Substituted 1,3-dioxoisoindoline-4-aminoquinolines coupled via amide linkers: Synthesis, antiplasmodial and cytotoxic evaluation

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 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.

Recent developments in the synthesis of hybrid antimalarial drug discovery

In this 21st century, Malaria remains a global burden and causes massive economic trouble to disease-endemic nations. The control and eradication of malaria is a major challenge that requires an urgent need to develop novel antimalarial drugs. To overcome the aforementioned situation, several researchers have given significant effort to develop hybrid antimalarial agents in the search for new antimalarial drugs. Hence, we have summarized those developments of hybrid antimalarial agents from 2017 to till date. This review illustrates the current progress in the recent synthesis of hybrid antimalarial agents along with focusing on their antimalarial evaluation to find the most potent hybrids. This present mini-review will also be useful for the scientific community for the development of new antimalarial drugs to eradicate malaria.

Recent contributions of quinolines to antimalarial and anticancer drug discovery research

Quinoline, a privileged scaffold in medicinal chemistry, has always been associated with a multitude of biological activities. Especially in antimalarial and anticancer research, quinoline played (and still plays) a central role, giving rise to the development of an array of quinoline-containing pharmaceuticals in these therapeutic areas. However, both diseases still affect millions of people every year, pointing to the necessity of new therapies. Quinolines have a long-standing history as antimalarial agents, but established quinoline-containing antimalarial drugs are now facing widespread resistance of the Plasmodium parasite. Nevertheless, as evidenced by a massive number of recent literature contributions, they are still of great value for future developments in this field. On the other hand, the number of currently approved anticancer drugs containing a quinoline scaffold are limited, but a strong increase and interest in quinoline compounds as potential anticancer agents can be seen in the last few years. In this review, a literature overview of recent contributions made by quinoline-containing compounds as potent antimalarial or anticancer agents is provided, covering publications between 2018 and 2020.

Design, synthesis, crystal structure and anti-plasmodial evaluation of tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine derivatives

Effective chemotherapy is essential for controlling malaria. However, resistance of Plasmodium falciparum to existing antimalarial drugs has undermined attempts to control and eventually eradicate the disease. In this study, a series of 2-((substituted)(4-(5,6,7,8-tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidin-4-yl)piperazin-1-yl)methyl)-6-substitutedphenol derivatives were prepared using Petasis reaction with a view to evaluate their activities against P. falciparum. The development of synthesized compounds (F1-F16) was justified through the study of H¹ NMR, C¹³ NMR, mass spectra. Compound F1 and F2 were also structurally validated by single crystal X-ray diffraction analysis. All the compounds were evaluated for their in vitro antiplasmodial assessment against the W2 strain (chloroquine-resistant) of P. falciparum IC₅₀ values ranging from 0.74-6.4 μM. Two compounds, F4 and F16 exhibited significant activity against W2 strain of P. falciparum with 0.75 and 0.74 μM. The compounds (F3-F6 and F16) were also evaluated for in vitro cytotoxicity against two cancer cell lines, human lung (A549) and cervical (HeLa) cells, which demonstrated non-cytotoxicity with significant selectivity indices. In addition, in silico ADME profiling and physiochemical properties predicts drug-like properties with a very low toxic effect. Thus, all these results indicate that tetrahydrobenzo[4,5]thieno[2,3-d]pyrimidine scaffolds may serve as models for the development of antimalarial agents.

A trio of quinoline-isoniazid-phthalimide with promising antiplasmodial potential: Synthesis, in-vitro evaluation and heme-polymerization inhibition studies

Quinoline-isoniazid-phthalimide triads have been synthesised to assess their antiplasmodial efficacy and cytotoxicity against chloroquine-resistant W2 strain of P. falciparum and Vero cells, respectively. Most of the synthesized compounds displayed IC₅₀ in lower nM range and appeared to be approximately five to twelve fold more active than chloroquine. Heme-binding studies were also carried out to delineate the mode of action. The promising compounds with IC_50s in range of 11-30 nM and selectivity index >2800, may act as promising template for the design of new antiplasmodials.

QSAR and molecular docking studies of 1,3-dioxoisoindoline-4-aminoquinolines as potent antiplasmodium hybrid compounds

Quantitative structure-activity relationships (QSAR) provides a model that link biological activities of compounds to thier chemical stuctures and molecular docking study reveals the interaction between drug and its target enzyme. These studies were conducted on 1,3-dioxoisoindoline-4-aminoquinolines with the aim of producing a model that could be used to design highly potent antiplasmodium. The compounds were first optimized using Density Functional Theory (DFT) with basis set B3LYP/6-31G∗ then their descriptors calculated. Genetic Function Algorithm (GFA) was used to select descriptors and build the model. One of the four models generated was found to be the best having internal and external squared correlation coefficient (R 2) of 0.9459 and 0.7015 respectively, adjusted squared correlation coefficient (R adj) of 0.9278, leave-one-out (LOO) cross-validation coefficient (Q 2 cv) of 0.8882. The model shows that antiplasmodial activities of 1,3-dioxoisoindoline-4-aminoquinolines depend on ATSC5i, GATS8p, minHBint3, minHBint5, MLFER_A and topoShape descriptors. The model was validated to be predictive, robust and reliable. Hence, it can predict the antiplasmodium activities of new 1,3-dioxoisoindoline-4-aminoquinolines.The docking result indicates strong binding between 1,3-dioxoisoindoline-4-aminoquinolines and Plasmodium falciparum lactate dehydrogenase (pfLDH), and revealed the important of the morpholinyl substituent and amide linker in inhibiting pfLDH. These results could serve as a model for designing novel 1,3-dioxoisoindoline-4-aminoquinolines as inhibitors of PfLDH with higher antiplasmodial activities.

Functionalized Naphthalimide-4-aminoquinoline Conjugates as Promising Antiplasmodials, with Mechanistic Insights

A series of 25 conjugates has been synthesized to evaluate their antiplasmodial potency and cytotoxicity against the chloroquine resistant (CQR) W2 strain of P. falciparum and Vero kidney cell lines, respectively. Most of the compounds showed IC₅₀ values in the lower nM range and proved to be many fold more active than chloroquine (CQ). The studies were extended to decipher modes of action using techniques including UV-vis absorption, NMR titrations, and mass spectrometry, and conclusions were strengthened by docking and density functional theory (DFT) simulations. The most active compound, with IC₅₀ 15 nM and selectivity index >4000, proved to be an interesting template for antimalarial drug discovery. To the best of our knowledge this is the first report of a potent naphthalimide based antiplasmodial conjugate.

Design, synthesis, heme binding and density functional theory studies of isoindoline-dione-4-aminoquinolines as potential antiplasmodials

Aim: WHO Malaria report 2017 estimated 216 million cases of malaria and 445,000 deaths worldwide, with 91% of deaths affecting the African region. Results/methodology: Microwave promoted the synthesis of cycloalkyl amine substituted isoindoline-1,3-dione-4-aminoquinolines was urbanized for evaluating their antiplasmodial activities. Compound with the optimum combination of propyl chain length and hydroxyethyl piperazine proved to be the most potent among the synthesized scaffolds against chloroquine-resistant W2 strain of Plasmodium falciparum with an IC50 value of 0.006 μM. Heme-binding along with density functional theory studies were further carried out in order to delineate the mechanism of action of the most active compound. Conclusion: The synthesized scaffold can act as a therapeutic template for further synthetic modifications toward the search for a new antimalarial agent.

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.

Combination Therapy Strategies for the Treatment of Malaria

Malaria is a vector- and blood-borne infection that is responsible for a large number of deaths around the world. Most of the currently used antimalarial therapeutics suffer from drug resistance. The other limitations associated with the currently used antimalarial drugs are poor drug bioavailability, drug toxicity, and poor water solubility. Combination therapy is one of the best approaches that is currently used to treat malaria, whereby two or more therapeutic agents are combined. Different combination therapy strategies are used to overcome the aforementioned limitations. This review article reports two strategies of combination therapy; the incorporation of two or more antimalarials into polymer-based carriers and hybrid compounds designed by hybridization of two antimalarial pharmacophores.