Recent developments in antimalarial activities of 4-aminoquinoline derivatives

Chiral separation and spectroscopic characterization of mefloquine analogues

Mefloquine, a widely used antimalarial agent, has spurred ongoing research into the development of derivatives with enhanced efficacy and reduced side effects. In this investigation, we synthesized two compounds containing N-allyl or N-tert-butylacetamid groups. A chiral liquid chromatography with polysaccharide chiral stationary phase was utilized to separate the enantiomers of both derivatives. We employed spectroscopic chiroptical and non-polarizable methods such as electronic and vibrational circular dichroism, infrared absorption and ultraviolet spectroscopies. Combined with density functional theory calculations, the stable conformers were found in solution and their spectra were subsequently simulated. We elucidated the three-dimensional structure of the enantiomerically pure compounds and assigned the absolute configuration of all prepared derivatives using both experimental and simulated spectra.

Optimization of pyrazolopyridine 4-carboxamides with potent antimalarial activity for which resistance is associated with the P. falciparum transporter ABCI3

Emerging resistance to current antimalarials is reducing their effectiveness and therefore there is a need to develop new antimalarial therapies. Toward this goal, high throughput screens against the P. falciparum asexual parasite identified the pyrazolopyridine 4-carboxamide scaffold. Structure-activity relationship analysis of this chemotype defined that the N1-tert-butyl group and aliphatic foliage in the 3- and 6-positions were necessary for activity, while the inclusion of a 7'-aza-benzomorpholine on the 4-carboxamide motif resulted in potent anti-parasitic activity and increased aqueous solubility. A previous report that resistance to the pyrazolopyridine class is associated with the ABCI3 transporter was confirmed, with pyrazolopyridine 4-carboxamides showing an increase in potency against parasites when the ABCI3 transporter was knocked down. The low metabolic stability intrinsic to the pyrazolopyridine scaffold and the slow rate by which the compounds kill asexual parasites resulted in poor performance in a P. berghei asexual blood stage mouse model. Lowering the risk of resistance and mitigating the metabolic stability and cytochrome P450 inhibition will be challenges in the future development of the pyrazolopyrimidine antimalarial class.

Design and synthesis of pyrano[2,3-c]pyrazole-4-aminoquinoline hybrids as effective antimalarial compounds

In this work, a series of nineteen novel pyrano[2,3-c]pyrazole-4-aminoquinoline hybrids were synthesized as potent antimalarial agents by covalently linking the scaffolds of 4-aminoquinoline and pyrano[2,3-c]pyrazoles via an ethyl linker and characterized using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance spectroscopy (NMR). Molecular docking was used to test each hybrid's and standard chloroquine's ability to bind to Plasmodium falciparum lactate dehydrogenase enzyme (PfLDH), an important enzyme in the parasite's glycolytic pathway. The hybrid compounds had a stronger binding affinity than the standard chloroquine (CQ). The schizontical antimalarial test of pyrano[2,3-c]pyrazole-4-aminoquinoline hybrid compound shows that all nineteen hybrid compounds were potent with the IC50 values ranging from 0.0151 to 0.301 μM against the CQ-sensitive 3D7 P. falciparum strain, and were active against the CQ-resistant K1 P. falciparum strain with the IC50 values ranging from 0.01895 to 2.746 μM. All the tested hybrid compounds were less potent than the standard drug chloroquine dipaspate (CQDP) against the CQ-sensitive 3D7 strain. In contrast, nine of the nineteen hybrids (16d, 16g, 16h, 16i, 16l, 16n, 16o, 16r, and 16s) displayed superior antimalarial activity than the CQDP against the CQ-resistant K1 P. falciparum strain. Among all the tested hybrids, 16c against the 3D7 strain and 16h against the K1 strain were the most promising antimalarial agents with 0.0151 and 0.01895 μM of IC50 values, respectively. In addition, the compounds were selective, showing moderate to low cytotoxic activity against a human normal liver WRL68 cell line. The synthesis of pyrano[2,3-c]pyrazole-4-aminoquinoline hybrids introduces new chemical entities that have the potential to exhibit potent antimalarial activity. It could address the ongoing challenge of drug resistance in malaria treatment.

Exploring antimalarial potential: Conjugating organometallic moieties with organic fragments for enhanced efficacy

In the search for novel ligands with efficacy against various diseases, particularly parasitic diseases, molecular hybridization of organometallic units into biologically active scaffolds has been hailed as an appealing strategy in medicinal chemistry. The conjugation to organometallic fragments can be achieved by an appropriate linker or by directly coordinating the existing drugs to a metal. The success of Ferroquine (FQ, SR97193), an effective chloroquine-ferrocene conjugate currently undergoing the patient-exploratory phase as a combination therapy with the novel triaminopyrimidine ZY-19489 for malaria, has sparked intense interest in organometallic compound drug discovery. We present the evolution of organometallic antimalarial agents over the last decade, focusing on the parent moiety's class and the type of organometallics involved. Four main organometallic antimalarial compounds have been chosen based on conjugated organic moieties: existing antimalarial drugs, other clinical drugs, hybrid drugs, and promising scaffolds of thiosemicarbazones, benzimidazoles, and chalcones, in particular. The presented insights contribute to the ongoing discourse on organometallic compound drug development for malaria diseases.

Exploring the Recent Pioneering Developments of Small Molecules in Antimalarial Drug Armamentarium: A Chemistry Prospective Appraisal

Malaria is a very destructive and lethal parasitic disease that causes significant mortality worldwide, resulting in the loss of millions of lives annually. It is an infectious disease transmitted by mosquitoes, which is caused by different species of the parasite protozoan belonging to the genus Plasmodium. The uncontrolled intake of antimalarial drugs often employed in clinical settings has resulted in the emergence of numerous strains of plasmodium that are resistant to these drugs, including multidrug-resistant strains. This resistance significantly diminishes the effectiveness of many primary drugs used in the treatment of malaria. Hence, there is an urgent need for developing unique classes of antimalarial drugs that function with distinct mechanisms of action. In this context, the design and development of hybrid compounds that combine pharmacophoric properties from different lead molecules into a single unit gives a unique perspective towards further development of malaria drugs in the next generation. In recent years, the field of medicinal chemistry has made significant efforts resulting in the discovery and synthesis of numerous small novel compounds that exhibit potent antimalarial properties, while also demonstrating reduced toxicity and desirable efficacy. In light of this, we have reviewed the progress of hybrid antimalarial agents from 2021 up to the present. This manuscript presents a comprehensive overview of the latest advancements in the medicinal chemistry pertaining to small molecules, with a specific focus on their potential as antimalarial agents. As possible antimalarial drugs that might target both the dual stage and multi-stage stages of the parasite life cycle, these small hybrid molecules have been studied. This review explores a variety of physiologically active compounds that have been described in the literature in order to lay a strong foundation for the logical design and eventual identification of antimalarial drugs based on lead frameworks.

A survey of isatin hybrids and their biological properties

The emergence of diverse infections worldwide, which is a serious global threat to human existence, necessitates the urgent development of novel therapeutic candidates that can combat these diseases with efficacy. Molecular hybridization has been established as an efficient technique in designing bioactive molecules capable of fighting infections. Isatin, a core nucleus of an array of compounds with diverse biological properties can be modified at different positions leading to the creation of novel drug targets, is an active area of medicinal chemistry. This review containing published articles from 2005 to 2022 highlights isatin hybrids which have been synthesized and reported in the literature alongside a discussion on their biological properties. The enriched structure-activity relationship studies discussed provides insights for the rational design of novel isatin hybrids with tailored biological properties as effective therapeutic candidates inspired by nature.

Recent advances in the synthesis and antimalarial activity of 1,2,4-trioxanes

The increasing resistance of various malarial parasite strains to drugs has made the production of a new, rapid-acting, and efficient antimalarial drug more necessary, as the demand for such drugs is growing rapidly. As a major global health concern, various methods have been implemented to address the problem of drug resistance, including the hybrid drug concept, combination therapy, the development of analogues of existing medicines, and the use of drug resistance reversal agents. Artemisinin and its derivatives are currently used against multidrug- resistant P. falciparum species. However, due to its natural origin, its use has been limited by its scarcity in natural resources. As a result, finding a substitute becomes more crucial, and the peroxide group in artemisinin, responsible for the drugs biological action in the form of 1,2,4-trioxane, may hold the key to resolving this issue. The literature suggests that 1,2,4-trioxanes have the potential to become an alternative to current malaria drugs, as highlighted in this review. This is why 1,2,4-trioxanes and their derivatives have been synthesized on a large scale worldwide, as they have shown promising antimalarial activity in vivo and in vitro against Plasmodium species. Consequently, the search for a more convenient, environment friendly, sustainable, efficient, and effective synthetic pathway for the synthesis of 1,2,4-trioxanes continues. The aim of this work is to provide a comprehensive analysis of the synthesis and mechanism of action of 1,2,4-trioxanes. This systematic review highlights the most recent summaries of derivatives of 1,2,4-trioxane compounds and dimers with potential antimalarial activity from January 1988 to 2023.

Exploring the antimalarial and antioxidant efficacy of transition metal(II) chelates of thiosemicarbazone ligands: spectral investigations, molecular docking, DFT, MESP and ADMET

Malaria, a relentless and ancient adversary, continues to cast its shadow over vast swathes of the globe, afflicting millions of people and have a heavy toll on human health and well-being. Despite substantial progress in the fight against this parasitic disease in recent decades, malaria still persists as a substantial global health concern, especially in some specific region which have limited resources and vulnerable populations. Thus, to ascertain an combating agent for malaria and its associated dysfunction, 4-(4-ethylphenyl)-3-thiosemicarbazide and benzaldehydes based two new thiosemicarbazone ligands (1-2) and their cobalt(II), nickel(II), copper(II), zinc(II) metal complexes (3-10) were synthesized in the present research work. The synthesized compounds were comprehensive characterized through spectral and physical investigations, demonstrating octahedral stereochemistry of the complexes. Further, the antimalarial and antioxidant potential of the compounds (1-10) were analyzed by micro assay and DPPH assay protocols, respectively, to examine the therapeutic aspect of the compounds. The performed biological evaluations revealed that the complexes are more efficient in controlling infectious ailment in comparison of ligands. The complexes (5), (6), (10) shows significant efficiency for malarial and oxidant dysfunctions whereas Zn(II) complex (6) exhibit highest potency with 1.02 ± 0.07 and 2.28 ± 0.05 µM IC50 value. Furthermore, to support the highest antimalarial potency of the (3-6) complexes and their associated ligand (1), the computational studies like molecular docking, DFT, MESP and ADMET analysis were executed which were supported the biological efficacy of the complex (6) by providing numerous parameters like binding interaction electronegativity, electrophilicity, HOMO value and electron density.

Recent developments of P-glycoprotein inhibitors and its structure-activity relationship (SAR) studies

P-glycoprotein (P-gp) over-expression is a key factor in multi-drug resistance (MDR), which is a major factor in the failure of cancer treatment. P-gp inhibitors have been demonstrated to have powerful pharmacological properties and may be used as a therapeutic approach to overcome the MDR in cancer cells. Combining clinical investigations with biochemical and computational research may potentially lead to a clearer understanding of the pharmacological properties and the mechanisms of action of these P-gp inhibitors. The task of turning these discoveries into effective therapeutic candidates for a variety of malignancies, including resistant and metastatic kinds, falls on medicinal chemists. A variety of P-gp inhibitors with great potency, high selectivity, and minimal toxicity have been identified in recent years. The latest advances in drug design, characterization, structure-activity relationship (SAR) research, and modes of action of newly synthesized, powerful small molecules P-gp inhibitors over the previous ten years are highlighted in this review. P-gp transporter over-expression has been linked to MDR, therefore the development of P-gp inhibitors will expand our understanding of the processes and functions of P-gp-mediated drug efflux, which will be helpful for drug discovery and clinical cancer therapies.

Exploring diverse frontiers: Advancements of bioactive 4-aminoquinoline-based molecular hybrids in targeted therapeutics and beyond

Amongst heterocyclic compounds, quinoline and its derivatives are advantaged scaffolds that appear as a significant assembly motif for developing new drug entities. Aminoquinoline moiety has gained significant attention among researchers in the 21stcentury. Considering the biological and pharmaceutical importance of aminoquinoline derivatives, herein, we review the recent developments (since 2019) in various biological activities of the 4-aminoquinoline scaffold hybridized with diverse heterocyclic moieties such as quinoline, pyridine, pyrimidine, triazine, dioxine, piperazine, pyrazoline, piperidine, imidazole, indole, oxadiazole, carbazole, dioxole, thiazole, benzothiazole, pyrazole, phthalimide, adamantane, benzochromene, and pyridinone. Moreover, by gaining knowledge about SARs, structural insights, and molecular targets, this review may help medicinal chemists design cost-effective, selective, safe, and more potent 4-aminoquinoline hybrids for diverse biological activities.

Triazole hybrid compounds: A new frontier in malaria treatment

Reviewing the advancements in malaria treatment, the emergence of triazole hybrid compounds stands out as a groundbreaking development. Combining the advantages of triazole and other moieties, these hybrid compounds offer a new frontier in the battle against malaria. Their potential as effective antimalarial agents has captured the attention of researchers and holds promise for overcoming the challenges posed by drug-resistant malaria strains. We focused on their broad spectrum of antimalarial activity of diverse hybridized 1,2,3-triazoles and 1,2,4-triazoles, structure-activity relationship (SAR), drug-likeness, bioavailability and pharmacokinetic properties reported since 2018 targeting multiple stages of the Plasmodium life cycle. This versatility makes them highly effective against both drug-sensitive and drug-resistant strains of P. falciparum, making them invaluable tools in regions where resistance is prevalent. The synergistic effects of combining the triazole moiety with other pharmacophores have resulted in even greater antimalarial potency. This approach has the potential to circumvent existing resistance mechanisms and provide a more sustainable solution to malaria treatment. While triazole hybrid compounds show great promise, further research and clinical trials are warranted to fully evaluate their safety, efficacy and long-term effects. As research progresses, these compounds can potentially revolutionize the field and contribute to global efforts to eradicate malaria, ultimately saving countless lives worldwide.

Evaluation of synthetic aminoquinoline derivatives as urease inhibitors: in vitro, in silico and kinetic studies

Background: Quinoline and acyl thiourea scaffolds have major chemical significance in medicinal chemistry. Quinoline-based acyl thiourea derivatives may potentially target the urease enzyme. Materials & methods: Quinoline-based acyl thiourea derivatives 1-26 were synthesized and tested for urease inhibitory activity. Results: 19 derivatives (1-19) showed enhanced urease enzyme inhibitory potential (IC50 = 1.19-18.92 μM) compared with standard thiourea (IC50 = 19.53 ± 0.032 μM), whereas compounds 20-26 were inactive. Compounds with OCH3, OC2H5, Br and CH3 on the aryl ring showed significantly greater inhibitory potential than compounds with hydrocarbon chains of varying length. Molecular docking studies were conducted to investigate ligand interactions with the enzyme's active site. Conclusion: The identified hits can serve as potential leads against the drug target urease in advanced studies.