Antibacterial activity of N-methylbenzofuro[3,2-b]quinoline and N-methylbenzoindolo[3,2-b]-quinoline derivatives and study of their mode of action

Mechanism of antibacterial phytoconstituents: an updated review

The increase of multiple drug resistance bacteria significantly diminishes the effectiveness of antibiotic armory and subsequently exaggerates the level of therapeutic failure. Phytoconstituents are exceptional substitutes for resistance-modifying vehicles. The plants appear to be a deep well for the discovery of novel antibacterial compounds. This is owing to the numerous enticing characteristics of plants, they are easily accessible and inexpensive, extracts or chemicals derived from plants typically have significant levels of action against infections, and they rarely cause serious adverse effects. The enormous selection of phytochemicals offers very distinct chemical structures that may provide both novel mechanisms of antimicrobial activity and deliver us with different targets in the interior of the bacterial cell. They can directly affect bacteria or act together with the crucial events of pathogenicity, in this manner decreasing the aptitude of bacteria to create resistance. Abundant phytoconstituents demonstrate various mechanisms of action toward multi drug resistance bacteria. Overall, this comprehensive review will provide insights into the potential of phytoconstituents as alternative treatments for bacterial infections, particularly those caused by multi drug resistance strains. By examining the current state of research in this area, the review will shed light on potential future directions for the development of new antimicrobial therapies.

Identification of novel 4-substituted 7H-pyrrolo[2,3-d]pyrimidine derivatives as new FtsZ inhibitors: Bioactivity evaluation and computational simulation

Bacterial infections and the consequent outburst of bactericide-resistance issues are fatal menace to both global health and agricultural produce. Hence, it is crucial to explore candidate bactericides with new mechanisms of action. The filamenting temperature-sensitive mutant Z (FtsZ) protein has been recognized as a new promising and effective target for new bactericide discovery. Hence, using a scaffold-hopping strategy, we designed new 7H-pyrrolo[2,3-d]pyrimidine derivatives, evaluated their antibacterial activities, and investigated their structure-activity relationships. Among them, compound B6 exhibited the optimal in vitro bioactivity (EC50 = 4.65 µg/mL) against Xanthomonas oryzae pv. oryzae (Xoo), which was superior to the references (bismerthiazol [BT], EC50 = 48.67 µg/mL; thiodiazole copper [TC], EC50 = 98.57 µg/mL]. Furthermore, the potency of compound B6 in targeting FtsZ was validated by GTPase activity assay, FtsZ self-assembly observation, fluorescence titration, Fourier-transform infrared spectroscopy (FT-IR) assay, molecular dynamics simulations, and morphological observation. The GTPase activity assay showed that the final IC50 value of compound B6 against XooFtsZ was 235.0 μM. Interestingly, the GTPase activity results indicated that the B6-XooFtsZ complex has an excellent binding constant (KA = 103.24 M-1). Overall, the antibacterial behavior suggests that B6 can interact with XooFtsZ and inhibit its GTPase activity, leading to bacterial cell elongation and even death. In addition, compound B6 showed acceptable anti-Xoo activity in vivo and low toxicity, and also demonstrated a favorable pharmacokinetic profile predicted by ADMET analysis. Our findings provide new chemotypes for the development of FtsZ inhibitors as well as insights into their underlying mechanisms of action.

Nanoarchitectonics-Based Materials as a Promising Strategy in the Treatment of Endodontic Infections

Endodontic infections arise from the interactive activities of microbial communities colonizing in the intricate root canal system. The present study aims to update the latest knowledge of nanomaterials, their antimicrobial mechanisms, and their applications in endodontics. A detailed literature review of the current knowledge of nanomaterials used in endodontic applications was performed using the PubMed database. Antimicrobial nanomaterials with a small size, large specific surface area, and high chemical activity are introduced to act as irrigants, photosensitizer delivery systems, and medicaments, or to modify sealers. The application of nanomaterials in the endodontic field could enhance antimicrobial efficiency, increase dentin tubule penetration, and improve treatment outcomes. This study supports the potential of nanomaterials as a promising strategy in treating endodontic infections.

Novel quinoline derivatives with broad-spectrum antiprotozoal activities

Several quinoline derivatives incorporating arylnitro and aminochalcone moieties were synthesized and evaluated in vitro against a broad panel of trypanosomatid protozoan parasites responsible for sleeping sickness (Trypanosoma brucei rhodesiense), nagana (Trypanosoma brucei brucei), Chagas disease (Trypanosoma cruzi), and leishmaniasis (Leishmania infantum). Several of the compounds demonstrated significant antiprotozoal activity. Specifically, compounds 2c, 2d, and 4i displayed submicromolar activity against T. b. rhodesiense with half-maximal effective concentration (EC50) values of 0.68, 0.8, and 0.19 µM, respectively, and with a high selectivity relative to human lung fibroblasts and mouse primary macrophages (∼100-fold). Compounds 2d and 4i also showed considerable activity against T. b. brucei with EC50 values of 1.4 and 0.4 µM, respectively.

Rational molecular design converting fascaplysin derivatives to potent broad-spectrum inhibitors against bacterial pathogens via targeting FtsZ

The filamentous temperature-sensitive mutant Z protein (FtsZ), a key player in bacterial cell division machinery, emerges as an attractive target to tackle the plight posed by the ever growing antibiotic resistance over the world. Therefore in this regard, agents with scaffold diversities and broad-spectrum antibacterial activity against Gram-positive and Gram-negative pathogens are highly needed. In this study, a new class of marine-derived fascaplysin derivatives has been designed and synthesized by Suzuki-Miyaura cross-coupling. Some compounds exhibited potent bactericidal activities against a panel of Gram-positive (MIC = 0.024-6.25 μg/mL) and Gram-negative (MIC = 1.56-12.5 μg/mL) bacteria including methicillin-resistant S. aureus (MRSA). They exerted their effects by dual action mechanism via disrupting the integrity of the bacterial cell membrane and targeting FtsZ protein. These compounds stimulated polymerization of FtsZ monomers and bundling of the polymers, and stabilized the resulting polymer network, thus leading to the dysfunction of FtsZ in cell division. In addition, these agents showed negligible hemolytic activity and low cytotoxicity to mammalian cells. The studies on docking and molecular dynamics simulations suggest that these inhibitors bind to the hydrophilic inter-domain cleft of FtsZ protein and the insights obtained in this study would facilitate the development of potential drugs with broad-spectrum bioactivities.

Intramolecular trapping of an iminium salt: rapid construction of quindoline derivatives

Construction of the pyridine ring is a practical and streamline way to construct a variety of quindoline derivatives. We have developed a novel method for synthesis of quindoline derivatives by means of intramolecular ring-closure reactions of 3-N-methylphenylindoles via an iminium salt intermediate. This practical method has the advantages of a short reaction time, operational simplicity, and nearly quantitative yields; and it can be used for the rapid synthesis of a variety of valuable quindoline derivatives.

Quinoline derivatives volunteering against antimicrobial resistance: rational approaches, design strategies, structure activity relationship and mechanistic insights

Emergence of antimicrobial resistance has become a great threat to human species as there is shortage of development of new antimicrobial agents. So, its mandatary to combat AMR by initiating research and developing new novel antimicrobial agents. Among phytoconstituents, Quinoline (nitrogen containing heterocyclic) have played a wide role in providing new bioactive molecules. So, this review provides rational approaches, design strategies, structure activity relationship and mechanistic insights of newly developed quinoline derivatives as antimicrobial agents.

Design and synthesis of fascaplysin derivatives as inhibitors of FtsZ with potent antibacterial activity and mechanistic study

The increase in antibiotic resistance has made it particularly urgent to develop new antibiotics with novel antibacterial mechanisms. Inhibition of bacterial cell division by disrupting filamentous temperature-sensitive mutant Z (FtsZ) function is an effective and promising approach. A series of novel fascaplysin derivatives with tunable hydrophobicity were designed and synthesized here. The in vitro bioactivity assessment revealed that these compounds could inhibit the tested Gram-positive bacteria including methicillin-resistant S. aureus (MRSA) (MIC = 0.049-25 μg/mL), B. subtilis (MIC = 0.024-12.5 μg/mL) and S. pneumoniae (MIC = 0.049-50 μg/mL). Among them, compounds B3 (MIC = 0.098 μg/mL), B6 (MIC = 0.098 μg/mL), B8 (MIC = 0.049 μg/mL) and B16 (MIC = 0.098 μg/mL) showed the best bactericidal activities against MRSA and no significant tendency to trigger bacterial resistance as well as rapid bactericidal properties. The cell surface integrity of bacteria was significantly disrupted by hydrophobic tails of fascaplysin derivatives. Further studies revealed that these highly active amphiphilic compounds showed low hemolytic activity and cytotoxicity to mammalian cells. Preliminary mechanistic exploration suggests that B3, B6, B8 and B16 are potent FtsZ inhibitors to promote FtsZ polymerization and inhibit GTPase activity of FtsZ, leading to the death of bacterial cells by inhibiting bacterial division. Molecular docking simulations and structure-activity relationship (SAR) study reveal that appropriate increase in the hydrophobicity of fascaplysin derivatives and the addition of additional hydrogen bonds facilitated their binding to FtsZ proteins. These amphiphilic fascaplysin derivatives could serve as a novel class of FtsZ inhibitors, which not only gives new prospects for the application of compounds containing this skeleton but also provides new ideas for the discovery of new antibiotics.

Antibacterial quaternary ammonium agents: Chemical diversity and biological mechanism

Bacterial infections have seriously threatened public health especially with the increasing resistance and the cliff-like decline of the number of newly approved antibacterial agents. Quaternary ammonium compounds (QACs) possess potent medicinal properties with 95 successfully marketed drugs, which also have a long history as antibacterial agents. In this review, we summarize the chemical diversity of antibacterial QACs, divided into chain-like and aromatic ring, reported over the past decade (2012 to mid-2022). Additionally, the structure-activity relationships, mainly covering hydrophobicity, charges and skeleton features, are discussed. In the cases where sufficient information is available, antibacterial mechanisms including biofilm, cell membrane, and intracellular targets are presented. It is hoped that this review will provide sufficient information for medicinal chemists to discover the new generation of antibacterial agents based on QACs.

Design, synthesis and biological evaluation of biphenyl-benzamides as potent FtsZ inhibitors

The rapid emergence of antibiotic resistance has become a prevalent threat to public health, thereby development of new antibacterial agents having novel mechanisms of action is in an urgent need. Targeting at the cytoskeletal cell division protein filamenting temperature-sensitive mutant Z (FtsZ) has been validated as an effective and promising approach for antibacterial drug discovery. In this study, a series of novel biphenyl-benzamides as FtsZ inhibitors has been rationally designed, synthesized and evaluated for their antibacterial activities against various Gram-positive bacteria strains. In particular, the most promising compound 30 exhibited excellent antibacterial activities, especially against four different Bacillus subtilis strains, with an MIC range of 0.008 μg/mL to 0.063 μg/mL. Moreover, compound 30 also showed good pharmaceutical properties with low cytotoxicity (CC₅₀ > 20 μg/mL), excellent human metabolic stability (T_1/2 = 111.98 min), moderate pharmacokinetics (T_1/2 = 2.26 h, F = 61.2%) and in vivo efficacy, which can be identified as a promising FtsZ inhibitor worthy of further profiling.

Design, Synthesis, and Antimicrobial Activity of Quindoline Derivatives Inspired by the Cryptolepine Alkaloid

Based on the structural characteristics of the cryptolepine alkaloid, a series of new quindoline derivatives bearing various substituents were prepared and evaluated for their fungicidal and antibacterial activities. Bioassay results showed that compound D7 displayed superior in vitro fungicidal activities against Sclerotinia sclerotiorum, Botrytis cinerea, Fusarium graminearum, and Rhizoctonia solani with EC₅₀ values of 0.780, 3.62, 1.59, and 2.85 μg/mL, respectively. Compound A7 showed apparent antibacterial activities toward Xanthomonas oryzae pv. oryzae with a minimum inhibitory concentration (MIC) value of 3.12 μg/mL. Significantly, in vivo antifungal activity suggested that the curative effect (98.3%) of compound D7 was comparable to that of the positive control azoxystrobin (96.7%) at 100 μg/mL. Preliminary mechanistic studies showed that compound D7 might cause mycelial abnormality of S. sclerotiorum, cell membrane breakage, accumulation of reactive oxygen species (ROS), and inhibition of sclerotia formation. Therefore, compound D7 could be a novel broad-spectrum fungicidal candidate against plant fungal diseases.

Synthesis, Characterization, and Biological Activities of Novel Vanadium(IV) and Cobalt(II) Complexes

Herein, we report novel Co(II) and V(IV) complexes synthesized from an (E)-2-(((2-((2-hydroxyethyl)amino)quinolin-3-yl)methylene)amino)ethan-1-ol ligand (L), cobalt(II) chloride hexahydrate, and vanadyl(IV) sulfate in methanolic solutions. The ligand and the complexes were characterized by ¹H NMR spectroscopy,¹³C NMR spectroscopy, UV-visible spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), mass spectroscopy (MS), thermal analysis, and molar conductance. The FT-IR spectral data showed that the ligand adopted a tridentate fashion when binding with the metal ions via the nitrogen atoms of the imine (C=N) and amine (N-H), and the oxygen atom of the hydroxyl group (O-H). The PXRD and SEM results indicated that the complexes are amorphous in nature. The density functional theory (DFT) calculated absorption and IR spectra agree very well with the corresponding experimental results. The antibacterial activities of the free ligand and its complexes were evaluated using a paper disk diffusion method. The complexes have better percent activitiy index than the free ligand. The cobalt complex exhibited a more recognizable antibacterial activity than the vanadium complex, specifically against Pseudomonas aeruginosa with a mean inhibition zone of 18.62 ± 0.19 mm, when compared with the positive control, ciprofloxacin, with a mean inhibition zone of 22.98 ± 0.08 mm at the same concentration. Furthermore, the antioxidant activities of the free ligand and its metal complexes were also determined in vitro using 2,2-diphenyl-1-picrylhydrazyl. The ligand exhibited less in vitro antioxidant activity than its transition metal complexes, in which the cobalt complex has a better antioxidant activity with half-inhibitory concentrations (IC₅₀ of 16.01 μg/mL) than the ligand and the vanadium complex. Quantum molecular descriptors from the DFT calculations further support the experimental results. Molecular docking analysis also shed more light on the biological activities of the novel cobalt and vanadium complexes.

Advances in polymer based Friedlander quinoline synthesis

Nitrogen containing heterocyclic compounds has acquired their remarkable and distinct place in the wide area of organic synthesis due to the broad range of applications. Among them, quinoline motifs have attracted researchers in the synthetic chemistry because of its presence in the large number of pharmacologically active compounds. Different methods for synthesis of quinoline derivatives are reported, among them the Friedlander synthesis have provided comparatively more efficient approach. Many of the reported conventional Friedlander methodologies have some problems such as difficult product isolation procedures, poor yields and use of expensive catalysts, etc. Recently, polymer or solid supported synthetic approaches have attracted the attention of researchers because of their easy execution, greater selectivity, increased product yields, simple work-up procedures, recoverability and reusability of the catalysts. In consideration with the advantages of polymer supported synthetic strategies, the proposed review covers the role of polymers in the Friedlander synthesis; which may use polymers of organic, inorganic or hybrid in nature and of nanolevel as well.

Synergy between Indoloquinolines and Ciprofloxacin: An Antibiofilm Strategy against Pseudomonas aeruginosa

Antibiotic treatments can participate in the formation of bacterial biofilm in case of under dosage. The interest of indoloquinoline scaffold for drug discovery incited us to study the preparation of new indolo [2,3-b]quinoline derivatives by a domino radical process. We tested the effect of two different “indoloquinoline” molecules (Indol-1 and Indol-2) without antimicrobial activity, in addition to ciprofloxacin, on biofilm formation thanks to crystal violet staining and enumeration of adhered bacteria. This association of ciprofloxacin and Indol-1 or Indol-2 attenuated the formation of biofilm up to almost 80% compared to ciprofloxacin alone, or even prevented the presence of adhered bacteria. In conclusion, these data prove that the association of non-antimicrobial molecules with an antibiotic can be a solution to fight against biofilm and antibiotic resistance emergence.

Targeting the Achilles Heel of FtsZ: The Interdomain Cleft

Widespread antimicrobial resistance among bacterial pathogens is a serious threat to public health. Thus, identification of new targets and development of new antibacterial agents are urgently needed. Although cell division is a major driver of bacterial colonization and pathogenesis, its targeting with antibacterial compounds is still in its infancy. FtsZ, a bacterial cytoskeletal homolog of eukaryotic tubulin, plays a highly conserved and foundational role in cell division and has been the primary focus of research on small molecule cell division inhibitors. FtsZ contains two drug-binding pockets: the GTP binding site situated at the interface between polymeric subunits, and the inter-domain cleft (IDC), located between the N-terminal and C-terminal segments of the core globular domain of FtsZ. The majority of anti-FtsZ molecules bind to the IDC. Compounds that bind instead to the GTP binding site are much less useful as potential antimicrobial therapeutics because they are often cytotoxic to mammalian cells, due to the high sequence similarity between the GTP binding sites of FtsZ and tubulin. Fortunately, the IDC has much less sequence and structural similarity with tubulin, making it a better potential target for drugs that are less toxic to humans. Over the last decade, a large number of natural and synthetic IDC inhibitors have been identified. Here we outline the molecular structure of IDC in detail and discuss how it has become a crucial target for broad spectrum and species-specific antibacterial agents. We also outline the drugs that bind to the IDC and their modes of action.

Modification of 5-methylphenanthridium from benzothiazoles to indoles as potent FtsZ inhibitors: Broadening the antibacterial spectrum toward vancomycin-resistant enterococci

The death caused by pathogenic bacteria has always been a severe threat to mankind. The prevalence of drug resistance among bacteria underscores an urgent goal for new antibacterial agents with novel mode of action. Here we first designed and synthesized a class of benzothiazolyl-5-methylphenanthridium derivatives and evaluated their antibacterial activity. On this basis, we further designed and synthesized another class of novel indolyl-5-methylphenanthridium derivatives by optimizing the benzothiazolyl-5-methylphenanthridium core and evaluated their antibacterial activity targeting the bacterial cell division protein FtsZ. The results showed that the indolyl-5-methylphenanthridium derivatives had greatly improved activity against various drug-resistant bacterial strains including methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus (VRE). Among them, compound C5 displayed excellent antibacterial activity against susceptible (MIC = 1 μg/mL), methicillin-resistant and clinical isolated S. aureus (MIC = 2 μg/mL). With low hemolytic activity towards mice red blood cells, C5 exhibited good antibacterial effect in vivo in preliminary pharmacodynamic assay. More importantly, C5 was difficult to induce bacterial resistance. Further mechanism studies proved that C5 could inhibit bacterial cell division by promoting FtsZ polymerization, leading to disorderly polymerization and disordered knots. Therefore, our findings suggest that this class of novel indolyl-5-methylphenanthridium derivatives are promising for future antibacterial agents.

Design, synthesis and evaluation of novel 9-arylalkyl-10-methylacridinium derivatives as highly potent FtsZ-targeting antibacterial agents

With the increasing incidence of antibiotic resistance, new antibacterial agents having novel mechanisms of action hence are in an urgent need to combat infectious diseases caused by multidrug-resistant (MDR) pathogens. Four novel series of substituted 9-arylalkyl-10-methylacridinium derivatives as FtsZ inhibitors were designed, synthesized and evaluated for their antibacterial activities against various Gram-positive and Gram-negative bacteria. The results demonstrated that they exhibited broad-spectrum activities with substantial efficacy against MRSA and VRE, which were superior or comparable to the berberine, sanguinarine, linezolid, ciprofloxacin and vancomycin. In particular, the most promising compound 15f showed rapid bactericidal properties, which avoid the emergence of drug resistance. However, 15f showed no inhibitory effect on Gram-negative bacteria but biofilm formation study gave possible answers. Further target identification and mechanistic studies revealed that 15f functioned as an effective FtsZ inhibitor to alter the dynamics of FtsZ self-polymerization, which resulted in termination of the cell division and caused cell death. Further cytotoxicity and animal studies demonstrated that 15f not only displayed efficacy in a murine model of bacteremia in vivo, but also no significant hemolysis to mammalian cells. Overall, this compound with novel skeleton could serve as an antibacterial lead of FtsZ inhibitor for further evaluation of drug-likeness.

Design, Synthesis, and Antifungal Evaluation of Cryptolepine Derivatives against Phytopathogenic Fungi

Inspired by the widely antiphytopathogenic application of diversified derivatives from natural sources, cryptolepine and its derivatives were subsequently designed, synthesized, and evaluated for their antifungal activities against four agriculturally important fungi Rhizoctonia solani, Botrytis cinerea, Fusarium graminearum, and Sclerotinia sclerotiorum. The results obtained from in vitro assay indicated that compounds a1-a24 showed great fungicidal property against B. cinerea (EC₅₀ < 4 μg/mL); especially, a3 presented significantly prominent inhibitory activity with an EC₅₀ of 0.027 μg/mL. In the pursuit of further expanding the antifungal spectrum of cryptolepine, ring-opened compound f1 produced better activity with an EC₅₀ of 3.632 μg/mL against R. solani and an EC₅₀ of 5.599 μg/mL against F. graminearum. Furthermore, a3 was selected to be a candidate to investigate its preliminary antifungal mechanism to B. cinerea, revealing that not only spore germination was effectively inhibited and the normal physiological structure of mycelium was severely undermined but also detrimental reactive oxygen was obviously accumulated and the normal function of the nucleus was fairly disordered. Besides, in vivo curative experiment against B. cinerea found that the therapeutic action of a3 was comparable to that of the positive control azoxystrobin. These results suggested that compound a3 could be regarded as a novel and promising agent against B. cinerea for its valuable potency.

Engineered N-doped graphene quantum dots/CoFe2O4 spherical composites as a robust and retrievable catalyst: fabrication, characterization, and catalytic performance investigation in microwave-assisted synthesis of quinoline-3-carbonitrile derivatives

Nitrogen-doped graphene quantum dots (N-GQDs), which are less than 10 nm in size, are an interesting member of the nanocarbon materials family. N-GQDs nanostructures have been broadly applied in various fields, such as drug-gene delivery systems, photocatalytic reactions, and catalysts, owing to their unique properties. However, N-GQDs have rarely been introduced as a catalyst in organic synthesis. Herein, CoFe₂O₄ nanocomposites with diverse morphologies are fabricated in various conditions (e.g. green routes, various pH adjusters, temperatures). Due to further active sites on the surface of the nanocomposites, morphology engineering can be effective in catalytic activities. Following the synthesis, the catalytic activity of the engineered CoFe₂O₄ nanocomposites was screened, and it presented the order of spherical > rod > prism > cubic. The uniform spherical morphology provides more accessible active sites. Then, the novel nano-sized N-GQDs/CoFe₂O₄ magnetic spherical composite was readily fabricated by a green, low-cost, and easy hydrothermal route. The engineered composite was applied as an efficient magnetic nanocatalyst for the MW-assisted one-pot synthesis of new and known quinoline-3-carbonitrile derivatives (83–96%) in the shortest reaction time (60–90 s). Furthermore, the green route, easy separation of the nanocatalyst, and reusability (7 runs) without noticeable loss of catalytic efficiency are other advantages.

Sustainable fabrication of spherical N-GQDs/CoFe₂O₄ nanocomposites as a novel magnetically retrievable catalyst for the synthesis of quinoline-3-carbonitrile derivatives has been developed.

Potential antibacterial and antifungal activities of novel sulfamidophosphonate derivatives bearing the quinoline or quinolone moiety

A series of new α‐sulfamidophosphonate/sulfonamidophosphonate (4a–n) and cyclosulfamidophosphonate (5a–d) derivatives containing the quinoline or quinolone moiety was designed and synthesized via Kabachnik–Fields reaction in the presence of ionic liquid under ultrasound irradiation. This efficient methodology provides new 1,2,5‐thiadiazolidine‐1,1‐dioxide derivatives 5a–d in one step and optimal conditions. The molecular structures of the novel compounds 4a–n and 5a–d were confirmed using various spectroscopic methods. All these compounds were evaluated for their in vitro antibacterial activity against Gram‐negative (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853) and Gram‐positive (Staphylococcus aureus ATCC 27923) bacteria, in addition to three clinical strains (E. coli 1, P. aeruginosa 1, and S. aureus 1). Most of the tested compounds showed more potent inhibitory activities against both Gram‐positive and ‐negative bacteria compared with the sulfamethoxazole reference. The following compounds, 4n, 4f, 4g, 4m, 4l, 4d, and 4e, are the most active sulfamidophosphonate derivatives. Furthermore, these molecules gave interesting zones of inhibition varying between 28 and 49 mm, against all tested bacterial strains, with a low minimum inhibitory concentration (MIC) value ranging from 0.125 to 8 μg/ml. All the synthesized derivatives were also evaluated for their in vitro antifungal activity against Fusarium oxyporum f. sp. lycopersici and Alternaria sp. The results revealed that all the synthesized compounds exhibited excellent antifungal inhibition and the compounds 4f, 4g, 4m, and 4i were the most potent derivatives with MIC values ranging from 0.25 to 1 µg/ml against the two tested fungal strains. The strongest inhibition of bacteria and fungi strains was detected by the effect of quinolone and sulfamide moieties.

Cell division protein FtsZ: from structure and mechanism to antibiotic target

Antimicrobial resistance to virtually all clinically applied antibiotic classes severely limits the available options to treat bacterial infections. Hence, there is an urgent need to develop and evaluate new antibiotics and targets with resistance-breaking properties. Bacterial cell division has emerged as a new antibiotic target pathway to counteract multidrug-resistant pathogens. New approaches in antibiotic discovery and bacterial cell biology helped to identify compounds that either directly interact with the major cell division protein FtsZ, thereby perturbing the function and dynamics of the cell division machinery, or affect the structural integrity of FtsZ by inducing its degradation. The impressive antimicrobial activities and resistance-breaking properties of certain compounds validate the inhibition of bacterial cell division as a promising strategy for antibiotic intervention.

A review on quinoline derivatives as anti-methicillin resistant Staphylococcus aureus (MRSA) agents

Methicillin Resistant Staphylococcus aureus (MRSA) consists of strains of S. aureus which are resistant to methicillin. The resistance is due to the acquisition of mecA gene which encodes PBP2a unlike of any PBPs normally produced by S. aureus. PBP2a shows unusually low β-Lactam affinity and remains active to allow cell wall synthesis at normally lethal β-Lactam concentrations. MRSA can cause different types of infections like Healthcare associated MRSA, Community associated MRSA and Livestock associated MRSA infections. It causes skin lesions, osteomyelitis, endocarditis and furunculosis. To treat MRSA infections, only a few options are available like vancomycin, clindamycin, co-trimoxazole, fluoroquinolones or minocycline and there is a dire need of discovering new antibacterial agents that can effectively treat MRSA infections. In the current review, an attempt has been made to compile the data of quinoline derivatives possessing anti-MRSA potential reported to date.

Ionically Tagged Magnetic Nanoparticles with Urea Linkers: Application for Preparation of 2-Aryl-quinoline-4-carboxylic Acids via an Anomeric-Based Oxidation Mechanism

In this exploration, we reported the design and synthesis of a novel ionically tagged magnetic nanoparticles bearing urea linkers, namely, Fe₃O₄@SiO₂@(CH₂)₃-urea-thiazole sulfonic acid chloride. The structure of the mentioned compound was fully characterized by using several techniques including Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis, elemental mapping analysis, thermogravimetric analysis/differential thermal analysis, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometer. In the presence of the novel reusable catalyst, applied starting materials including aryl aldehydes, pyruvic acid, and 1-naphthylamine condensed to afford the desired 2-aryl-quinoline-4-carboxylic acid derivatives via an anomeric-based oxidation pathway under solvent-free conditions.

The cell division protein FtsZ as a cellular target to hit cystic fibrosis pathogens

Cystic fibrosis is a rare genetic disease characterized by the production of dehydrated mucus in the lung able to trap bacteria and rendering their proliferation particularly dangerous, thus leading to chronic infections. Among these bacteria, Staphylococcus aureus and Pseudomonas aeruginosa play a major role while, within emerging pathogens, Stenotrophomonas maltophilia, Achromobacter xylosoxidans, Burkholderia cepacia complex species, as well as non-tuberculous mycobacteria are listed. Since a common feature of these bacteria is the high level of drug resistance, cell division, and in particular FtsZ, has been explored as a novel therapeutic target for the design of new molecules with antibacterial properties. This review summarizes and provides insight into recent advances in the discovery of compounds targeting FtsZ: the majority of them exhibit anti-staphylococcal activity, while a few were directed against the cystic fibrosis Gram negative pathogens.

Targeting Bacterial Cell Division: A Binding Site-Centered Approach to the Most Promising Inhibitors of the Essential Protein FtsZ

Binary fission is the most common mode of bacterial cell division and is mediated by a multiprotein complex denominated the divisome. The constriction of the Z-ring splits the mother bacterial cell into two daughter cells of the same size. The Z-ring is formed by the polymerization of FtsZ, a bacterial protein homologue of eukaryotic tubulin, and it represents the first step of bacterial cytokinesis. The high grade of conservation of FtsZ in most prokaryotic organisms and its relevance in orchestrating the whole division system make this protein a fascinating target in antibiotic research. Indeed, FtsZ inhibition results in the complete blockage of the division system and, consequently, in a bacteriostatic or a bactericidal effect. Since many papers and reviews already discussed the physiology of FtsZ and its auxiliary proteins, as well as the molecular mechanisms in which they are involved, here, we focus on the discussion of the most compelling FtsZ inhibitors, classified by their main protein binding sites and following a medicinal chemistry approach.

Recent advances and prospects in the metal-free synthesis of quinolines

Metal-free synthesis of quinolines has recently gained attention, and this review focuses on the recent advances in the metal-free synthesis of quinolines.

Recent Progress in the Development of Small-Molecule FtsZ Inhibitors as Chemical Tools for the Development of Novel Antibiotics

Antibiotics are potent pharmacological weapons against bacterial pathogens, nevertheless their efficacy is becoming compromised due to the worldwide emergence and spread of multidrug-resistant bacteria or "superbugs". Antibiotic resistance is rising to such dangerous levels that the treatment of bacterial infections is becoming a clinical challenge. Therefore, urgent action is needed to develop new generations of antibiotics that will help tackle this increasing and serious public health problem. Due to its essential role in bacterial cell division, the tubulin-like protein FtsZ has emerged as a promising target for the development of novel antibiotics with new mechanisms of action. This review highlights the medicinal chemistry efforts towards the identification of small-molecule FtsZ inhibitors with antibacterial activity in the last three years.

Indole-core-based novel antibacterial agent targeting FtsZ

Background

The prevalence of drug-resistant bacterial infections urges the development of new antibacterial agents that possess a mechanism of action different from traditional antibiotics. FtsZ has been recognized as a key functional protein in bacterial cell division and it is currently believed to be a potential target for the development of novel antibacterial agents.

Purpose

The primary aim of the study is to screen out an inhibitor targeting at FtsZ and followed to investigate its antibacterial activity and mode of action.

Methods

Cell-based cell division inhibitory screening assay, antimicrobial susceptibility test, minimum bactericidal concentration assay, time-killing curve determination, FtsZ polymerization assay, GTPase activity assay, and molecular modeling were performed in the present study.

Results

The screening study from a small library consisting of benzimidazole and indole derivatives discovered a compound (CZ74) with an indole-core structure. The compound exhibited strong cell division inhibitory effect. In addition, CZ74 shows high antibacterial potency against a number of tested Gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus. The minimum inhibitory concentration values obtained were within the range of 2–4 µg/mL. The results of biological study revealed that CZ74 at 2 µg/mL is able to disrupt FtsZ polymerization and inhibit GTPase activity and cell division. From molecular modeling study, CZ74 is found possibly binding into the interdomain cleft of FtsZ protein and then leads to inhibitory effects.

Conclusion

This indole-cored molecule CZ74 could be a potential lead compound and could be further developed as a new generation of antibacterial agents targeting FtsZ to combat against multidrug-resistant bacteria.

Review on plant antimicrobials: a mechanistic viewpoint

Microbial resistance to classical antibiotics and its rapid progression have raised serious concern in the treatment of infectious diseases. Recently, many studies have been directed towards finding promising solutions to overcome these problems. Phytochemicals have exerted potential antibacterial activities against sensitive and resistant pathogens via different mechanisms of action. In this review, we have summarized the main antibiotic resistance mechanisms of bacteria and also discussed how phytochemicals belonging to different chemical classes could reverse the antibiotic resistance. Next to containing direct antimicrobial activities, some of them have exerted in vitro synergistic effects when being combined with conventional antibiotics. Considering these facts, it could be stated that phytochemicals represent a valuable source of bioactive compounds with potent antimicrobial activities.

Antibacterial evaluation and mode of action study of BIMQ, a novel bacterial cell division inhibitor

The worldwide spreading of antibiotic resistant bacteria is currently an extremely serious health risk and therefore to develop new antibiotics is an urgent need. In the present study, the antibacterial activity of a new indolyl quinolinium compound and its underline mechanism were investigated. The compound shows an outstanding antibacterial activity against the tested Gram-positive bacteria. The MIC values are in the range of 1-4 μg/mL. The elongation of B. subtilis cells indicates that the compound can inhibit cell division effectively. In addition, the biochemical studies prove that the compound is able to disrupt FtsZ polymerization effectively through a stimulatory mechanism. Furthermore, the compound can delay the development of drug resistance mutants.

Antibacterial activity and mechanism of action of a thiophenyl substituted pyrimidine derivative

The issue of multidrug resistant bacteria is a worldwide health threat. To develop new antibacterial agents with new mechanisms of action is thus an urgent request to address this antibiotic resistance crisis. In the present study, a new thiophenyl-pyrimidine derivative was prepared and utilized as an effective antibacterial agent against Gram-positive strains. In the tests against MRSA and VREs, the compound showed higher antibacterial potency than that of vancomycin and methicillin. The mode of action is probably attributed to the effective inhibition of FtsZ polymerization, GTPase activity, and bacterial cell division, which cause bactericidal effects. The compound could be a potential candidate for further development as an effective antibiotic to combat drug-resistant bacteria.

F20 exhibits strong antibacterial activity through interacting with FtsZ.

Green recipes to quinoline: A review

The quinoline core possesses a vast number of biological activities such as anticancer, antimalarial, antimicrobial, antifungal, antitubercular and antileishmanial. The conventional classical synthetic methods require the use of expensive and harsh conditions such as high temperature. Currently the scientific communities are searching new methodology to eliminate the use of chemicals, solvents and catalysts, which are hazardous to human health as well as to environment. This review provides a concise overview of new dimensions of green chemistry approaches in designing quinoline scaffold that would encourage the researchers towards green chemistry as well as future application of these greener, non-toxic, environment friendly methods in designing quinoline scaffold.

Antibacterial activity of 3-methylbenzo[d]thiazol-methylquinolinium derivatives and study of their action mechanism

The increasing incidence of multidrug resistant bacterial infection renders an urgent need for the development of new antibiotics. To develop small molecules disturbing FtsZ activity has been recognized as promising approach to search for antibacterial of high potency systematically. Herein, a series of novel quinolinium derivatives were synthesized and their antibacterial activities were investigated. The compounds show strong antibacterial activities against different bacteria strains including MRSA, VRE and NDM-1 Escherichia coli. Among these derivatives, a compound bearing a 4-fluorophenyl group (A2) exhibited a superior antibacterial activity and its MICs to the drug-resistant strains are found lower than those of methicillin and vancomycin. The biological results suggest that these quinolinium derivatives can disrupt the GTPase activity and dynamic assembly of FtsZ, and thus inhibit bacterial cell division and then cause bacterial cell death. These compounds deserve further evaluation for the development of new antibacterial agents targeting FtsZ.

Competitive Fitness of Essential Gene Knockdowns Reveals a Broad-Spectrum Antibacterial Inhibitor of the Cell Division Protein FtsZ

To streamline the elucidation of antibacterial compounds' mechanism of action, comprehensive high-throughput assays interrogating multiple putative targets are necessary. However, current chemogenomic approaches for antibiotic target identification have not fully utilized the multiplexing potential of next-generation sequencing. Here, we used Illumina sequencing of transposon insertions to track the competitive fitness of a Burkholderia cenocepacia library containing essential gene knockdowns. Using this method, we characterized a novel benzothiadiazole derivative, 10126109 (C109), with antibacterial activity against B. cenocepacia, for which whole-genome sequencing of low-frequency spontaneous drug-resistant mutants had failed to identify the drug target. By combining the identification of hypersusceptible mutants and morphology screening, we show that C109 targets cell division. Furthermore, fluorescence microscopy of bacteria harboring green fluorescent protein (GFP) cell division protein fusions revealed that C109 prevents divisome formation by altering the localization of the essential cell division protein FtsZ. In agreement with this, C109 inhibited both the GTPase and polymerization activities of purified B. cenocepacia FtsZ. C109 displayed antibacterial activity against Gram-positive and Gram-negative cystic fibrosis pathogens, including Mycobacterium abscessus C109 effectively cleared B. cenocepacia infection in the Caenorhabditis elegans model and exhibited additive interactions with clinically relevant antibiotics. Hence, C109 is an enticing candidate for further drug development.

Study of Benzofuroquinolinium Derivatives as a New Class of Potent Antibacterial Agent and the Mode of Inhibition Targeting FtsZ

New generation of antibacterial agents are urgently needed in order to fight the emergence of multidrug-resistant bacteria. FtsZ is currently identified as a promising target for new types of antimicrobial compounds development because of its conservative characteristics and its essential role played in bacterial cell division. In the present study, the antibacterial activity of a series of benzofuroquinolinium derivatives was investigated. The results show that the compounds possess potent antibacterial activity against drug resistant pathogens including MRSA, VREF and NDM-1 Escherichia coli. Biological studies reveal that the compound is an effective inhibitor that is able to suppress FtsZ polymerization and GTPase activity and thus stopping the cell division and causing cell death. More importantly, this series of compounds shows low cytotoxicity on mammalian cells and therefore they could be new chemotypes for the development of new antibacterial agents targeting the cell-division protein FtsZ.