Phenylhydrazides as inhibitors of Leishmania amazonensis arginase and antileishmanial activity

Exploring the Potential of Malvidin and Echiodinin as Probable Antileishmanial Agents Through In Silico Analysis and In Vitro Efficacy

Leishmaniasis, a neglected tropical disease caused by Leishmania species, presents serious public health challenges due to limited treatment options, toxicity, high costs, and drug resistance. In this study, the in vitro potential of malvidin and echioidinin is examined as antileishmanial agents against L. amazonensis, L. braziliensis, and L. infantum, comparing their effects to amphotericin B (AmpB), a standard drug. Malvidin demonstrated greater potency than echioidinin across all parasite stages and species. Against L. amazonensis, malvidin's IC50 values were 197.71 ± 17.20 µM (stationary amastigotes) and 258.07 ± 17 µM (axenic amastigotes), compared to echioidinin's 272.99 ± 29.90 μM and 335.96 ± 19.35 μM. AmpB was more potent, with IC50 values of 0.06 ± 0.01 µM and 0.10 ± 0.03 µM. Malvidin exhibited lower cytotoxicity (CC50: 2920.31 ± 80.29 µM) than AmpB (1.06 ± 0.12 µM) and a favorable selectivity index. It reduced infection rates by 35.75% in L. amazonensis-infected macrophages. The in silico analysis revealed strong binding between malvidin and Leishmania arginase, with the residues HIS139 and PRO258 playing key roles. Gene expression analysis indicated malvidin's modulation of oxidative stress and DNA repair pathways, involving genes like GLO1 and APEX1. These findings suggest malvidin's potential as a safe, natural antileishmanial compound, warranting further in vivo studies to confirm its therapeutic efficacy and pharmacokinetics in animal models.

Immunotherapeutic Strategies as Potential Treatment Options for Cutaneous Leishmaniasis

Cutaneous leishmaniasis (CL), caused by protozoan parasites of the Leishmania genus, is prevalent in tropical and subtropical regions, with important morbidity, particularly in low- to middle-income countries. Current systemic treatments, including pentavalent antimonials and miltefosine, are associated with significant toxicity, reduced efficacy, and are frequently ineffective in cases of severe or chronic CL. Immunotherapies leverage the immune system to combat microbial infection and offer a promising adjunct or alternative approach to the current standard of care for CL. However, the heterogeneous clinical presentation of CL, which is dependent on parasite species and host immunity, may require informed clinical intervention with immunotherapies. This review explores the clinical and immunological characteristics of CL, emphasising the current landscape of immunotherapies in in vivo models and clinical studies. Such immune-based interventions aim to modulate immune responses against Leishmania, with additive therapeutic effects enabling the efficacy of lower drug doses and decreasing the associated toxicity. Understanding the mechanisms that underlie immunotherapy for CL provides critical insights into developing safer and more effective treatments for this neglected tropical disease. Identifying suitable therapeutic candidates and establishing their safety and efficacy are essential steps in this process. However, the feasibility and utility of these treatments in resource-limited settings must also be considered, taking into account factors such as cost of production, temperature stability, and overall patient access.

Py-CoMFA, docking, and molecular dynamics simulations of Leishmania (L.) amazonensis arginase inhibitors

Leishmaniasis is a disease caused by a protozoan of the genus Leishmania, affecting millions of people, mainly in tropical countries, due to poor social conditions and low economic development. First-line chemotherapeutic agents involve highly toxic pentavalent antimonials, while treatment failure is mainly due to the emergence of drug-resistant strains. Leishmania arginase (ARG) enzyme is vital in pathogenicity and contributes to a higher infection rate, thus representing a potential drug target. This study helps in designing ARG inhibitors for the treatment of leishmaniasis. Py-CoMFA (3D-QSAR) models were constructed using 34 inhibitors from different chemical classes against ARG from L. (L.) amazonensis (LaARG). The 3D-QSAR predictions showed an excellent correlation between experimental and calculated pIC50 values. The molecular docking study identified the favorable hydrophobicity contribution of phenyl and cyclohexyl groups as substituents in the enzyme allosteric site. Molecular dynamics simulations of selected protein-ligand complexes were conducted to understand derivatives' interaction modes and affinity in both active and allosteric sites. Two cinnamide compounds, 7g and 7k, were identified, with similar structures to the reference 4h allosteric site inhibitor. These compounds can guide the development of more effective arginase inhibitors as potential antileishmanial drugs.

Metalloenzyme Inhibitors against Zoonotic Infections: Focus on Leishmania and Schistosoma

The term "zoonosis" denotes diseases transmissible among vertebrate animals and humans. These diseases constitute a significant public health challenge, comprising 61% of human pathogens and causing an estimated 2.7 million deaths annually. Zoonoses not only affect human health but also impact animal welfare and economic stability, particularly in low- and middle-income nations. Leishmaniasis and schistosomiasis are two important neglected tropical diseases with a high prevalence in tropical and subtropical areas, imposing significant burdens on affected regions. Schistosomiasis, particularly rampant in sub-Saharan Africa, lacks alternative treatments to praziquantel, prompting concerns regarding parasite resistance. Similarly, leishmaniasis poses challenges with unsatisfactory treatments, urging the development of novel therapeutic strategies. Effective prevention demands a One Health approach, integrating diverse disciplines to enhance diagnostics and develop safer drugs. Metalloenzymes, involved in parasite biology and critical in different biological pathways, emerged in the last few years as useful drug targets for the treatment of human diseases. Herein we have reviewed recent reports on the discovery of inhibitors of metalloenzymes associated with zoonotic diseases like histone deacetylases (HDACs), carbonic anhydrase (CA), arginase, and heme-dependent enzymes.

Compounds with potentialities as novel chemotherapeutic agents in leishmaniasis at preclinical level

Leishmaniasis are neglected infectious diseases caused by kinetoplastid protozoan parasites from the genus Leishmania. These sicknesses are present mainly in tropical regions and almost 1 million new cases are reported each year. The absence of vaccines, as well as the high cost, toxicity or resistance to the current drugs determines the necessity of new treatments against these pathologies. In this review, several compounds with potentialities as new antileishmanial drugs are presented. The discussion is restricted to the preclinical level and molecules are organized according to their chemical nature, source and molecular targets. In this manner, we present antimicrobial peptides, flavonoids, withanolides, 8-aminoquinolines, compounds from Leish-Box, pyrazolopyrimidines, and inhibitors of tubulin polymerization/depolymerization, topoisomerase IB, proteases, pteridine reductase, N-myristoyltransferase, as well as enzymes involved in polyamine metabolism, response against oxidative stress, signaling pathways, and sterol biosynthesis. This work is a contribution to the general knowledge of these compounds as antileishmanial agents.

Synthetic strategies for the construction of C3-fluorinated oxindoles

C3-fluorinated oxindoles are important scaffolds known to demonstrate various biological properties. As bio-isosteres of oxindoles, these compounds have shown tremendous potential in drug research discovery programs. Besides, they also serve as starting materials for synthesizing other fluorine-containing new architectures, thus launching research for developing new methods for their synthesis. Consequently, various approaches have been developed over the years to synthesize C3-fluorinated oxindoles. This review highlights the strategies developed to date to access C3-difluoro and monofluorooxindoles via intermolecular and intramolecular approaches. The key findings of the strategies developed are discussed along with the prevailing mechanism.

Design and Synthesis of New Anthranyl Phenylhydrazides: Antileishmanial Activity and Structure-Activity Relationship

Leishmaniasis is a neglected tropical disease affecting millions of people worldwide. A centenary approach to antimonial-based drugs was first initiated with the synthesis of urea stibamine by Upendranath Brahmachari in 1922. The need for new drug development led to resistance toward antimoniates. New drug development to treat leishmaniasis is urgently needed. In this way, searching for new substances with antileishmanial activity, we synthesized ten anthranyl phenylhydrazide and three quinazolinone derivatives and evaluated them against promastigotes and the intracellular amastigotes of Leishmania amazonensis. Three compounds showed good activity against promastigotes 1b, 1d, and 1g, with IC50 between 1 and 5 μM. These new phenylhydrazides were tested against Leishmania arginase, but they all failed to inhibit this parasite enzyme, as we have shown in a previous study. To explain the possible mechanism of action, we proposed the enzyme PTR1 as a new target for these compounds based on in silico analysis. In conclusion, the new anthranyl hydrazide derivatives can be a promising scaffold for developing new substances against the protozoa parasite.

Molecular-level strategic goals and repressors in Leishmaniasis - Integrated data to accelerate target-based heterocyclic scaffolds

Leishmaniasis is a complex of neglected tropical diseases caused by various species of leishmanial parasites that primarily affect the world's poorest people. A limited number of standard medications are available for this disease that has been used for several decades, these drugs have many drawbacks such as resistance, higher cost, and patient compliance, making it difficult to reach the poor. The search for novel chemical entities to treat leishmaniasis has led to target-based scaffold research. Among several identified potential molecular targets, enzymes involved in the purine salvage pathway include polyamine biosynthetic process, such as arginase, ornithine decarboxylase, S-adenosylmethionine decarboxylase, spermidine synthase, trypanothione reductase as well as enzymes in the DNA cell cycle, such as DNA topoisomerases I and II plays vital role in the life cycle survival of leishmanial parasite. This review mainly focuses on various heterocyclic scaffolds, and their specific inhibitory targets against leishmaniasis, particularly those from the polyamine biosynthesis pathway and DNA topoisomerases with estimated activity studies of various heterocyclic analogs in terms of their IC₅₀ or EC₅₀ value, reported molecular docking analysis from available published literatures.

Inhibiting Human and Leishmania Arginases Using Cannabis sativa as a Potential Therapy for Cutaneous Leishmaniasis: A Molecular Docking Study

Cutaneous leishmaniasis (CL), a vector-borne parasitic disease caused by the Leishmania protozoan, is a serious public health problem in Morocco. The treatment of this disease is still based on pentavalent antimonials as the primary therapy, but these have associated side effects. Thus, the development of effective, risk-free alternative therapeutics based on natural compounds against leishmaniasis is urgent. Arginase, the key enzyme in the polyamine biosynthetic pathway, plays a critical role in leishmaniasis outcome and has emerged as a potential therapeutic target. The objective of this study was to test Cannabis sativa's phytochemical components (cannabinoids and terpenoids) through molecular docking against Leishmania and human arginase enzymes. Our results showed that delta-9-tetrahydrocannabinol (THC) possessed the best binding energies of -6.02 and -6.35 kcal/mol with active sites of Leishmania and human arginases, respectively. Delta-9-THC interacted with Leishmania arginase through various amino acids including His139 and His 154 and linked to human arginase via His 126. In addition to delta-9-THC, caryophyllene oxide and cannabidiol (CBD) also showed a good inhibition of Leishmania and human arginases, respectively. Overall, the studied components were found to inhibit both arginases active sites via hydrogen bonds and hydrophobic interactions. These components may serve as therapeutic agents or in co-administrated therapy for leishmaniasis.

In Silico Antiprotozoal Evaluation of 1,4-Naphthoquinone Derivatives against Chagas and Leishmaniasis Diseases Using QSAR, Molecular Docking, and ADME Approaches

Chagas and leishmaniasis are two neglected diseases considered as public health problems worldwide, for which there is no effective, low-cost, and low-toxicity treatment for the host. Naphthoquinones are ligands with redox properties involved in oxidative biological processes with a wide variety of activities, including antiparasitic. In this work, in silico methods of quantitative structure-activity relationship (QSAR), molecular docking, and calculation of ADME (absorption, distribution, metabolism, and excretion) properties were used to evaluate naphthoquinone derivatives with unknown antiprotozoal activity. QSAR models were developed for predicting antiparasitic activity against Trypanosoma cruzi, Leishmania amazonensis, and Leishmania infatum, as well as the QSAR model for toxicity activity. Most of the evaluated ligands presented high antiparasitic activity. According to the docking results, the family of triazole derivatives presented the best affinity with the different macromolecular targets. The ADME results showed that most of the evaluated compounds present adequate conditions to be administered orally. Naphthoquinone derivatives show good biological activity results, depending on the substituents attached to the quinone ring, and perhaps the potential to be converted into drugs or starting molecules.

An Update on Arginase Inhibitors and Inhibitory Assays

Arginase, which converts arginine into ornithine and urea, is a promising therapeutic target. Arginase is involved in cardiovascular diseases, parasitic infections and, through a critical role in immunity, in some cancers. There is a need to develop effective arginase inhibitors and therefore efforts to identify and optimize new inhibitors are increasing. Several methods of evaluating arginase activity are available, but few directly measure the product. Radiometric assays need to separate urea and dying reactions require acidic conditions and sometimes heating. Hence, there are a variety of different approaches available, and each approach has its own limits and benefits. In this review, we provide an update on arginase inhibitors, followed by a discussion on available arginase assays and alternative methods, with a focus on the intrinsic biases and parameters that are likely to impact results.

Identification of Chalcone Derivatives as Inhibitors of Leishmania infantum Arginase and Promising Antileishmanial Agents

Arginase catalyzes the hydrolysis of l-arginine into l-ornithine and urea, acting as a key enzyme in the biosynthesis of polyamines. Leishmania growth and survival is dependent on polyamine biosynthesis; therefore, inhibition of Leishmania arginase may be a promising therapeutic strategy. Here, we evaluated a series of thirty-six chalcone derivatives as potential inhibitors of Leishmania infantum arginase (LiARG). In addition, the activity of selected inhibitors against L. infantum parasites was assessed in vitro. Seven compounds exhibited LiARG inhibition above 50% at 100 μM. Among them, compounds LC41, LC39, and LC32 displayed the greatest inhibition values (72.3 ± 0.3%, 71.9 ± 11.6%, and 69.5 ± 7.9%, respectively). Molecular docking studies predicted hydrogen bonds and hydrophobic interactions between the most active chalcones (LC32, LC39, and LC41) and specific residues from LiARG's active site, such as His140, Asn153, His155, and Ala193. Compound LC32 showed the highest activity against L. infantum promastigotes (IC₅₀ of 74.1 ± 10.0 μM), whereas compounds LC39 and LC41 displayed the best results against intracellular amastigotes (IC₅₀ of 55.2 ± 3.8 and 70.4 ± 9.6 μM, respectively). Moreover, compound LC39 showed more selectivity against parasites than host cells (macrophages), with a selectivity index (SI) of 107.1, even greater than that of the reference drug Fungizone®. Computational pharmacokinetic and toxicological evaluations showed high oral bioavailability and low toxicity for the most active compounds. The results presented here support the use of substituted chalcone skeletons as promising LiARG inhibitors and antileishmanial drug candidates.

Umpolung of donor–acceptor cyclopropanes via N-heterocyclic carbene organic catalysis

A carbene-catalyzed formal umpolung of donor–acceptor (D–A) cyclopropanes is disclosed with chiral spirocyclic lactones bearing multiple functional groups afforded with excellent enantio- and diastereoselectivities.

Cinnamides Target Leishmania amazonensis Arginase Selectively

Caffeic acid and related natural compounds were previously described as Leishmania amazonensis arginase (L-ARG) inhibitors, and against the whole parasite in vitro. In this study, we tested cinnamides that were previously synthesized to target human arginase. The compound caffeic acid phenethyl amide (CAPA), a weak inhibitor of human arginase (IC₅₀ = 60.3 ± 7.8 μM) was found to have 9-fold more potency against L-ARG (IC₅₀ = 6.9 ± 0.7 μM). The other compounds that did not inhibit human arginase were characterized as L-ARG, showing an IC₅₀ between 1.3–17.8 μM, and where the most active was compound 15 (IC₅₀ = 1.3 ± 0.1 μM). All compounds were also tested against L. amazonensis promastigotes, and only the compound CAPA showed an inhibitory activity (IC₅₀ = 80 μM). In addition, in an attempt to gain an insight into the mechanism of competitive L-ARG inhibitors, and their selectivity over mammalian enzymes, we performed an extensive computational investigation, to provide the basis for the selective inhibition of L-ARG for this series of compounds. In conclusion, our results indicated that the compounds based on cinnamoyl or 3,4-hydroxy cinnamoyl moiety could be a promising starting point for the design of potential antileishmanial drugs based on selective L-ARG inhibitors.