Design, synthesis and biological evaluation of 3-[4-(7-chloro-quinolin-4-yl)-piperazin-1-yl]-propionic acid hydrazones as antiprotozoal agents

New supramolecules of bis(acylhydrazones)-linked bisphenol sulfide for Alzheimer's: targeting cholinesterases by in vitro and in silico approaches

In current research, two functional components, i.e., hydrazone and bisphenol sulfide were combined to get useful supramolecules in medicinal chemistry. Herein 25 new 4,4'-thiodiphenol bis-acylhydrazones were synthesized in good to excellent yields. Initially ethyl-2-chloroacetate was reacted with 4,4'-thiodiphenol, which was further reacted with excess hydrazine hydrate to produce 2,2'-((thiobis(4,1-phenylene))bis(oxy))di(acetohydrazide), which was then combined with various aromatic and aliphatic aldehydes to get the desired products (hydrazones, 4a-4y). The synthesized supramolecules were characterized by contemporary spectroscopic techniques such as 1H NMR, 13C NMR, and mass spectroscopy. The synthetic compound's cholinesterase blocking activity was tested against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes where compounds 4n, and 4h showed excellent inhibitory potential for AChE, while 4b, and 4h, demonstrated most potent inhibition of BChE. The starting compound (SM3) and compounds 4h and SM3 depicted excellent dual inhibitory capabilities for both enzymes. The chemical basis of anticholinesterase activity was investigated using a structure-based molecular docking approach. The biological significance and the ease of synthesis of this class of compounds should be considered in therapeutic development for Alzheimer's disease treatments.

Novel N-Acyl Hydrazone Compounds as Promising Anticancer Agents: Synthesis and Molecular Docking Studies

In this study, a new series of N-acyl hydrazones 7a-e, 8a-e, and 9a-e, starting from methyl δ-oxo pentanoate with different substituted groups 1a-e, were synthesized as anticancer agents. The structures of obtained target molecules were identified by spectrometric analysis methods (FT-IR, ¹¹H NMR, ¹³C NMR, and LC-MS). The antiproliferative activity of the novel N-acyl hydrazones was evaluated on the breast (MCF-7) and prostate (PC-3) cancer cell lines by an MTT assay. Additionally, breast epithelial cells (ME-16C) were used as reference normal cells. All newly synthesized compounds 7a-e, 8a-e, and 9a-e exhibited selective antiproliferative activity with high toxicity to both cancer cells simultaneously without any toxicity to normal cells. Among these novel N-acyl hydrazones, 7a-e showed the most potent anticancer activities with IC₅₀ values at 7.52 ± 0.32-25.41 ± 0.82 and 10.19 ± 0.52-57.33 ± 0.92 μM against MCF-7 and PC-3 cells, respectively. Also, molecular docking studies were applied to comprehend potential molecular interactions between compounds and target proteins. It was seen that the docking calculations and the experimental data are in good agreement.

Investigation on Hydrazonobenzenesulfonamides as Human Carbonic Anhydrase I, II, IX and XII Inhibitors

A small series of hydrazonobenzenesulfonamides was designed, synthesized and studied for their human carbonic anhydrase (hCA) inhibitory activity. The synthesized compounds were evaluated against hCA I, II, IX and XII isoforms using acetazolamide (AAZ) as the standard inhibitor. Various hydrazonosulfonamide derivatives showed inhibitory activity at low nanomolar levels with selectivity against the cytosolic hCA II isoform, as well as the transmembrane, tumor-associated enzymes hCA IX and XII. The most potent and selective hydrazones 8, 9, 10, 11, 19 and 24 were docked into isoforms I, II, IX and XII to better understand their activity and selectivity for the different CA isoforms.

Acylhydrazones and Their Biological Activity: A Review

Due to the structure of acylhydrazones both by the pharmacophore -CO-NH-N= group and by the different substituents present in the molecules of compounds of this class, various pharmacological activities were reported, including antitumor, antimicrobial, antiviral, antiparasitic, anti-inflammatory, immunomodulatory, antiedematous, antiglaucomatous, antidiabetic, antioxidant, and actions on the central nervous system and on the cardiovascular system. This fragment is found in the structure of several drugs used in the therapy of some diseases that are at the top of public health problems, like microbial infections and cardiovascular diseases. Moreover, the acylhydrazone moiety is present in the structure of some compounds with possible applications in the treatment of other different pathologies, such as schizophrenia, Parkinson's disease, Alzheimer's disease, and Huntington's disease. Considering these aspects, we consider that a study of the literature data regarding the structural and biological properties of these compounds is useful.

In Vitro Anticancer Screening, Molecular Docking and Antimicrobial Studies of Triazole-Based Nickel(II) Metal Complexes

Herein we describe the synthesis of a series of nickel(II) complexes (C1–C3) with Schiff bases (HL1–HL3) derived from 4-amino-5-mercapto-3-methyl-1,2,4-triazole and ortho/meta/para-nitrobenzaldehyde having composition [Ni(L)₂(H₂O)₂]. The obtained ligands and their complexes were characterized using physico-chemical techniques viz., elemental analysis, magnetic moment study, spectral (electronic, FT-IR, 1H-NMR) and thermal analysis. The elemental analysis and spectral analysis revealed that Schiff bases behave as monoanionic bidentate ligands towards the Ni(II) ion. Whereas, the magnetic moment study suggested the octahedral geometry of all the Ni(II) complexes. The thermal behavior of the complexes has been studied by thermogravimetric analysis and agrees well with the composition of complexes. Further, the biological activities such as antimicrobial and antifungal studies of the Schiff bases and Ni(II) complexes have been screened against bacterial species (Staphylococcus aureus and Pseudomonas aeruginosa) and fungal species (Aspergillus niger and Candida albicans) activity by MIC method, the results of which revealed that metal complexes exhibited significant antimicrobial activities than their respective ligands against the tested microbial species. Furthermore, the molecular docking technique was employed to investigate the active sites of the selected protein, which indeed helped us to screen the potential anticancer agents among the synthesized ligand and complexes. Further, these compounds have been screened for their in vitro anticancer activity using OVCAR-3 cell line. The results revealed that the complexes are more active than the ligands.

Evaluation of antiplasmodial activity in silico and in vitro of N-acylhydrazone derivatives

N-acylhydrazones are considered privileged structures in medicinal chemistry, being part of antimicrobial compounds (for example). In this study we show the activity of N-acylhydrazone compounds, namely AH1, AH2, AH4, AH5 in in vitro tests against the chloroquine-resistant strain of Plasmodium falciparum (W2) and against WI26 VA-4 human cell lines. All compounds showed low cytotoxicity (LC₅₀ > 100 µM). The AH5 compound was the most active against Plasmodium falciparum, with an IC₅₀ value of 0.07 μM. AH4 and AH5 were selected among the tested compounds for molecular docking calculations to elucidate possible targets involved in their mechanism of action and the SwissADME analysis to predict their pharmacokinetic profile. The AH5 compound showed affinity for 12 targets with low selectivity, while the AH4 compound had greater affinity for only one target (3PHC). These compounds met Lipinski's standards in the ADME in silico tests, indicating good bioavailability results. These results demonstrate that these N-acylhydrazone compounds are good candidates for future preclinical studies against malaria.

Antiplasmodial activity of sulfonylhydrazones: in vitro and in silico approaches

Malaria is still a life-threatening public health issue, and the upsurge of resistant strains requires continuous generation of active molecules. In this work, 35 sulfonylhydrazone derivatives were synthesized and evaluated against Plasmodium falciparum chloroquine-sensitive (3D7) and resistant (W2) strains. The most promising compound, 5b, had an IC₅₀ of 0.22 μM against W2 and was less cytotoxic and 26-fold more selective than chloroquine. The structure-activity relationship model, statistical analysis and molecular modeling studies suggested that antiplasmodial activity was related to hydrogen bond acceptor count, molecular weight and partition coefficient of octanol/water and displacement of frontier orbitals to the heteroaromatic ring beside the imine bond. This study demonstrates that the synthesized molecules with a simple scaffold allow the hit-to-lead process for new antimalarials to commence.

Effective methods for the synthesis of hydrazones, quinazolines, and Schiff bases: reaction monitoring using a chemometric approach

Synthesis of hydrazones (1a-4a and 1b-4b), quinazolines (3c·MeOH and 3d·MeOH), and hydrazone-Schiff bases (4c and 4d) is achieved by combining suitable aldehydes (2,3- or 2,4-dihydroxybenzaldehyde) with four hydrazides (isonicotinic, nicotinic, and 2- or 4-aminobenzoic acid hydrazide). A suite of approaches for their preparation is described: solution-based synthesis, mechanosynthesis, and solid-state melt reactions. The mechanochemical approach is generally a better choice for the quinazolines, while the solid-state melt reaction is more efficient for derivatives of (iso)nicotinic based hydrazones. Crystalline amine-functionalised hydrazones 4a and 4b undergo post-synthetic modifications in reactions with 3- or 4-pyridinecarbaldehyde vapours to form hydrazone-Schiff bases 4a-3py, 4b-3py, 4a-4py, and 4b-4py. Mechanochemical and vapour-mediated reactions are followed by ex situ powder X-ray diffraction and IR-ATR methods, respectively. The chemometric analysis of these data using principal component analysis provided an insight into the reaction profiles and reaction times. Azines (5a and 5b), achieved from aldehydes and hydrazine, reversibly change colour in response to temperature changes. The structures of all products are ascertained by a combined use of spectroscopic and X-ray diffraction methods. The cytotoxic and antimicrobial activities of all compounds against selected human cancer cell lines and bacterial strains are evaluated.

Design, Synthesis and Study of Antibacterial and Antitubercular Activity of Quinoline Hydrazone Hybrids

Emerging bacterial resistance is causing widespread problems for the treatment of various infections. Therefore, the search for antimicrobials is a never-ending task. Hydrazones and quinolines possess a wide variety of biological activities. Herewith, eleven quinoline hydrazone derivatives have been designed, synthesized, characterized and evaluated for their antibacterial activity and antitubercular potential against Mtb WT H37Rv. Compounds QH-02, QH-04 and QH-05 were found to be promising compounds with an MIC value of 4 μg/mL against Mtb WT H37Rv. Compounds QH-02, QH-04, QH-05, and QH-11 were also found to be active against bacterial strains including Acinetobacter baumanii, Escherichia coli and Staphylococcus aureus. Further, we have carried out experiments to confirm the cytotoxicity of the active compounds and found them to be non-toxic.

Structural and biological survey of 7-chloro-4-(piperazin-1-yl)quinoline and its derivatives

The 7-chloro-4-(piperazin-1-yl)quinoline structure is an important scaffold in medicinal chemistry. It exhibited either alone or as hybrid with other active pharmacophores diverse pharmacological profiles such as: antimalarial, antiparasitic, anti-HIV, antidiabetic, anticancer, sirtuin Inhibitors, dopamine-3 ligands, acetylcholinesterase inhibitors, and serotonin antagonists. In the presented review, a comprehensive discussion of compounds having this structural core is surveyed and illustrated.

Hybrid molecules with potential in vitro antiplasmodial and in vivo antimalarial activity against drug-resistant Plasmodium falciparum

Malaria is a tropical disease, leading to around half a million deaths annually. Antimalarials such as quinolines are crucial to fight against malaria, but malaria control is extremely challenged by the limited pipeline of effective pharmaceuticals against drug-resistant strains of Plasmodium falciparum which are resistant toward almost all currently accessible antimalarials. To tackle the growing resistance, new antimalarial drugs are needed urgently. Hybrid molecules which contain two or more pharmacophores have the potential to overcome the drug resistance, and hybridization of quinoline privileged antimalarial building block with other antimalarial pharmacophores may provide novel molecules with enhanced in vitro and in vivo activity against drug-resistant (including multidrug-resistant) P falciparum. In recent years, numerous of quinoline hybrids were developed, and their activities against a panel of drug-resistant P falciparum strains were screened. Some of quinoline hybrids were found to possess promising in vitro and in vivo potency. This review emphasized quinoline hybrid molecules with potential in vitro antiplasmodial and in vivo antimalarial activity against drug-resistant P falciparum, covering articles published between 2010 and 2019.

Recent Advances in the Discovery of Novel Antiprotozoal Agents

Parasitic diseases have serious health, social, and economic impacts, especially in the tropical regions of the world. Diseases caused by protozoan parasites are responsible for considerable mortality and morbidity, affecting more than 500 million people worldwide. Globally, the burden of protozoan diseases is increasing and is been exacerbated because of a lack of effective medication due to the drug resistance and toxicity of current antiprotozoal agents. These limitations have prompted many researchers to search for new drugs against protozoan parasites. In this review, we have compiled the latest information (2012-2017) on the structures and pharmacological activities of newly developed organic compounds against five major protozoan diseases, giardiasis, leishmaniasis, malaria, trichomoniasis, and trypanosomiasis, with the aim of showing recent advances in the discovery of new antiprotozoal drugs.

Current scenario of ferrocene-containing hybrids for antimalarial activity

Hybrid molecules have the potential to enhance the efficacy against both drug-sensitive and drug-resistant organisms, and Ferroquine, a ferrocene hybrid, has demonstrated great potency in clinical trials against both drug-sensitive and drug-resistant malaria. Accordingly, hybridization of ferrocene with other antimalarial pharmacophores represents a promising strategy to develop novel antimalarial candidates. This work attempts to systematically review the recent study of ferrocene hybrids in the design and development of antimalarial agents, and the structure-activity relationship (SAR) is also discussed to provide an insight for rational design of more effective antibacterial candidates.

Synthesis and Biological Evaluation of (E)-N’-Benzylidene-7-methyl-2-propyl-1H-benzo[d] imidazole-5-carbohydrazides as Antioxidant, Anti-inflammatory and Analgesic agents

(E)-N’-Benzylidene-7-methyl-2-propyl-1H-benzo [d]imidazole-5-carbohydrazides (5a-r) have been synthesized from 7-methyl-2-propyl-1H-benzo[d]imidazole-5-carbohydrazide (3) by condensing with different aromatic aldehydes (4a-r). Title compounds (5a-r) were evaluated for in vitro antioxidant activity and based on their potential for antioxidant property, selected compounds 5d and 5m-p were screened for in vivo anti-inflammatory and analgesic activity. The results indicate that the compound 5o and 5p are effective against anti-inflammatory and analgesic activity. The biological data was further supported by molecular docking studies, which revealed the binding pattern and the affinity of the molecules in the active site of COX-2.

Ni(II) Complexes with Schiff Base Ligands: Preparation, Characterization, DNA/Protein Interaction and Cytotoxicity Studies

In this study, two Ni(II) complexes, namely [Ni(HL1)₂(OAc)₂] (1) and [Ni(L2)₂] (2) (where HL1 and HL2 are (E)-1-((1-(2-hydroxyethyl)-1H-pyrazol-5-ylimino)methyl)-naphthalen-2-ol) and (E)-ethyl-5-((2-hydroxynaphthalen-1-yl)methyleneamino)-1-methyl-1H-pyrazole-4-carboxylate, respectively), were synthesized and characterized by X-ray crystallography, Electrospray Ionization Mass Spectrometry (ESI-MS), elemental analysis, and IR. Their uptake in biological macromolecules and cancer cells were preliminarily investigated through electronic absorption (UV-Vis), circular dichroism (CD) and fluorescence quenching measurements. Bovine serum albumin (BSA) interaction experiments were investigated by spectroscopy which showed that the complexes and ligands could quench the intrinsic fluorescence of BSA through an obvious static quenching process. The spectroscopic studies indicated that these complexes could bind to DNA via groove, non-covalent, and electrostatic interactions. Furthermore, in vitro methyl thiazolyl tetrazolium (MTT) assays and Annexin V/PI flow cytometry experiments were performed to assess the antitumor capacity of the complexes against eight cell lines. The results show that both of the complexes possess reasonable cytotoxicities.

Synthesis, characterization of 1,2,4-triazole Schiff base derived 3d-metal complexes: Induces cytotoxicity in HepG2, MCF-7 cell line, BSA binding fluorescence and DFT study

Two novel Schiff base ligands H₂L¹ and H₂L² have been synthesized by condensation reaction of amine derivative of 1,2,4-triazole moiety with 2-hydroxy-4-methoxybenzaldehyde. Co(II), Ni(II), Cu(II) and Zn(II) of the synthesized Schiff bases were prepared by using a molar ratio of ligand:metal as 1:1. The structure of the Schiff bases and synthesized metal complexes were established by ¹H NMR, UV-Vis, IR, Mass spectrometry and molar conductivity. The thermal stability of the complexes was study by TGA. Fluorescence quenching mechanism of metal complexes 1-4 show that Zn(II) and Cu(II) complex binds more strongly to BSA. In DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6-31+g(d,p) basis set. The spectral data shows that the ligands behaves as binegative tridentate. On the basis of the spectral studies, TGA and DFT data an octahedral geometry has been assigned for Co(II), Ni(II), square planar for Cu(II) and tetrahedral for Zn(II) complexes. The anticancer activity were screened against human breast cancer cell line (MCF-7) and human hepatocellular liver carcinoma cell line (Hep-G2). Result indicates that metal complexes shows increase cytotoxicity in proliferation to cell lines as compared to free ligand.

New antiprotozoal agents: Synthesis and biological evaluation of different 4-(7-chloroquinolin-4-yl) piperazin-1-yl)pyrrolidin-2-yl)methanone derivatives

In an endeavor to develop efficacious antiprotozoal agents 4-(7-chloroquinolin-4-yl) piperazin-1-yl)pyrrolidin-2-yl)methanone derivatives (5-14) were synthesized, characterized and biologically evaluated for antiprotozoal activity. The compounds were screened in vitro against the HM1: IMSS strain of Entamoeba histolytica and NF54 chloroquine-sensitive strain of Plasmodium falciparum. Among the synthesized compounds six exhibited promising antiamoebic activity with IC₅₀ values (0.14-1.26μM) lower than the standard drug metronidazole (IC₅₀ 1.80μM). All nine compounds exhibited antimalarial activity (IC₅₀ range: 1.42-19.62μM), while maintaining a favorable safety profile to host red blood cells. All the compounds were less effective as an antimalarial and more toxic (IC₅₀ range: 14.67-81.24μM) than quinine (IC₅₀: 275.6±16.46μM) against the human kidney epithelial cells. None of the compounds exhibited any inhibitory effect on the viability of Anopheles arabiensis mosquito larvae.

Hydrazide-hydrazones as potential antimicrobial agents: overview of the literature since 2010

Hydrazide-hydrazone derivatives are present in many bioactive molecules and display a wide variety of biological activities, such as antibacterial, antitubercular, antifungal, anticancer, anti-inflammatory, anticonvulsant, antiviral, and antiprotozoal action. Therefore, many medicinal chemists synthesize various hydrazide-hydrazones and evaluate them for biological activities. Among biological properties of this class of compounds, antimicrobial activity is the most frequently encountered in scientific literature. This paper is focused on the overview of the literature findings of the last six years (2010-2016) covering the research on antimicrobial activity of hydrazide-hydrazone derivatives. This review may also serve as a useful guide for the development of new hydrazide-hydrazones as potential antimicrobial agents.

Recent progress on the discovery of antiamoebic agents

A large number of protozoans infect humans but Entamoeba histolytica is the only organism responsible for causing amoebiasis, a deadly disease after malaria. Numerous heterocycle-based antiamoebic agents have been previously synthesized as E. histolytica inhibitors and while some of these agents have shown moderate activity, the search for a novel and ideal antiamoebic compound is still ongoing. In this digest Letter, we present the latest data on antiamoebic agents from 2011 to 2016 based on the different classes of heterocyclic agents.

Conjugation of N-acylhydrazone and 1,2,4-oxadiazole leads to the identification of active antimalarial agents

Malaria, caused by several Plasmodium species, is the major life-threatening parasitic infection worldwide. Due to the parasite resistance to quinoline based drugs, the search for antimalarial agents is necessary. Here, we report the structural design, synthesis and antiparasitic evaluation of two novel series of 1,2,4-oxadiazoles in conjugation to N-acylhydrazones, both groups recognized as privileged structures, as well as the studies on the antimalarial activity of 16 previous described analogues. By varying substituents attached to the phenyl ring, it was possible to retain, enhance or increase the antiparasitic activity in comparison to the nonsubstituted derivatives. Replacement of substituted aryl rings by ferrocenyl and cinnamyl moieties attached in the N-acylhydrazone ablated the antiparasitic response, evidencing the structural features associated with the activity. Active compounds exhibited in vitro potency similar to mefloquine, but not all inhibited β-hematin formation. Additionally, the active compounds displayed low cytotoxicity in HepG2 cells and did not cause hemolysis in uninfected erythrocytes. In Plasmodium berghei-infected mice, the compounds reduced parasitemia but exhibited limited efficacy in increasing mice survival when compared to chloroquine, suggesting that pharmacological improvement is still necessary.

Design, synthesis, and in vitro antimicrobial activity of hydrazide-hydrazones of 2-substituted acetic acid

In this study, 30 hydrazide-hydrazones of phenylacetic (3-10) and hydroxyacetic acid (11-32) were synthesized by the condensation reaction of appropriate 2-substituted acetic acid hydrazide with different aromatic aldehydes. The obtained compounds were characterized by spectral data and evaluated in vitro for their potential antimicrobial activities against a panel of reference strains of micro-organisms, including Gram-positive bacteria, Gram-negative bacteria, and fungi belonging to the Candida spp. The results from our antimicrobial assays indicated that among synthesized compounds 3-32, especially compounds 6, 14, and 26 showed high bactericidal activity (MIC = 0.488-7.81 μg/ml) against reference Gram-positive bacteria, and in some cases, their activity was even better than that of commonly used antibiotics, such as cefuroxime or ampicillin.

Parasitic diarrheal disease: drug development and targets

Diarrhea is the manifestation of gastrointestinal infection and is one of the major causes of mortality and morbidity specifically among the children of less than 5 years age worldwide. Moreover, in recent years there has been a rise in the number of reports of intestinal infections continuously in the industrialized world. These are largely related to waterborne and food borne outbreaks. These occur by the pathogenesis of both prokaryotic and eukaryotic organisms like bacteria and parasites. The parasitic intestinal infection has remained mostly unexplored and under assessed in terms of therapeutic development. The lack of new drugs and the risk of resistance have led us to carry out this review on drug development for parasitic diarrheal diseases. The major focus has been depicted on commercially available drugs, currently synthesized active heterocyclic compounds and unique drug targets, that are vital for the existence and growth of the parasites and can be further exploited for the search of therapeutically active anti-parasitic agents.

Piperazine scaffold: A remarkable tool in generation of diverse pharmacological agents

Piperazine is one of the most sought heterocyclics for the development of new drug candidates. This ring can be traced in a number of well established, commercially available drugs. Wide array of pharmacological activities exhibited by piperazine derivatives have made them indispensable anchors for the development of novel therapeutic agents. The review herein highlights the therapeutic significance of piperazine derivatives. Various therapeutically active piperazine derivatives developed by several chemists are reported here.

Coordination behavior of new bis Schiff base ligand derived from 2-furan carboxaldehyde and propane-1,3-diamine. Spectroscopic, thermal, anticancer and antibacterial activity studies

Novel bis Schiff base ligand, [N1,N3-bis(furan-2-ylmethylene)propane-1,3-diamine], was prepared by the condensation of furan-2-carboxaldehyde with propane-1,3-diamine. Its conformational changes on complexation with transition metal ions [Co(II), Ni(II), Cu(II), Mn(II), Cd(II), Zn(II) and Fe(III)] have been studied on the basis of elemental analysis, conductivity measurements, spectral (infrared, (1)H NMR, electronic), magnetic and thermogravimetric studies. The conductance data of the complexes revealed their electrolytic nature suggesting them as 1:2 (for bivalent metal ions) and 1:3 (for Fe(III) ion) electrolytes. The complexes were found to have octahedral geometry based on magnetic moment and solid reflectance measurements. Thermal analysis data revealed the decomposition of the complexes in successive steps with the removal of anions, coordinated water and bis Schiff base ligand. The thermodynamic parameters were calculated using Coats-Redfern equation. The Anticancer screening studies were performed on human colorectal cancer (HCT), hepatic cancer (HepG2) and breast cancer (MCF-7) cell lines. The antimicrobial activity of all the compounds was studied against Gram negative (Escherichia coli and Proteus vulgaris) and Gram positive (Bacillus vulgaris and Staphylococcus pyogones) bacteria. It was observed that the coordination of metal ion has a pronounced effect on the microbial activities of the bis Schiff base ligand. All the metal complexes have shown higher antimicrobial effect than the free bis Schiff base ligand.

Chloroquinoline–acetamide hybrids: a promising series of potential antiprotozoal agents

In an endeavour to develop efficacious antiprotozoal agents chloroquinoline–acetamide hybrids were synthesized and screened in vitro against E. histolytica and P. falciparum and molecular docking studies were performed against PfDHFR.

Quinoline-based antimalarial hybrid compounds

Quinoline-containing compounds, such as quinine and chloroquine, have a long-standing history as potent antimalarial agents. However, the increasing resistance of the Plasmodium parasite against these drugs and the lack of licensed malaria vaccines have forced chemists to develop synthetic strategies toward novel biologically active molecules. A strategy that has attracted considerable attention in current medicinal chemistry is based on the conjugation of two biologically active molecules into one hybrid compound. Since quinolines are considered to be privileged antimalarial building blocks, the synthesis of quinoline-containing antimalarial hybrids has been elaborated extensively in recent years. This review provides a literature overview of antimalarial hybrid molecules containing a quinoline core, covering publications between 2009 and 2014.

Synthesis of functionalized 3-, 5-, 6- and 8-aminoquinolines via intermediate (3-pyrrolin-1-yl)- and (2-oxopyrrolidin-1-yl)quinolines and evaluation of their antiplasmodial and antifungal activity

(3-Pyrrolin-1-yl)- and (2-oxopyrrolidin-1-yl)quinolines were prepared via cyclization of diallylaminoquinolines and 4-chloro-N-quinolinylbutanamides, respectively, as novel synthetic intermediates en route to N-functionalized 3-, 5-, 6- and 8-aminoquinolines with potential biological activity. (3-Pyrrolin-1-yl)quinolines were subjected to bromination reactions, and the reactivity of (2-oxopyrrolidin-1-yl)quinolines toward lithium aluminum hydride and methyllithium was assessed, providing an entry into a broad range of novel functionalized (pyrrolidin-1-yl)- and (hydroxyalkylamino)quinolines. Antiplasmodial evaluation of these novel quinolines and their functionalized derivatives revealed moderate micromolar potency against a chloroquine-sensitive strain of the malaria parasite Plasmodium falciparum, and the two most potent compounds also showed micromolar activity against a chloroquine-resistant strain of P. falciparum. Antifungal assessment of (hydroxyalkylamino)quinolines revealed three compounds with promising MIC values against Rhodotorula bogoriensis and one compound with potent activity against Aspergillus flavus.