine Compound as a Pteridine Reductase 1 Inhibitor: in silico Target Fishing and in vitro Studies

Among the many neglected tropical diseases, leishmaniasis ranks second in mortality rate and prevalence. In a previous study, acridine derivatives were synthesized and tested for their antileishmanial activity against L. chagasi. The most active compound identified in that study (1) showed a single digit IC50 value against the parasite (1.10 μg/mL), but its macromolecular target remained unknown. Aiming to overcome this limitation, this work exploited inverse virtual screening to identify compound 1's putative molecular mechanism of action. In vitro assays confirmed that compound 1 binds to Leishmania chagasi pteridine reductase 1 (LcPTR1), with moderate affinity (Kd=33,1 μM), according to differential scanning fluorimetry assay. Molecular dynamics simulations confirm the stability of LcPTR1-compound 1 complex, supporting a competitive mechanism of action. Therefore, the workflow presented in this work successfully identified PTR1 as a macromolecular target for compound 1, allowing the designing of novel potent antileishmanial compounds.

Design, synthesis, and biological evaluation of quinoline-piperazine/pyrrolidine derivatives as possible antileishmanial agents

In pursuance of our efforts to expand the scope of novel antileishmanial entities, a series of thirty-five quinoline-piperazine/pyrrolidine, and other heterocyclic amine derivatives were synthesized via a molecular hybridization approach and examined against intracellular amastigotes of luciferase-expressing Leishmania donovani. The preliminary in vitro screening suggests that twelve compounds in the series exhibited better inhibition against amastigote form with good IC50 values ranging from 2.09 to 8.89 μM and lesser cytotoxicity in contrast to the standard drug miltefosine (IC50 9.25 ± 0.17 μM). Based on the satisfactory selectivity index (SI), two compounds were tested for in vivo leishmanicidal efficacy against Leishmania donovani/golden hamster model. Compounds 33 and 46 have shown significant inhibition of 56.32%, and 49.29%, respectively, in vivo screening at a daily dose of 50 mg/kg for 5 days. The pharmacokinetic results confirmed that 33 and 46 have satisfactory IP exposure with adequate parameters. Collectively, Compound 33 was identified as the most significant potential lead that could be employed as a prototype for future optimizations.

Chemlali

This study aimed to assess the antileishmanial activity of biomolecules obtained from Olea europaea L. leaves and twigs recovered from eight Tunisian cultivars. The extraction was first carried out with 80% methanol, and then the obtained extract was fractionated using three solvents of increasing polarity: cyclohexane (CHX), dichloromethane (DCM) and ethyl acetate (EtOAc). The antileishmanial activity was determined against leishmanial strains responsible for cutaneous, visceral, and mucocutaneous leishmaniasis. The cyclohexane fraction of the leaves of cv. Chemlali from the region of Sidi-Bouzid exhibited the strongest leishmanicidal activity against all the tested leishmanial strains. The inhibition concentrations (IC50) were 16.5, 14.5, and 7.4 μg mL-1 for Leishmania mexicana (cutaneous), Leishmania braziliensis (mucocutaneous), and Leishmania donovani (visceral), respectively. Interestingly, low cytotoxicity was observed on THP-1 cells with selective indexes (SI) ranging from 22.8 to 50.5. HPLC-HRMS and full-house NMR analysis allowed the identification of three triterpenic compounds, oleanolic acid (IC50 = 64.1 μg mL-1), erythrodiol (IC50 = 52.0 µg mL-1), and uvaol (IC50 = 53.8 μg mL-1). Antileishmanial activity of uvaol and oleanolic acid has been previously reported. However, this work constitutes the first report of the antileishmanial activity of erythrodiol which showed combinatorial interaction with uvaol (IC50 = 26.1 μg mL-1) against Leishmania tropica. The mixture of the three compounds, as major ones, exhibited an enhanced activity against Leishmania tropica (IC50 = 16.3 µg mL-1) compared to erythrodiol alone or the combination of uvaol and erythrodiol. This finding is of great importance and needs further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03825-3.

Design, synthesis and antitrypanosomatid activity of 2-nitroimidazole-3,5-disubstituted isoxazole compounds based on benznidazole

Chagas disease and leishmaniasis are neglected diseases of high priority as a public health problem. Pharmacotherapy is based on the administration of a few drugs, which exhibit hazardous adverse effects and toxicity to the patients. Thus, the search for new antitrypanosomatid drugs is imperative to overcome the limitations of the treatments. In this work, 46 2-nitroimidazole 3,5-disubstituted isoxazole compounds were synthesized in good yields by [3 + 2] cycloaddition reaction between terminal acetylene (propargyl-2-nitroimidazole) and chloro-oximes. The compounds were non-toxic to LLC-MK2 cells. Compounds 30, 35, and 44 showed in vitro antichagasic activity, 15-fold, 12-fold, and 10-fold, respectively, more active than benznidazole (BZN). Compounds 30, 35, 44, 45, 53, and 61 acted as substrates for the TcNTR enzyme, indicating that this might be one of the mechanisms of action involved in their antiparasitic activity. Piperazine series and 4-monosubstituted compounds were potent against T. cruzi parasites. Besides the in vitro activity observed in compound 45, the in vivo assay showed that the compound only reduced the parasitemia levels by the seventh-day post-infection (77%, p > 0.001) compared to the control group. However, 45 significantly reduced the parasite load in cardiac tissue (p < 0.01) 11 days post-infection. Compounds 49, 52, and 54 showed antileishmanial activity against intracellular amastigotes of Leishmania (L.) amazonensis at the same range as amphotericin B. These findings highlight the antitrypanosomatid properties of 2-nitroimidazole 3,5-disubstituted isoxazole compounds and the possibility in using them as antitrypanosomatid agents in further studies.

Synthesis of new 3-acetyl-1,3,4-oxadiazolines combined with pyrimidines as antileishmanial and antiviral agents

A new series of 3-acetyl-1,3,4-oxadiazoline hybrid molecules was designed and synthesized using a condensation between acyclonucleosides and substituted phenylhydrazone. All intermediates and final products were screened against Leishmania donovani, a Protozoan parasite and against three viruses SARS-CoV-2, HCMV and VZV. While no significant activity was observed against the viruses, the intermediate with 6-azatymine as thymine and 5-azathymine-3-acetyl-1,3,4-oxadiazoline hybrid exhibited a significant antileishmanial activity. The later compound was the most promising, exhibiting an IC50 value at 8.98 µM on L. donovani intramacrophage amastigotes and a moderate selectivity index value at 2.4.

Phytochemical, antileishmanial, antifungal and cytotoxic profiles of Thymelaea tartonraira (L.) All. extracts

Extracts from leaves and stems of Thymelaea tartonraira (L.) All. growing in Tunisia were characterised for the presence of flavonoids and phenolic acids by LC-ESI-MS analysis. Twelve flavonoids and ten phenolic acids were detected for the first time in the aerial parts of this plant species, the most abundant compounds being gallic acid, kaempferol, catechin, chlorogenic acid, naringenin and acacetin. The extracts were subjected to in vitro antileishmanial, antifungal and cytotoxic assays, showing promising antileishmanial activity for the E6 dichloromethane extract from the stems (IC50 values of 1.12 ± 0.50 and 5.41 ± 1.84 µg/mL on L. donovani axenic and intramacrophagic amastigotes, respectively) at the level of the reference drug miltefosine for axenic model. No antifungal activity was observed against Candida albicans (CAAL) and Aspergillus fumigatus (ASFU) strains, with the exception of the E6 dichloromethane extract (IC50 value of 25.28 ± 4.89 µg/mL on CAAL93 strain). Low toxicity was also highlighted against macrophages Raw 264.7 cells. These promising results point out Thymelaea tartonraira (L.) All. extracts as a valuable source of new natural products to combat leishmaniasis.

Thiazolidin-4-one-based derivatives - Efficient tools for designing antiprotozoal agents. A review of the last decade

Thiazolidin-4-one derivatives have a wide range of therapeutic implementations and clinical significance for medicinal chemistry. This heterocyclic ring has been reported to possess a variety of biological activities, including antiprotozoal activities that have inspired scientists to integrate this scaffold with different pharmacophoric fragments to design novel and effective antiprotozoal compounds. There are reviews describing thiazolidin-4-ones small molecules as good candidates with a single type of antiprotozoal activity, but none of these show collected news associated with the antiprotozoal activity of thiazolidin-4-ones and their SAR analysis from the last decade. In this review we are focusing on the antitoxoplasmic, anti-trypanosomal, antimalarial, antileishmanial, and antiamoebic activity of these derivatives, we attempt to summarize and analyze the recent developments with regard to the antiprotozoal potential of 4-TZD covering the structure-activity relationship and main molecular targets. The importance of various structural modifications at C2, N3, and C5 of the thiazolidine-4-one core has also been discussed in this review. We hope that all information concluded in this review can be useful for other researchers in constructing new effective antiprotozoal agents.

Antileishmanial Activity of the Essential Oils from Three Trees Obtained in Different Phenological Stages

PURPOSE

Leishmaniasis is a parasitic disease found in tropical areas, and it affects up to 12 million individuals globally. Chemotherapies now available include drawbacks such as toxicity, high cost, and parasite resistance. This work aimed to evaluate the antileishmanial properties of essential oils (EOs) extracted from aerial parts of Cupressus sempervirens (C. sempervirens), Tetraclinis articulata (T. articulata), and Pistacia lentiscus (P. lentiscus) trees.

METHODS

The EOs were obtained by hydro-distillation, and chemical composition was determined by gas chromatography coupled to mass spectrometry at three phenological stages. The EOs were evaluated in vitro for antileishmanial activities against Leishmania major (L. major) and Leishmania infantum (L. infantum). The cytotoxicity effect was also tested against murine macrophagic cells (Raw264.7 lines).

RESULTS

Results showed that P. lentiscus and T. articulata EOs presented low and moderate antileishmanial activity against L. infantum and L. major. However, C. sempervirens EO from the fructification stage gave an important selectivity index (23.89 and 18.96 against L. infantum and L. major, respectively). This activity was more interesting than those of amphotericin chemical drugs. Antileishmanial activity for this EO was highly correlated with germacrene D content (r = 1.00). This compound presented a SI equal to 13.34 and 10.38 for the two strains. According to the Principal Component Analysis (PCA), the distribution of the three phenological stages proved that the chemical composition of the EOs affected the antileishmanial activity. PCA revealed that SI was positively correlated with α-pinene, germacrene D and the sesquiterpene hydrocarbon class. Cupressus sempervirens EO can provide a source of germacrene D that can be used as a new alternative to chemical drugs for the treatment of antileishmanial diseases.

CONCLUSION

C. sempervirens EO seemed to be a highly active antileishmanial agent and a natural alternative for chemical drugs to treat several leishmanial strains.

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

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

Wharton Jelly Derived Mesenchymal Stem Cell's Exosomes Demonstrate Significant Antileishmanial and Wound Healing Effects in Combination with Aloe-Emodin: An in Vitro Study

The aim of the present study was to explore the antileishmanial performance and wound healing effect of exosomes isolated from Wharton Jelly derived mesenchymal stem cells (WJ-MSCs) in combination with aloe-emodin. MSCs obtained from Wharton Jelly were characterized by flow cytometry. Exosomes were isolated from cultivated stem cells by ultacentrifugation method. Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), Nanoparticle Tracking Analysis (NTA) and flow cytometry were used for characterization of obtained exosomes. The cytotoxicities of characterized exosomes and aloe-emodin at different concentrations were investigated on L929 and J774 cell lines. Non-toxic concentrations of each agent were combined and their inhibitory efficacies on L.major promastigotes and amastigotes were investigated by different techniques such as MTT, parasite count and measurements of infection index. Finally, wound healing activities of combinations were examined on in vitro artifical wound model and compared with the use of exosomes alone. According to outcome of flow cytometic analysis, vesicles isolated from WJ-MSCs highly expressed the markers such as CD63 special for exosome profile. SEM and NTA results demonstrated that derived exosomes possessed dimensions between 150 to 200 nanometers and elicited the cup-shape specific to exosomes. Combinations including non-toxic dosages of exosomes and aloe-emodin demonstrated superior antileishmanial effectivenesses both on promastigotes and amastigotes in contrast to use of exosome alone since they lead to inhibition of promastigotes and amastigotes for 4 and 10-folds in comparison to control, respectively. Additionally, combinations elicited more rapidly and effective in vitro wound-healing performance in contrast to use of exosome alone. At the end of 24 h incubation application of combinations gave rise to wound closure at a rate of 72 %, while in the control group 52 % of wound area has not been healed, yet. These results reflect that mentioned combination has great potential to be used in treatment of cutaneus leishmaniasis (CL) since they have magnificient capacity to inhibit Leishmania parasites while enhancing wound healing.

Antileishmanial activity, cytotoxicity and cellular response of amphotericin B in combination with crotamine derived from Crotalus durissus terrificus venom using in vitro and in silico approaches

OBJECTIVE

To investigate the in vitro activity, synergism, cytotoxicity and cellular immunological response, as well as the molecular affinity between amphotericin B (AmB) and crotamine (CTA), derived from Crotalus durissus terrificus venom against Leishmania amazonensis.

METHODS

This study performed the inhibition of promastigotes and amastigotes' growth under different concentrations of the drug and pharmacological combinations (AmB + CTA) based on the Berimbaum method (synergism study). The lactate dehydrogenase (LDH) quantification method was used to determine the cytotoxicity of the drug and combinations employing four cell lines (J774, HepG2, VERO, and C2C12). Following, the levels of Tumour Necrose Factor-alpha (TNF-α) and Interleukin-12 (IL-12) cytokines, using enzyme-linked immunosorbent assay (ELISA) and nitrites, as an indirect measure of Nitric Oxide (NO), using the Griess reaction were assessed in the supernatants of infected macrophages. In silico approach (molecular docking and dynamics) and binding affinity (surface plasmon resonance) between the drug and toxin were also investigated.

RESULTS

CTA enhanced AmB effect against promastigote and amastigote forms of L. amazonensis, decreased the drug toxicity in different cell lines and induced the production of important Th1-like cytokines and NO by infected macrophages. The pharmacological combination also displayed consistent molecular interactions with low energy of coupling and a concentration-dependent profile.

CONCLUSION

Our data suggest that this pharmacological approach is a promising alternative treatment against L. amazonensis infection due to the improved activity (synergistic effect) achieved against the parasites' forms and to the decreased cytotoxic effect.

Absolute configuration and antileishmanial activity of (-)-cyclocolorenone isolated from Duguetia lanceolata (Annonaceae)

BACKGROUND

The fractionation of the n-hexane phase of the EtOH extract from the leaves of Duguetia lanceolata (Annonaceae) led to the identification of the sesquiterpene (-)- cyclocolorenone.

OBJECTIVE

Chemical characterization, including determination of the absolute stereochemistry, and in vitro evaluation of antileishmanial activity of the sesquiterpene (-)-cyclocolorenone, isolated from D. lanceolata were carried out.

METHODS

(-)-Cyclocolorenone was isolated from D. lanceolata leaves using different chromatographic steps and its structure was defined by analysis of NMR and ESI-HRMS data. Additionally, the absolute configuration of (-)-cyclocolorenone was ambiguously assigned by means of vibrational circular dichroism (VCD). Antileishmanial activity of (-)-cyclocolorenone was evaluated on promastigote and amastigote forms of Leishmania (Leishmania) amazonensis. The integrity of the cell membrane of L. (L.) amazonensis was analyzed using the SYTOX green probe.

RESULTS

(-)-(1R,6S,7R,10R)-Cyclocolorenone displayed activity against promastigotes and amastigotes forms of L. (L.) amazonensis with IC50 of 4.54 and 28.44 , respectively. Furthermore, this compound was non-toxic in J774 macrophage cells (CC50 > 458.71 ) with a selectivity index > 100 (promastigotes) and > 32.2 (amastigotes). Additionally, (-)-cyclocolorenone was observed to target the parasite cell membrane.

CONCLUSION

Obtained data suggested that (-)-cyclocolorenone, in which absolute configuration was determined, can be considered as a scaffold for the development of new drugs for the treatment of leishmaniasis.

The anti-Leishmania potential of bioactive compounds derived from naphthoquinones and their possible applications. A systematic review of animal studies

Leishmaniasis affects millions of people worldwide, and available treatments have severe limitations. Natural and derivative products are significant sources of innovative therapeutic agents. Naphthoquinones are natural or synthetic chemical compounds with broad biological activity. This systematic review aimed to evaluate the potential anti-Leishmania activity of bioactive compounds derived from naphthoquinones in animal models. Conducted in accordance with PRISMA guidelines, two blocks of MeSH terms were assembled: group I, Leishmania OR Leishmaniasis; group II, Atovaquone OR Lapachol OR Beta lapachone OR Naphthoquinones. The search was performed on PubMed, Web of Science, SCOPUS, EMBASE, and Lilacs databases. Twenty-four articles were retrieved and submitted for quality assessment using the SYRCLE critical appraisal tool. The in vivo anti-Leishmania potential of naphthoquinones was evaluated in visceral and cutaneous leishmaniasis using several measurement parameters. Analyzed compounds varied in structure, association with reference drugs, and encapsulation using a drug delivery system. The study design, including treatment protocol, differed between studies. The findings of the studies in this systematic review indicate the anti-Leishmania potential of naphthoquinones in vivo, with different treatment regimens directed against different Leishmania species. The employed drug delivery systems improve the results concerning selectivity, distribution, and required therapeutic dose. The immunomodulatory action was shown to be beneficial to the host, favoring an adequate immune response against infection by Leishmania parasites since it favored Th₁ responses. All studies presented a moderate to high risk of bias. These findings suggest that more studies are needed to assess the overall effectiveness and safety of these treatments.

Antimicrobial, antioxidant and antileishmanial activities of Ziziphus lotus leaves

The aim of this study was to investigate antimicrobial and antioxidant activities of different fractions obtained from edible Tunisian Ziziphus Lotus leaves of Tozeur region. Different organic extracts were tested: cyclohexane, dichloromethane, ethyl acetate, n-butanol and water. Bio-guided fractionation revealed that dichloromethane fraction is the most active against S. aureus and Methicillin-resistant S. aureus strains. Moreover, this fraction showed the highest antileishmanial activity with IC₅₀ values of 20.55 ± 0.34 μg/mL and 15.37 ± 0.17 μg/mL against L. major and L. infantum, respectively. The potentialities of antibacterial and leishmanicidal activities found in dichloromethane could be explained by the presence of major flavonoids such as catechin, rutin and luteolin 7-O-glucoside as revealed by HPLC system. The observed moderate antifungal activity, which was only given by butanolic fraction against pathogen fungi, may be attributed to the presence of chlorogenic acid. Furthermore, dichloromethane and butanolic fraction showed a good DPPH (2,2-diphenyl-1-picryl hydrazyl) scavenging activity and Ferric reducing power. These results suggest that Ziziphus lotus leaf fractions might be used as antioxidant and antimicrobialagent.

In vitro anti-Leishmania activity and molecular docking of spiro-acridine compounds as potential multitarget agents against Leishmania infantum

Leishmaniasis is an infectious disease with several limitations regarding treatment schemes. This work reports the anti-Leishmania activity of spiroacridine compounds against the promastigote (IC₅₀ = 1.1 to 6.0 µg / mL) and amastigote forms of the best compounds (EC₅₀ = 4.9 and 0.9 µg / mL) inLeishmania (L.) infantumand proposes an in-silico study with possible selective therapeutic targets for L. infantum. The substituted dimethyl-amine compound (AMTAC 11) showed the best leishmanicidal activity in vitro, and was found to interact with TryRandLdTopoI. comparisons with standard inhibitors were performed, and its main interactions were elucidated. Based on the biological assessment and the structure-activity relationship study, the spiroacridine compounds appear to be promisinganti-leishmaniachemotherapeutic agents to be explored.

Amentoflavone isolated from Selaginella sellowii Hieron induces mitochondrial dysfunction in Leishmania amazonensis promastigotes

Leishmaniasis chemotherapy is a bottleneck in disease treatment. Although available, chemotherapy is limited, toxic, painful, and does not lead to parasite clearance, with parasite resistance also being reported. Therefore, new therapeutic options are being investigated, such as plant-derived anti-parasitic compounds. Amentoflavone is the most common biflavonoid in the Selaginella genus, and its antileishmanial activity has already been described on Leishmania amazonensis intracellular amastigotes but its direct action on the parasite is controversial. In this work we demonstrate that amentoflavone is active on L. amazonensis promastigotes (IC₅₀ = 28.5 ± 2.0 μM) and amastigotes. Transmission electron microscopy of amentoflavone-treated promastigotes showed myelin-like figures, autophagosomes as well as enlarged mitochondria. Treated parasites also presented multiple lipid droplets and altered basal body organization. Similarly, intracellular amastigotes presented swollen mitochondria, membrane fragments in the lumen of the flagellar pocket as well as autophagic vacuoles. Flow cytometric analysis after TMRE staining showed that amentoflavone strongly decreased mitochondrial membrane potential. In silico analysis shows that amentoflavone physic-chemical, drug-likeness and bioavailability characteristics suggest it might be suitable for oral administration. We concluded that amentoflavone presents a direct effect on L. amazonensis parasites, causing mitochondrial dysfunction and parasite killing. Therefore, all results point for the potential of amentoflavone as a promising candidate for conducting advanced studies for the development of drugs against leishmaniasis.

Synthesis and biological activity of novel 4-aminoquinoline/1,2,3-triazole hybrids against Leishmania amazonensis

Quinoline and 1,2,3-triazoles are well-known nitrogen-based heterocycles presenting diverse pharmacological properties, although their antileishmanial activity is still poorly exploited. As an effort to contribute with studies involving these interesting chemical groups, in the present study, a series of compounds derived from 4-aminoquinoline and 1,2,3-triazole were synthetized and biological studies using L. amazonensis species were performed. The results pointed that the derivative 4, a hybrid of 4-aminoquinoline/1,2,3-triazole exhibited the best antileishmanial action, with inhibitory concentration (IC₅₀) values of ~1 µM against intramacrophage amastigotes of L. amazonensis , and being 16-fold more active to parasites than to the host cell. The mechanism of action of derivative 4 suggest a multi-target action on Leishmania parasites, since the treatment of L. amazonensis promastigotes caused mitochondrial membrane depolarization, accumulation of ROS products, plasma membrane permeabilization, increase in neutral lipids, exposure of phosphatidylserine to the cell surface, changes in the cell cycle and DNA fragmentation. The results suggest that the antileishmanial effect of this compound is primarily altering critical biochemical processes for the correct functioning of organelles and macromolecules of parasites, with consequent cell death by processes related to apoptosis-like and necrosis. No up-regulation of reactive oxygen and nitrogen intermediates was promoted by derivative 4 on L. amazonensis -infected macrophages, suggesting a mechanism of action independent from the activation of the host cell. In conclusion, data suggest that derivative 4 presents selective antileishmanial effect, which is associated with multi-target action, and can be considered for future studies for the treatment against disease.

Design, synthesis, in vitro and in vivo biological evaluation of pyranone-piperazine analogs as potent antileishmanial agents

The current therapeutic regimen for visceral leishmaniasis is inadequate and unsatisfactory due to toxic side effects, high cost and emergence of drug resistance. Alternative, safe and affordable antileishmanials are, therefore, urgently needed and toward these we synthesized a series of arylpiperazine substituted pyranone derivatives and screened them against both in vitro and in vivo model of visceral leishmaniasis. Among 22 synthesized compounds, 5a and 5g showed better activity against intracellular amastigotes with an IC₅₀ of 11.07 μM and 15.3 μM, respectively. In the in vivo, 5a significantly reduced hepatic and splenic amastigotes burden in Balb/c mice model of visceral leishmaniasis. On a mechanistic node, we observed that 5a induced direct Leishmania killing via mitochondrial dysfunction like cytochrome c release and loss of membrane potential. Taken together, our results suggest that 5a is a promising lead for further development of antileishmanial drugs.

essential oil and γ-elemene its major constituent exhibit antileishmanial activity, promoting cell membrane damage and in vitro immunomodulation

Leishmaniasis is considered as one of the most Neglected Tropical Diseases (NTDs) in the world, caused by protozoan parasites of the genus Leishmania. Treatment of leishmaniasis by chemotherapy remains a challenge because of limited efficacy, toxic side effects, and drug resistance. The search for new therapeutic agents from natural sources has been a constant for the treatment of diseases such as leishmaniasis. The objective of this study was to evaluate the biological activity of Eugenia piauhiensis Vellaff. essential oil (EpEO) and its major constituent γ-elemene on promastigote and amastigote forms of Leishmania (Leishmania) amazonensis, its cytotoxicity, and possible mechanisms of action. EpEO was more active (IC₅₀ 6.43 ± 0.18 μg/mL) against promastigotes than γ-elemene [9.82 ± 0.15 μg/mL (48.05 ± 0.73 μM)] and the reference drug miltefosine [IC₅₀ 17.25 ± 0.26 μg/mL (42.32 ± 0.64 μM)]. EpEO and γ-elemene exhibited low cytotoxicity against J774.A1 macrophages, with CC₅₀ 225.8 ± 3.57 μg/mL and 213.21 ± 3.3 μg/mL (1043 ± 16.15 μM), respectively. Additionally, EpEO and γ-elemene present direct activity against the parasite, decreasing plasma membrane integrity. EpEO and γ-elemene also proved to be even more active against intracellular amastigotes of the parasite [IC₅₀ 4.59 ± 0.07 μg/mL and 8.06 ± 0.12 μg/mL (39.44 ± 0.59 μM)], respectively), presenting indirect effects through macrophage activity modulation. Anti-amastigote activity was associated with increased TNF-α, IL-12, NO, and ROS levels. In conclusion, our results suggest EpEO and γ-elemene as promising candidates for new drug development against leishmaniasis.

Novel coumarin-isatin hybrids as potent antileishmanial agents: Synthesis, in silico and in vitro evaluations

Leishmaniasis being one of the six major tropical diseases that affects nearly 0.7-1.3 million people annually, has so far limited and high toxic therapeutic options. Herein, we report the synthesis, in silico, and in vitro evaluations of novel coumarin-incorporated isatin hydrazones (Spf-1 - Spf-10) as highly potent and safe antileishmanial agents. Molecular docking was initially carried out to decipher the binding confirmation of lead molecules towards the active cavity of the target protein (Leishmanolysin gp63) of Leishmania tropica. Among all the docked compounds, only Spf-6, Spf-8, and Spf-10 showed high binding affinities due to a pattern of strong conventional hydrogen bonds and hydrophobic π-interactions. The molecular dynamics simulations showed the stable pattern of such bonding and structure-based confirmation with a time scale of 50 ns towards the top compound (Spf-10) and protein. These analyses affirmed the high stability of the system. Three out of ten compounds evaluated for their antileishmanial activity against Leishmania tropica promastigotes and amastigotes were found to be active at micromolar concentrations (IC₅₀ range 0.1-4.13 μmol/L), and most importantly, they were also found to be highly biocompatible when screened for their toxicity in human erythrocytes.

Antiplasmodial and antileishmanial inhibitory activity of triterpenes and steroidal alkaloid from the leaves of Funtumia elastica (Preuss) Stapf (Apocynaceae)

The phytochemical study of leaves of Funtumia elastica led to the isolation of three undescribed ursane derivatives, funtumic acids A, B and C (1-3), as well as one steroidal alkaloid, elasticine (4) and five other known compounds (5-9). Their structures were elucidated on the basis of NMR, MS, IR, UV spectroscopic data as well as by comparison with the literature. The compound 5-hydroxypyridine-3-carboxamide (9) was isolated for the first time from the Apocynaceae family. All the isolated compounds were evaluated for their antiparasitic effects against 3D7 and Dd2 strains of Plasmodium falciparum and promastigotes of Leishmania donovani (MHOM/SD/62/1S). Compounds 1-4 possessed good in vitro antimalarial activities against CQR Dd2 with IC₅₀ values ranging from 4.68 to 5.36 μg/mL and moderate on CQS 3D7. Only compounds 1 and 2 showed leishmanicidal activities with IC₅₀ values ranging between 10.49 and 13.21 μg/mL. In addition, crude extract exhibited potent antiplasmodial (IC₅₀ 0.91 and 3.12 μg/mL) and antileishmanial (IC₅₀ 3.32 μg/mL) activities, thus demonstrating their potential synergistic action.

In vitro antileishmanial potentialities of essential oils from Citrus limon and Pistacia lentiscus harvested in Tunisia

Leishmaniasis is a tropical parasitic disease that affects up to 12 million people worldwide. Current chemotherapies have limitations such as toxicity, high cost, and parasite resistance. This work aims to select an essential oil (EssOil) isolated from the Tunisian flora as a new antileishmanial candidate. Two plants were chosen for their antileishmanial potential: Citrus limon (Citrus) and Pistacia lentiscus (Pistacia). Each of these plants was harvested from two different sites (area 1 and area 2). Extracted EssOils were characterized using GC-MS. Their antiparasitic activity against axenic and intracellular Leishmania major amastigotes and their cytotoxicity were assessed. Citrus EssOil from area 1 displayed an interesting activity against L. major intramacrophage amastigotes with IC₅₀ value at 4.2 ± 1.3 μg/mL. Interestingly, this activity was close to that of miltefosine. Moderate activities against intracellular amastigote were observed for Pistacia EssOil from area 1 and Citrus EssOil from area 2. However, low cytotoxicity with high selectivity index was proved only for Citrus EssOil from area 1, revealing its safety for macrophages. This study also demonstrated for the first time the antileishmanial activity of EssOil extracted from Citrus limon leaves. The EssOil interesting activity could be related to the lipophilic properties of terpenes that were shown in literature to contribute to the disruption of parasite intracellular metabolic pathways.

Nanoemulsions with Chloroaluminium Phthalocyanine and Paromomycin for Combined Photodynamic and Antibiotic Therapy for Cutaneous Leishmaniasis

BACKGROUND

Photodynamic therapy (PDT) using chloroaluminium phthalocyanine (ClAlPc) and paromomycin sulfate (PM) can be effective against New World Leishmania species involved in cutaneous leishmaniasis (CL). The aim of this study is to assay the skin permeation and the antileishmanial effects of a nanoemulsion (NE) containing both ClAlPc and PM in experimental CL by Leishmania (Viannia) braziliensis.

MATERIAL AND METHODS

Cremophor ELP/castor oil-based NEs were prepared by a low-energy method and characterized for their physicochemical parameters. The NEs were used to deliver both ClAlPc and PM to leishmania cells. The in vitro toxicity of NEs were tested in vitro against L. (V.) braziliensis and THP-1 cells. The in vivo toxicity was assessed in non-infected BALB/c mice. Ex-vivo permeation and retention studies using healthy mice skin were also conducted. Finally, the in vivo activity of NE-PM+ClAlPc after PDT was tested in BALB/c mice infected with parasites.

RESULTS

NEs are colloidally stable with average droplet diameter of 30 nm, polydispersity index (PDI) below 0.2, and zeta potential near zero. Both promastigotes and intracellular amastigotes treated with NE-PM, NE-ClAlPc and NE-PM+ClAlPc were inhibited at >50%, >95%, >88%, respectively, after PDT with a phototoxic index (PI) >1.2. No skin ClAlPc permeation was observed. In contrast, PM skin permeation was 80-fold higher using PM-loaded NE formulation in comparison to aqueous PM solution. Topical treatment with NE formulations showed no signs of local toxicity or genotoxicity. In addition, concentrations of PM between 27.3 - 292.5 μM/25 mg of tissue were detected in different organs. In vivo, the NE-PM+ClAlPc treatment did not reduce skin lesions.

CONCLUSION

The Cremophor ELP/castor oil NE formulation increases the permeation of PM through the skin and can be used to co-deliver PM plus ClAlPc for combined PDT protocols. However, the lack of efficacy in the in vivo model evidences that the therapeutical scheme has to be improved.

Antileishmanial Activity of New Synthesized Schiff and Mannich (Morpholine) Base Compounds

Objective

Leishmaniasis is an important parasitic disease in many countries, including ours. A variety of drugs are currently used for its treatment. However, certain side effects of these drugs, such as teratogenicity, hepatotoxicity and nephrotoxicity, have been reported in some patients. The goal of this research is to determine the antileishmanial effects of eight different previously synthesised compounds containing Schiff and Mannich bases (morpholine) against Leishmania infantum (L. infantum) promastigotes by the liquid microdilution method utilising alamarBlue.

Methods

Compounds containing Schiff bases (a-d) and both Schiff bases and morpholine rings (e-h) were tested. Compounds were diluted in the range of 20000-39 μg/mL. L. infantum promastigotes were added to the wells, which were then incubated at 27 °C. The proliferation of Leishmania promastigotes was evaluated after 24, 48 and 72 hours.

Results

In this study, compounds b, c and d (MIC values 156 μg/mL, 78 μg/mL and 156 μg/mL) were found to be effective against L. infantum promastigotes, whereas compound f (MIC >20000 μg/mL) was found to be more the most ineffective compound.

Conclusion

These compounds may be potential drug candidates for the treatment of leishmaniasis. According to the results, there is a need for further studies, such as in vivo experimental animal models and ex vivo Leishmania amastigote macrophage cultures for compounds showing antileishmanial effects.

leaves

Solanum paniculatum L. is species whose fruits are widely consumed in Brazil as a tonic beverage with higher content of steroidal saponins. In this work, we developed an analytical method for the quantification of the eight saponins present in the 70 % ethanol extract from the leaves using ultra-high-performance liquid chromatography coupled to mass spectrometry (UHPLC-MS). Besides, the eight spirostanic saponins were screened for in vitro antileishmanial activity against promastigote and amastigote forms of Leishmania (L.) amazonensis. Substances 1, 2 and 3 were found to be the most active compounds, with inhibitory concentration (IC₅₀) values of 8.51 ± 4.38, 10.75 ± 6.85 and 10.45 ± 4.21 μM, respectively, against promastigote forms and effective concentration (EC₅₀) values of >25, 17.73 ± 0.99 and 19.57 ± 0.84 μM, respectively, against amastigote forms. The cytotoxic test with compounds 1-3 evidenced low toxicity in murine macrophage cells, with values above 50 μM at concentration lower than 25 μM. These findings show that saponins 1-3 should be evaluated in further studies for the treatment of cutaneous leishmaniasis.

Assessing different thiazolidine and thiazole based compounds as antileishmanial scaffolds

The compounds from eight different thiazolidine and thiazole series were assessed as potential antileishmanial scaffolds. They were tested for antileishmanial activity against promastigotes of Leishmania major using in vitro primary screen and dose response assays. The compounds from six thiazolidine and thiazole series were identified as the hits with antileishmanial activity against L. major. However, the analyses of structure-activity relations (SARs) showed that the interpretable SARs were obtained only for phenyl-indole hybrids (compounds C1, C2, C3 and C5) as the most effective compounds against L. major promastigotes (IC₅₀ < 10 µM) with low toxicity to human fibroblasts. For the scaffold of these compounds, the most significant SAR patterns were: free N3 position of thiazolidinone core, absence of big fragments at the C5 position of thiazolidinone core and presence of halogen atoms or nitro group in the phenyl ring of phenyl-indole fragment. As previous studies showed that these compounds also have activity against the two Trypanosoma species, Trypanosoma brucei and Trypanosoma gambiense, their scaffold could be associated with a broader antiparasitic activity.

Liposome-based nanocarrier loaded with a new quinoxaline derivative for the treatment of cutaneous leishmaniasis

The use of nanocarriers for drug delivery is a strategy aimed to improve therapeutic indices through changes in their pharmacokinetic and pharmacodynamic characteristics. Liposomes are well-investigated nanocarriers for drug delivery to macrophage-targeted therapy, the main hosts of intracellular pathogens of some infectious diseases, such as leishmaniasis. In this study, we developed hyaluronic acid (HA)-coated liposomes by different methods that can encapsulate a new quinoxaline derivative, the LSPN331, to increase its solubility and improve its bioavailability. The surface modification of liposomes and their physicochemical characteristics may depend on the coating method, which may be a critical parameter with regard to the route of administration of the antileishmanial drug. Liposomes with identical phospholipid composition containing the same drug were developed, and different biological responses were verified, and our hypothesis is that it is related to the type of modification of the surface. Different physicochemical characterization techniques (dynamic light scattering, transmission electron microscopy and UV-vis quantification of labeled-HA) were used to confirm the successful modification of liposomes as well as their stability upon storage. The encapsulation of LSPN331 was performed using HPLC method, and the entrapment efficiency (EE%) was satisfatory in all formulations, considering results of similar formulations in the literature. Furthermore, in vitro and in vivo studies were carried out to evaluate the efficacy against the parasite Leishmania amazonensis. The in vitro activity was maintained or even improved and HA-coated liposomes showed the ability to target to the site of action by the proposed routes of administration, topically and intravenously. Both formulations are promising for future tests of antileishmania activity in vivo.

Leishmanicidal activity of Piper marginatum Jacq. from Santarém-PA against Leishmania amazonensis

Leishmaniasis is an infectious disease that has high endemicity and is among the six parasitic diseases of higher occurrence in the world. The current treatments are limited due to their toxicity, treatment resistance and high cost which have increased the search for new substances of natural origin for its therapy. Based on this, an in vitro biological and chemical investigation was carried out to evaluate the potential of Piper marginatum against Leishmania amazonesis. P. marginatum leaves were collected to obtain the essential oil (EO) and the ethanolic extract (CE). The chemical profile of the CE and fractions was obtained by 1H NMR. The analysis of the EO chemical composition was performed by GC-MS. EO, CE and fractions were submitted to antileishmanial and cytotoxicity assays against macrophages. The chromatographic profiles of EO, CE and fractions showed the presence of phenolic compounds and terpenoids, having 3,4-Methylenedioxypropiophenone as a major compound. All P. marginatum samples showed low toxicity to macrophages. The CE and the methanolic, hexane and ethyl acetate fractions had low cytotoxicity when compared to Pentamidine. All tested samples inhibited growth of L. amazonensis promastigotes. The antileishmanial activity of EO, CE and fractions were evaluated in macrophages infected with L. (L.) amazonensis and treated with the concentrations 1, 10 and 100 μg/mL for 48 h. All samples were active, but EO and CE showed superior activity against amastigote forms when compared to the promastigote forms of L. amazonensis. This work describes for the first time the antileishmanial activity of the species P. marginatum and its cytotoxicity against macrophages, suggesting that it can be an alternative source of natural products in the phytotherapeutic treatment of leishmaniasis.

Synthesis and antileishmanial activity of fluorinated rhodacyanine analogues: The 'fluorine-walk' analysis

In a search for potent antileishmanial drug candidates, eighteen rhodacyanine analogues bearing fluorine or perfluoroalkyl substituents at various positions were synthesized. These compounds were tested for their inhibitory activities against Leishmania martiniquensis and L. orientalis. This 'fluorine-walk' analysis revealed that the introduction of fluorine atom at C-5, 6, 5', or 6' on the benzothiazole units led to significant enhancement of the activity, correlating with the less negative reduction potentials of the fluorinated analogues confirmed by the electrochemical study. On the other hand, CF₃ and OCF₃ groups were found to have detrimental effects, which agreed with the poor aqueous solubility predicted by the in silico ADMET analysis. In addition, some of the analogues including the difluorinated species showed exceptional potency against the promastigote and axenic amastigote stages (IC₅₀ = 40-85 nM), with the activities surpassing both amphotericin B and miltefosine.

A chloroquinoline derivate presents effective in vitro and in vivo antileishmanial activity against Leishmania species that cause tegumentary and visceral leishmaniasis

The identification of new therapeutics to treat leishmaniasis is desirable, since available drugs are toxic and present high cost and/or poor availability. Therefore, the discovery of safer, more effective and selective pharmaceutical options is of utmost importance. Efforts towards the development of new candidates based on molecule analogs with known biological functions have been an interesting and cost-effective strategy. In this context, quinoline derivatives have proven to be effective biological activities against distinct diseases. In the present study, a new chloroquinoline derivate, AM1009, was in vitro tested against two Leishmania species that cause leishmaniasis. The present study analyzed the necessary inhibitory concentration to preclude 50% of the Leishmania promastigotes and axenic amastigotes (EC₅₀ value), as well as the inhibitory concentrations to preclude 50% of the murine macrophages and human red blood cells (CC₅₀ and RBC₅₀ values, respectively). In addition, the treatment of infected macrophages and the inhibition of infection using pre-treated parasites were also investigated, as was the mechanism of action of the molecule in L. amazonensis. To investigate the in vivo therapeutic effect, BALB/c mice were infected with L. amazonensis and later treated with AM1009. Parasitological and immunological parameters were also evaluated. Clioquinol, a known antileishmanial quinoline derivate, and amphotericin B (AmpB), were used as molecule and drug controls, respectively. Results in both in vitro and in vivo experiments showed a better and more selective action of AM1009 to kill the in vitro parasites, as well as in treating infected mice, when compared to results obtained using clioquinol or AmpB. AM1009-treated animals presented significantly lower average lesion diameter and parasite burden in the infected tissue and organs evaluated in this study, as well as a more polarized antileishmanial Th1 immune response and low renal and hepatic toxicity. This result suggests that AM1009 should be considered a possible therapeutic target to be evaluated in future studies for treatment against leishmaniasis.

White jute (Corchorus capsularis L.) leaf extract has potent leishmanicidal activity against Leishmania donovani

In pursuit of effective, safe and affordable antileishmanial drugs, the current study was designed to explore Corchorus capsularis L. leaf extract (CCEx) as an effective leishmanicidal substitute against Leishmania donovani. The leaf extract displays potent antileishmanial activity against L. donovani promastigotes with an IC₅₀ value of 79.00 ± 0.3 μg/ml. CCEx also significantly induces intracellular reactive oxygen species (ROS) with a concomitant decrease in the level of non-protein thiols in virulent parasites. Additionally, CCEx treatment induces substantial morphological alterations in parasites. Moreover, reagent-based phytochemical analysis of the extract revealed the presence of various phytochemical constituents. Further study is underway to identify the bioactive component(s) or fraction(s) of CCEx through bioassay-guided fractionation.

Repurposing azole antifungals into antileishmanials: Novel 3-triazolylflavanones with promising in vitro antileishmanial activity against Leishmania major

Previously, we have described a series of azole antifungals namely 3-(1,2,4-triazol-1-yl)flavanones (TFs) containing an N-(phenethyl)azole framework required for sterol 14α-demethylase (CYP51) inhibitory activity. Similar mechanism of action of azoles in fungi and protozoan parasites prompted us to investigate the potential effects of TFs against promastigote and amastigote forms of Leishmania major (L. major), as well as their toxicity against macrophages, apoptosis induction and in silico interactions with the target enzyme. All compounds showed more potent anti-parasitic activity against L. major in comparison with reference azole drug fluconazole and standard antileishmanial agent glucantime. Among the tested compounds, the 4-chloro derivative (TF-2) was found to be the most potent one, being about 13 times more potent than fluconazole against promastigotes. TF-2 decreased both mean infection rate of macrophages (MIR) and mean number of amastigotes per macrophages (MNAPM), significantly more than fluconazole (P < .001). Furthermore, the cytotoxicity assay against J774.A.1 macrophages revealed that this compound displays high selectivity against amastigotes over macrophages (SI = 30.21). The in silico study showed that TF-2 can properly accommodated in the active site of parasitic CYP51 and coordinated to the heme. The SAR analysis showed that the introduction of 4-chloro on 2-phenyl moiety results in the best profile of activity and selectivity. Accordingly, the compound TF-2 prototype can be considered as promising candidate for development of new antileishmanial agents.

Fruticulosin: A novel type 2 ribosome-inactivating protein from Abrus fruticulosus seeds that exhibits toxic and antileishmanial activity

Plant ribosome-inactivating proteins (RIPs) are a family of toxins that inhibit protein synthesis. In this study, we have isolated a novel type 2 ribosome-inactivating protein (RIP) present in seeds of the Abrus fruticulosus, named of fruticulosin. Fruticulosin, shows characteristics common to other type 2 RIPs, as specificity by galactosides (d-galactose, N-acetyl-d-galactosamine, and d-lactose), mass of approximately 60 kDa and presence of the of disulfide bonds. The N-terminal amino acid sequence (26 residues) of A-chain fruticulosin, determined by Edman degradation, revealed high similarity of the A-chain with those of other type 2 RIPs. The secondary structure of fruticulosin was analysed by circular dichroism, which showed that fruticulosin contains α-helices (22.3%), β-sheets (43.5%), and random coils and corners (34.2%). Furthermore, fruticulosin showed high toxicity in Artemia sp. (3.12 μg/mL), inhibited in vitro protein synthesis by a cell-free system and showed RNA N-glycosidase activity. Fruticulosin presented biological activities such as agglutination and antileishmanial activity on promastigote forms of Leishmania major.

Neolignans isolated from twigs of Nectandra leucantha Ness & Mart (Lauraceae) displayed in vitro antileishmanial activity

Background

The therapeutic arsenal for the treatment of Leishmaniasis is limited and includes toxic compounds (antimonials, amphotericin B, pentamidine and miltefosine). Given these aspects, the search for new compounds based on floristic biodiversity is crucial. In the present work, we report the isolation, characterization and antileishmanial activity of six related neolignans (1–6) of bioactive extract from Nectandra leucantha (Lauraceae) twigs.

Methods

Dried and powdered twigs of N. leucantha were exhaustively extracted using n-hexane. The crude extract was dereplicated by HPLC/HRESIMS and subjected to column chromatography to yield pure compounds 1–6. Their chemical structures were identified via NMR and comparison of obtained data with those previously published in the literature. Biological assays of compounds 1–6 and their respective monomers (eugenol and methyleugenol) were performed using promastigote and amastigote forms of Leishmania (L.) infantum.

Results

Dereplication procedures followed by chemical characterization of isolated compounds by NMR enabled the identification of related neolignans 1–6. Neolignans 2, 4 and 6 showed potential against amastigote forms of L. (L.) infantum (EC₅₀ values of 57.9, 67.7 and 13.7 μM, respectively), while compounds 1 and 3 were inactive. As neolignans 2–4 are chemically related, it may be suggested that the presence of the methoxyl group at C4 constitutes an important structural aspect to increase antileishmanial potential against amastigote forms. Compound 6, which consists of a methylated derivative of compound 5 (inactive) showed antileishmanial activity similar to that of the standard drug miltefosine (EC₅₀ = 16.9 μM) but with reduced toxicity (SI = 14.6 and 7.2, respectively). Finally, two related monomers, eugenol and methyleugenol, were also tested and did not display activity, suggesting that the formation of dimeric compounds by oxidative coupling is crucial for antiparasitic activity of dimeric compounds 2, 4 and 6.

Conclusion

This study highlights compound 6 against L. (L.) infantum amastigotes as a scaffold for future design of new compounds for drug treatment of visceral leishmaniasis.

Novel organic salts based on quinoline derivatives: The in vitro activity trigger apoptosis inhibiting autophagy in Leishmania spp

Leishmaniases are infectious diseases, caused by protozoa of the Leishmania genus. These drugs present high toxicity, long-term administration, many adverse effects and are expensive, besides the identification of resistant parasites. In this work, the antileishmanial activity of quinoline derivative salts (QDS) was evaluated, as well as the toxicity on mammalian cells and the mechanism of action of the most promising compound. Among the compound tested, only the compound QDS3 showed activity against promastigotes and amastigotes of Leishmania spp., being more active against the intracellular amastigotes of L. amazonensis-GFP (IC₅₀ of 5.48 μM). This value is very close to the one observed for miltefosine (IC₅₀ of 4.05 μM), used as control drug. Furthermore, the compound QDS3 exhibited a selective effect, being 40.35 times more toxic to the amastigote form than to the host cell. Additionally, promastigotes of L. amazonensis treated with this compound exhibited characteristics of cells in the process of apoptosis such as mitochondrial membrane depolarization, mitochondrial swelling, increase of ROS production, phosphatidylserine externalization, reduced and rounded shape, and cell cycle alteration. The integrity of the plasma membrane remained unaltered, excluding necrosis in treated promastigotes. The compound QDS3 inhibited the formation of autophagic vacuoles, which may have contributed to parasite death by preventing autophagic mechanisms in the removal of damaged organelles, intensifying the damage caused by the treatment, highlighting the antileishmanial effect of this compound. In addition, treatment with QDS3 induced increased ROS levels in L. amazonensis-infected macrophages, but not in uninfected host cell. These data reinforce that the induction of oxidative stress is one of the main toxic effects caused by the treatment with the compound QDS3 in L. amazonensis, causing irreversible damage and triggering a selective death of intracellular parasites. Data shown here confirm the biological activity of quinoline derivatives and encourage future in vivo studies with this compound in the murine model.

Ethanolic leaf extract of Coccinia grandis is effective against both drug resistant and drug sensitive clinical isolates of Indian Kala-azar

The emergence of resistance to the current available drugs used for treatment against Indian Kala-azar (KA) or Visceral Leishmaniasis makes the control strategy inadequate for the disease. This grave epidemiological situation directed researches towards alternative treatments including herbal therapy. In this background, the aim of the present study was to evaluate the antileishmanial activity of the leaves of Coccinia grandis (a tropical vine) against both the Sodium Stibo Gluconate (SSG) sensitive and resistant as well as Miltefosine (MIL) sensitive and resistant field isolates of Leishmania donovani. The cytotoxicity effect of ethanolic extract of leaves of C. grandis (Cg-LE) against the clinical isolates of L. donovani was checked both in promastigotes and intracellular amastigotes stages. In both sensitive and resistant promastigotes, Cg-LE stimulated reactive oxygen species generation and apoptosis. Parasites infected macrophages showing enhanced nitric oxide production after Cg-LE treatment suggested the leishmanicidal activity of the leaf extract. Furthermore, Cg-LE treatment led to mitochondrial membrane damage and DNA fragmentation in promastigotes. The present study is very encouraging for the fact that Cg-LE showed promising antileishmanial activity against both SSG and MIL drug resistant clinical isolates of Indian KA.

In vitro activity of Morinda citrifolia Linn. fruit juice against the axenic amastigote form of Leishmania amazonensis and its hydrogen peroxide induction capacity in BALB/c peritoneal macrophages

OBJECTIVE

The current treatment of leishmaniasis induces strong side effects and increasing numbers of cases of resistance to reference drugs have been reported. The discovery of the therapeutic properties of active substances in plant extracts represents an interesting field of research into a more efficient treatment against leishmaniasis. Morinda citrifolia, commonly known as noni, has demonstrated promising results as antileishmanial and immunomodulator. Thus, the aim of this work was to evaluate activity against axenic amastigote and hydrogen peroxide induction capacity by M. citrifolia fruit juice.

RESULTS

Phytochemical screening identified anthraquinones, flavonoids, alkaloids, terpenoids, steroids, saponins, coumarins, phenolic compounds, tannins, anthocyanidins and chalcones. Noni juice exhibited dose-dependent activity and an IC₅₀ of 240.1 µg/mL for axenic amastigotes. An absence of endotoxins was observed at the concentrations analyzed, while no cytotoxic effects were identified. Noni juice induced hydrogen peroxide production in BALB/c peritoneal macrophages but not in macrophages infected with Leishmania amazonensis. M. citrifolia fruit juice exhibited antileishmanial activity against L. amazonensis axenic amastigotes and activated macrophages by hydrogen peroxide induction, asserting its potential for further research into new forms of leishmaniasis treatment.

Promising antileishmanial activity of novel imidazole antifungal drug luliconazole against Leishmania major: In vitro and in silico studies

OBJECTIVES

Pentavalent antimonials have been used for the treatment of leishmaniasis for over 70 years, however they are limited by their toxicity. Unfortunately, the efficacy of first-line drugs for the treatment of leishmaniasis has decreased and resistance is noticeable. Luliconazole is a new azole with unique effects on fungi that has not yet been tested on Leishmania parasites.

METHODS

In this study, the cytotoxicity and antileishmanial activity of luliconazole were evaluated in vitro against promastigotes and intracellular amastigotes of Leishmania major. The docking simulation with the target enzyme, sterol 14α-demethylase (CYP51) was performed using AutoDock 4.2 program.

RESULTS

The IC₅₀ (concentration of test compound required for 50% inhibition) against promastigotes revealed that luliconazole (IC₅₀=0.19μM) has greater potency than ketoconazole (KET), meglumine antimoniate (MA) and amphotericin B (AmB) (IC₅₀ values of 135, 538 and 2.52μM, respectively). Against the amastigote stage, luliconazole at a concentration of 0.07μM decreased the mean infection rate and the mean number of amastigotes per macrophage more effectively than MA (P<0.004) and KET (P<0.043), but there was no difference compared with AmB (P>0.05). A docking study of luliconazole with the cytochrome P450 enzyme sterol 14α-demethylase (CYP51) revealed that this azole drug can properly interact with the target enzyme in Leishmania mainly via coordination with heme and multiple hydrophobic interactions.

CONCLUSION

These results show the potent activity of luliconazole at extremely low concentrations against L. major. It may therefore be considered as a new candidate for treatment of leishmaniasis in the near future.

amazonensis species

Leishmaniasis has become a significant public health issue in several countries in the world. New products have been identified to treat against the disease; however, toxicity and/or high cost is a limitation. The present work evaluated the antileishmanial activity of a new naphthoquinone derivate, Flau-A [2-(2,3,4-tri-O-acetyl-6-deoxy-β-L-galactopyranosyloxy)-1,4-naphthoquinone], against promastigote and amastigote-like stages of Leishmania amazonensis and L. infantum. In addition, the cytotoxicity in murine macrophages and human red cells was also investigated. The mechanism of action of Flau-A was assessed in L. amazonensis as well as its efficacy in treating infected macrophages and inhibiting infection of pretreated parasites. Results showed that Flau-A was effective against promastigotes and amastigote-like forms of both parasite species, as well as showed low toxicity in mammalian cells. Results also highlighted the morphological and biochemical alterations induced by Flau-A in L. amazonensis, including loss of mitochondrial membrane potential, as well as increased reactive oxygen species production, cell shrinkage, and alteration of the plasma membrane integrity. The present study demonstrates for the first time the antileishmanial activity of Flau-A against two Leishmania species and suggests that the mitochondria of the parasites may be the main target organelle. Data shown here encourages the use of this molecule in new studies concerning treatment against Leishmania infection in mammalian hosts.

In vivo studies of the effectiveness of novel N-halomethylated and non-halomethylated quaternary ammonium salts in the topical treatment of cutaneous leishmaniasis

The physicochemical properties of four N-halomethylated and one non-halomethylated ammonium salts, with proven in vitro antileishmanial activity, were determined according to pharmaceutical standard procedures. The effectiveness and toxicity of these compounds were assessed in hamsters infected with Leishmania (Viannia) braziliensis and compared to that showed by meglumine antimoniate. Animals were followed during 90 days after the completion of treatment. Therapeutic response was determined according to the reduction of size of skin lesions. Toxicity was determined by the effect of compounds on body weight changes and serum levels of renal and hepatic metabolites. The effectiveness of compound 4 was similar to that showed by intralesional administration of meglumine antimoniate and better than that of the other ammonium salts. Levels of creatinine, alanine amino transferase, and blood urea nitrogen in serum were not significantly different between treatment groups, including healthy or untreated hamsters. Results imply that compound 4 has potential as a pharmaceutical active ingredient in the development of new and better formulations for the treatment of cutaneous leishmaniasis.

Cytotoxicity and anti-Leishmania amazonensis activity of Citrus sinensis leaf extracts

CONTEXT

Leishmania amazonensis is the main agent of diffuse cutaneous leishmaniasis, a disease characterized by lesional polymorphism and the commitment of skin surface. Previous reports demonstrated that the Citrus genus possess antimicrobial activity.

OBJECTIVE

This study evaluated the anti-L. amazonensis activity of Citrus sinensis (L.) Osbeck (Rutaceae) extracts.

MATERIALS AND METHODS

Citrus sinensis dried leaves were subjected to maceration with hexane (CH), ethyl acetate (CEA), dichloromethane/ethanol (CD/Et - 1:1) or ethanol/water (CEt/W - 7:3). Leishmania amazonensis promastigotes were treated with C. sinensis extracts (1-525 μg/mL) for 120 h at 27 °C. Ultrastructure alterations of treated parasites were evaluated by transmission electron microscopy. Cytotoxicity of the extracts was assessed on RAW 264.7 and J774.G8 macrophages after 48-h treatment at 37 °C using the tetrazolium assay. In addition, Leishmania-infected macrophages were treated with CH and CD/Et (10-80 μg/mL).

RESULTS

CH, CD/Et and CEA displayed antileishmanial activity with 50% inhibitory activity (IC₅₀) of 25.91 ± 4.87, 54.23 ± 3.78 and 62.74 ± 5.04 μg/mL, respectively. Parasites treated with CD/Et (131.2 μg/mL) presented severe alterations including mitochondrial swelling, lipid body formation and intense cytoplasmic vacuolization. CH and CD/Et demonstrated cytotoxic effects similar to that of amphotericin B in the anti-amastigote assays (SI of 2.16, 1.98 and 1.35, respectively). Triterpene amyrins were the main substances in CH and CD/Et extracts. In addition, 80 μg/mL of CD/Et reduced the number of intracellular amastigotes and the percentage of infected macrophages in 63% and 36%, respectively.

CONCLUSION

The results presented here highlight C. sinensis as a promising source of antileishmanial agents.

In vitro activity of new N-benzyl-1H-benzimidazol-2-amine derivatives against cutaneous, mucocutaneous and visceral Leishmania species

The identification of specific therapeutic targets and the development of new drugs against leishmaniasis are urgently needed, since chemotherapy currently available for its treatment has several problems including many adverse side effects. In an effort to develop new antileishmanial drugs, in the present study a series of 28 N-benzyl-1H-benzimidazol-2-amine derivatives was synthesized and evaluated in vitro against Leishmania mexicana promastigotes. Compounds 7 and 8 with the highest antileishmanial activity (micromolar) and lower cytotoxicity than miltefosine and amphotericin B were selected to evaluate their activity against L. braziliensis 9and L. donovani, species causative of mucocutaneous and visceral leishmaniasis, respectively. Compound 7 showed significantly higher activity against L. braziliensis promastigotes than compound 8 and slightly lower than miltefosine. Compounds 7 and 8 had IC₅₀ values in the micromolar range against the amastigote of L. mexicana and L. braziliensis. However, both compounds did not show better activity against L. donovani than miltefosine. Compound 8 showed the highest SI against both parasite stages of L. mexicana. In addition, compound 8 inhibited 68.27% the activity of recombinant L. mexicana arginase (LmARG), a therapeutic target for the treatment of leishmaniasis. Docking studies were also performed in order to establish the possible mechanism of action by which this compound exerts its inhibitory effect. Compound 8 shows promising potential for the development of more potent antileishmanial benzimidazole derivatives.

Synthesis, characterization, and antileishmanial activity of neutral N-heterocyclic carbenes gold(I) complexes

A series of five new mononuclear neutral gold(I) complexes containing N-heterocyclic carbenes (NHCs) was synthesized and fully characterized by spectroscopic methods. The X-ray structures of four complexes are presented. These gold(I) complexes together with four other neutral gold(I)-NHC complexes previously described were evaluated in vitro against Leishmania infantum promastigotes and axenic amastigotes. Moreover, their cytotoxicity was assessed on the murine macrophages J774A.1. Except one complex (10), eight gold(I)-NHC-Cl complexes show potent activity against the pathological relevant form of L. infantum amastigote with IC₅₀ in the low micromolar and submicromolar range and five of them exhibit a SI close to 10. The lead-complex 11 displays a very high and selective activity (IC₅₀ = 190 nM, SI = 40.29) and constitutes the best promising gold(I)-based drug of this series.

Chemical composition of Mentha pulegium and Rosmarinus officinalis essential oils and their antileishmanial, antibacterial and antioxidant activities

The aim of the study was the determination of the chemical composition of Mentha pulegium L. and Rosmarinus officinalis L. essential oils and the evaluation of their antileishmanial, antibacterial and antioxidant activities. Essential oils (EOs) were isolated using steam distillation and the chemical composition was determined using GC-MS analysis. The antibacterial activity was tested against ten pathogenic strains using the diffusion method, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) by microtitration assay. The antioxidant activity was estimated by DPPH free radical scavenging ability and ferric-reducing power. The antileishmanial activity was tested against Leishmania major, Leishmania tropica and Leishmania infantum using MTT (3-(4.5-dimethylthiazol-2yl)-2.5-diphenyltetrazolium bromide) assay. The yield of essential oils (v/w %) M. puleguim and R. officinalis based on dry weight were 5.4 and 2.7% respectively. GC/MS analysis of R. officinalis essential oil (ROEO) revealed the presence of 29 components, mainly represented by oxygenated monoterpenes (63.743%) and hydrocarbons monoterpenes (21.231%). Mentha pulegium essential oil (MPEO) revealed 21 components, mainly represented by oxygenated monoterpenes (83.865%). The major components of ROEO were α-pinene (14.076), 1,8-Cineole (23.673) and camphor (18.743), while menthone (21.164) and pulegone (40.98) were the main major components of MPEO. M. pulegium and R. officinalis EOs showed a significant antioxidant activity compared with ascorbic acid and Trolox to the IC₅₀ values of 58.27 ± 2.72 and 85.74 ± 7.57 μg/mL respectively revealed by reducing power assay. As for the antibacterial effect, the highest zone diameters were shown by the MPEO against Bacillus subtilis (30 ± 1.43 mm) and Proteus mirabilis (28 ± 1.32 mm). These values are significantly important compared with those of the commercialized antibiotic (Erythromycin and Chlorophenicol). The lowest MIC and MBC values were obtained with MPEO against S. aureus MBLA (MIC = MBC = 0.25% (v/v)). While, ROEO has exhibited a bactericidal effect against Listeria monocytogenes (MIC = MBC = 0.5% (v/v)), Bacillus subtilis (MIC = MBC = 1% (v/v)) and Escherichia coli (MIC = MBC = 1% (v/v)). For the antileishmanial effect, ROEO is the most active against L. major (IC₅₀ = 1.2 ± 0.36 μg/mL. While, the MPEO has the most leishmanicidal effect against L. major (IC₅₀ = 1.3 ± 0.45 μg/mL). These findings show that the EOs of M. pulegium and R. officinalis are good sources of bioactive molecules that could have potential applications in the food and pharmaceutical industries.

Antileishmanial potential of fused 5-(pyrazin-2-yl)-4H-1,2,4-triazole-3-thiols: Synthesis, biological evaluations and computational studies

A series of newer 1,2,4-triazole-3-thiol derivatives 5(a-m) and 6(a-i) containing a triazole fused with pyrazine moiety of pharmacological significance have been synthesized. All the synthesized compounds were screened for their in vitro antileishmanial and antioxidant activities. Compounds 5f (IC₅₀=79.0µM) and 6f (IC₅₀=79.0µM) were shown significant antileishmanial activity when compared with standard sodium stibogluconate (IC₅₀=490.0µM). Compounds 5b (IC₅₀=13.96µM) and 6b (IC₅₀=13.96µM) showed significant antioxidant activity. After performing molecular docking study and analyzing overall binding modes it was found that the synthesized compounds had potential to inhibit L. donovani pteridine reductase 1 enzyme. In silico ADME and metabolic site prediction studies were also held out to set an effective lead candidate for the future antileishmanial and antibacterial drug discovery initiatives.

Chemical profile and anti-leishmanial activity of three Ecuadorian propolis samples from Quito, Guayaquil and Cotacachi regions

Three propolis samples were collected from different regions of Ecuador (Quito, Guayaquil and Cotacachi) and their methanolic extracts were prepared. Preliminary information supplied by TLC and NMR data, allowed us to define two main types of propolis: Cotacachi propoli sample (CPS), rich in flavonoids and Quito and Guayaquil samples (QPS and GPS) containing triterpenic alcohols and acetyl triterpenes as the main constituents. Two different approaches based on RP-HPLC preparative procedure and NMR structural determination (CPS) and GC-MS analysis (QPS and GPS) were successfully used for the chemical characterization of their major compounds. All three propolis extracts were able to inhibit Leishmania amazonensis growth but propolis sample rich in flavonoids was the most active (IC₅₀=17.1±1.7μg/mL). In the literature this is the first study on propolis from Ecuador.

Alkylphospholipids: An update on molecular mechanisms and clinical relevance

Alkylphospholipids (APLs) represent a new class of drugs which do not interact directly with DNA but act on the cell membrane where they accumulate and interfere with lipid metabolism and signalling pathways. This review summarizes the mode of action at the molecular level of these compounds. In this sense, a diversity of mechanisms has been suggested to explain the actions of clinically-relevant APLs, in particular, in cancer treatment. One consistently reported finding is that APLs reduce the biosynthesis of phosphatidylcholine (PC) by inhibiting the rate-limiting enzyme CTP:phosphocholine cytidylyltransferase (CT). APLs also alter intracellular cholesterol traffic and metabolism in human tumour-cell lines, leading to an accumulation of cholesterol inside the cell. An increase in cholesterol biosynthesis associated with a decrease in the synthesis of choline-containing phospholipids and cholesterol esterification leads to a change in the free-cholesterol:PC ratio in cells exposed to APLs. Akt phosphorylation status after APL exposure shows that this critical regulator for cell survival is modulated by changes in cholesterol levels induced in the plasma membrane by these lipid analogues. Furthermore, APLs produce cell ultrastructural alterations with an abundant autophagic vesicles and autolysosomes in treated cells, indicating an interference of autophagy process after APL exposure. Thus, antitumoural APLs interfere with the proliferation of tumour cells via a complex mechanism involving phospholipid and cholesterol metabolism, interfere with lipid-dependent survival-signalling pathways and autophagy. Although APLs also exert antiparasitic, antibacterial, and antifungal effects, in this review we provide a summary of the antileishmanial activity of these lipid analogues. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

Synthesis and Leishmanicidal Activity of 1-[5-(5-Nitrofuran-2-yl)-1, 3, 4-Thiadiazole-2-yl]-4-BenzoylePiperazines

A series of (5-nitrofuran-2-yl)-1, 3, 4-thiadiazole-2-yl derivatives 6a-6e have been synthesized and screened for in-vitro anti-leishmanial activity against the promastigote form of L. major. The structure of Schiff bases were confirmed by ¹H NMR, IR. Screening results indicate that all of the designed and synthesized final compounds (6a-6e) significantly reduced the viability of promastigotes of L. major in comparison toglucantime (IC₅₀ 3× 10³ μg/mL). Meta and Para substitutions in benzene ring containing compounds were more potent than other derivative and the most potent compounds were 6d, 6e with IC₅₀ value 94 µm and 77.6 µm, respectively. The experimental data proposes that (5-nitrofuran-2-yl)-1, 3, 4-thiadiazole-2-yl derivatives may be further investigated as a candidate drug for treatment of cutaneous leishmaniasis.

Synthesis and evaluation against Leishmania amazonensis of novel pyrazolo[3,4-d]pyridazinone-N-acylhydrazone-(bi)thiophene hybrids

A new series of pyrazolo[3,4-d]pyridazin-7-one derivatives were synthesised and evaluated for their in vitro antileishmanial activity against Leishmania amazonensis promastigote and axenic amastigote forms. The results showed that the pyrazolo[3,4-d]-pyridazin-7-one-N-acylhydrazone-(bi)thiophene hybrids 5b, 6b and 6d exhibit better antileishmanial activity with IC₅₀ 84.96, 3.63 and 10.79 μM, against the promastigote form and IC₅₀ 32.71, 2.32 and >100 μM against the axenic amastigote form, respectively. The active compounds had their cytotoxicity tested against macrophages and fibroblast cells with a higher selectivity index than 10 for compounds 6b and 6d. Molecular docking studies were performed for all active compounds using the enzyme trypanothione reductase (TR) to investigate a possible action mechanism. The results suggested that active compounds had interactions with the residues of amino acids Gly 13, Thr 51, Thr 160, Gly 161, Tyr 198, Arg 287, Asp 327, Thr 335, which may inhibit the enzyme TR.