Synthesis and biological evaluation of new quinoline derivatives as antileishmanial and antitrypanosomal agents

Screening of the antileishmanial and antiplasmodial potential of synthetic 2-arylquinoline analogs

In this study, six analogs of 2-arylquinoline were synthesized and evaluated for their in vitro and in vivo antiplasmodial and leishmanicidal activity. At a later stage, hemolytic activity and druggability were tested in vitro and in silico, respectively, observing as a result: firstly, compounds showed half-maximal effective concentration (EC50) values between 3.6 and 19.3 µM. Likewise, a treatment using the compounds 4a-f caused improvement in most of the treated hamsters and cured some of them. Regarding the antiplasmodial activity, the compounds showed moderate to high activity, although they did not show hemolytic activity. Furthermore, 4e and 4f compounds were not able to control P. berghei infection when administered to animal models. Molecular dynamic simulations, molecular docking and ligand binding affinity indicate good characteristics of the studied compounds, which are expected to be active. And lastly, the compounds are absorbable at the hematoencephalic barrier but not in the gastrointestinal tract. In summary, ADMET properties suggest that these molecules may be used as a safe treatment against Leishmania.

Enzymatic synthesis of amlodipine amides and evaluation of their anti-Trypanosoma cruzi activity

Advancing with our project about the development of new antiparasitic agents, we have enzymatically synthesized a series of amides derived from amlodipine, a calcium channel blocker used as an antihypertensive drug. Through lipase-catalyzed acylation with different carboxylic acids, nineteen amlodipine derivatives were obtained, eighteen of which were new compounds. To optimize the reaction conditions, the influence of several reaction parameters was analyzed, finding different requisites for aliphatic carboxylic acids and phenylacetic acids. All synthesized compounds were evaluated as antiproliferative agents against Trypanosoma cruzi, the etiological agent of American trypanosomiasis (Chagas' disease). Some of them showed significant activity against the amastigote form of T. cruzi, the clinically relevant form of the parasite. Among synthesized compounds, the derivatives of myristic and linolenic acids showed higher efficacy and lower cytotoxicity. These results added to the advantages shown by the enzymatic methodology, such as mild reaction conditions and low environmental impact, making this approach a valuable way to synthesize these amlodipine derivatives with an application as promising antiparasitic agents.

Lipase-Catalyzed Synthesis and Biological Evaluation of N-Picolineamides as Trypanosoma cruzi Antiproliferative Agents

In our search for new safe antiparasitic agents, an enzymatic pathway was applied to synthesize a series of N-pyridinylmethyl amides derived from structurally different carboxylic acids. Thirty derivatives, including 11 new compounds, were prepared through lipase-catalyzed acylation in excellent yields. In order to optimize the synthetic methodology, the impact of different reaction parameters was analyzed. Some compounds were evaluated as antiproliferative agents against Trypanosoma cruzi, the parasite responsible for American trypanosomiasis (Chagas' disease). Some of them showed significant activity as parasite proliferation inhibitors. Amides derived from 2-aminopicoline and stearic and elaidic acids were as potent as nifurtimox against the amastigote form of T. cruzi, the clinically relevant form of the parasite. Even more, a powerful synergism between nifurtimox and N-(pyridin-2-ylmethyl)stereamide was observed, almost completely inhibiting the proliferation of the parasite. Besides, the obtained compounds showed no toxicity in Vero cells, making them excellent potential candidates as lead drugs.

Quinoline-derivatives as privileged scaffolds for medicinal and pharmaceutical chemists: A comprehensive review

The quinoline scaffolds are privileged for their numerous biological activities in the pharmaceutical field. This moiety constitutes a well-known space in several marketed preparations. The quinoline scaffolds gained attention in modern days being an important chemical moiety in the identification, designing, and synthesis of novel potent derivatives. The current review is developed to shine the light on critical and significant insights on the quinoline derivatives possessing diverse biological activities such as analgesic, anti-inflammatory, antialzheimer, anti-convulsant, anti-oxidant, antimicrobial, anti-cancer activities and so on. A detailed summary of quinoline ring from its origin to the recent advancements regarding its synthesis, green chemistry approaches, patented methods, and its marketed drugs is presented in the review. We attempted to review the literature compiling the critical information that has potential to encourage fellow researchers and scientists for the design and development of quinoline scaffold based active molecules that have improved therapeutic performance along with profound pharmacological properties.

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.

Homology Modeling, de Novo Design of Ligands, and Molecular Docking Identify Potential Inhibitors of Leishmania donovani 24-Sterol Methyltransferase

The therapeutic challenges pertaining to leishmaniasis due to reported chemoresistance and toxicity necessitate the need to explore novel pathways to identify plausible inhibitory molecules. Leishmania donovani 24-sterol methyltransferase (LdSMT) is vital for the synthesis of ergosterols, the main constituents of Leishmania cellular membranes. So far, mammals have not been shown to possess SMT or ergosterols, making the pathway a prime candidate for drug discovery. The structural model of LdSMT was elucidated using homology modeling to identify potential novel 24-SMT inhibitors via virtual screening, scaffold hopping, and de-novo fragment-based design. Altogether, six potential novel inhibitors were identified with binding energies ranging from −7.0 to −8.4 kcal/mol with e-LEA3D using 22,26-azasterol and S1–S4 obtained from scaffold hopping via the ChEMBL, DrugBank, PubChem, ChemSpider, and ZINC15 databases. These ligands showed comparable binding energy to 22,26-azasterol (−7.6 kcal/mol), the main inhibitor of LdSMT. Moreover, all the compounds had plausible ligand efficiency-dependent lipophilicity (LELP) scores above 3. The binding mechanism identified Tyr92 to be critical for binding, and this was corroborated via molecular dynamics simulations and molecular mechanics Poisson–Boltzmann surface area (MM-PBSA) calculations. The ligand A1 was predicted to possess antileishmanial properties with a probability of activity (Pa) of 0.362 and a probability of inactivity (Pi) of 0.066, while A5 and A6 possessed dermatological properties with Pa values of 0.205 and 0.249 and Pi values of 0.162 and 0.120, respectively. Structural similarity search via DrugBank identified vabicaserin, daledalin, zanapezil, imipramine, and cefradine with antileishmanial properties suggesting that the de-novo compounds could be explored as potential antileishmanial agents.

The Potential of 2-Substituted Quinolines as Antileishmanial Drug Candidates

There is a need for new, cost-effective drugs to treat leishmaniasis. A strategy based on traditional medicine practiced in Bolivia led to the discovery of the 2-substituted quinoline series as a source of molecules with antileishmanial activity and low toxicity. This review documents the development of the series from the first isolated natural compounds through several hundred synthetized molecules to an optimized compound exhibiting an in vitro IC₅₀ value of 0.2 µM against Leishmania donovani, and a selectivity index value of 187, together with in vivo activity on the L. donovani/hamster model. Attempts to establish structure–activity relationships are described, as well as studies that have attempted to determine the mechanism of action. For the latter, it appears that molecules of this series act on multiple targets, possibly including the immune system, which could explain the observed lack of drug resistance after in vitro drug pressure. We also show how nanotechnology strategies could valorize these drugs through adapted formulations and how a mechanistic targeting approach could generate new compounds with increased activity.

A study of structure-activity relationship and anion-controlled quinolinyl Ag(I) complexes as antimicrobial and antioxidant agents as well as their interaction with macromolecules

In this communication, we feature the synthesis and in-depth characterization of a series of silver(I) complexes obtained from the complexation of quinolin-4-yl Schiff base ligands ((E)-2-((quinolin-4-ylmethylene)amino)phenol L_a, 2-(quinolin-4-yl)benzo[d]thiazole L_b, (E)-N-(2-fluorophenyl)-1-(quinolin-4-yl)methanimine L_c, (E)-N-(4-chlorophenyl)-1-(quinolin-4-yl)methanimine L_d, (E)-1-(quinolin-4-yl)-N-(p-tolyl)methanimine L_e, (E)-1-(quinolin-4-yl)-N-(thiophen-2-ylmethyl)methanimine L_f) and three different silver(I) anions (nitrate, perchlorate and triflate). Structurally, the complexes adopted different coordination geometries, which included distorted linear or distorted tetrahedral geometry. The complexes were evaluated in vitro for their potential antibacterial and antioxidant activities. In addition, their interactions with calf thymus-DNA (CT-DNA) and bovine serum albumin (BSA) were evaluated. All the complexes had a wide spectrum of effective antibacterial activity against gram-positive and gram-negative bacterial and good antioxidant properties. The interactions of the complexes with CT-DNA and BSA were observed to occur either through intercalation or through a minor groove binder, while the interaction of the complexes with BSA reveals that some of the complexes can strongly quench the fluorescence of BSA through the static mechanism. The molecular docking studies of the complexes were also done to further elucidate the modes of interaction with CT-DNA and BSA.

New antiparasitic derivatives of the furoquinoline alkaloids kokusaginine and flindersiamine

In this work is reported the synthesis of 16 new compounds obtained from kokusaginine and flindersiamine, the main alkaloids isolated from the bark of Balfourodendron riedelianum . The activity of the compounds against axenic cultures of Trypanosoma cruzi epimastigtotes and trypomastigotes, as well as intracellular amastigotes, is described, together with their cytotoxic activity against three different human cell lines. The synthetic strategy for the preparation of the new compounds was based on the reactivity at the position C-4 of the furoquinoline core towards nucleophiles. The new derivatives were synthesized by a Buchwald-Hartwig reaction, in most cases under green, solvent free conditions. Compounds 1c and 1e displayed better in-vitro activity against trypomastigotes than benznidazole and nifurtimox (positive controls) with IC 50 < 4 µM. In addition, both compounds were not cytotoxic activity against the three human cell lines K562 (erytroleukimia), LM2 (breast cancer) and HaCat (keratinocyte). Interestingly, when evaluated against intracellular amastigotes, compound 1c was able to significantly reduce the number of this parasite form, compared to the negative control.

Novel phenanthridine amide analogs as potential anti-leishmanial agents: In vitro and in silico insights

In the current work, sixteen novel amide derivatives of phenanthridine were designed and synthesized using 9-fluorenone, 4-Methoxy benzyl amine, and alkyl/aryl acids. The characterization of the title compounds was performed using LCMS, elemental analysis, ¹HNMR, ¹³CNMR and single crystal XRD pattern was also developed for compounds A8. All the final analogs were screened in vitro for anti-leishmanial activity against promastigote form of L. infantum strain. Among the tested analogs, four compounds (A-06, A-11, A-12, and A-15) exhibited significant anti-leishmanial activity with EC₅₀ value ranges from 8.9 to 21.96 μM against amastigote forms of tested L. infantum strain with SI ranges of 1.0 to 4.3. From the activity results it was found that A-11 was the most active compound in both promastigote and amastigotes forms with EC₅₀ values 8.53 and 8.90 µM respectively. In-silico ADME prediction studies depicted that the titled compounds obeyed Lipinski's rule of five as that of the approved marketed drugs. The predicted in-silico toxicity profile also confirmed that the tested compounds were non-toxic. Finally, molecular docking and molecular dynamics study was also performed for significantly active compound (A-11) in order to study it's putative binding pattern at the active site of the selected leishmanial trypanothione reductase target as well as to understand the stability pattern of target-ligand complex for 100 ns. Single crystal XRD of compound A-08 revealed that the compound crystallizes in monoclinic C2/c space group and showed interesting packing arrangements.

Quinoline-based Compounds as Key Candidates to Tackle Drug Discovery Programs of Microbicidal Agents

Quinolines are heterocyclic nitrogen compounds, ubiquitous in nature and largely used as a structural component of dyes, solvent for resins, terpenes as well as during the production of several other chemical stuffs, including pesticides. Quinolines, such as quinine and chloroquine, exhibit various pharmacological properties, acting as antimalarial drugs, antiparasitic, antibacterial, antiviral, antifungal, and anticancer agents, besides being in clinical use for autoimmune diseases. A brief review has been presented regarding the biological effect and clinical use of quinolines and derivatives upon three trypanosomatids agents of important neglected tropical diseases; Trypanosoma cruzi, Trypanosoma brucei spp and Leishmania spp, which trigger Chagas disease, sleeping sickness and leishmaniasis, respectively, also extending to a glance update of their potential application towards other microbes relevant for emerging illness caused by fungi, bacteria and virus, including the pandemic Covid-19.

Recent advancements in anti-leishmanial research: Synthetic strategies and structural activity relationships

Leishmaniasis is a parasitic neglected tropical disease caused by various species of Leishmania parasite. Despite tremendous advancements in the therapeutic sector and drug development strategies, still the existing anti-leishmanial agents are associated with some clinical issues like drug resistance, toxicity and selectivity. Therefore, several research groups are continuously working towards the development of new therapeutic candidates to overcome these issues. Many potential heterocyclic moieties have been explored for this purpose including triazoles, chalcones, chromone, thiazoles, thiosemicarbazones, indole, quinolines, etc. It is evident from the literature that the majority of anti-leishmanial agents act by interacting with key regulators including PTR-I, DHFR, LdMetAP1, MAPK, 14 α-demethylase and pteridine reductase-I, etc. Also, these tend to induce the production of ROS which causes damage to parasites. In the present compilation, authors have summarized various significant synthetic procedures for anti-leishmanial agents reported in recent years. A brief description of the pharmacological potentials of synthesized compounds along with important aspects related to structural activity relationship has been provided. Important docking outcomes highlighting the possible mode of interaction for the reported compounds have also been included. This review would be helpful to the scientific community to design newer strategies and also to develop novel therapeutic candidates against leishmaniasis.

Design, synthesis and biological evaluation of mono- and bisquinoline methanamine derivatives as potential antiplasmodial agents

Several classes of antimalarial drugs are currently available, although issues of toxicity and the emergence of drug resistant malaria parasites have reduced their overall therapeutic efficiency. Quinoline based antiplasmodial drugs have unequivocally been long-established and continue to inspire the design of new antimalarial agents. Herein, a series of mono- and bisquinoline methanamine derivatives were synthesised through sequential steps; Vilsmeier-Haack, reductive amination, and nucleophilic substitution, and obtained in low to excellent yields. The resulting compounds were investigated for in vitro antiplasmodial activity against the 3D7 chloroquine-sensitive strain of Plasmodium falciparum, and compounds 40 and 59 emerged as the most promising with IC₅₀ values of 0.23 and 0.93 µM, respectively. The most promising compounds were also evaluated in silico by molecular docking protocols for binding affinity to the {001} fast-growing face of a hemozoin crystal model.

Microwave-Assisted Synthesis of (Piperidin-1-yl)quinolin-3-yl)methylene)hydrazinecarbothioamides as Potent Inhibitors of Cholinesterases: A Biochemical and In Silico Approach

Alzheimer’s disease (AD), a progressive neurodegenerative disorder, characterized by central cognitive dysfunction, memory loss, and intellectual decline poses a major public health problem affecting millions of people around the globe. Despite several clinically approved drugs and development of anti-Alzheimer’s heterocyclic structural leads, the treatment of AD requires safer hybrid therapeutics with characteristic structural and biochemical properties. In this endeavor, we herein report a microwave-assisted synthesis of a library of quinoline thiosemicarbazones endowed with a piperidine moiety, achieved via the condensation of 6/8-methyl-2-(piperidin-1-yl)quinoline-3-carbaldehydes and (un)substituted thiosemicarbazides. The target N-heterocyclic products were isolated in excellent yields. The structures of all the synthesized compounds were fully established using readily available spectroscopic techniques (FTIR, ¹H- and ¹³C-NMR). Anti-Alzheimer potential of the synthesized heterocyclic compounds was evaluated using acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. The in vitro biochemical assay results revealed several compounds as potent inhibitors of both enzymes. Among them, five compounds exhibited IC₅₀ values less than 20 μM. N-(3-chlorophenyl)-2-((8-methyl-2-(piperidin-1-yl)quinolin-3-yl)methylene)hydrazine carbothioamide emerged as the most potent dual inhibitor of AChE and BChE with IC₅₀ values of 9.68 and 11.59 μM, respectively. Various informative structure–activity relationship (SAR) analyses were also concluded indicating the critical role of substitution pattern on the inhibitory efficacy of the tested derivatives. In vitro results were further validated through molecular docking analysis where interactive behavior of the potent inhibitors within the active pocket of enzymes was established. Quinoline thiosemicarbazones were also tested for their cytotoxicity using MTT assay against HepG2 cells. Among the 26 novel compounds, there were five cytotoxical and 18 showed proliferative properties.

Neto JDB, de Abreu FC, Figueiredo IM, Carinhanha C. Santos J, Pessoa CDÓ, da Silva-Júnior EF, de Araújo-Júnior JX, M. de Aquino T. Synthesis of hybrids thiazole–quinoline, thiazole–indole and their analogs: in vitro anti-proliferative effects on cancer cell lines, DNA binding properties and molecular modeling

A quinoline–thiazole hybrid was synthesized, which showed cytotoxicity against the HL-60 cell line. Electrochemical and spectroscopic experiments suggested DNA as the biological target.

Bioprospecting of Nitrogenous Heterocyclic Scaffolds with Potential Action for Neglected Parasitosis: A Review

Neglected parasitic diseases are a group of infections currently considered as a worldwide concern. This fact can be attributed to the migration of these diseases to developed and developing countries, associated with therapeutic insufficiency resulted from the low investment in the research and development of new drugs. In order to overcome this situation, bioprospecting supports medicinal chemistry in the identification of new scaffolds with therapeutically appropriate physicochemical and pharmacokinetic properties. Among them, we highlight the nitrogenous heterocyclic compounds, as they are secondary metabolites of many natural products with potential biological activity. The objective of this work was to review studies within a 10-year timeframe (2009- 2019), focusing on the pharmacological application of nitrogen bioprospectives (pyrrole, pyridine, indole, quinoline, acridine, and their respective derivatives) against neglected parasitic infections (malaria, leishmania, trypanosomiases, and schistosomiasis), and their application as a template for semi-synthesis or total synthesis of potential antiparasitic agents. In our studies, it was observed that among the selected articles, there was a higher focus on the attempt to identify and obtain novel antimalarial compounds, in a way that an extensive amount of studies involving all heterocyclic nitrogen nuclei were found. On the other hand, the parasites with the lowest number of publications up until the present date have been trypanosomiasis, especially those caused by Trypanosoma cruzi, and schistosomiasis, where some heterocyclics have not even been cited in recent years. Thus, we conclude that despite the great biodiversity on the planet, little attention has been given to certain neglected tropical diseases, especially those that reach countries with a high poverty rate.

An Overview of Recent Advances in Biological and Pharmaceutical Developments of Fluoro-containing Drugs

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This review article provides a brief assessment of the biological and pharmaceutical developments of fluorinated drugs. It also discusses possible impacts on the further development of new fluoro-containing pharmaceuticals. Structural aspects of new drug-candidates currently under development and their biological properties, therapeutic potential and syntheses are critically evaluated

N-substituted noscapine derivatives as new antiprotozoal agents: Synthesis, antiparasitic activity and molecular docking study

Novel N-substituted noscapine derivatives were synthesized by a three-component Strecker reaction of cyclic ether of N-nornoscapine with varied aldehydes, in the presence of cyanide ion. Moreover, the corresponding amides were synthesized by the oxidation of cyanide moieties in good yields. The in vitro antiprotozoal activity of the products was also investigated. Interestingly, some analogues did put on display promising antiparasitic activity against Trypanosoma brucei rhodesiense with IC₅₀ values between 2.5 and 10.0 µM and selectivity index (SI) ranged from 0.8 to 13.2. Eight compounds exhibited activity against Plasmodium falciparum K1 strain with IC₅₀ ranging 1.7-6.4 µM, and SI values between 2.8 and 10.5 against L6 rat myoblast cell lines. Molecular docking was carried out on trypanothione reductase (TbTR, PDB ID: 2WOW) and UDP-galactose 4' epimerase (TbUDPGE PDB: 1GY8) as targets for studying the envisaged mechanism of action. Compounds 6j₂ and 6b₂ displayed excellent docking scores with -8.59 and -8.86 kcal/mol for TbTR and TbUDPGE, respectively.

A simple and convenient synthesis of 3-salicyloylquinoline-4-carboxylic esters from chromone and isatin

A simple and convenient synthesis of 3-salicyloylquinoline-4-carboxylic esters has been developed through AlCl₃-catalyzed reaction of Baylis–Hillman adducts from chromones and isatin-derivatives.

Quinolines and Quinolones as Antibacterial, Antifungal, Anti-virulence, Antiviral and Anti-parasitic Agents

Infective diseases have become health threat of a global proportion due to appearance and spread of microorganisms resistant to majority of therapeutics currently used for their treatment. Therefore, there is a constant need for development of new antimicrobial agents, as well as novel therapeutic strategies. Quinolines and quinolones, isolated from plants, animals, and microorganisms, have demonstrated numerous biological activities such as antimicrobial, insecticidal, anti-inflammatory, antiplatelet, and antitumor. For more than two centuries quinoline/quinolone moiety has been used as a scaffold for drug development and even today it represents an inexhaustible inspiration for design and development of novel semi-synthetic or synthetic agents exhibiting broad spectrum of bioactivities. The structural diversity of synthetized compounds provides high and selective activity attained through different mechanisms of action, as well as low toxicity on human cells. This review describes quinoline and quinolone derivatives with antibacterial, antifungal, anti-virulent, antiviral, and anti-parasitic activities with the focus on the last 10 years literature.