Mode of action of a formulation containing hydrazones and saponins against leishmania spp. Role in mitochondria, proteases and reinfection process

Modified Hederagenin Derivatives Demonstrate Ex Vivo Anthelmintic Activity against Fasciola hepatica

Infection with Fasciola hepatica (liver fluke) causes fasciolosis (or fascioliasis) and poses a considerable economic as well as welfare burden to both the agricultural and animal health sectors. Here, we explore the ex vivo anthelmintic potential of synthetic derivatives of hederagenin, isolated in bulk from Hedera helix. Thirty-six compounds were initially screened against F. hepatica newly excysted juveniles (NEJs) of the Italian strain. Eleven of these compounds were active against NEJs and were selected for further study, using adult F. hepatica derived from a local abattoir (provenance unknown). From these eleven compounds, six demonstrated activity and were further assessed against immature liver flukes of the Italian strain. Subsequently, the most active compounds (n = 5) were further evaluated in ex vivo dose response experiments against adult Italian strain liver flukes. Overall, MC042 was identified as the most active molecule and the EC₅₀ obtained from immature and adult liver fluke assays (at 24 h post co-culture) are estimated as 1.07 μM and 13.02 μM, respectively. When compared to the in vitro cytotoxicity of MDBK bovine cell line, MC042 demonstrated the highest anthelmintic selectivity (44.37 for immature and 3.64 for adult flukes). These data indicate that modified hederagenins display properties suitable for further investigations as candidate flukicides.

Biological activities of 4H-thiochromen-4-one 1,1-dioxide derivatives against tropical disease parasites: A target-based drug design approach

A promising strategy for developing novel therapies against tropical diseases, including malaria, leishmaniasis, and trypanosomiasis, is to detect biological targets such as trypanothione reductase, a vital parasite enzyme that regulates oxidative stress. This enzyme is highly selective and conserved in the Trypanosotidae family and has an ortholog in the Plasmodium genus. Previous studies have established that an isosteric replacement of naphthoquinone's carbonyl group with a sulfone group leads to compounds with high bioactivity and selectivity (half-maximal inhibitory concentration = 3 μM against intracellular amastigotes of L. panamensis, selectivity index = 153 over monocytes U-937). In this study, we analyzed the reactive oxygen species (ROS) levels of parasites through indirect measurements of the tryparedoxin system after treatment with these isosteric compounds. This strategy proved that a significant increase in the ROS levels and strong mitochondrial perturbation led to the death of parasites due to cell homeostatic imbalance, confirming the compounds' effectiveness in disrupting this important metabolic pathway. To improve understanding of the parasite-molecule interaction, 27 new compounds were synthesized and assessed against parasites of the three principal tropical diseases (malaria, leishmaniasis, and trypanosomiasis), displaying an EC₅₀ below 10 μM and good correlation with in-silico studies, indicating that the 4H-thiochromen-4-one 1,1-dioxide core is a special allosteric modulator. It can interact in the binding pocket through key amino acids like Ser-14, Leu-17, Trp-21, Ser-109, Tyr-110, and Met-113, leading to interhelical disruption.

Promising natural products for the treatment of cutaneous leishmaniasis: A review of in vitro and in vivo studies

Although there are available treatments for cutaneous leishmaniasis (CL), the drugs used are far from ideal, toxic, and costly, in addition to the challenge faced by the development of resistance. Plants have been used as a source of natural compounds with antileishmanial action. However, few have reached the market and become phytomedicines with registration in regulatory agencies. Difficulties related to the extraction, purification, chemical identification, efficacy, safety, and production in sufficient quantity for clinical studies, hinder the emergence of new effective phytomedicines against leishmaniasis. Despite the difficulties reported, the major research centers in the world see that natural products are a trend concerning the treatment of leishmaniasis. The present work consists of a literature review of articles with in vivo studies, covering the period from January 2011 to December 2022, providing an overview of promising natural products for CL treatment. The papers show encouraging antileishmanial action of natural compounds with reduced parasite load and lesion size in animal models, suggesting new strategies for the treatment of the disease. The results reported in this review show advances in using natural products as safe and effective formulations, which can stimulate clinical studies to establish clinical therapy. In conclusion, the information in this review article serves as a preliminary basis for establishing a therapeutic protocol for future clinical trials that can validate the safety and efficacy of natural compounds, providing the development of affordable and safe phytomedicines for the treatment of CL.

Nanoemulsions for increased penetrability and sustained release of leishmanicidal compounds

In the last decade, the World Health Organization has driven the development of drugs for topical use in patients with cutaneous leishmaniasis (CL), the most prevalent clinical form of leishmaniasis, a neglected tropical disease. The chemicals C₆ I, TC1, and TC2 were reported as promising antileishmanial drugs. We aimed to develop a topical nanoformulation that enhances the advantageous effect of C₆ I, TC1, and TC2, guaranteeing higher stability and bioavailability of the pharmacologically active components through the topical route. Nanoemulsions were prepared by ultrasonication based on oleic acid (0.5 g). A relation of Tween®-80/ethanol (1:3) and water was obtained; physicochemical characterization of all formulations was performed, and the preliminary stability and transdermal penetration of these nanoemulsions were also investigated. Newtonian-type fluids with high load capacity, 147-273 nm globule size, and -15 to -18 mV zeta potential were obtained with differential permeability rates in the first pig ear skin assay, first-order kinetics-release model for C₆ I, and Weibull for TC1 and TC2. The nanoemulsion showed good stability, high encapsulation efficiency, and higher leishmanicidal activity against Leishmania braziliensis with lower cytotoxicity in U937 macrophages. In conclusion, nanoemulsions of ethanol-oleic acid/Tween®-80 increase the activity of compounds with leishmanicidal activity by increasing their penetration and sustained release.

Antileishmanial Activity and In Silico Molecular Docking Studies of Malachra alceifolia Jacq. Fractions against Leishmania mexicana Amastigotes

Malachra alceifolia Jacq. (family Malvaceae), known as "malva," is a medicinal plant used as a traditional therapy in many regions of America, Africa and Asia. Traditionally, this plant is used in the form of extracts, powder and paste by populations for treating fever, stomachache, inflammation, and parasites. However, the ethnopharmacological validation of M. alceifolia has been scarcely researched. This study showed that the chloroform fraction (MA-IC) and subfraction (MA-24F) of the leaves of M. alceifolia exhibited a potential antileishmanial activity against axenic amastigotes of Leishmania mexicana pifanoi (MHOM/VE/60/Ltrod) and had high and moderate cytotoxic effects on the viability and morphology of macrophages RAW 264.7. This study reports, for the first time, possible terpenoid metabolites and derivatives present in M. alceifolia with activity against some biosynthetic pathways in L. mexicana amastigotes. The compounds from the subfractions MA-24F were highly active and were analyzed by gas chromatography-mass spectrometry (GC-MS) and by a molecular docking study in L. mexicana target protein. This study demonstrates the potential modes of interaction and the theoretical affinity energy of the metabolites episwertenol, α-amyrin and methyl commate A, which are present in the active fraction MA-24F, at allosteric sites of the pyruvate kinase, glyceraldehyde-3-phosphate dehydrogenase, triose phosphate isomerase, aldolase, phosphoglucose isomerase, transketolase, arginase and cysteine peptidases A, target proteins in some vital biosynthetic pathways were responsible for the survival of L. mexicana. Some phytoconstituents of M. alceifolia can be used for the search for potential new drugs and molecular targets for treating leishmaniases and infectious diseases. Furthermore, contributions to research and the validation and conservation of traditional knowledge of medicinal plants are needed globally.

Models for cytotoxicity screening of antileishmanial drugs: what has been done so far?

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

Utility of the combination of hederagenin glucoside saponins and chromane hydrazone in the topical treatment of canine cutaneous leishmaniasis. An observational study

Canine cutaneous leishmaniasis (CCL) is an emerging zoonotic infection endemic in several countries of the world. Due to variable response to therapy and frequency of relapses, a more effective, safer, and inexpensive treatment is needed. Recently, it was reported that the hederagenin glucoside saponins (SS) and chromane-derived hydrazone (TC2) combined in a 1:1 ratio has high potential in antileishmanial therapy since both compounds alter the survival of Leishmania and the ability to infect adjacent macrophage. Not only the skin permeation and the absorption of an ointment containing 2% TC2 and 2% SS (w/w) was determined in this work, but also the acute dermal toxicity in both in vitro and in vivo assays. Last, the effectiveness and safety of the topical therapy with 2% TC2-2% SS ointment was evaluated in an observational study in dogs with diagnosis of cutaneous leishmaniasis (CL). Both TC2 and SS diffused through pig ear skin and traces of TC2 (but not SS) were detected in the stratum corneum of mice at 6-24 h. Neither TC2 nor SS was detected in plasma. The acute dermal toxicity was negative. Treatment with 2% TC2-2% SS ointment produced a complete long-term clinical cure in 56 dogs (24 females and 32 males) from the Orinoco and Amazonas regions in southeastern Colombia without adverse effects. All dogs have remained disease-free for the last 24 months. In conclusion, these results support the use of this topical therapy as a safer and new first-line local treatment of CCL that could help limit the spread of CL from dogs to humans.

Anti-leishmanial activity of Avicennia marina (Avicenniaceae family) leaves hydroalcoholic extract and its possible cellular mechanisms

Natural products are the main source of potent antioxidants and anti-leishmanial agents. This study was aimed to evaluate Avicennia marina (Avicenniaceae family) extract inhibitory effect against Leishmania tropica by accessing apoptotic markers and arginase activity. The A. marina were extracted and phytochemical analysis conducted. The inhibitory effect of A. marina was evaluated on L. tropica promastigote and amastigote forms, compared to meglumine antimoniate (Glucantime, MA) as standard drug. The level of apoptosis, Reactive Oxygen Species (ROS) production and arginase activity was assessed in A. marina-treated cells compared to control group. Phytochemical screening of A. marina extract showed strong presence of tannins and saponins. We demonstrated the inhibitory effect of A. marina on promastigote stages in a dose dependent manner. Also, lower 50% inhibitory concentration (IC₅₀) value of amastigotes was indicated in A. marina group compared with the standard group of Glucantime (60.57 ± 1.46 vs. 73.19 ± 10.12 μg/mL, respectively, P < 0.05). Besides, A. marina represented no cytotoxicity as the selectivity index (SI) was 10.7. Also, it showed the potential to induce early apoptosis of 46.5% in promastigotes at 125 μg/mL concentration. Significant reduction of arginase level was observed in both A. marina-treated cells and promastigotes. The promising results indicated higher effectiveness of A. marina in decreasing parasite growth, inducing apoptosis in promastigotes, increasing ROS production and decreasing arginase level. So, A. marina can be a native plant candidate for anti-leishmanial drug in tropical regions with cutaneous leishmaniasis due to L. tropica.

Synthesis and Evaluation of Novel 2,2-Dimethylthiochromanones as Anti-Leishmanial Agents

Within this work, we describe the design and synthesis of a range of novel thiochromanones based on natural products reported to possess anti-leishmanial action, and their synthetic derivatives. All compounds were elaborated via the key intermediate 2,2,6-trimethoxythiochromanone, which was modified at the benzylic position to afford various ester, amine and amide analogues, substituted by chains of varying lipophilicity. Upon testing in Leishmania, IC₅₀ values revealed the most potent compounds to be phenylalkenyl and haloalkyl amides 11a and 11e, with IC₅₀ values of 10.5 and 7.2 μM, respectively.

Exploring Antiparasitic Molecule Sources from Timber by-Product Industries-Leishmanicidal and Trypanocidal Compounds from Clathrotropis brunnea Amshoff

Through bioguided in vitro assays, the leishmanicidal and trypanocidal effects of an ethanol extract, seven fractions, and two pure substances obtained from Clathrotropis brunnea Amshoff sawdust were established. The effectiveness of the two metabolites was confirmed in a hamster model of cutaneous Leishmaniasis by Leishmania braziliensis and in Balb/c mice infected by Trypanosoma cruzi. In vitro, 3,5-dimethoxystilbene was the most active against L. braziliensis amastigotes, with a median lethal concentration (LC₅₀) of 4.18 μg/ml (17.40 μM) and a selectivity index of 3.55, but showed moderate activity for T. cruzi, with a median effective concentration (EC₅₀) value of 27.7 μg/ml (115.36 μM). Flavanone pinostrobin, meanwhile, showed high activity against L. braziliensis, with an EC₅₀ of 13.61 μg/ml (50.39 μM), as well as for T. cruzi, with an EC₅₀ of 18.2 μg/ml (67.38 μM). The animal model assay of cutaneous Leishmaniasis showed that 50% of the hamsters treated with pinostrobin were definitively cured the cutaneous ulcer, and 40% showed an improvement, with a reduction in the size of the of 84–87%. Moreover, Balb/c mice experimentally infected with T. cruzi and treated for 25 days with pinostrobin experienced a reduction in their parasitemia by 71%. These results demonstrate the high potential of C. brunnea Amshoff against cutaneous Leishmaniasis and American trypanosomiasis and indicate the pharmacological potential of waste from the wood industry, which has tons of potentially useful chemicals for the development of new medicines.