Potential of the natural products against leishmaniasis in Old World - a review of in-vitro studies

Antileishmanial activity of Ptilostemon chamaepeuce subsp. cyprius

BACKGROUND

Phytochemicals from unexplored plant species may be vital to unlocking pharmaceutical antibiotic and antiparasitic discoveries. New compounds need to be discovered to combat antimicrobial resistance. This study aimed to investigate ethanolic leaf extracts from five endemic and four indigenous plants from Cyprus for antibacterial, antileishmanial, and antioxidant activities.

METHODS

Ethanolic leaf extracts were screened for antibacterial activity using a broth microdilution assay and iodonitrotetrazolium chloride (INT) as a colourimetric redox indicator for determining the minimum inhibitory concentration (MIC) against four Gram-positive and two Gram-negative American Type Culture Collection (ATCC) reference bacteria. Total phenolic content (TPC), total flavonoid content (TFC) and radical scavenging activity assays were performed to screen for antioxidant potential. Leishmania infantum clinical culture (MCAN/CY/2005/CD57) was used to screen the extracts for in vitro antileishmanial activity. Their cytotoxicity in vitro was assessed using the resazurin fluorometric assay with a HepG2 cell line. As an estimate of in vitro toxicity, a brine shrimp lethality assay was performed.

RESULTS

The ethanol extract of Ptilostemon chamaepeuce subsp. cyprius (Greuter) Chrtek & B. Slavik demonstrated antibacterial activity against Enterococcus faecalis (ATCC 29212) with minimum inhibitory concentration (MIC) < 0.625 mg/mL and antileishmanial activity against a clinical isolate of L.infantum (MCAN/CY/2005/CD57) from an infected dog (promastigote IC50 of 105.7 ± 2.5 μg/mL and amastigote IC50 of 118.5 ± 4.3 μg/mL) after 48 h and compared to the activity of the reference drug, miltefosine (IC50 of 3.7 ± 0.1 μg/mL and 18.5 ± 2.3 μg/mL, respectively). Liquid-chromatography-mass spectrometry (LC-MS) analysis revealed the presence of at least five sesquiterpene lactones (STLs) in P. cham. subsp. cyprius ethanolic extract. The main compound, deacylcynaropicrin, based on its high-resolution mass spectrum, is believed to be primarily responsible for the antileishmanial activity observed in vitro. Quercus alnifolia Poech ethanolic extract showed antibacterial activity against four Gram-positive and one Gram-negative bacteria with MIC values of < 0.625 mg/mL, respectively, and antioxidant capacity in DPPH radical scavenging assay with IC50 of 0.155 ± 0.002 mg/mL and compared to ascorbic acid (IC50 of 0.036 ± 0.000 mg/mL) and Trolox (IC50 of 0.047 ± 0.001 mg/mL).

CONCLUSION

The ethanolic extract of Ptilostemon chamaepeuce subsp. cyprius demonstrated dose-dependent antileishmanial activity. This is the first data report of P.cham. subsp. cyprius and Q.alnifolia ethanolic extracts to indicate antibacterial, antileishmanial and antioxidant activities in preliminary investigations. Moreover, this is the first report on STLs in P. cham. subsp. cyprius, and future studies are needed to confirm if they are responsible for the in vitro antileishmanial activity. These findings highlight the potential of these endemic plants as sources for developing new drugs targeting Gram-positive bacterial infections and leishmaniasis, encouraging further pharmaceutical research.

Evaluation of the Anti-Leishmanial Activity of the Hydroalcoholic Extract of Green Algae (Spirogyra): Investigation of Weight Indicators (Lesion Size and Organ Weights) in BALB/c Mice

BACKGROUND

Leishmaniasis remains a significant global health concern, ranking among the top ten infectious diseases and causing substantial mortality and socioeconomic burden. Effective and accessible treatments are needed. This study investigated the potential of a hydroalcoholic extract from readily available urban green algae as an anti-leishmanial agent, focusing on its impact on key weight-related indicators of Leishmania major infection in BALB/c mice. To evaluate the in vivo anti-leishmanial activity of the hydroalcoholic extract from the common green algae genus Spirogyra against Leishmania major in BALB/c mice, specifically by assessing its effects on weight loss, lesion size, liver weight, and spleen weight-key indicators of disease progression.

METHODS

Spirogyra algae were collected and identified in Yazd Province, Iran. A hydroalcoholic extract was prepared and administered via intraperitoneal injection into Leishmania major-infected BALB/c mice at doses of 3, 6, and 12 mg/kg/day, starting after lesion development. The control groups included untreated infected mice (negative control), healthy uninfected mice (control), and infected mice treated with Glucantime (positive control). We assessed treatment efficacy by monitoring weight loss, lesion diameter, liver weight, and spleen weight.

RESULTS

Treatment with the highest concentration of Spirogyra extract (12 mg/kg/day) significantly mitigated weight loss in infected mice, demonstrating comparable efficacy to Glucantime. Both the 12 mg/kg/day algae extract and Glucantime significantly controlled lesion growth. Importantly, both treatments significantly reduced liver and spleen weight compared with the negative control group, indicating a reduction in organomegaly. Specifically, the negative control and 3 mg/kg extract groups exhibited the highest liver weights, whereas the negative control group showed significantly higher spleen weights than the other groups. The 12 mg/kg extract and Glucantime groups showed liver and spleen sizes comparable to the healthy control group, demonstrating effective control of organ size changes associated with leishmaniasis.

CONCLUSION

The hydroalcoholic extract of urban Spirogyra green algae, particularly at a dose of 12 mg/kg/day, exhibited significant in vivo anti-leishmanial activity in BALB/c mice. Evaluated through weight indicators such as reduced weight loss, controlled lesion growth, and normalized liver and spleen weights, the extract showed promise in mitigating the detrimental effects of Leishmania major infection and warrants further investigation as a potential source for novel anti-leishmanial therapeutics.

Nanotechnological Formulation Incorporating Pectis brevipedunculata (Asteraceae) Essential Oil: An Ecofriendly Approach for Leishmanicidal and Anti-Inflammatory Therapy

Cutaneous leishmaniasis caused by Leishmania amazonensis is a significant public health issue. This study aimed to evaluate an ecofriendly, thermosensitive nanogel, developed using a low-energy, solvent-free method, incorporating F127 and Carbopol 974P copolymers, and enriched with Pectis brevipedunculata essential oil (EOPb) for its leishmanicidal and anti-inflammatory properties. The nanogel was prepared and characterized through FTIR, DLS, SEM, and AFM to confirm the incorporation of EOPb as well as its stability and rheological properties. In vitro leishmanicidal activity was evaluated on Leishmania amazonensis promastigotes, and in vivo anti-inflammatory effects were assessed using a rat paw edema model. In vitro, nGF3 (EOPb-loaded nanogel) demonstrated significant leishmanicidal activity, with promastigote mortality rates exceeding 80% at 24 h and 90% at 48 h. In vivo, nGF1, nGF2, and nGF3 exhibited anti-inflammatory effects, with nGF2 and nGF3 reducing edema by 62.7% at 2 h post-treatment. The empty nanogel (nGF0) showed minimal anti-inflammatory activity. The ecofriendly EOPb-loaded nanogel (nGF3) demonstrated strong leishmanicidal and anti-inflammatory effects, presenting a promising candidate for cutaneous leishmaniasis treatment. Further studies are necessary to explore its clinical potential.

Structure-based Virtual Screening and Drug Design Development of Leishmanicidal Pyrimidines

Leishmaniasis is a neglected disease caused by parasites of the genus Leishmania sp. that causes approximately 1 million cases and 650,000 deaths annually worldwide. Its treatment has several limitations mainly due to high toxicity and clinical resistance, and the search for alternatives is highly desirable. The present work aimed to design new antileishmanial compounds through a virtual screening of a small in-house library of pyrimidine compounds, never tested against Leishmania, using the active site of trypanothione reductase (TR) as a target model. The compounds showed favorable affinity with the amino acid residues of the active site of TR. Pyr 1-9 were synthesized and tested against Leishmania amazonensis strain. Four derivatives demonstrated activity against promastigote (IC50 value between 11.23 and 91.5 µM) and three other compounds demonstrated discreet activity against amastigote, IC50 value between 81.29 and 153.21 µM. Based on the results obtained in the screening, three new pyrimidines Pyr 10-12 were designed to optimize activity, cytotoxicity, and selectivity. Pyr 10 and Pyr 11 demonstrated good activity against promastigotes, with IC50 of 11.38 ± 9.7 and 20.01 ± 13.55 µM, respectively, and improved cytotoxicity and selectivity. No activity was obtained against amastigotes. Thus, this study contributes important information for the development of new pyrimidines active against Leishmania.

Anti-leishmanial activity of Hypericum Scabrum extract against Leishmania major

Leishmaniasis is a vector-borne disease and one of the most significant neglected tropical diseases. Current anti-leishmanial treatments are often ineffective over extended periods and are associated with toxic side effects, highlighting the urgent need for new, effective, and safe alternative treatments for this infectious disease. The objective of this study was to evaluate the anti-leishmanial effects of a hydroalcoholic extract of Hypericum scabrum (H. scabrum), comparing its efficacy to that of the control drug glucantime against the standard strain of Leishmania major. The H. scabrum plants were collected from the western regions of Iran. A hydroalcoholic extract was prepared from the flower and stem of the plant using a maceration method. High-performance liquid chromatography analysis was conducted to identify the chemical compounds present in the extract. Promastigotes of L. major were cultured, and the anti-leishmanial activity of the extracts was assessed at concentrations ranging from 12.5 to 800 µg/ml using the MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] assay. The half-maximal inhibitory concentration (IC50) values for the H. scabrum plant extract at 24, 48, and 72 h were 245.47, 141.25 and 85.11 μg/ml, respectively. The IC50 values for glucantime (the control drug) at 24 h, 48 h, and 72 h were 30.19, 21.37, and 12.58 μg/ml, respectively. While the H. scabrum extract exhibited a lower effect compared to the control drug, it still demonstrated a significant inhibitory effect on the promastigote form of L. major. Given that the plant extract of H. scabrum has demonstrated promising anti-leishmanial effects against L. major promastigotes, further studies are warranted to evaluate the efficacy of these extracts in animal models of leishmaniasis.

Zein Nanoparticles-Loaded Flavonoids-Rich Fraction from Fridericia platyphylla: Potential Antileishmanial Applications

Background/Objectives: Leishmaniasis, caused by protozoa of the genus Leishmania, is a major global health issue due to the limitations of current treatments, which include low efficacy, high costs, and severe side effects. This study aimed to develop a more effective and less toxic therapy by utilizing zein nanoparticles (ZNPs) in combination with a nonpolar fraction (DCMF) from Fridericia platyphylla (Syn. Arrabidaea brachypoda), a plant rich in dimeric flavonoids called brachydins. Methods: Zein nanoparticles were used as carriers to encapsulate DCMF. The system was characterized by measuring particle diameter, polydispersity index, zeta potential, and encapsulation efficiency. Analytical techniques such as FTIR, DSC, and AFM were employed to confirm the encapsulation and stability of DCMF. Antileishmanial activity was assessed against Leishmania amazonensis promastigotes and amastigotes, while cytotoxicity was tested on RAW264.7 macrophages. Results: The ZNP-DCMF system exhibited favorable properties, including a particle diameter of 141 nm, a polydispersity index below 0.2, and a zeta potential of 11.3 mV. DCMF was encapsulated with an efficiency of 94.6% and remained stable for 49 days. In antileishmanial assays, ZNP-DCMF inhibited the viability of promastigotes with an IC50 of 36.33 μg/mL and amastigotes with an IC50 of 0.72 μg/mL, demonstrating higher selectivity (SI = 694.44) compared to DCMF alone (SI = 43.11). ZNP-DCMF was non-cytotoxic to RAW264.7 macrophages, with a CC50 > 500 μg/mL. Conclusions: Combining F. platyphylla DCMF with zein nanoparticles as a carrier presents a promising approach for leishmaniasis treatment, offering improved efficacy, reduced toxicity, and protection of bioactive compounds from degradation.

Promising Antileishmanial Activity of Micromeria nervosa Essential Oil: In Vitro and In Silico Studies

The present study aimed to evaluate the leishmanicidal potential of the essential oil (EO) of Micromeria (M.) nervosa and to investigate its molecular mechanism of action by qPCR. Furthermore, in silicointeraction study of the major M. nervosa EO compounds with the enzyme cytochrome P450 sterol 14α-demethylase (CYP51) was also performed. M. nervosa EO was analyzed by gas chromatography-mass spectrometry (GC-MS). Results showed that α-pinene (26.44%), t-cadinol (26.27%), caryophyllene Oxide (7.73 ± 1.04%), and α-Cadinene (3.79 ± 0.12%) are the major compounds of M. nervosa EO. However, limited antioxidant activity was observed, as this EO was ineffective in neutralizing DPPH free radicals and in inhibiting β-carotene bleaching. Interestingly, it displayed effective leishmanicidal potential against promastigote (IC50 of 6.79 and 5.25 μg/mL) and amastigote (IC50 of 8.04 and 7.32 μg/mL) forms of leishmania (L.) infantum and L. major, respectively. Molecular mechanism investigation showed that M. nervosa EO displayed potent inhibition on the thiol regulatory pathway. Furthermore, a docking study of the main components of the EO with cytochrome P450 sterol 14α-demethylase (CYP51) enzyme revealed that t-cadinol exhibited the best binding energy values (-7.5 kcal/mol), followed by α-cadinene (-7.3 kcal/mol) and caryophyllene oxide (-7 kcal/mol). These values were notably higher than that of the conventional drug fluconazole showing weaker binding energy (-6.9 kcal/mol). These results suggest that M. nervosa EO could serve as a potent and promising candidate for the development of alternative antileishmanial agent in the treatment of leishmaniasis.

The Potential Use of Peptides in the Fight against Chagas Disease and Leishmaniasis

Chagas disease and leishmaniasis are both neglected tropical diseases that affect millions of people around the world. Leishmaniasis is currently the second most widespread vector-borne parasitic disease after malaria. The World Health Organization records approximately 0.7-1 million newly diagnosed leishmaniasis cases each year, resulting in approximately 20,000-30,000 deaths. Also, 25 million people worldwide are at risk of Chagas disease and an estimated 6 million people are infected with Trypanosoma cruzi. Pentavalent antimonials, amphotericin B, miltefosine, paromomycin, and pentamidine are currently used to treat leishmaniasis. Also, nifurtimox and benznidazole are two drugs currently used to treat Chagas disease. These drugs are associated with toxicity problems such as nephrotoxicity and cardiotoxicity, in addition to resistance problems. As a result, the discovery of novel therapeutic agents has emerged as a top priority and a promising alternative. Overall, there is a need for new and effective treatments for Chagas disease and leishmaniasis, as the current drugs have significant limitations. Peptide-based drugs are attractive due to their high selectiveness, effectiveness, low toxicity, and ease of production. This paper reviews the potential use of peptides in the treatment of Chagas disease and leishmaniasis. Several studies have demonstrated that peptides are effective against Chagas disease and leishmaniasis, suggesting their use in drug therapy for these diseases. Overall, peptides have the potential to be effective therapeutic agents against Chagas disease and leishmaniasis, but more research is needed to fully investigate their potential.

Anti-Leishmania major activity of Calotropis procera extract by increasing ROS production and upregulating TNF-α, IFN-γ and iNOS mRNA expression under in vitro conditions

BACKGROUND

Leishmaniasis, caused by protozoan parasites of the genus Leishmania, is a neglected tropical disease with 700,000 to 1,000,000 global new cases annually. Adverse effects associated with expense, long-term treatment and drug resistance have made conventional therapies unfavorable, encouraging the search for alternative drugs based on plant products. In this study, the effect of Calotropis procera (Asclepiadaceae) extract against viability of promastigotes and amastigotes of Leishmania major was evaluated in vitro.

METHODS

The extract from the leaves of C. procera seedlings was prepared using a methanol maceration method. The colorimetric cell viability 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine the growth-inhibitory effect of the extract on promastigotes. The level of reactive oxygen species (ROS) in promastigote cultures was determined after treatment with the extract using the 2',7'-dichlorofluorescein diacetate (DCFH-DA) method and compared with untreated cultures (control). After exposure to the extract the expression levels of tumor necrosis factor-α (TNF-α), interferon gamma (IFN-γ) and inducible nitric oxide synthase (iNOS) genes were determined and compared to control in peripheral blood mononuclear cells (PBMCs) infected with L. major.

RESULTS

Based on the MTT assay, the C. procera extract significantly reduced the proliferation of L. major promastigotes with IC50 values of 377.28 and 222.44 μg/mL for 24 and 72 h, respectively (p < 0.01). After treatment with 222.44 and 377.28 μg/mL of C. procera extract, ROS production in L. major promastigote cultures increased 1.2- to 1.65-fold and 2- to 4-fold compared to the control, respectively (p < 0.05). C. procera extract induced significant increases in gene expression of TNF-α (2.76-14.83 fold), IFN-γ (25.63-threefold) and iNOS (16.32-3.97 fold) in infected PBMCs compared to control (p < 0.01).

CONCLUSIONS

On the basis of its anti-leishmanial activity, C. procera can be considered as a promising new plant source for the potential treatment of leishmaniasis.

Leishmanicidal activity and 4D quantitative structure-activity relationship and molecular docking studies of vanillin-containing 1,2,3-triazole derivatives

Aim: The assessment of the antileishmanial potential of 22 vanillin-containing 1,2,3-triazole derivatives against Leishmania braziliensis is reported. Materials & methods: Initial screening was performed against the parasite promastigote form. The most active compound, 4b, targeted parasites within amastigotes (IC50 = 4.2 ± 1.0 μmol l-1), presenting low cytotoxicity and a selective index value of 39. 4D quantitative structure-activity relationship and molecular docking studies provided insights into structure-activity and biological effects. Conclusion: A vanillin derivative with significant antileishmanial activity was identified. Enhanced activity was linked to increased electrostatic and Van der Waals interactions near the benzyl ring of the derivatives. Molecular docking indicated the inhibition of the Leishmania amazonensis sterol 14α-demethylase, using Leishmania infantum sterol 14α-demethylase as a model, without affecting the human isoform. Inhibition was active site competition with lanosterol.

In vitro evaluation of antileishmanial activity, mode of action and cellular response induced by vanillin synthetic derivatives against Leishmania species able to cause cutaneous and visceral leishmaniasis

The treatment against leishmaniasis presents problems, mainly due to their toxicity of the drugs, high cost and/or by the emergence of parasite resistant strains. In this context, new therapeutics should be searched. In this study, two novel synthetic derivatives from vanillin: [4-(2-hydroxy-3-(4-octyl-1H-1,2,3-triazol-1-yl)propoxy)-3-methoxybenzaldehyde] or 3s and [4-(3-(4-decyl-1H-1,2,3-triazol-1-yl)-2-hydroxypropoxy)-3-methoxybenzaldehyde] or 3t, were evaluated regarding their antileishmanial activity against distinct parasite species able to cause cutaneous and visceral leishmaniasis. Results showed that compounds 3s and 3t were effective against Leishmania infantum, L. amazonensis and L. braziliensis promastigote and amastigote-like forms, showing selectivity index (SI) of 25.1, 18.2 and 22.9, respectively, when 3s was used against promastigotes, and of 45.2, 7.5 and 15.0, respectively, against amastigote-like stage. Using the compound 3t, SI values were 45.2, 53.0 and 80.0, respectively, against promastigotes, and of 35.9, 46.0 and 58.4, respectively, against amastigote-like forms. Amphotericin B (AmpB) showed SI values of 5.0, 7.5 and 15.0, respectively, against promastigotes, and of 3.8, 5.0 and 7.5, respectively, against amastigote-like stage. The treatment of infected macrophages and inhibition of the infection upon pre-incubation with the molecules showed that they were effective in reducing the infection degree and inhibiting the infection in pre-incubated parasites, respectively, as compared to data obtained using AmpB. The mechanism of action of 3s and 3t was evaluated in L. infantum, revealing that both 3s and 3t altered the parasite mitochondrial membrane potential leading to reactive oxygen species production, increase in lipid corps and changes in the cell cycle, causing the parasite' death. A preliminary assay using the cell culture supernatant from treated and infected macrophages showed that 3s and 3t induced higher IL-12 and lower IL-10 values; suggesting the development of an in vitro Th1-type response in the treated cells. In this context, data indicated that 3s and 3t could be considered therapeutic agents to be tested in future studies against leishmaniasis.

Natural products derived steroids as potential anti-leishmanial agents; disease prevalence, underlying mechanisms and future perspectives

Leishmaniasis is a vector-borne infection caused by protozoan parasites from the genus leishmania and is among the most neglected tropical diseases. It is highly prevalent disease, affecting about 350 million population worldwide. Only limited number of anti-leishmanial agents are approved for clinical use till now and they are associated with side effects and have limited efficacy. Subsequently, natural products based discovery of more safe and effective drugs against leishmania is under scientific consideration. Various studies reported the efficacy of natural products against intracellular and extracellular forms of leishmania species. This work is aimed to evaluate current literature focused on the anti-leihmanial efficacy of steroidal moieties from natural products and their mechanism of action. Compounds including steroidal saponins, steroidal alkaloids and phytosterols were found to exhibit considerable anti-leishmanial efficacy. For instance, steroidal saponin, (25R)-spirost-5-en-3b-ol,3-O-α-rhamnopyranosyl-(1 → 4)-α-rhamnopyranosyl-(1 → 4)-[a-rhamnopyranosyl-(1 → 2)]-glucopyranoside isolated from A. paradoxum has completely eradicated Leishmania major promastigotes at 50 µg mL-1 dose. Spirostanic saponins isolated from Solanum paniculatum L. were effective against Leishmania amazonensis promastigotes. Turgidosterones isolated from Panicum turgidum exhibited high leishmanicidal potentials against Leishmania donovani promastigotes with IC50 of 4.95-8.03 µg mL-1 and even better activity against amastigotes exhibiting an IC50 of 4.50-9.29 µg mL-1. Likewise, racemoside-A from Asparagus racemosus was found effective against an antimonial sensitive (AG83) and antimonial resistant (GE1F8R) strains of the L. donovani. Moreover, steroidal alkaloids including hookerianamide-1, hookerianamide-H, hookerianamide-J, hookerianamide-K, dehydrosarsalignone, vagenine-A, sarcovagine-C, holaphylline, saracodine, holamine, 15-α hydroxyholamine, holacurtin, N-desmethyl holacurtine and elasticine has exhibited time and dose-dependent efficacy against various strains of leishmania. β-sitosterol was found active against multiple strains of leishmania. These compounds mainly exhibit their therapeutic efficacy via liberation of ROS, mitochondrial depolarization, morphological and ultra-structural changes, accumulation of lipid droplets, depletion of non-protein thiols and triggering apoptotic pathways. In conclusion, leishmaniasis is a major health problem in many countries. Plants-derived steroids moieties have reveled efficacy against leishmaniasis and is a source of lead compounds. Further detailed molecular studies are warranted for the discovery of more effective and safe anti-leishmanial drugs.

A review on new natural and synthetic anti-leishmanial chemotherapeutic agents and current perspective of treatment approaches

Leishmaniases are considered among the most neglected yet dangerous parasitic diseases worldwide. According to the recent WHO report (Weekly Epidemiological Record, Sep, 2021), 200 countries and territories reported leishmanises cases in 2020; of which 89 (45%) for CL, and 79 (40%) for VL were endemic. Indian subcontinent (India, Bangladesh and Nepal), one of the three eco-epidemiological hotspots of VL, currently reported 18% of the total cases of VL worldwide. Eastern Mediterranean region and the Region of the Americas together reported >90% of the new CL cases, of which >80% were from Afghanistan, Algeria, Brazil, Colombia, Iraq, Pakistan and the Syrian Arab Republic. While considering the current therapeutic options, conventional anti-leishmanial drugs have long been proved to be toxic and/or expensive and have resulted in extensive drug resistance in India. Recent searches for novel anti-leishmanial drugs have led to find out the prime cellular targets and metabolic pathways to bridge the gap between the known facts and unexplored data. Cutting edge knowledge based drug designing has simplified the search for novel molecules with leishmanicidal efficacy by identifying ligand-receptor interactions and has accelerated the cost effective primary discovery of molecules through computational validation against Leishmaniases. This review focuses on the limitations of conventional drugs, and discusses the chemotherapeutic potential of many novel natural and synthetic anti-leishmanial agents reported since the last decade. It is also interpreted that some of the reported molecules might be tested singly or as a part of combinatorial therapy on pre-clinical and clinical level.

Integrated computational and experimental approach for novel anti-leishmanial molecules by targeting Dephospho-coenzyme A kinase

Coenzyme A acts as a necessary cofactor for many enzymes and is a part of many biochemical processes. One of the critical enzymes involved in Coenzyme A synthesis is Dephospho-coenzyme A-kinase (DPCK). In this study, we have used integrated computational and experimental approaches for promising inhibitors of DPCK using the natural products available in the ZINC database for anti-leishmanial drug development. The top hit compounds chosen after molecular docking were Veratramine, Azulene, Hupehenine, and Hederagenin. The free binding energy of Veratramine, Azulene, Hupehenine, and Hederagenin was estimated. Besides the favourable binding point, the ligands also showed good hydrogen bonding and other interactions with key residues of the enzyme's active site. The natural compounds were also experimentally investigated for their effect on the L. donovani promastigotes and murine macrophage (J774A.1). A good antileishmanial activity by the compounds on the promastigotes was observed as estimated by the MTT assay. The in-vitro experiments revealed that Hupehenine (IC₅₀ = 7.34 ± 0.37 μM) and Veratramine (IC₅₀ = 12.46 ± 2.28 μM) exhibited better inhibition than Hederagenin (IC₅₀ = 23.36 ± 0.54 μM) and Azulene (IC₅₀ = 24.42 ± 3.28 μM). This work has identified novel anti-leishmanial molecules possibly acting through the inhibition of DPCK.

Leishmaniasis: Recent epidemiological studies in the Middle East

Leishmaniasis, one of the most neglected tropical diseases (NTDs), is the third most important vector-borne disease worldwide. This disease has a global impact and severity of the infection and is greatest in the Middle East. The agent of infection is a protozoan parasite of the genus, Leishmania, and is generally transmitted by blood-sucking female sandflies. In humans, there are three clinical forms of infection: (1) cutaneous (CL), (2) mucocutaneous (ML), and (3) visceral leishmaniasis (VL). This review aims to discuss the current epidemiological status of leishmaniasis in Saudi Arabia, Iraq, Syria, and Yemen with a consideration of treatment options. The elevated risk of leishmaniasis is influenced by the transmission of the disease across endemic countries into neighboring non-infected regions.

Insights into the drug screening approaches in leishmaniasis

Leishmaniasis, a tropically neglected disease, is responsible for the high mortality and morbidity ratio in poverty-stricken areas. Currently, no vaccine is available for the complete cure of the disease. Current chemotherapeutic regimens face the limitations of drug resistance and toxicity concerns indicating a great need to develop better chemotherapeutic leads that are orally administrable, potent, non-toxic, and cost-effective. The anti-leishmanial drug discovery process accelerated the desire for large-scale drug screening assays and high-throughput screening (HTS) technology to identify new chemo-types that can be used as potential drug molecules to control infection. Using the HTS approach, about one million compounds can be screened daily within the shortest possible time for biological activity using automation tools, miniaturized assay formats, and large-scale data analysis. Classical and modern in vitro screening assays have led to the progression of active compounds further to ex vivo and in vivo studies. In the present review, we emphasized on the HTS approaches employed in the leishmanial drug discovery program. Recent in vitro screening assays are widely explored to discover new chemical scaffolds. Developing appropriate experimental animal models and their related techniques is necessary to understand the pathophysiological processes and disease host responses, paving the way for unraveling novel therapies against leishmaniasis.

Synthesis, Structure and Antileishmanial Evaluation of Endoperoxide–Pyrazole Hybrids

Leishmaniases are among the most impacting neglected tropical diseases. In attempts to repurpose antimalarial drugs or candidates, it was found that selected 1,2,4-trioxanes, 1,2,4,5-tetraoxanes, and pyrazole-containing chemotypes demonstrated activity against Leishmania parasites. This study reports the synthesis and structure of trioxolane–pyrazole (OZ1, OZ2) and tetraoxane–pyrazole (T1, T2) hybrids obtained from the reaction of 3(5)-aminopyrazole with endoperoxide-containing building blocks. Interestingly, only the endocyclic amine of 3(5)-aminopyrazole was found to act as nucleophile for amide coupling. However, the fate of the reaction was influenced by prototropic tautomerism of the pyrazole heterocycle, yielding 3- and 5-aminopyrazole containing hybrids which were characterized by different techniques, including X-ray crystallography. The compounds were evaluated for in vitro antileishmanial activity against promastigotes of L. tropica and L. infantum, and for cytotoxicity against THP-1 cells. Selected compounds were also evaluated against intramacrophage amastigote forms of L. infantum. Trioxolane–pyrazole hybrids OZ1 and OZ2 exhibited some activity against Leishmania promastigotes, while tetraoxane–pyrazole hybrids proved inactive, most likely due to solubility issues. Eight salt forms, specifically tosylate, mesylate, and hydrochloride salts, were then prepared to improve the solubility of the corresponding peroxide hybrids and were uniformly tested. Biological evaluations in promastigotes showed that the compound OZ1•HCl was the most active against both strains of Leishmania. Such finding was corroborated by the results obtained in assessments of the L. infantum amastigote susceptibility. It is noteworthy that the salt forms of the endoperoxide–pyrazole hybrids displayed a broader spectrum of action, showing activity in both strains of Leishmania. Our preliminary biological findings encourage further optimization of peroxide–pyrazole hybrids to identify a promising antileishmanial lead.

1,2,4-Trioxolane and 1,2,4,5-Tetraoxane Endoperoxides against Old-World Leishmania Parasites: In Vitro Activity and Mode of Action

Leishmaniasis remains one of the ten Neglected Tropical Diseases with significant morbidity and mortality in humans. Current treatment of visceral leishmaniasis is difficult due to a lack of effective, non-toxic, and non-extensive medications. This study aimed to evaluate the selectivity of 12 synthetic endoperoxides (1,2,4-trioxolanes; 1,2,4,5-tetraoxanes) and uncover their biochemical effects on Leishmania parasites responsible for visceral leishmaniasis. The compounds were screened for in vitro activity against L. infantum and L. donovani and for cytotoxicity in two monocytic cell lines (J774A.1 and THP-1) using the methyl thiazol tetrazolium assay. Reactive oxygen species formation, apoptosis, and mitochondrial impairment were measured by flow cytometry. The compounds exhibited fair to moderate anti-proliferative activity against promastigotes of the 2 Leishmania species, with IC₅₀ values ranging from 13.0 ± 1.7 µM to 793.0 ± 37.2 µM. Tetraoxanes LC132 and LC138 demonstrated good leishmanicidal activity on L. infantum amastigotes (IC₅₀ 13.2 ± 5.2 and 23.9 ± 2.7 µM) with low cytotoxicity in mammalian cells (SIs 22.1 and 118.6), indicating selectivity towards the parasite. Furthermore, LC138 was able to induce late apoptosis and dose-dependent oxidative stress without affecting mithocondria. Compounds LC132 and LC138 can be further explored as potential antileishmanial chemotypes.

The Effect of Curcumin on the Expression of INFγ, TNF-α, and iNOS Genes in PBMCs Infected with Leishmania major [MRHO/IR/75/ER]

BACKGROUND

Leishmaniasis, caused by the Leishmania parasite, is one of the most important tropical neglected diseases. The urgent search for effective, inexpensive, and preferably herbal anti-leishmanial agents, is needed.

OBJECTIVE

Curcumin is a natural polyphenolic compound derived from turmeric that is well known for its antioxidant, anti-inflammatory, anti-tumor, and anti-cancer activity.

METHODS

The present work evaluates the anti-leishmanial [Leishmania major] activity of curcumin. The infected PBMCs were treated with curcumin. The ROS level at 6, 12, 24 h and gene expression levels at 24, 48, and 72 h of PBMCs after treatment with curcumin were determined.

RESULTS

Based on the results, the curcumin concentrations of 268 μM [24 h] and 181.2 μM [72 h] were defined as IC50 against L. major promastigotes. Treatment of L. major infected-peripheral blood mononuclear cells [PBMCs] with IC50 concentrations of curcumin, depending on exposure time, significantly induced the reactive oxygen species [ROS] generation and increased the expression levels of interferongamma [IFN-γ], tumor necrosis factor-alpha [TNF-α], and nitric oxide synthase [iNOS] genes.

CONCLUSION

These findings suggest the potential of curcumin against Leishmaniasis.

Therapeutic effect of Prosopis strombulifera (LAM) BENTH aqueous extract on a murine model of cutaneous leishmaniasis

Background and aim

Prosopis strombulifera (Lam.) Benth is a rhizomatous shrub native from different zones of Argentine Republic. P. strombulifera aqueous extract (PsAE) has different effects and several biological activities have been reported. The goal of this study was to analyze the activity of PsAE on a murine model of cutaneous leishmaniasis caused by Leishmania amazonensis.

Experimental procedure

PsAE was orally administered at 150 mg/animal/day on BALB/c mice infected in the right footpad (RFP) with 1 × 10⁵ promastigotes of L. amazonensis. As a chemotherapeutic control of treatment, animals receive a commercial form of meglumine antimoniate (MA) (Glucantime®, Aventis, Paris, France).

Results and conclusion

We observe that the size of RFP lesions of infected mice without treatment showed a grade of inflammation, ulceration and necrosis at the site of infection much greater than that observed with PsAE or MA treatment. Moreover, PsAE was capable of decreasing parasite burden and splenic index. Furthermore, PsAE treated mice showed a significant decrease in O.D. of total anti-Leishmania IgG antibody responses against L. amazonensis. This decrease was similar to those observed when the reference drug, MA, was used. This would indicate that PsAE treatment inhibits or delays disease progression in mice. In conclusion, our findings suggest that PsAE could be a potential candidate to be used, as a new therapeutic strategy, to treat cutaneous leishmaniasis caused by L. amazonensis.

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Prosopis strombulifera aqueous extract (PsAE) has antileishmanial effect.

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PsAE treatment reduces inflammation and ulceration at the site of infection.

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PsAE decreased parasite burden and splenic index.

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PsAE decreased total anti-Leishmania IgG antibody responses against L. amazonensis.

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PsAE produces a switch to Th1 humoral immune response after infection.

In vitro and in vivo antileishmanial activity of β-acetyl-digitoxin, a cardenolide of Digitalis lanata potentially useful to treat visceral leishmaniasis

Current treatments of visceral leishmaniasis face limitations due to drug side effects and/or high cost, along with the emergence of parasite resistance. Novel and low-cost antileishmanial agents are therefore required. We report herein the antileishmanial activity of β-acetyl-digitoxin (b-AD), a cardenolide isolated from Digitalis lanata leaves, assayed in vitro and in vivo against Leishmania infantum. Results showed direct action of b-AD against parasites, as well as efficacy for the treatment of Leishmania-infected macrophages. In vivo experiments using b-AD-containing Pluronic^® F127 polymeric micelles (b-AD/Mic) to treat L. infantum-infected mice showed that this composition reduced the parasite load in distinct organs in more significant levels. It also induced the development of anti-parasite Th1-type immunity, attested by high levels of IFN-γ, IL-12, TNF-α, GM-CSF, nitrite and specific IgG2a antibodies, in addition to low IL-4 and IL-10 contents, along with higher IFN-γ-producing CD4⁺ and CD8⁺ T-cell frequency. Furthermore, low toxicity was found in the organs of the treated animals. Comparing the therapeutic effect between the treatments, b-AD/Mic was the most effective in protecting animals against infection, when compared to the other groups including miltefosine used as a drug control. Data found 15 days after treatment were similar to those obtained one day post-therapy. In conclusion, the results obtained suggest that b-AD/Mic is a promising antileishmanial agent and deserves further studies to investigate its potential to treat visceral leishmaniasis.

Antileishmanial compounds from Connarus suberosus: Metabolomics, isolation and mechanism of action

Leishmaniasis is a disease impacting public health worldwide due to its high incidence, morbidity and mortality. Available treatments are costly, lengthy and toxic, not to mention the problem of parasite resistance. The development of alternative treatments is warranted and natural products demonstrate promising activity. This study investigated the activity of Connarus suberosus extracts and compounds against Leishmania species. Several C. suberosus extracts were tested against L. amazonensis promastigotes. Active and inactive extracts were analyzed by UHPLC-MS and data evaluated using a metabolomics platform, revealing an unknown neoflavonoid (connarin, 3), isolated together with the pterocarpans: hemileiocarpin (1) and leiocarpin (2). The aforementioned compounds (1-3), together with the benzoquinones: rapanone (4), embelin (5) and suberonone (6) previously isolated by our group from the same species, were tested against: (i) L. amazonensis and L. infantum promastigotes, and (ii) L. amazonensis intracellular amastigotes, with the most active compound (3) also tested against L. infantum amastigotes. Cytotoxicity against murine peritoneal macrophages was also investigated. Compounds 2 and 3 presented an IC50 33.8 μM and 11.4 μM for L. amazonensis promastigotes; and 44.3 μM and 13.3 μM for L. infantum promastigotes, respectively. For L. amazonensis amastigotes, the IC50 of 2 was 20.4 μM with a selectivity index (SI) of 5.7, while the IC50 of 3 was 2.9 μM with an SI of 6.3. For L. infantum amastigotes, the IC50 of 3 was 7.7 μM. Compounds 2 and 3 presented activity comparable with the miltefosine positive control, with compound 3 found to be 2-4 times more active than the positive control, depending on the Leishmania species and form. The extracts and isolated compounds showed moderate toxicity against macrophages. Compounds 2 and 3 altered the mitochondrial membrane potential (ΔΨm) and neutral lipid body accumulation, while 2 also impacted plasma membrane permeabilization, culminating in cellular disorder and parasite death. Transmission electron microscopy of L. amazonensis promastigotes treated with compound 3 confirmed the presence of lipid bodies. Leiocarpin (2) and connarin (3) demonstrated antileishmanial activity. This study provides knowledge of natural products with antileishmanial activity, paving the way for prototype development to fight this neglected tropical disease.