New Efforts toward Aminothiazolylquinolones with Multitargeting Antibacterial Potential

Identification of hydroxyphenyl cyanovinyl thiazoles as new structural scaffold of potential antibacterial agents

Unique hydroxyphenyl cyanovinyl thiazoles (HCTs) as new structural scaffolds of potential antibacterial agents were developed to overcome global increasingly serious drug resistance. Some synthesized HCTs could suppress the growth of the tested strains, especially, benzothiophenyl HCT 5c exhibited superior anti-Escherichia coli activity with a lower MIC of 0.5 μg/mL to norfloxacin (MIC = 1 μg/mL). The active benzothiophenyl HCT 5c displayed no obvious hemolysis, low cytotoxicity and a much lower trend for the development of drug-resistance than norfloxacin. Further exploration revealed that benzothiophenyl HCT 5c could intercalate to DNA to form a DNA-5c complex, which disturbed the biological functions to facilitate bacterial death. ADME analysis indicated that compound 5c possessed favorable druggability and promising pharmacokinetic properties. This work provided an insight into further developing hydroxyphenyl cyanovinyl thiazoles as new structural scaffold of promising antibacterial candidates.

Cationic conjugated microporous polymers for efficient quinolone antibiotics extraction: Experimental and DFT study

The development of exquisitely sensitive analytical methods for the surveillance of quinolone antibiotics (QAs) holds pivotal significance in safeguarding both ecosystems and human well-being. In this work, a cationic conjugated microporous polymer (iCMP) was constructed through a facile post-synthetic approach. Capitalizing on its unique dual-porosity architecture, cationic framework, and π-conjugated backbone, iCMP exhibited exceptional adsorption capabilities and remarkable repeatability. Integrating with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), a solid-phase extraction (SPE) method founded on iCMP was meticulously developed for the sensitive and accurate detection of QAs within complex matrices. This proposed analytical method exhibited remarkably low limits of detection, specifically 0.0200-0.128 ng·L-1 for water samples and 0.0250-0.105 ng·g-1 for meat samples, along with good accuracy in the range of 70.9 %-115 %. The underlying adsorption mechanism was comprehensively investigated using a synergistic approach that combined systematic adsorption experiments, density functional theory (DFT) calculations, and in-depth material characterizations. Overall, this study presents viable strategies for the precise trace-level analysis of QAs in complex environmental and food samples.

Benzo-α-pyrone-derived multitargeting actions to enhance the antibacterial performance of sulfanilamides against Escherichia coli

A novel class of benzopyrone-sulfanilamide hybrids was synthesized from phenols via multi-step reactions. Some prepared compounds effectively suppressed bacterial growth at low concentrations, and especially, sulfanilamide-hybridized 2-methyl-5-nitroimidazolyl benzopyrone 11c exhibited significant inhibitory potency against Escherichia coli (MIC = 0.0022 mM), which was 11-fold more active than clinical norfloxacin. Furthermore, compound 11c showed negligible hemolytic activity, low cytotoxicity and no drug resistance. Mechanistic studies indicated that the highly active 11c disrupted bacterial membrane integrity, reduced metabolic activity, bound DNA grooves to inhibit replication without the ability to cleave DNA, and induced reactive oxygen species (ROS) accumulation, collectively leading to bacterial death. These results highlight the potential of sulfanilamide-hybridized benzopyrones as multitarget antibacterial agents, warranting further development to combat bacterial infections.

A comprehensive insight into naphthalimides as novel structural skeleton of multitargeting promising antibiotics

The globally growing antimicrobial resistance seriously threatens human health, increasing efforts have been devoting to the development of novel antibiotics. Naphthalimides contain a special skeleton of cyclic double imides and the naphthalene framework, this unique structure can exert multitargeting abilities which are helpful to overcome the escalating issue of resistance. Therefore, research in connection with the development of naphthalimides as novel antimicrobial agents is becoming progressively active. It has been revealed that naphthalimides as novel structural skeleton of multitargeting promising antibiotics could not only target DNAs and enzymes, disturb membrane, produce reactive oxygen species, etc. suggesting the multitargeting actions which do not induce resistance, but also show a broad antimicrobial spectrum with safety profile and pharmacokinetic characteristics, implying large potential as a new type of antibiotics via continuous efforts toward antimicrobial naphthalimides. This review presents naphthalimides as a new type of potential antimicrobial agents and discusses rational design strategies, structure-activity relationships, and mechanisms of action, with a comprehensive view to providing a new insight for in the rational design of efficient, broad-spectrum, and low-toxic naphthalimide antibiotics.

Design, Synthesis, and Bioactivity Evaluation of Novel 1-Methyl-2-phenylpyridin-1-ium Derivatives as Broad-Spectrum FtsZ Inhibitors

To address the threat of bacterial infections in animal husbandry, a novel class of 1-methyl-2-phenylpyridin-1-ium derivatives has been designed and synthesized as broad-spectrum antibacterial agents to counteract increasing multidrug resistance. Biological assays revealed that compounds 4n, 16b, 16c, and 16e exhibited superior inhibition of S. aureus ATCC25923 (MICs = 0.0625-0.5 μg/mL) and A. baumannii ATCC19606 (MICs = 1-4 μg/mL) compared to linezolid and vancomycin. Mechanistic studies revealed that 16e promoted FtsZ polymerization, disrupted proton gradients, and increased the bacterial membrane permeability. Hemolytic toxicity assessments confirmed the favorable biological safety profile of 16e. In vivo studies using a mouse model of bacteremia demonstrated the superior antibacterial efficacy of 16e to linezolid. Molecular dynamics simulations showed that 16e could maintain the FtsZ protein in the T state, which was conducive to FtsZ polymerization. These results provide new therapeutic strategies to deal with the emerging bacterial resistance in animal husbandry.

Unlocking the Antibacterial Potential of Naphthalimide-Coumarins to Overcome Drug Resistance with Antibiofilm and Membrane Disruption Ability against Escherichia coli

Resistance by bacteria to available antibiotics is a threat to human health, which demands the development of new antibacterial agents. Considering the prevailing conditions, we have developed a library of new naphthalimide-coumarin moieties as broad-spectrum antibacterial agents to fight against awful drug resistance. Preliminary studies indicate that compounds 8e and 8h display excellent antibacterial activity against Escherichia coli, exceeding the performance of marketed drug amoxicillin. These drug candidates effectively inhibit biofilm formation and disrupt the biofilm virulence factor, which is accountable for the formation of strong biofilm. In addition to this, both compounds exhibit fast bactericidal properties, thus shortening the time of treatment and resisting the emergence of drug resistance for up to 20 passages. Further, biofunctional evaluation reveals that both compounds effectively disrupt the membrane, causing the leakage of cytoplasmic contents and loss in metabolic activity. Both compounds 8e and 8h efficiently induce the ROS, leading to the oxidation of GSH to GSSG, decreasing the GSH activity of the cell, and causing oxidative damage to the cells. Additionally, both compounds effectively bind with DNA to block DNA replication and form supramolecular complexes, thus exhibiting antibacterial activity. Moreover, these compounds readily bind human serum albumin with high binding constants and can be transported to the target site easily. These findings reveal that newly synthesized naphthalimide-coumarin conjugates have the potential to build as potent antibacterial agents and can be used further for clinical trials.

Discovery of Quinazolone Pyridiniums as Potential Broad-Spectrum Antibacterial Agents

The overprescription of antibiotics in medicine and agriculture has accelerated the development and spread of antibiotic resistance in bacteria, which severely limits the arsenal available to clinicians for treating bacterial infections. This work discovered a new class of heteroarylcyanovinyl quinazolones and quinazolone pyridiniums to surmount the increasingly severe bacterial resistance. Bioactive assays manifested that the highly active compound 19a exhibited strong inhibition against MRSA and Escherichia coli with extremely low MICs of 0.5 μg/mL, being eightfold more active than that of norfloxacin (MICs = 4 μg/mL). The highly active 19a with rapid bactericidal properties displayed imperceptible resistance development trends, negligible hemolytic toxicity, and effective biofilm inhibitory effects. Preliminary explorations on antibacterial mechanisms revealed that compound 19a could cause membrane damage, embed in intracellular DNA to hinder bacterial DNA replication, and induce metabolic dysfunction. Surprisingly, active 19a was found to trigger the conformational change in PBP2a of MRSA to open the active site, which might account for its high inhibition against MRSA. In addition, the little effect of molecule 19a on the production of reactive oxygen species indicated that bacterial death was not caused by oxidative stress. The above comprehensive analyses highlighted the large potential of quinazolone pyridiniums as multitargeting broad-spectrum antibacterial agents.

Synthesis and antibacterial medicinal evaluation of carbothioamido hydrazonyl thiazolylquinolone with multitargeting antimicrobial potential to combat increasingly global resistance

The global microbial resistance is a serious threat to human health, and multitargeting compounds are considered to be promising to combat microbial resistance. In this work, a series of new thiazolylquinolones with multitargeting antimicrobial potential were developed through multi-step reactions using triethoxymethane and substituted anilines as start materials. Their structures were confirmed by 1H NMR, 13C NMR and HRMS spectra. Antimicrobial evaluation revealed that some of the target compounds could effectively inhibit microbial growth. Especially, carbothioamido hydrazonyl aminothiazolyl quinolone 8a showed strong inhibitory activity toward drug-resistant Staphylococcus aureus with MIC value of 0.0047 mM, which was 5-fold more active than that of norfloxacin. The highly active compound 8a exhibited negligible hemolysis, no significant toxicity in vitro and in vivo, low drug resistance, as well as rapidly bactericidal effects, which suggested its favorable druggability. Furthermore, compound 8a was able to effectively disrupt the integrity of the bacterial membrane, intercalate into DNA and inhibit the activity of topoisomerase IV, suggesting multitargeting mechanism of action. Compound 8a could form hydrogen bonds and hydrophobic interactions with DNA-topoisomerase IV complex, indicating the insertion of aminothiazolyl moiety was beneficial to improve antibacterial efficiency. These findings indicated that the active carbothioamido hydrazonyl aminothiazolyl quinolone 8a as a chemical therapeutic candidate demonstrated immense potential to tackle drug-resistant bacterial infections.

Natural Prenylflavonoids from Sophora flavescens Root Bark against Multidrug-Resistant Methicillin-Sensitive Staphylococcus aureus Targeting the Membrane Permeability

The overuse of antibiotics in animal farming and aquaculture has led to multidrug-resistant methicillin-sensitive Staphylococcus aureus (MR-MSSA) becoming a common pathogen in foodborne diseases. Sophora flavescens Ait. serves as a traditional plant antibacterial agent and functional food ingredient. A total of 30 compounds (1-30) were isolated from the root bark of S. flavescens, consisting of 20 new compounds (1-20). In the biological activity assay, compound 1 demonstrated a remarkable inhibitory effect on MR-MSSA, with an MIC of 2 μg/mL. Furthermore, 1 was found to rapidly eliminate bacteria, inhibit biofilm growth, and exhibit exceptionally low cytotoxicity. Mechanistic studies have revealed that 1 possesses an enhanced membrane-targeting ability, binding to the bacterial cell membrane components phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and cardiolipin (CL). This disruption of bacterial cell membrane integrity increases intracellular reactive oxygen species, protein and DNA leakage, reduced bacterial metabolism, and ultimately bacterial death. In summary, these findings suggest that compound 1 holds promise as a lead compound against MR-MSSA.

Unique aminothiazolyl coumarins as potential DNA and membrane disruptors towards Enterococcus faecalis

Aminothiazolyl coumarins as potentially new antimicrobial agents were designed and synthesized in an effort to overcome drug resistance. Biological activity assay revealed that some target compounds exhibited significantly inhibitory efficiencies toward bacteria and fungi including drug-resistant pathogens. Especially, aminothiazolyl 7-propyl coumarin 8b and 4-dichlorobenzyl derivative 11b exhibited bactericidal potential (MBC/MIC = 2) toward clinically drug-resistant Enterococcus faecalis with low cytotoxicity to human lung adenocarcinoma A549 cells, rapidly bactericidal effects and no obvious bacterial resistance development against E. faecalis. The preliminary antibacterial action mechanism studies suggested that compound 11b was able to disturb E. faecalis membrane effectively, and interact with bacterial DNA isolated from resistant E. faecalis through noncovalent bonds to cleave DNA, thus inhibiting the growth of E. faecalis strain. Further molecular modeling indicated that compounds 8b and 11b could bind with SER-1084 and ASP-1083 residues of gyrase-DNA complex through hydrogen bonds and hydrophobic interactions. Moreover, compound 11b showed low hemolysis and in vivo toxicity. These findings of aminothiazolyl coumarins as unique structural scaffolds might hold a large promise for the treatments of drug-resistant bacterial infection.

Cyanomethylquinolones as a New Class of Potential Multitargeting Broad-Spectrum Antibacterial Agents

This work identified a class of cyanomethylquinolones (CQs) and their carboxyl analogues as potential multitargeting antibacterial candidates. Most of the prepared compounds showed high antibacterial activities against most of the tested bacteria, exhibiting lower MIC values (0.125-2 μg/mL) than those of clinical norfloxacin, ciprofloxacin, and clinafloxacin. The low hemolysis, drug resistance, and cytotoxicity, as well as good predictive pharmacokinetics of active CQs and carboxyl analogues revealed their development potential. Furthermore, they could eradicate the established biofilm, facilitating bacterial exposure to these antibacterial candidates. These active compounds could induce bacterial death through multitargeting effects, including intercalating into DNA, up-regulating reactive oxygen species, damaging membranes directly, and impeding metabolism. Moreover, the highly active cyclopropyl CQ 15 exhibited more effective in vivo anti-MRSA potency than ciprofloxacin. These findings highlight the potential of CQs and their carboxyl analogues as multitargeting broad-spectrum antibacterial candidates for treating intractable bacterial infections.

Bacterial cell death to overcome drug resistance with multitargeting bis-naphthalimides as potent antibacterial agents against Enterococcus faecalis

The increasing frequency of drug-resistant pathogens poses serious health issues to humans around the globe, leading to the development of new antibacterial agents to conquer drug resistance and bacterial infections. In view of this, we have synthesized a series of bis-naphthalimides to respond to awful drug resistance. Bioactivity assay and structure-activity relationship disclosed that compounds 5d and 5o exhibit potent antibacterial activity against E. faecalis, outperforming the marketed antibiotics. These drug candidates not only inhibit the biofilm formation of E. faecalis but also display rapid bactericidal properties, thus delaying the development of drug resistance within 20 passages. To explore the mechanism of antibacterial activity against E. faecalis, biofunctional examination was carried out which unveiled that 5d and 5o effectively disrupt bacterial cell membranes, causing the leakage of cytoplasmic contents and metabolic activity loss. Concurrently, 5d and 5o effectively intercalate with DNA to block DNA replication, causing the build-up of excessive reactive oxygen species and inhibiting the glutathione activity, ultimately leading to oxidative damage of E. faecalis and cell death. In addition, these compounds readily bind with HSA with a high binding constant, indicating that these drug candidates could be easily delivered to the target site. The above finding manifested that these newly synthesized bis-naphthalimides with multitargeting antibacterial properties offer a new prospect to overcome drug resistance.

Hydrazyl hydroxycoumarins as new potential conquerors towards Pseudomonas aeruginosa

A class of unique hydrazyl hydroxycoumarins (HHs) as novel structural scaffold was developed to combat dreadful bacterial infections. Some HHs could effectively suppress bacterial growth at low concentrations, especially, pyridyl HH 7 exhibited a good inhibition against Pseudomonas aeruginosa 27853 with a low MIC value of 0.5 μg/mL, which was 8-fold more active than norfloxacin. Furthermore, pyridyl HH 7 with low hemolytic activity and low cytotoxicity towards NCM460 cells showed much lower trend to induce the drug-resistant development than norfloxacin. Preliminarily mechanism exploration indicated that pyridyl HH 7 could eradicate the integrity of bacterial membrane, result in the leakage of intracellular proteins, and interact with bacterial DNA gyrase via non-covalent binding, and ADME analysis manifested that compound 7 gave good pharmacokinetic properties. These results suggested that the newly developed hydrazyl hydroxycoumarins as potential multitargeting antibacterial agents should be worthy of further investigation for combating bacterial infection.

Discovery of indolylacryloyl-derived oxacins as novel potential broad-spectrum antibacterial candidates

The emergence of serious bacterial resistance towards clinical oxacins poses a considerable threat to global public health, necessitating the development of novel structural antibacterial agents. Seven types of novel indolylacryloyl-derived oxacins (IDOs) were designed and synthesized for the first time from commercial 3,4-difluoroaniline via an eight-step procedure. The synthesized compounds were characterized by modern spectroscopic techniques. All target molecules were evaluated for antimicrobial activities. Most of the prepared IDOs showed a broad antibacterial spectrum and strong activities against the tested strains, especially ethoxycarbonyl IDO 10d (0.25-0.5 μg/mL) and hydroxyethyl IDO 10e (0.25-1 μg/mL) exhibited much superior antibacterial efficacies to reference drug norfloxacin. These highly active IDOs also displayed low hemolysis, cytotoxicity and resistance, as well as rapid bactericidal capacity. Further investigations indicated that ethoxycarbonyl IDO 10d and hydroxyethyl IDO 10e could effectively reduce the exopolysaccharide content and eradicate the formed biofilm, which might delay the development of drug resistance. Preliminary exploration of the antibacterial mechanism revealed that active IDOs could not only destroy membrane integrity, resulting in changes in membrane permeability, but also promote the accumulation of reactive oxygen species, leading to the production of malondialdehyde and decreased bacterial metabolism. Moreover, they exhibited the capability to bind with DNA and DNA gyrase, forming supramolecular complexes through various noncovalent interactions, thereby inhibiting DNA replication and causing bacterial death. All the above results suggested that the newly developed indolylacryloyl-derived oxacins should hold great promise as potential multitargeting broad-spectrum antibacterial candidates to overcome drug resistance.

Novel aminothiazoximone-corbelled ethoxycarbonylpyrimidones with antibiofilm activity to conquer Gram-negative bacteria through potential multitargeting effects

The emergence of drug-resistant microorganisms threatens human health, and it is usually exacerbated by the formation of biofilm, which forces the development of new antibacterial agents with antibiofilm activity. In this work, a novel category of aminothiazoximone-corbelled ethoxycarbonylpyrimidones (ACEs) was designed and synthesized, and some of the prepared ACEs showed potent bioactivity against the tested bacteria. In particular, imidazolyl ACE 6c showed better inhibitory activity towards Acinetobacter baumannii and Escherichia coli with MIC values both of 0.0066 mmol/L than norfloxacin. It was also revealed that imidazolyl ACE 6c not only possessed inconspicuous hemolytic rate and cytotoxicity, low drug resistance and no risk of penetrating the blood-brain barrier, but also exhibited obvious biofilm inhibition and eradication activities. The preliminary mechanism research suggested that imidazolyl ACE 6c could induce metabolic dysfunction by deactivating lactate dehydrogenase and promote the accumulation of reactive oxygen species to decrease the reduced glutathione and ultimately cause oxidative damage in bacteria. Furthermore, ACE 6c was also found that could insert into DNA to form the supramolecular complex of 6c-DNA and trigger cell death. The multidimensional effect might promote bacterial cell rupture, leading to the leakage of intracellular content. These findings manifested that novel imidazolyl ACE 6c as a potential multitargeting antibacterial agent with potent antibiofilm activity could provide new possibility for the treatment of refractory biofilm-intensified bacterial infections.

Discovery of benzopyridone cyanoacetates as new type of potential broad-spectrum antibacterial candidates

Unique benzopyridone cyanoacetates (BCs) as new type of promising broad-spectrum antibacterial candidates were discovered with large potential to combat the lethal multidrug-resistant bacterial infections. Many prepared BCs showed broad antibacterial spectrum with low MIC values against the tested strains. Some highly active BCs exhibited rapid sterilization capacity, low resistant trend and good predictive pharmacokinetic properties. Furthermore, the highly active sodium BCs (NaBCs) displayed low hemolysis and cytotoxicity, and especially octyl NaBC 5g also showed in vivo potent anti-infective potential and appreciable pharmacokinetic profiles. A series of preliminary mechanistic explorations indicated that these active BCs could effectively eliminate bacterial biofilm and destroy membrane integrity, thus resulting in the leakage of bacterial cytoplasm. Moreover, their unique structures might further bind to intracellular DNA, DNA gyrase and topoisomerase IV through various direct noncovalent interactions to hinder bacterial reproduction. Meanwhile, the active BCs also induced bacterial oxidative stress and metabolic disturbance, thereby accelerating bacterial apoptosis. These results provided a bright hope for benzopyridone cyanoacetates as potential novel multitargeting broad-spectrum antibacterial candidates to conquer drug resistance.

Benzopyrone-mediated quinolones as potential multitargeting antibacterial agents

A new type of benzopyrone-mediated quinolones (BMQs) was rationally designed and efficiently synthesized as novel potential antibacterial molecules to overcome the global increasingly serious drug resistance. Some synthesized BMQs effectively suppressed the growth of the tested strains, outperforming clinical drugs. Notably, ethylidene-derived BMQ 17a exhibited superior antibacterial potential with low MICs of 0.5-2 μg/mL to clinical drugs norfloxacin, it not only displayed rapid bactericidal performance and inhibited bacterial biofilm formation, but also showed low toxicity toward human red blood cells and normal MDA-kb2 cells. Mechanistic investigation demonstrated that BMQ 17a could effectually induce bacterial metabolic disorders and promote the enhancement of reactive oxygen species to disrupt the bacterial antioxidant defense system. It was found that the active molecule BMQ 17a could not only form supramolecular complex with lactate dehydrogenase, which disturbed the biological functions, but also effectively embed into calf thymus DNA, thus affecting the normal function of DNA and achieving cell death. This work would provide an insight into developing new molecules to reduce drug resistance and expand antibacterial spectrum.

Discovery of novel cannabidiol derivatives with augmented antibacterial agents against methicillin-resistant Staphylococcus aureus

Drug-resistant bacterium infections are a severe threat to public health and novel antimicrobial agents combating drug-resistant bacteria are an unmet medical need. Although cannabidiol (CBD) has been reported to show antibacterial effects, whether its antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) can be improved remains unclear. Herein, a series of novel CBD derivatives were designed and synthesized using various chemical approaches including amidation, Friedel-Crafts alkylation, and Negishi cross-coupling reaction for the modifications at the C-7, C-2', C-4', and C-6' positions of CBD skeleton. Derivative 21f showed augmented antibacterial activity against MRSA with a minimum inhibitory concentration of 4 μM without cytotoxic effect in microglia BV2 cells. Further mechanistic studies suggested that 21f inhibited the formation of biofilms, induced excess reactive oxygen species, and reduced bacterial metabolism, which collectively led to the acceleration of bacterial death. Findings from this study expand the understanding of CBD derivatives as promising antibacterial agents, which provides useful information for the development of cannabinoid-based antibacterial agents.

Identification of unique indolylcyanoethylenyl sulfonylanilines as novel structural scaffolds of potential antibacterial agents

The increasing incidence of antibiotic resistance has forced the development of unique antimicrobials with novel multitargeting mechanisms to combat infectious diseases caused by multidrug-resistant pathogens. Structurally unique indolylcyanoethylenyl sulfonylanilines (ISs) were exploited as novel promising antibacterial agents to confront stubborn drug resistance. Some prepared ISs possessed favorable bacteriostatic action towards the tested bacteria. Especially, hydroxyethyl IS 14a exerted 8-fold more potent inhibitory efficacy against multidrug-resistant A. baumannii and E. coli 25922 with the low MIC of 0.5 μg/mL than norfloxacin, and showed low cell toxicity and rapid bactericidal property. Moreover, this compound also possessed obvious effect of eradicating bacterial biofilm, which could effectually relieve the development of drug resistance. A preliminary assessment of the antibacterial mechanism indicated that compound 14a could disintegrate membrane integrity leading to the leakage of intracellular protein, inactivation of lactate dehydrogenase and metabolism inhibition. Hydroxyethyl IS 14a mediated the accumulation of excess reactive oxygen species, which further contributed to reducing glutathione, resulting in oxidative damage to bacteria. Furthermore, IS 14a could intercalate into DNA to hinder the biological function of DNA. Quantum chemical study disclosed that IS 14a with the lowest energy gap was conducive to displaying high bioactivity. These findings demonstrated that hydroxyethyl IS 14a as a prospective antimicrobial candidate for combating A. baumannii and E. coli 25922 would be a promising starting point.

Novel Thiazolylketenyl Quinazolinones as Potential Anti-MRSA Agents and Allosteric Modulator for PBP2a

Bacterial infections caused by methicillin-resistant Staphylococcus aureus have seriously threatened public health. There is an urgent need to propose an existing regimen to overcome multidrug resistance of MRSA. A unique class of novel anti-MRSA thiazolylketenyl quinazolinones (TQs) and their analogs were developed. Some synthesized compounds showed good bacteriostatic potency. Especially TQ 4 was found to exhibit excellent inhibition against MRSA with a low MIC of 0.5 μg/mL, which was 8-fold more effective than norfloxacin. The combination of TQ 4 with cefdinir showed stronger antibacterial potency. Further investigation revealed that TQ 4, with low hemolytic toxicity and low drug resistance, was not only able to inhibit biofilm formation but also could reduce MRSA metabolic activity and showed good drug-likeness. Mechanistic explorations revealed that TQ 4 could cause leakage of proteins by disrupting membrane integrity and block DNA replication by intercalated DNA. Furthermore, the synergistic antibacterial effect with cefdinir might be attributed to TQ 4 with the ability to induce PBP2a allosteric regulation of MRSA and further trigger the opening of the active site to promote the binding of cefdinir to the active site, thus inhibiting the expression of PBP2a, thereby overcoming MRSA resistance and significantly enhancing the anti-MRSA activity of cefdinir. A new strategy provided by these findings was that TQ 4, possessing both excellent anti-MRSA activity and allosteric effect of PBP2a, merited further development as a novel class of antibacterial agents to overcome increasingly severe MRSA infections.

An Update Review of Approaches to Multiple Action-Based Antibacterials

Many approaches are being pursued to address the major global health challenge posed by the increasing resistance of pathogenic bacteria to antibacterial agents. One of the promising approaches being investigated includes the design and development of multiple action-based small-molecule antibacterials. Aspects of this broad area have been reviewed previously, and recent developments are addressed in this update review covering the literature mainly over the past three years. Considerations encompassing drug combinations, single-molecule hybrids and prodrugs are summarised in regard to the intentional design and development of multiple-action agents with a focus on potential triple or greater activities in bacteria. The hope for such single agents or combinations of single agents is that resistance development will be significantly hindered, and they may be useful in tackling bacterial disease caused by both resistant and non-resistant bacteria.

Thiazolyl hydrazineylidenyl indolones as unique potential multitargeting broad-spectrum antimicrobial agents

The emergence of pathogenic and drug-resistant microorganisms seriously threatens public safety. This work constructed a unique type of thiazolyl hydrazineylidenyl indolones (THIs) to combat global microbial multidrug-resistance. Bioactive evaluation discovered that some target THIs displayed much superior antimicrobial efficacy than clinical chloromycetin, norfloxacin, cefdinir or fluconazole against the tested strains. Eminently, butyl THI 6c displayed a broad antimicrobial spectrum with low MICs of 0.25-1 μg/mL. The highly active THI 6c not only showed low cytotoxicity and hemolysis, rapidly bactericidal ability, good antibiofilm activity and promising pharmacokinetic properties, but also could significantly impede the development of bacterial resistance. Preliminary exploration of antibacterial mechanism revealed that THI 6c could effectively penetrate the cell membrane of MRSA and embed DNA to form 6c‒DNA supramolecular complex and thus hinder DNA replication. Moreover, THI 6c could reduce cell metabolic activity, which might be attributed to the fact that THI 6c could target the pyruvate kinase of MRSA and interfere with the function of the enzyme. These results provided powerful information for further developing thiazolyl hydrazineylidenyl indolones as new broad-spectrum antimicrobial agents.

Comprehensive Insights into Medicinal Research on Imidazole-Based Supramolecular Complexes

The electron-rich five-membered aromatic aza-heterocyclic imidazole, which contains two nitrogen atoms, is an important functional fragment widely present in a large number of biomolecules and medicinal drugs; its unique structure is beneficial to easily bind with various inorganic or organic ions and molecules through noncovalent interactions to form a variety of supramolecular complexes with broad medicinal potential, which is being paid an increasing amount of attention regarding more and more contributions to imidazole-based supramolecular complexes for possible medicinal application. This work gives systematical and comprehensive insights into medicinal research on imidazole-based supramolecular complexes, including anticancer, antibacterial, antifungal, antiparasitic, antidiabetic, antihypertensive, and anti-inflammatory aspects as well as ion receptors, imaging agents, and pathologic probes. The new trend of the foreseeable research in the near future toward imidazole-based supramolecular medicinal chemistry is also prospected. It is hoped that this work provides beneficial help for the rational design of imidazole-based drug molecules and supramolecular medicinal agents and more effective diagnostic agents and pathological probes.

Synthesis and Biological Evaluation of Piperazine Hybridized Coumarin Indolylcyanoenones with Antibacterial Potential

A class of piperazine hybridized coumarin indolylcyanoenones was exploited as new structural antibacterial frameworks to combat intractable bacterial resistance. Bioactive assessment discovered that 4-chlorobenzyl derivative 11f showed a prominent inhibition on Pseudomonas aeruginosa ATCC 27853 with a low MIC of 1 μg/mL, which was four-fold more effective than norfloxacin. Importantly, the highly active 11f with inconspicuous hemolysis towards human red blood cells displayed quite low proneness to trigger bacterial resistance. Preliminary explorations on its antibacterial behavior disclosed that 11f possessed the ability to destroy bacterial cell membrane, leading to increased permeability of inner and outer membranes, the depolarization and fracture of membrane, and the effusion of intracellular components. Furthermore, bacterial oxidative stress and metabolic turbulence aroused by 11f also accelerated bacterial apoptosis. In particular, 11f could not only effectively inset into DNA, but also bind with DNA gyrase through forming supramolecular complex, thereby affecting the biological function of DNA. The above findings of new piperazine hybridized coumarin indolylcyanoenones provided an inspired possibility for the treatment of resistant bacterial infections.