2-Aryl-quinazolin-4(3H)-ones as an inhibitor of leishmania folate pathway: In vitro biological evaluation, mechanism studies and molecular docking

A series of quinazolin-4(3H)-one-morpholine hybrids as anti-lung-cancer agents: Synthesis, molecular docking, molecular dynamics, ADME prediction and biological activity studies

In this study, we synthesized 15 novel quinazoline-morpholinobenzylideneamino hybrid compounds from methyl anthranilate and we assessed their cytotoxicity via in vitro assays against A549 and BEAS-2B cell lines. Molecular docking studies were conducted to evaluate the protein-ligand interactions and inhibition mechanisms on nine different molecular targets, while molecular dynamics (MD) simulations were carried out to assess the stability of the best docked ligand-protein complexes. Additionally, ADME prediction was carried out to determine physicochemical parameters and drug likeness. According to the cytotoxicity assays, compound 1 (IC50 = 2.83 μM) was found to be the most active inhibitor against A549 cells. While the selectivity index (SI) of compound 1 is 29, the SI of the reference drugs paclitaxel and sorafenib, used in this study, are 2.40 and 4.92, respectively. Among the hybrid compounds, 1 has the best docking scores against VEGFR1 (-11.744 kcal/mol), VEGFR2 (-12.407 kcal/mol) and EGFR (-10.359 kcal/mol). During MD simulations, compound 1 consistently exhibited strong hydrogen bond interactions with the active sites of VEGFR1 and 2, and these interactions were maintained for more than 90% of the simulation time. Additionally, the RMSD and RMSF values of the ligand-protein complexes exhibited high stability at their minimum levels around 1-2 Å. In conclusion, these findings suggest that compound 1 may be a potent and selective inhibitor candidate for lung cancer treatment and inhibition of VEGFR2, especially.

Optimization of the 2-arylquinazoline-4(3H)one scaffold for a selective and potent antitrypanosomal agent: modulation of the mechanism of action through chemical functionalization

We sought to identify a potent and selective antitrypanosomal agent through modulation of the mechanism of action of a 2-arylquinazoline scaffold as an antitrypanosomal agent via chemical functionalization at the 4-position. We wished to use the: (i) susceptibility of trypanosomatids towards nitric oxide (NO) and reactive oxygen species (ROS); (ii) capacity of the 4-substituted quinazoline system to act as an antifolate agent. Three quinazolin-based moieties that differed from each other by having at the 4-position key pharmacophores targeting the induction of NO and ROS production were evaluated in vitro against Leishmania infantum and Trypanosoma cruzi parasites and their modes of action were explored. Replacement of an oxygen moiety at the 4-position of the antifolate 2-arylquinazolin-4(3H)one by hydrazinyl and 5-nitrofuryl-hydrazinyl pharmacophores enhanced antitrypanosomatid activity significantly due to promotion of an additional mechanism beyond the antifolate response such as NO or ROS production, respectively. Among the three types of chemical functionalization, the 5-nitrofuryl-hydrazinyl moiety generated the most potent compounds. Compound 3b was a potential candidate thanks to its sub-micromolar response against the promastigotes/amastigotes of L. infantum and epimastigote of T. cruzi, moderate toxicity on macrophages (J774.1), good selectivity index (∼15.1-17.6) and, importantly, non-mutagenic effects. 2-Arylquinazoline could be an attractive platform to design new anti-trypanosomatid agents with the use of key pharmacophores.

The Synthesis and Biological Evaluation of 2-(1H-Indol-3-yl)quinazolin-4(3H)-One Derivatives

The treatment of many bacterial diseases remains a significant problem due to the increasing antibiotic resistance of their infectious agents. Among others, this is related to Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA) and Mycobacterium tuberculosis. In the present article, we report on antibacterial compounds with activity against both S. aureus and MRSA. A straightforward approach to 2-(1H-indol-3-yl)quinazolin-4(3H)-one and their analogues was developed. Their structural and functional relationships were also considered. The antimicrobial activity of the synthesized compounds against Mycobacterium tuberculosis H₃₇Rv, S. aureus ATCC 25923, MRSA ATCC 43300, Candida albicans ATCC 10231, and their role in the inhibition of the biofilm formation of S. aureus were reported. 2-(5-Iodo-1H-indol-3-yl)quinazolin-4(3H)-one (3k) showed a low minimum inhibitory concentration (MIC) of 0.98 μg/mL against MRSA. The synthesized compounds were assessed via molecular docking for their ability to bind long RSH (RelA/SpoT homolog) proteins using mycobacterial and streptococcal (p)ppGpp synthetase structures as models. The cytotoxic activity of some synthesized compounds was studied. Compounds 3c, f, g, k, r, and 3z displayed significant antiproliferative activities against all the cancer cell lines tested. Indolylquinazolinones 3b, 3e, and 3g showed a preferential suppression of the growth of rapidly dividing A549 cells compared to slower growing fibroblasts of non-tumor etiology.

Modulating leishmanial pteridine metabolism machinery via some new coumarin-1,2,3-triazoles: Design, synthesis and computational studies

In accordance with WHO statistics, leishmaniasis is one of the top neglected tropical diseases, affecting around 700 000 to one million people per year. To that end, a new series of coumarin-1,2,3-triazole hybrid compounds was designed and synthesized. All new compounds exerted higher activity than miltefosine against L. major promastigotes and amastigotes. Seven compounds showed single digit micromolar IC₅₀ values whereas three compounds (13c, 14b and 14c) displayed submicromolar potencies. A mechanistic study to elucidate the antifolate-dependent activity of these compounds revealed that folic and folinic acids abrogated their antileishmanial effects. These compounds exhibited high safety margins in normal VERO cells, expressed as high selectivity indices. Docking simulation studies on the folate pathway enzymes pteridine reductase and DHFR-TS imparted strong theoretical support to the observed biological activities. Besides, docking experiments on human DHFR revealed minimal binding interactions thereby highlighting the selectivity of these compounds. Predicted in silico physicochemical and pharmacokinetic parameters were adequate. In view of this, the structural characteristics of these compounds demonstrated their suitability as antileishmanial lead compounds.

Room temperature ligand-free Cu2O-H2O2 catalyzed tandem oxidative synthesis of quinazoline-4(3H)-one and quinazoline derivatives

An efficient and simple copper catalytic system has been developed for the synthesis of medicinally important 2-substituted quinazoline-4(3H)-ones from 2-aminobenzonitrile and benzyl alcohol derivatives and additionally 2-substituted quinazolines from 2-aminobenzylamine and benzaldehyde derivatives. Mild oxidant H₂O₂ was utilized, providing excellent product yields. The molecular structure of one of the compounds was substantiated through SC-XRD. The versatility of the protocol was demonstrated through gram-scale syntheses.

New antileishmanial quinoline linked isatin derivatives targeting DHFR-TS and PTR1: Design, synthesis, and molecular modeling studies

In a search for new drug candidates for one of the neglected tropical diseases, leishmaniasis, twenty quinoline-isatin hybrids were synthesized and tested for their in vitro antileishmanial activity against Leishmaniamajor strain. All the synthesized compounds showed promising in vitro activity against the promastigote form in a low micromolar range (IC₅₀ = 0.5084-5.9486 μM) superior to the reference miltefosine (IC₅₀ = 7.8976 μM). All the target compounds were then tested against the intracellular amastigote form and showed promising inhibition effects (IC₅₀ = 0.60442-8.2948 μM versus 8.08 μM for miltefosine). Compounds 4e, 4b and 4f were shown to possess the highest antileishmanial activity against both promastigote and amastigote forms. The most active compounds were proven to exhibit their significant antileishmanial effects through antifolate mechanism, targeting DHFR-TS and PTR1. To evaluate the safety profile of the most active derivatives 4e, 4b and 4f, the in vitro cytotoxicity test was carried out and displayed higher selectivity indices than the reference miltefosine. Molecular docking within putative target protein PTR1 confirmed the high potentiality of the most active compounds 4e, 4b and 4f to block the catalytic activity of Lm-PTR1.

Synthesis and Antitrypanosomal and Mechanistic Studies of a Series of 2-Arylquinazolin-4-hydrazines: A Hydrazine Moiety as a Selective, Safe, and Specific Pharmacophore to Design Antitrypanosomal Agents Targeting NO Release

Nitric oxide (NO) represents a valuable target to design antitrypanosomal agents by its high toxicity against trypanosomatids and minimal side effects on host macrophages. The progress of NO-donors as antitrypanosomal has been restricted by the high toxicity of their agents, which usually is based on NO-heterocycles and metallic NO-complexes. Herein, we carried out the design of a new class of NO-donors based on the susceptibility of the hydrazine moiety connected to an electron-deficient ring to be reduced to the amine moiety with release of NO. Then, a series of novel 2-arylquinazolin-4-hydrazine, with the potential ability to disrupt the parasite folate metabolism, were synthesized. Their in vitro evaluation against Leishmania and Trypanosoma cruzi parasites and mechanistic aspects were investigated. The compounds displayed significant leishmanicidal activity, identifying three potential candidates, that is, 3b, 3c, and 3f, for further assays by their good antiamastigote activities against Leishmania braziliensis, low toxicity, non-mutagenicity, and good ADME profile. Against T. cruzi parasites, derivatives 3b, 3c, and 3e displayed interesting levels of activities and selectivities. Mechanistic studies revealed that the 2-arylquinazolin-4-hydrazines act as either antifolate or NO-donor agents. NMR, fluorescence, and theoretical studies supported the fact that the quinazolin-hydrazine decomposed easily in an oxidative environment via cleavage of the N-N bond to release the corresponding heterocyclic-amine and NO. Generation of NO from axenic parasites was confirmed by the Griess test. All the evidence showed the potential of hydrazine connected to the electron-deficient ring to design effective and safe NO-donors against trypanosomatids.

Metabolic Pathways of Leishmania Parasite: Source of Pertinent Drug Targets and Potent Drug Candidates

Leishmaniasis is a tropical disease caused by a protozoan parasite Leishmania that is transmitted via infected female sandflies. At present, leishmaniasis treatment mainly counts on chemotherapy. The currently available drugs against leishmaniasis are costly, toxic, with multiple side effects, and limitations in the administration route. The rapid emergence of drug resistance has severely reduced the potency of anti-leishmanial drugs. As a result, there is a pressing need for the development of novel anti-leishmanial drugs with high potency, low cost, acceptable toxicity, and good pharmacokinetics features. Due to the availability of preclinical data, drug repurposing is a valuable approach for speeding up the development of effective anti-leishmanial through pointing to new drug targets in less time, having low costs and risk. Metabolic pathways of this parasite play a crucial role in the growth and proliferation of Leishmania species during the various stages of their life cycle. Based on available genomics/proteomics information, known pathways-based (sterol biosynthetic pathway, purine salvage pathway, glycolysis, GPI biosynthesis, hypusine, polyamine biosynthesis) Leishmania-specific proteins could be targeted with known drugs that were used in other diseases, resulting in finding new promising anti-leishmanial therapeutics. The present review discusses various metabolic pathways of the Leishmania parasite and some drug candidates targeting these pathways effectively that could be potent drugs against leishmaniasis in the future.

Identification of 2-arylquinazolines with alkyl-polyamine motifs as potent antileishmanial agents: synthesis and biological evaluation studies

2-Arylquinazolines with a range of alkyl polyamines as side chain/ring functional motifs at the 4th-position were considered for antileishmanial study with the rationale that related heterocyclic scaffolds and polyamine functionalities are present in drugs, clinical trial agents, natural products and anti-parasitic/leishmanial agents. Synthesis involves construction of the 2-arylquinazolin-4-one ring and deoxyamination via deoxychlorination followed by SNAr-based amination or a methodology of SNAr-deoxyamination driven by BOP-mediated hydroxyl-activation. Various alkyl-polyamines important for activities were incorporated. A total of 26 compounds were prepared and screened against Leishmania donovani (Ld) promastigote cells using the MTT assay. Most of the investigated series of compounds showed characteristic leishmanicidal properties. Several compounds showed pronounced leishmanicidal activities (IC50: 5-6.5 μM) with higher efficiency than the antileishmanial drug miltefosine (IC50: 10.5 μM), and relatively less cytotoxicity to macrophage host cells (SI: 9.27-13.5) compared to miltefosine (SI: 3.42). Important pharmacophoric skeletons were identified.

Antimalarial Activity of Highly Coordinative Fused Heterocycles Targeting β-Hematin Crystallization

The β-hematin formation is a unique process adopted by Plasmodium sp. to detoxify free heme and represents a validated target to design new effective antimalarials. Most of the β-hematin inhibitors are mainly based on 4-aminoquinolines, but the parasite has developed diverse defense mechanisms against this type of chemical system. Thus, the identification of other molecular chemical entities targeting the β-hematin formation pathway is highly needed to evade resistance mechanisms associated with 4-aminoquinolines. Herein, we showed that the highly coordinative character can be a useful tool for the rational design of antimalarial agents targeting β-hematin crystallization. From a small library consisting of five compound families with recognized antitrypanosomatid activity and coordinative abilities, a group of tetradentate 1,4-disubstituted phthalazin-aryl/heteroarylhydrazinyl derivatives were identified as potential antimalarials. They showed a remarkable curative response against Plasmodium berghei-infected mice with a significant reduction of the parasitemia, which was well correlated with their good inhibitory activities on β-hematin crystallization (IC₅₀ = 5-7 μM). Their in vitro inhibitory and in vivo responses were comparable to those found for a chloroquine reference. The active compounds showed moderate in vitro toxicity against peritoneal macrophages, a low hemolysis response, and a good in silico ADME profile, identifying compound 2f as a promising antimalarial agent for further experiments. Other less coordinative fused heterocycles exhibited moderate inhibitory responses toward β-hematin crystallization and modest efficacy against the in vivo model. The complexation ability of the ligands with iron(III) was experimentally and theoretically determined, finding, in general, a good correlation between the complexation ability of the ligand and the inhibitory activity toward β-hematin crystallization. These findings open new perspectives toward the rational design of antimalarial β-hematin inhibitors based on the coordinative character as an alternative to the conventional β-hematin inhibitors.

An appraisal of the scientific current situation and new perspectives in the treatment of cutaneous leishmaniasis

Leishmaniasis is a Neglected Tropical Diseases caused by protozoan parasites of the genus Leishmania. It is a major health problem in many tropical and subtropical regions of the world and can produce three different clinical manifestations, among which cutaneous leishmaniasis has a higher incidence in the world than the other clinical forms. There are no recognized and reliable means of chemoprophylaxis or vaccination against infections with different forms of leishmaniasis. In addition, chemotherapy, unfortunately, remains, in many respects, unsatisfactory. Therefore, there is a continuing and urgent need for new therapies against leishmaniasis that are safe and effective in inducing a long-term cure. This review summarizes the latest advances in currently available treatments and improvements in the development of drug administration. In addition, an analysis of the in vivo assays was performed and the challenges facing promising strategies to treat CL are discussed. The treatment of leishmaniasis will most likely evolve into an approach that uses multiple therapies simultaneously to reduce the possibility of developing drug resistance. There is a continuous effort to discover new drugs to improve the treatment of leishmaniasis, but this is mainly at the level of individual researchers. Undoubtedly, more funding is needed in this area, as well as greater participation of the pharmaceutical industry to focus efforts on the development of chemotherapeutic agents and vaccines for this and other neglected tropical diseases.

In vitro evaluation and in vivo efficacy of nitroimidazole-sulfanyl ethyl derivatives against Leishmania (V.) braziliensis and Leishmania (L.) mexicana

The aim of this study was to synthesize several small molecules of the type 5-nitroimidazole-sulfanyl and evaluate biological properties against the main Leishmania species that cause cutaneous leishmaniasis in Venezuela. Final compounds 4-7 were generated through simple nucleophilic substitution of 1-(2-chloroethyl)-2-methyl-5-nitroimidazole 3 with 2-mercaptoethanol, 1-methyl-2-mercaptoethanol, and 2-thyolacetic acid derivative. Compound 8 was synthesized via a coupling reaction between 7 and (S)-Methyl 2-amino-4-methylpentanoate hydrochloride. The inhibitory concentrations of (3, 4, 7, 8) against Leishmania (L.) mexicana and (V.) braziliensis in promastigotes and experimentally infected macrophages were determined by in vitro activity assays. Compounds 7 and 8 shown high activity against both species of Leishmania and were selected for the in vivo evaluation. Animals were infected with promastigotes of the two species and divided into four groups of ten (10) animals and a control group. Intralesional injection way was used for the treatment. The parasitological diagnostic after treatment was obtained by PCR using species specific oligonucleotides. The two Leishmania species were susceptible to compounds 7 and 8 in vivo assays. The results indicated that both compounds reduce significantly (96%) the size of the lesion and cure 63% of the mice infected with L (L) mexicana or L (V) braziliensis as was determined by PCR. The results are indicating that both compounds may represent an alternative treatment for these two Leishmania species.

Axenic amastigotes of Leishmania species as a suitable model for in vitro studies

Leishmania spp. are etiological agents of infection diseases, which in some cases can be fatal. The main forms of their biological cycle, promastigotes and amastigotes, can be maintained in vitro. While promastigotes are easier to maintain, amastigotes are more complex and can be obtained through different ways, including infection assays of tissues or in vitro cells, and differentiation from promastigotes to axenic amastigotes. Several protocols have been proposed for in vitro differentiation for at least 12 Leishmania spp. of both subgenera, Leishmania and Viannia. In this review we propose a critical summary of axenic amastigotes induction, as well as the impact of these strategies on metabolic pathways and regulatory networks analyzed by omics approaches. The parameters used by different research groups show considerable variations in temperature, pH and induction stages, as highlighted here for Leishmania (Viannia) braziliensis. Therefore, a consensus on strategies for inducing amastigogenesis is necessary to improve accuracy and even define stage-specific biomarkers. In fact, the axenic amastigote model has contributed to elucidate several aspects of the parasite cycle, however, since it does not reproduce the intracellular environment, its use requires several precautions. In addition, we present a discussion about using axenic amastigotes for drug screening, suggesting the need of a more sensitive methodology to verify cell viability in these tests. Collectively, this review explores the advantages and limitations found in studies with axenic amastigotes, done for more than 30 years, and discuss the gaps that impair their use as a suitable model for in vitro studies.

Optimization of phthalazin-based aryl/heteroarylhydrazones to design new promising antileishmanicidal agents: synthesis and biological evaluation of 3-aryl-6-piperazin-1,2,4-triazolo[3,4-a]phthalazines

1-Monosubstituted and 1,4-substituted phthalazins based on aryl/heteroarylhydrazinyl have demonstrated attractive antileishmanial profiles against amastigote forms of the Leishmania braziliensis parasite.

Dual and selective inhibitors of pteridine reductase 1 (PTR1) and dihydrofolate reductase-thymidylate synthase (DHFR-TS) from Leishmania chagasi

Leishmaniasis is a tropical disease found in more than 90 countries. The drugs available to treat this disease have nonspecific action and high toxicity. In order to develop novel therapeutic alternatives to fight this ailment, pteridine reductase 1 (PTR1) and dihydrofolate reductase-thymidylate synthase (DHF-TS) have been targeted, once Leishmania is auxotrophic for folates. Although PTR1 and DHFR-TS from other protozoan parasites have been studied, their homologs in Leishmania chagasi have been poorly characterized. Hence, this work describes the optimal conditions to express the recombinant LcPTR1 and LcDHFR-TS enzymes, as well as balanced assay conditions for screening. Last but not the least, we show that 2,4 diaminopyrimidine derivatives are low-micromolar competitive inhibitors of both enzymes (LcPTR1 Ki = 1.50-2.30 µM and LcDHFR Ki = 0.28-3.00 µM) with poor selectivity index. On the other hand, compound 5 (2,4-diaminoquinazoline derivative) is a selective LcPTR1 inhibitor (Ki = 0.47 µM, selectivity index = 20).

Identification of dehydroxy isoquine and isotebuquine as promising antileishmanial agents

Traditional antimalarial drugs based on 4-aminoquinolines have exhibited good antiproliferative activities against Leishmania parasites; however, their clinical use is currently limited. To identify new 4-aminoquinolines to combat American cutaneous leishmaniasis, we carried out a full in vitro evaluation of a series of dehydroxy isoquines and isotebuquines against two Leishmania parasites such as Leishmania braziliensis and Leishmania mexicana. First, the antiproliferative activity of the quinolines was studied against the promastigote forms of L. braziliensis and L. mexicana parasites, finding that five of them exhibited good antileishmanial responses with micromolar IC₅₀ values ranging from 3.84 to 10 μM. A structure-activity relationship analysis gave evidence that a piperidine or a morpholine attached as N-alkyamino terminal substituent as well as the inclusion of an extra phenyl ring attached at the aniline ring of the isotebuquine core constitute important pharmacophores to generate the most active derivatives, with antileishmanial responses by far superior to those found for the reference drug, glucantime. All compounds showed a relatively low toxicity on human dermis fibroblasts, with CC₅₀ ranging from 69 to >250 μM. The five most active compounds displayed moderate to good antileishmanial activity against the intracellular amastigote form of L. braziliensis, compared to the reference drug. In particular, compound 2j was identified as the most potent agent against antimony-resistant amastigotes of L. braziliensis with acceptable biological response and selectivity, emerging as a promising candidate for further in vivo antileishmanial evaluation. Diverse mechanism-of-action studies and molecular docking simulations were performed for the most active 4-aminoquinoline.