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

Design, Synthesis, Antitumor, and Antiplasmodial Evaluation of New 7-Chloroquinoline-Benzimidazole Hybrids

Newly synthesized 7-chloro-4-aminoquinoline-benzimidazole hybrids were characterized by NMR and elemental analysis. Compounds were tested for their effects on the growth of the non-tumor cell line MRC-5 (human fetal lung fibroblasts) and carcinoma (HeLa and CaCo-2), leukemia, and lymphoma (Hut78, THP-1, and HL-60) cell lines. The obtained results, expressed as the concentration at which 50% inhibition of cell growth is achieved (IC50 value), show that the tested compounds affect cell growth differently depending on the cell line and the applied dose (IC50 ranged from 0.2 to >100 µM). Also, the antiplasmodial activity of these hybrids was evaluated against two P. falciparum strains (Pf3D7 and PfDd2). The tested compounds showed potent antiplasmodial activity, against both strains, at nanomolar concentrations. Quantitative structure-activity relationship (QSAR) analysis resulted in predictive models for antiplasmodial activity against the 3D7 strain (R2 = 0.886; Rext2 = 0.937; F = 41.589) and Dd2 strain (R2 = 0.859; Rext2 = 0.878; F = 32.525) of P. falciparum. QSAR models identified the structural features of these favorable effects on antiplasmodial activities.

Designing novel anti-plasmodial quinoline-furanone hybrids: computational insights, synthesis, and biological evaluation targeting Plasmodium falciparum lactate dehydrogenase

To combat resistance against current antimalarials, modifying key pharmacophores and exploring novel parasite-specific drug targets remained one of the key drug design strategies. The resistance to quinoline-based antimalarials arises often due to the efflux of the drug. Hence, the development of newer agents containing bulkier pharmacophores will enable medicinal chemists to counteract drug resistance. In view of this, herein we designed bulkier quinoline-furanone hybrids. Initially, virtual drug-likeness and ADMET screening were conducted to optimize physicochemical properties followed by docking of the hybrids against the Plasmodium falciparum lactate dehydrogenase (PfLDH) enzyme. The most potent hybrids that emerged from the computational screening were synthesized and screened for their bioactivity against the resistant strain of Plasmodium through Schizont Maturation Inhibition assays. Among the compounds tested, 5g and 6e demonstrated the best activity, with IC50 values similar to chloroquine (CQ), and 5g exhibited superior LDH inhibition compared to CQ. Compounds 5f, 7a, and 7f showed IC50 values comparable to CQ and moderate LDH inhibition. Structure-activity relationship (SAR) analysis revealed that halogen substitutions, particularly Br and Cl, enhanced antimalarial activity, while strong electron-withdrawing (-NO2) or -donating (-OH) groups led to diminished activity. Additionally, bulkier aromatic substitutions were favoured for antimalarial activity and LDH inhibition. The investigation successfully found potent anti-plasmodial quinoline-furanone hybrids, demonstrating promising prospects for combating malaria.

A Novel Tetramethylpyrazine Chalcone Hybrid- HCTMPPK, as a Potential Anti-Lung Cancer Agent by Downregulating MELK

Purpose

Lung adenocarcinoma currently ranks the leading causes of cancer-related mortality worldwide. Many anti-inflammation herbs, like tetramethylpyrazine, have shown their anti-tumor potentials. Here, we evaluated the role of a novel chalcone derivative of tetramethylpyrazine ((E) -1- (E) -1- (2-hydroxy-5-chlorophenyl) -3- (3,5,6-trimethylpyrazin-2-yl) -2-propen-1, HCTMPPK) in lung adenocarcinoma.

Methods

The effects of HCTMPPK on cell proliferation, apoptosis, and invasion were investigated by in-vitro assays, including CCK-8, colony formation assay, flow cytometry, transwell assay, and wound-healing assay. The therapeutic potential of HCTMPPK in vivo was evaluated in xenograft mice. To figure out the target molecules of HCTMPPK, a network pharmacology approach and molecular docking studies were employed, and subsequent experiments were conducted to confirm these candidate molecules.

Results

HCTMPPK effectively suppressed the proliferative activity and migration, as well as enhanced the apoptosis of A549 cells in a concentration-dependent manner. Consistent with this, tumor growth was inhibited by HCTMPPK significantly in vivo. Regarding the mechanisms, HCTMPPK down-regulated Bcl-2 and MMP-9 and up-regulating Bax and cleaved-caspase-3. Subsequently, we identified 601 overlapping DEGs from LUAD patients in TCGA and GEO database. Then, 15 hub genes were identified by PPI network and CytoHubba. Finally, MELK was verified to be the HCTMPPK targeted site, through the molecular docking studies and validation experiments.

Conclusion

Overall, our study indicates HCTMPPK as a potential MELK inhibitor and may be a promising candidate for the therapy of lung cancer.

Biological properties of pyrroloquinoline and pyrroloisoquinoline derivatives

In this review, we summarize pyrroloquinoline and pyrroloisoquinoline derivatives (PQs and PIQs) that act on a broad spectrum of biological targets and are used as bacteriostatic, antiviral, plasmodial, anticancer, antidiabetic and anticoagulant agents. Many of these compounds play important roles in the study of DNA and its interactions, the regulation of the cell cycle and programmed cell death. This review involves twenty-five types of skeletally analogical compounds bearing pyrrole and (iso)quinoline scaffolds with different mutual annelations.

1,2,3-triazole and chiral Schiff base hybrids as potential anticancer agents: DFT, molecular docking and ADME studies

A series of novel 1,2,3-triazole and chiral Schiff base hybrids 2-6 were synthesized by Schiff base condensation reaction from pre-prepared parent component of the hybrids (1,2,3-triazole 1) and series of primary chiral amines and their chemical structure were confirmed using NMR and FTIR spectroscopies, and CHN elemental analysis. Compounds 1-6 were evaluated for their anticancer activity against two cancer PC3 (prostate) and A375 (skin) and MRC-5 (healthy) cell lines by Almar Blue assay method. The compounds exhibited significant cytotoxicity against the tested cancer cell lines. Among the tested compounds 3 and 6 showed very good activity for the inhibition of the cancer cell lines and low toxicity for the healthy cell lines. All the compounds exhibited high binding affinity for Androgen receptor modulators (PDB ID: 5t8e) and Human MIA (PDB ID: 1i1j) inhibitors compared to the reference anticancer drug (cisplatin). Structure activity relationships (SARs) of the tested compounds is in good agreement with DFT and molecular docking studies. The compounds exhibited desirable physicochemical properties for drug likeness.

Tretinoin (2,4-difluoro-phenyl) triazole activates proapoptotic protein expression and targets NRP2 protein to inhibit esophageal carcinoma cell growth

The present study investigated the effect of tretinoin (2,4-difluoro-phenyl) triazole (TDFPT) on the growth and proliferation of Kyse-270 and EC9706 esophageal carcinoma cells and explored the underlying mechanism. The results demonstrated that TDFPT treatment of Kyse-270 and EC9706 cells led to a dose-dependent reduction in cell proliferation. Colony formation was significantly (p < .05) reduced in Kyse-270 and EC9706 cells on treatment with various concentrations of TDFPT. In TDFPT-treated Kyse-270 and EC9706 cells, the expression of Bcl-2 protein showed a remarkable decrease, whereas the level of Bax protein was found to be higher compared with the control cells. Cell invasion showed a prominent decrease in Kyse-270 and EC9706 cells on treatment with TDFPT. Treatment with TDFPT led to a prominent suppression in the expression of MMP-9 and NRP2 in Kyse-270 and EC9706 cells. In silico studies using the AutoDock Vina and discovery studio software revealed that various confirmations of TDFPT bind to NRP2 protein with the affinity ranging from -8.6 to -6.1 kcal/mol. It was found that the TDFPT interacts with NRP2 protein by binding to alanine (ALA A:295), proline (PRO A:306), glutamine (GLN A:307), and isoleucine (ILE A:293) amino acid residues. In summary, TDFPT exposure suppresses esophageal carcinoma cell proliferation, inhibits colony formation ability, and activates apoptotic pathway. Thus, TDFPT acts as an effective antiproliferative agent for esophageal carcinoma cells and needs to be investigated further as chemotherapeutic molecule.

An overview on the antimalarial activity of 1,2,4-trioxanes, 1,2,4-trioxolanes and 1,2,4,5-tetraoxanes

The demand for novel, fast-acting, and effective antimalarial medications is increasing exponentially. Multidrug resistant forms of malarial parasites, which are rapidly spreading, pose a serious threat to global health. Drug resistance has been addressed using a variety of strategies, such as targeted therapies, the hybrid drug idea, the development of advanced analogues of pre-existing drugs, and the hybrid model of resistant strains control mechanisms. Additionally, the demand for discovering new potent drugs grows due to the prolonged life cycle of conventional therapy brought on by the emergence of resistant strains and ongoing changes in existing therapies. The 1,2,4-trioxane ring system in artemisinin (ART) is the most significant endoperoxide structural scaffold and is thought to be the key pharmacophoric moiety required for the pharmacodynamic potential of endoperoxide-based antimalarials. Several derivatives of artemisinin have also been found as potential treatments for multidrug-resistant strain in this area. Many 1,2,4-trioxanes, 1,2,4-trioxolanes, and 1,2,4,5-tetraoxanes derivatives have been synthesised as a result, and many of these have shown promise antimalarial activity both in vivo and in vitro against Plasmodium parasites. As a consequence, efforts to develop a functionally straight-forward, less expensive, and vastly more effective synthetic pathway to trioxanes continue. This study aims to give a thorough examination of the biological properties and mode of action of endoperoxide compounds derived from 1,2,4-trioxane-based functional scaffolds. The present system of 1,2,4-trioxane, 1,2,4-trioxolane, and 1,2,4,5-tetraoxane compounds and dimers with potentially antimalarial activity will be highlighted in this systematic review (January 1963-December 2022).

Synthesis and in-vitro anti-proliferative with antimicrobial activity of new coumarin containing heterocycles hybrids

A series of new coumarin-N-heterocyclic hybrids, coumarin-quinolines 7a-e, coumarin-acridines 10b,c and coumarin-neocryptolepines 13b,c were synthesized and evaluated for their anticancer and antimicrobial activities. The structures of all synthesized hybrids were confirmed by FT-IR, 1H-NMR, 13C-NMR, and MS spectrometry. The anti-proliferative activity of hybrids 7a-e, 10c and 13c were bio-evaluated using MTT-assay against colon (CaCo-2), lung (A549), breast (MDA-MB-231), and hepatocellular carcinoma (HepG-2) human cancer cell lines using doxorubicin as a reference drug. The results demonstrated that, all hybrids displayed moderate to good anti-proliferative activity against the cell lines. The most active hybrids were 7a-d and 10c against CaCo-2 cancer cell line with IC50: 57.1, 52.78, 57.29, 51.95 and 56.74 µM, and selectivity index 1.38, 1.76, 2.6, 1.96 and 0.77; respectively. While, 7a,d were potent against A549 cancer cell line with IC50: 51.72, 54.8 µM and selectivity index 1.5, 0.67; respectively. Moreover, 7c showed the most potency against MDA-MB-231 cancer cell line with IC50: 50.96 µM and selectivity index 2.20. Interestingly, docking results revealed that binding energy of the current compounds showed marked affinity values ranging from -6.54 to -5.56 kcal with interactions with the reported key amino acid SER 79. Furthermore, the antimicrobial activity of the synthesized hybrids 7a-e, 10b,c, 13b and 13c were evaluated against Gram-positive and Gram-negative bacterial and fungal strains. The hybrids 10b, 13b, 10c, and 13c exhibited broad-spectrum antibacterial activity against E.coli, S. mutans, and S. aureus with MIC from 3.2 to 66 µM, this hybrids also displayed antifungal activity against C. albicans with MIC values ranging from 0.0011 to 29.5 µM. In-silico investigation of the pharmacokinetic properties indicated that tested hybrids had high GI absorption, low Blood Brain Barrier (BBB) permeability in addition to cell membrane penetrability.

Antimalarial activity assay of artesunate-3-chloro-4(4-chlorophenoxy) aniline in vitro and in mice models

The global spread of multi-drug resistant P. falciparum, P. vivax, and P. malariae strains and absence of long-term effective vaccine makes chemotherapy the mainstay of malaria control strategies in endemic settings. The Mossman's assay and the Organization for Economic Co-operation and Development (OECD), 2001 guideline 423, were used to determine the cytotoxicity and acute oral toxicity of a novel hybrid drug, artesunate-3-Chloro-4(4-chlorophenoxy) aniline (ATSA), in vitro and in vivo, respectively. A modified Desjardins method was used to screen for antiplasmodial activity using P. falciparum (3D₇ and W₂) strains in vitro. The Peter's 4-day suppressive tests (4DTs) was used to evaluate the in vivo antimalaria activity using P. berghei ANKA strain, lumefantrine resistant (LuR), and piperaquine resistant (PQR) P. berghei lines. In silico prediction of absorption, distribution, metabolism, excretion, and toxicity (ADMET) profiles was assayed using PreADMET online prediction tool. The reference drug in all experiments was artesunate (ATS). Statistical significance between ATSA's activities in treated and control mice was evaluated by one-way analysis of variance (ANOVA). Results show that inhibitory concentrations-50 (IC₅₀) of ATSA is 11.47 ± 1.3 (3D₇) and 1.45 ± 0.26 (W₂) against 4.66 ± 0.93 (3D₇) and 0.60 ± 0.15 (W₂) ng/ml of ATS with a selective index of 2180.91(3D₇) and a therapeutic index (TI) of > 71). No mortalities were observed in acute oral toxicity assays and mean weight differences for test and controls were statistically insignificant (P > 0.05). The in vivo activity of ATSA was above 40% with effective dosage-50 (ED₅₀) of 4.211, 2.601, and 3.875 mg/kg body weight against P. berghei ANKA, LuR, and PQR lines, respectively. The difference between treated and control mice was statistically significant (P < 0.05). ATSA has high intestinal absorption (HIA) > 95% and has medium human ether-a-go-go related gene (hERG) K⁺ channel inhibition risks. Preclinical and clinical studies on ATSA are recommended to evaluate its value in developing novel drugs for future management of multi-drug resistant malaria parasites.

Antiplasmodial, Antioxidant and Cytotoxicity Activity of Ethanol and Aqueous Extracts of Khaya grandifoliola Stem Bark

Background. Malaria is a serious public health problem, especially in sub-Saharan Africa. The aim of this study was to scientifically provide baseline information on the use of Khaya grandifoliola stem bark as an antimalaria drug by traditional healers. Method. The stem barks of K.grandifoliola were harvested and dried to obtain powder, and fifty grams of the powder were soaked in ethanol and hot distilled water respectively, for the preparation of ethanol and aqueous extracts, then dried in an oven at 40°C for the ethanol extract and 50°C for the aqueous extract. Plasmodium falciparum strains 3D7 sensitive and Dd2 resistant to chloroquine, were used to evaluate in vitro antiplasmodial activity using SYBR Green. The ability of the extracts to prevent oxidative stress was assessed by trapping 2, 2′-diphenyl-1-picrylhydrazyl (DPPH); nitric oxide, hydrogen peroxide and ferric reducing power. The cytotoxicity test of the extracts was carried out on RAW 264.7 cell lines and on erythrocytes. The data obtained were entered in the Excel software, then in Graph pad where the IC50 was calculated and the curves plotted. Results. The fifty percent inhibition (IC50) of the antiplasmodial activity of the chloroquine-resistant strain PfDd2 were 54.27 ± 2.41 μg/mL and 31.19 ± 4.06 μg/mL respectively, for the aqueous and ethanol extracts. As for the Chloroquino-sensitive Pf3D7, IC50 of 53.06 μg/mL was obtained for the aqueous extract and 28.03 ± 1.90 μg/mL for ethanol. The DPPH radical scavenging activity presented IC50 of 104 μg/mL for the aqueous and 2.617 μg/mL for the ethanol extract; for the Nitric oxide (NO) presented an IC50 of 301 ± 21 μg/mL for the aqueous extract 140.7 ± 21 μg/mL for the ethanol; for hydrogen peroxide the ethanol and aqueous presented IC50 of 845.1 ± 21 μg/mL and 509.4 ± 21 μg/mL respectively. The cytotoxicity on RAW 264.7 cells presented High CC50 in particular >1000 μg/mL and 467.4 μg/mL respectively for the aqueous and ethanol extract. Conclusion. Extracts of Khaya grandifoliola exhibited antiplasmodial activity. The ability to inhibit oxidative stress as well as lower cell toxicity on RAW 264.7 and erythrocytes, is a good indicator. However, in vivo tests remain important in order to confirm the use of this plant for the treatment of malaria.

Novel Erlotinib-Chalcone Hybrids Diminish Resistance in Head and Neck Cancer by Inducing Multiple Cell Death Mechanisms

In a search for novel therapeutic options for head and neck squamous cell carcinomas (HNSCCs) generally treated with limited therapeutic success, we synthesized a series of novel erlotinib-chalcone molecular hybrids with 1,2,3-triazole and alkyne linkers and evaluated them for their anticancer activity on Fadu, Detroit 562 and SCC-25 HNSCC cell lines. Time- and dose-dependent cell viability measurements disclosed a significantly increased efficiency of the hybrids compared to the 1:1 combination of erlotinib and a reference chalcone. The clonogenic assay demonstrated that hybrids eradicate HNSCC cells in low micromolar concentrations. Experiments focusing on potential molecular targets indicate that the hybrids trigger the anticancer effect by a complementary mechanism of action that is independent of the canonical targets of their molecular fragments. Confocal microscopic imaging and real-time apoptosis/necrosis detection assay pointed to slightly different cell death mechanisms induced by the most prominent triazole- and alkyne-tethered hybrids (6a and 13, respectively). While 6a featured the lowest IC₅₀ values on each of the three HNSCC cell lines, in Detroit 562 cells, this hybrid induced necrosis more markedly compared to 13. The therapeutic potential indicated by the observed anticancer efficacy of our selected hybrid molecules validates the concept of development and justifies further investigation to reveal the underlying mechanism of action.

Hitting drug-resistant malaria infection with triazole-linked flavonoid-chloroquine hybrid compounds

Background: Malaria represents the major parasitic disease in tropical regions, and the development of new potent drugs is of pivotal importance. In this study, a series of hybrid molecules were designed by linking the 7-chloroquinoline core of chloroquine to different fluorinated flavonoid-related scaffolds. Materials & methods: Compounds were prepared by exploiting the click chemistry approach, allowing the introduction of a 1,2,3-triazole, a privileged structural motif in antiparasitic dug discovery. Results: Compounds 1b and 1c were the most interesting and were endowed with the highest in vitro activity, mainly against a resistant Plasmodium falciparum strain. They also inhibited hemozoin formation, and 1c was more effective than chloroquine against stage V gametocytes. Conclusion: The homoisoflavone core is a new, promising antimalarial scaffold that deserves further investigation.

Evaluation of ferrocenyl-containing γ-hydroxy-γ-lactam-derived tetramates as potential antiplasmodials

A series of ferrocenyl-containing γ-hydroxy-γ-lactam tetramates were prepared in 2-3 steps through ring opening-ring closure (RORC) process of γ-ylidene-tetronate derivatives in the presence of ferrocenyl alkylamines. The compounds were screened in vitro for their antiplasmodial activity against chloroquine-sensitive (3D7) and chloroquine-resistant (W2) clones of P. falciparum, displaying activity in the range of 0.12-100 μM, with generally good resistance index. The most active ferrocene in these series exhibited IC₅₀ equal to 0.09 μM (3D7) and 0.12 μM (W2). The low cytotoxicity of the ferrocenyl-containing γ-hydroxy-γ-lactam tetramates against Human Umbilical Vein Endothelial (HUVEC) cell line demonstrated selective antiparasitic activity. The redox properties of these ferrocene-derived tetramates were studied and physico-biochemical studies evidenced that these derivatives can exert potent antimalarial activities via a mechanism distinct from ferroquine.

Cinnamic acid hybrids as anticancer agents: A mini-review

Cancer, as a long-lasting and dramatic disease, affects almost one-third of human beings globally. Chemotherapeutics play an important role in cancer treatment, but multidrug resistance and severe adverse effects have already become the main causes of failure in tumor chemotherapy. Therefore, it is an urgent need to develop novel chemotherapeutics. Cinnamic acid contains a ubiquitous α,β-unsaturated acid moiety presenting potential therapeutic effects in the treatment of cancer as these derivatives could act on cancer cells by diverse mechanisms of action. Accordingly, cinnamic acid derivatives are critical scaffolds in discovering novel anticancer agents. This review provides a comprehensive overview of cinnamic acid hybrids as anticancer agents. The structure-activity relationship, as well as the mechanisms of action, are also discussed, covering articles published from 2012 to 2021.

The antimalarial activity of 1,2,4-trioxolane/trioxane hybrids and dimers: A review

Malaria, a mosquito-borne parasitic infection caused by protozoan parasites belonging to the genus Plasmodium, is a dangerous disease that contributes to millions of hospital visits and hundreds and thousands of deaths across the world, especially in Sub-Saharan Africa. Antimalarial agents are vital for treating malaria and controlling transmission, and 1,2,4-trioxolane/trioxane-containing agents, especially artemisinin and its derivatives, own antimalarial efficacy and low toxicity with unique mechanisms of action. Moreover, artemisinin-based combination therapies were recommended by the World Health Organization as the first-line treatment for uncomplicated malaria infection and have remained as the mainstay of the treatment of malaria, demonstrating that 1,2,4-trioxolane/trioxane derivatives are useful prototypes for the control and eradication of malaria. However, malaria parasites have already developed resistance to almost all of the currently available antimalarial agents, creating an urgent need for the search of novel pharmaceutical interventions for malaria. The purpose of this review article is to provide an emphasis on the current scenario (January 2012 to January 2022) of 1,2,4-trioxolane/trioxane hybrids and dimers with potential antimalarial activity and the structure-activity relationships are also discussed to facilitate further rational design of more effective candidates.

The antibacterial potential of ciprofloxacin hybrids against Staphylococcus aureus

Staphylococcus aureus (S. aureus), an important pathogen of both humans and animals, is able to cause a variety of infections at any site of the body. The evolution of S. aureus resistance is notorious, and the widespread of drug-resistant S. aureus, especially methicillin-resistant S. aureus (MRSA), has made the treatment difficult in recent decades. Nowadays, S. aureus is among the leading causes of bacterial infections, creating an urgent need for the development of novel antibacterial agents. Ciprofloxacin, characterized by high clinical efficacy, is a broad-spectrum antibacterial agent with frequency of prescription for various Gram-positive and Gram-negative pathogens, many of which are resistant to a wide range of antibiotics. However, the long-term and widespread use of this antibiotic has led to the emergence of ciprofloxacin-resistant pathogens, and ciprofloxacin-resistant S. aureus has been noted in clinical practice. Ciprofloxacin hybrids have been recognized as advanced chemical entities to simultaneously modulate multiple drug targets in bacteria, so ciprofloxacin hybrids have the potential to overcome drug resistance. The present review provides an overview of ciprofloxacin hybrids with anti-S. aureus potential that have been reported in the last decade with emphasis on their structure-activity relationships and mechanisms of action.

Design, Synthesis and Anti-Lung Cancer Evaluation of 1, 2, 3-Triazole Tethered Dihydroartemisinin-Isatin Hybrids

A series of 1,2,3-triazole tethered dihydroartemisinin-isatin hybrids 8a-c and 9a-k were designed and synthesized. Their antiproliferative activity against A549, doxorubicin-resistant A549 (A549/DOX) as well as cisplatin-resistant A549 (A549/DDP) lung cancer cell lines was also investigated in this study. All hybrids (half maximal inhibitory concentration/IC₅₀: 7.54–73.8 μM) were more potent than the parent drug dihydroartemisinin (IC₅₀: 69.4–88.0 μM) and also non-cytotoxic towards mouse embryonic fibroblast cells NIH/3T3 (IC₅₀: >100 μM). The structure-activity relationships illustrated that the substituents on C-3 and C-5 position of isatin moiety influenced the activity significantly. Imine at C-3 position decreased the activity, whereas fluoro at C-5 position enhanced the activity. In particular, hybrids 8a,c (IC₅₀: 7.54–12.1 μM) and 9i (IC₅₀: 9.10–15.9 μM) were comparable to cisplatin (IC₅₀: 7.54–15.9 μM vs 9.38–19.7 μM) against A549 and A549/DOX, but 4.6–7.6 folds more potent than that of cisplatin (IC₅₀: 8.77–14.3 μM vs 66.9 μM) against A549/DDP cells. Moreover, hybrids 8a,c exhibited excellent stability (liver microsomes: 68–83%) in mouse/human microsomes and good pharmacokinetic properties, demonstrating their potential as a novel anti-lung cancer chemotherapeutic candidates.

Novel Small-Molecule Hybrid-Antibacterial Agents against S. aureus and MRSA Strains

Ongoing resistance developments against antibiotics that also affect last-resort antibiotics require novel antibacterial compounds. Strategies to discover such novel structures have been dimerization or hybridization of known antibacterial agents. We found novel antibacterial agents by dimerization of indols and hybridization with carbazoles. They were obtained in a simple one-pot reaction as bisindole tetrahydrocarbazoles. Further oxidation led to bisindole carbazoles with varied substitutions of both the indole and the carbazole scaffold. Both the tetrahydrocarbazoles and the carbazoles have been evaluated in various S. aureus strains, including MRSA strains. Those 5-cyano substituted derivatives showed best activities as determined by MIC values. The tetrahydrocarbazoles partly exceed the activity of the carbazole compounds and thus the activity of the used standard antibiotics. Thus, promising lead compounds could be identified for further studies.

Enantioselective vinylogous aldol reaction of acylphosphonates with 3-alkylidene oxindoles

A simple strategy for yielding chiral tertiary α-hydroxy phosphonates that integrates two highly biologically relevant scaffolds namely 3-alkylidene-2-oxindoles and phosphonates has been described. The hydrogen bonding ability of the bifunctional thiourea catalyst allows simultaneous dual activation of a vinylogous oxindole nucleophile and an acylphosphonate electrophile, affording hydroxyphosphonato-3-alkylidene-2-oxindoles as aldol adducts in high yields (up to 92%) with excellent stereocontrol (up to 99% ee).

Chalcone Derivatives and their Activities against Drug-resistant Cancers: An Overview

Drug resistance, including multidrug resistance resulting from different defensive mechanisms in cancer cells, is the leading cause of the failure of the cancer therapy, posing an urgent need to develop more effective anticancer agents. Chalcones, widely distributed in nature, could act on diverse enzymes and receptors in cancer cells. Accordingly, chalcone derivatives possess potent activity against various cancers, including drug-resistant, even multidrug-resistant cancer. This review outlines the recent development of chalcone derivatives with potential activity against drug-resistant cancers covering articles published between 2010 and 2020 so as to facilitate further rational design of more effective candidates.

Indole Alkaloids, Synthetic Dimers and Hybrids with Potential In Vivo Anticancer Activity

Indole, a heterocyclic organic compound, is one of the most promising heterocycles found in natural and synthetic sources since its derivatives possess fascinating structural diversity and various therapeutic properties. Indole alkaloids, synthetic dimers and hybrids could act on diverse targets in cancer cells, and consequently, possess potential antiproliferative effects on various cancers both in vitro and in vivo. Vinblastine, midostaurin, and anlotinib as the representative of indole alkaloids, synthetic dimers and hybrids respectively, have already been clinically applied to treat many types of cancers, demonstrating indole alkaloids, synthetic dimers and hybrids are useful scaffolds for the development of novel anticancer agents. Covering articles published between 2010 and 2020, this review emphasizes the recent development of indole alkaloids, synthetic dimers and hybrids with potential in vivo therapeutic application for cancers.

Quinoline-based Compounds with Potential Activity against Drugresistant Cancers

Drug resistance is the major cause of the failure of cancer chemotherapy, so one of the most important features in developing effective cancer therapeutic strategies is to overcome drug resistance. Quinoline moiety has become one of the most privileged structural motifs in anticancer agent discovery since its derivatives possess potent activity against various cancers including drug-resistant cancers. Several quinoline-based compounds which are represented by Anlotinib, Bosutinib, Lenvatinib, and Neratinib have already been applied in clinical practice to fight against cancers, so quinoline-based compounds are potential anticancer agents. The present short review article provides an overview of the recent advances of quinoline-based compounds with potential activity against drug-resistant cancers. The structure-activity relationship and mechanisms of action are also discussed.

Chalcone Derivatives: Role in Anticancer Therapy

Chalcones (1,3-diaryl-2-propen-1-ones) are precursors for flavonoids and isoflavonoids, which are common simple chemical scaffolds found in many naturally occurring compounds. Many chalcone derivatives were also prepared due to their convenient synthesis. Chalcones as weandhetic analogues have attracted much interest due to their broad biological activities with clinical potentials against various diseases, particularly for antitumor activity. The chalcone family has demonstrated potential in vitro and in vivo activity against cancers via multiple mechanisms, including cell cycle disruption, autophagy regulation, apoptosis induction, and immunomodulatory and inflammatory mediators. It represents a promising strategy to develop chalcones as novel anticancer agents. In addition, the combination of chalcones and other therapies is expected to be an effective way to improve anticancer therapeutic efficacy. However, despite the encouraging results for their response to cancers observed in clinical studies, a full description of toxicity is required for their clinical use as safe drugs for the treatment of cancer. In this review, we will summarize the recent advances of the chalcone family as potential anticancer agents and the mechanisms of action. Besides, future applications and scope of the chalcone family toward the treatment and prevention of cancer are brought out.

1,2,3-Triazole-Containing Compounds as Anti-Lung Cancer Agents: Current Developments, Mechanisms of Action, and Structure-Activity Relationship

Lung cancer is the most common malignancy and leads to around one-quarter of all cancer deaths. Great advances have been achieved in the treatment of lung cancer with novel anticancer agents and improved technology. However, morbidity and mortality rates remain extremely high, calling for an urgent need to develop novel anti-lung cancer agents. 1,2,3-Triazole could be readily interact with diverse enzymes and receptors in organisms through weak interaction. 1,2,3-Triazole can not only be acted as a linker to tether different pharmacophores but also serve as a pharmacophore. This review aims to summarize the recent advances in 1,2,3-triazole-containing compounds with anti-lung cancer potential, and their structure-activity relationship (SAR) together with mechanisms of action is also discussed to pave the way for the further rational development of novel anti-lung cancer candidates.

Novel molecule combinations and corresponding hybrids targeting artemisinin-resistant Plasmodium falciparum parasites

Malaria is still considered as the major parasitic disease and the development of artemisinin resistance does not improve this alarming situation. Based on the recent identification of relevant malaria targets in the artemisinin resistance context, novel drug combinations were evaluated against artemisinin-sensitive and artemisinin-resistant Plasmodium falciparum parasites. Corresponding hybrid molecules were also synthesized and evaluated for comparison with combinations and individual pharmacophores (e.g. atovaquone, mefloquine or triclosan). Combinations and hybrids showed remarkable antimalarial activity (IC₅₀ = 0.6 to 1.1 nM for the best compounds), strong selectivity, and didn't present any cross-resistance with artemisinin. Moreover, the combination triclosan + atovaquone showed high activity against artemisinin-resistant parasites at the quiescent stage but the corresponding hybrid lost this pharmacological property. This result is essential since only few molecules active against quiescent artemisinin-resistant parasites are reported. Our promising results highlight the potential of these combinations and paves the way for pharmacomodulation work on the best hybrids.

Physicochemical Profiling and Comparison of Research Antiplasmodials and Advanced Stage Antimalarials with Oral Drugs

To understand the property space of antimalarials, we collated a large dataset of research antiplasmodial (RAP) molecules with known in vitro potencies and advanced stage antimalarials (ASAMs) with established oral bioavailability. While RAP molecules are "non-druglike", ASAM molecules display properties closer to Lipinski's and Veber's thresholds. Comparison within the different potency groups of RAP molecules indicates that the in vitro potency is positively correlated to the molecular weight, the calculated octanol-water partition coefficient (clog P), aromatic ring counts (#Ar), and hydrogen bond acceptors. Despite both categories being bioavailable, the ASAM molecules are relatively larger and more lipophilic, have a lower polar surface area, and possess a higher count of heteroaromatic rings than oral drugs. Also, antimalarials are found to have a higher proportion of aromatic (#ArN) and basic nitrogen (#BaN) counts, features implicitly used in the design of antimalarial molecules but not well studied hitherto. We also propose using descriptors scaled by the sum of #ArN and #BaN (SBAN) to define an antimalarial property space. Together, these results may have important applications in the identification and optimization of future antimalarials.

Triazole-containing hybrids with anti-Mycobacterium tuberculosis potential - Part I: 1,2,3-Triazole

Tuberculosis regimens currently applied in clinical practice require months of multidrug therapy, which imposes a major challenge of patient compliance and drug resistance development. Moreover, because of the increasing emergence of hard-to-treat tuberculosis, this disease continues to be a significant threat to the human population. 1,2,3-triazole as a privileged structure has been widely used as an effective template for drug discovery, and 1,2,3-triazole-containing hybrids that can simultaneously act on dual or multiple targets in Mycobacterium tuberculosis have the potential to circumvent drug resistance, enhance efficacy, reduce side effects and improve pharmacokinetic as well as pharmacodynamic profiles. Thus, 1,2,3-triazole-containing hybrids are useful scaffolds for the development of antitubercular agents. This review aims to highlight recent advances of 1,2,3-triazole-containing hybrids with potential activity against various forms of M. tuberculosis, covering articles published between 2015 and 2020. The structure-activity relationship and the mechanism of action are also discussed to facilitate further rational design of more effective drug candidates.

Coumarin-based derivatives with potential anti-HIV activity

Acquired immunodeficiency syndrome (AIDS), as a result of human immunodeficiency virus (HIV) infection which leads to severe suppression of immune functions, is an enormous world-wide health threat. The anti-HIV agents are critical for the HIV/AIDS therapy, but the generation of viral mutants and the severe side effects of the anti-HIV agents pose serious hurdles in the treatment of HIV infection, and creat an urgent need to develop novel anti-HIV agents. The plant-derived compounds possess structural and mechanistic diversity, and among them, coumarin-based derivatives have the potential to inhibit different stages in the HIV replication cycle, inclusive of virus-host cell attachment, cell membrane fusion, integration, assembly besides the conventional target like inhibition of the reverse transcriptase, protease, and integrase. Moreover, (+)-calanolide A, a coumarin-based natural product, is a potential anti-HIV agent. Thus, coumarin-based derivatives are useful scaffolds for the development of anti-HIV agents. This review article describes the recent progress in the discovery, structural modification, and structure-activity relationship studies of potent anti-HIV coumarin-based derivatives including natural coumarin compounds, synthetic hybrids, dimers, and other synthetic derivatives covering articles published between 2000 and 2020.

Medicinal chemistry updates on quinoline- and endoperoxide-based hybrids with potent antimalarial activity

The resistance of conventional antimalarial drugs against the malarial parasite continues to pose a challenge to control the disease. The indiscriminate exploitation of the available antimalarials has resulted in increasing treatment failures, which urges on the search for novel lead molecules. Artemisinin-based combination therapy (ACT) is the current WHO-recommended first-line treatment for the majority of malaria cases. Hybrid molecules offer a newer strategy for the development of next-generation antimalarial drugs. These comprise molecules, each with an individual pharmacological activity, linked together into a single hybrid molecule. This approach has been utilized by several research groups to develop molecules with potent antimalarial activity. In this review, we provide an overview of the pivotal roles of quinoline- and endoperoxide-based hybrids as inhibitors of the life-cycle progression of Plasmodium. Based on the exhaustive literature reports, we have collated the structural and functional analyses of quinoline- and endoperoxide-based hybrid molecules that show potency equal to or greater than those of the individual compounds, offering an effective therapeutics option for clinical use.

Amide Tethered 4-Aminoquinoline-naphthalimide Hybrids: A New Class of Possible Dual Function Antiplasmodials

A series of amide tethered 4-aminoquinoline-naphthalimide hybrids has been synthesized to assess their in vitro antiplasmodial potential against chloroquine-susceptible (3D7) and chloroquine-resistant (W2) strains of Plasmodium falciparum. The most active and noncytotoxic compound had an IC₅₀ value of 0.07 μM against W2 strain and was more active than standard antimalarial drugs, including chloroquine, desethylamodiaquine, and quinine, particularly for drug resistant malaria. The promising scaffold, when subjected to heme binding and molecular modeling studies, was identified as a possible potent inhibitor of hemozoin formation and P. falciparum chloroquine resistance transporter (PfCRT), respectively, and, therefore, could act as a dual function antiplasmodial.

4,9-Diaminoacridines and 4-Aminoacridines as Dual-Stage Antiplasmodial Hits

Multi-stage drugs have been prioritized in antimalarial drug discovery, as targeting more than one process in the Plasmodium life cycle is likely to increase efficiency, while decreasing the chances of emergence of resistance by the parasite. Herein, we disclose two novel acridine-based families of compounds that combine the structural features of primaquine and chloroquine. Compounds prepared and studied thus far retained the in vitro activity displayed by the parent drugs against the erythrocytic stages of chloroquine-sensitive and -resistant Plasmodium falciparum strains, and against the hepatic stages of Plasmodium berghei, hence acting as dual-stage antiplasmodial hits.

Recent advances in indole dimers and hybrids with antibacterial activity against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA), one of the major and most dangerous pathogens in humans, is a causative agent of severe pandemic of mainly skin and soft tissue and occasionally fatal infections. Therefore, it is imperative to develop potent and novel anti-MRSA agents. Indole derivatives could act against diverse enzymes and receptors in bacteria, occupying a salient place in the development of novel antibacterial agents. Dimerization and hybridization are common strategies to discover new drugs, and a number of indole dimers and hybrids possess potential antibacterial activity against a panel of clinically important pathogens including MRSA. Accordingly, indole dimers and hybrids are privileged scaffolds for the discovery of novel anti-MRSA agents. This review outlines the recent development of indole dimers and hybrids with a potential activity against MRSA, covering articles published between 2010 and 2020. The structure-activity relationship and the mechanism of action are also discussed to facilitate further rational design of more effective candidates.

1,2,3-Triazole hybrids with anti-HIV-1 activity

The human immunodeficiency virus type 1 (HIV-1) is the major etiological agent responsible for the acquired immunodeficiency syndrome (AIDS), which is a serious infectious disease and remains one of the most prevalent problems at present. Currently, combined antiretroviral therapy is the primary modality for the treatment and management of HIV/AIDS, but the long-term use can result in major drawbacks such as the development of multidrug-resistant viruses and multiple side effects. 1,2,3-Triazole is the common framework in the development of new drugs, and its derivatives have the potential to inhibit various HIV-1 enzymes such as reverse transcriptase, integrase, and protease, consequently possessing a potential anti-HIV-1 activity. This review covers the recent advances regarding the 1,2,3-triazole hybrids with potential anti-HIV-1 activity; it focuses on the chemical structures, structure-activity relationship, and mechanisms of action, covering articles published from 2010 to 2020.

1,2,3-Triazole-containing hybrids with potential antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA), as a classic reason for genuine skin and flimsy tissues diseases, is a worldwide general wellbeing risk and has already tormented humanity for a long history, creating a critical need for the development of new classes of antibacterials. 1,2,3-Triazole moiety, readily interact with diverse enzymes and receptors in organisms through weak bond interaction, is among the most common frameworks present in the bioactive molecules. 1,2,3-Triazole derivatives, especially 1,2,3-triazole-containing hybrids, possess broad-spectrum activity against a panel of clinically important bacteria including drug-resistant pathogens, so rational design of 1,2,3-triazole derivatives may open a door for the opportunities on the development of novel anti-MRSA agents. This review is an endeavour to highlight the current scenario of 1,2,3-triazole-containing hybrids with potential anti-MRSA activity, covering articles published between 2010 and 2020.

Indole/isatin-containing hybrids as potential antibacterial agents

The emergence and worldwide spread of drug-resistant bacteria have already posed a serious threat to human life, creating the urgent need to develop potent and novel antibacterial drug candidates with high efficacy. Indole and isatin (indole-2,3-dione) present a wide structural and mechanistic diversity, so their derivatives possess various pharmacological properties and occupy a salient place in the development of new drugs. Indole/isatin-containing hybrids, which demonstrate a promising activity against a panel of clinically important Gram-positive and Gram-negative bacteria, are privileged scaffolds for the discovery of novel antibacterial candidates. This review, covering articles published between January 2015 and May 2020, focuses on the development and structure-activity relationship (SAR) of indole/isatin-containing hybrids with potential application for fighting bacterial infections, to facilitate further rational design of novel drug candidates.

Chalcone hybrids as potential anticancer agents: Current development, mechanism of action, and structure-activity relationship

The continuous emergency of drug-resistant cancers and the low specificity of anticancer agents have been the major challenges in the control and treatment of cancer, making an urgent need to develop novel anticancer agents with high efficacy. Chalcones, precursors of flavonoids and isoflavonoids, exhibit structural heterogeneity and can act on various drug targets. Chalcones which demonstrated potential in vitro and in vivo activity against both drug-susceptible and drug-resistant cancers, are useful templates for the development of novel anticancer agents. Hybridization of chalcone moiety with other anticancer pharmacophores could provide the hybrids which have the potential to overcome drug resistance and improve the specificity, so it represents a promising strategy to develop novel anticancer agents. This review emphasizes the development, the mechanisms of action as well as structure-activity relationships of chalcone hybrids with potential therapeutic application for many cancers in recent 10 years.

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.