Design, synthesis and in vivo evaluation of 3-arylcoumarin derivatives of rhenium(I) tricarbonyl complexes as potent antibacterial agents against methicillin-resistant Staphylococcus aureus (MRSA)

Synthetic indole derivatives as an antibacterial agent inhibiting respiratory metabolism of multidrug-resistant gram-positive bacteria

The survival of modern medicine depends heavily on the effective prevention and treatment of bacterial infections, are threatened by antibacterial resistance. The increasing use of antibiotics and lack of stewardship have led to an increase in antibiotic-resistant pathogens, so the growing issue of resistance can be resolved by emphasizing chemically synthesized antibiotics. This study discovered SMJ-2, a synthetic indole derivative, is effective against all multidrug-resistant gram-positive bacteria. SMJ-2 has multiple targets of action, but the primary mechanism inhibits respiratory metabolism and membrane potential disruption. SMJ-2 was discovered to interfere with the mevalonate pathway, ultimately preventing the synthesis of farnesyl diphosphate, a precursor to the antioxidant staphyloxanthin, eventually releasing reactive oxygen species, and leading phagocytic cells to destroy pathogens. Additionally, no discernible biochemical and histopathological alterations were found in the mouse acute toxicity model. This study emphasizes mechanistic insights into SMJ-2 as a potential antibacterial with an unusual method of action.

Carbamoylation at C-8 position of natural 3-arylcoumarin scaffold for the discovery of novel PARP-1 inhibitors with potent anticancer activity

Structural modification based on natural privileged scaffolds has proven to be an attractive approach to generate potential antitumor candidates with high potency and specific targeting. As a continuation of our efforts to identify potent PARP-1 inhibitors, natural 3-arylcoumarin scaffold was served as the starting point for the construction of novel structural unit for PARP-1 inhibition. Herein, a series of novel 8-carbamyl-3-arylcoumarin derivatives were designed and synthesized. The antiproliferative activities of target compounds against four BRCA-mutated cancer cells (SUM149PT, HCC1937, MDA-MB-436 and Capan-1) were evaluated. Among them, compound 9b exhibited excellent antiproliferative effects against SUM149PT, HCC1937 and Capan-1 cells with IC50 values of 0.62, 1.91 and 4.26 μM, respectively. Moreover, 9b could significantly inhibit the intracellular PARP-1/2 activity in SUM149PT cells with IC50 values of 2.53 nM and 6.45 nM, respectively. Further mechanism studies revealed that 9b could aggravate DNA double-strand breaks, increase ROS production, decrease mitochondrial membrane potential, arrest cell cycle at G2/M phase and ultimately induce apoptosis in SUM149PT cells. In addition, molecular docking study demonstrated that the binding mode of 9b with PARP-1 was similar to that of niraparib, forming multiple hydrogen bond interactions with the active site of PARP-1. Taken together, these findings suggest that 8-carbamyl-3-arylcoumarin scaffold could serve as an effective structural unit for PARP-1 inhibition and offer a valuable paradigm for the structural modification of natural products.

Multimodal antibacterial potency of newly designed and synthesized Schiff's/Mannich based coumarin derivatives: potential inhibitors of bacterial DNA gyrase and biofilm production

The briskened urge to develop potential antibacterial candidates against multidrug-resistant pathogens has motivated the present research study. Herein, newly synthesized coumarin derivatives with azomethine and amino-methylated as the functional groups have been focused on their antibacterial efficacy. The study proposed two distinct series: 3-acetyl substituted coumarin derivatives, followed by the Schiff base approach (5a-5i), and formaldehyde-secondary cyclic amine-based derivatives (7a-7g), using the Mannich base approach, further the compounds have been confirmed through various spectral studies. Further, target-specific binding affinity has been affirmed via in silico study. In vitro antibacterial study suggested compounds 5d and 5f to be most effective against S. aureus and multidrug-resistant K. pneumoniae, with MIC values of 8 and 16 μg mL-1. Among them, the compounds 5d and 5f showed excellent binding scores against different bacterial gyrase compared to the standard novobiocin. Based on RMRS, RMSF, Rg, and H-bond plots, MD simulation study at 100 ns also suggested better stability of 5d inside gyraseB of E. coli than the complex of E. coli-GyrB-novobiocin. The toxicity and pharmacokinetic profiles showed favorable drug-likeness. Overall, systematic in vitro and in silico assessment suggested that multimodal antibacterial derivatives 5d and 5f strongly inhibit both bacterial DNA gyrase and biofilm formation of drug-resistant pathogens, suggesting their potency in mainstream antibacterial therapy.

Exploration of Rhenium Bisquinoline Tricarbonyl Complexes for their Antibacterial Properties

Metal complexes have emerged as a promising source for novel classes of antibacterial agents to combat the rise of antimicrobial resistance around the world. In the exploration of the transition metal chemical space for novel metalloantibiotics, the rhenium tricarbonyl moiety has been identified as a promising scaffold. Here we have prepared eight novel rhenium bisquinoline tricarbonyl complexes and explored their antibacterial properties. Significant activity against both Gram-positive and Gram-negative bacteria was observed. However, all complexes also showed significant toxicity against human cells, putting into question the prospects of this specific rhenium compound class as metalloantibiotics. To better understand their biological effects, we conduct the first mode of action studies on rhenium bisquinoline complexes and show that they are able to form pores through bacterial membranes. Their straight-forward synthesis and tuneability suggests that further optimisation of this compound class could lead to compounds with enhanced bacterial specificity.

Antimicrobial and anticancer properties of carbon monoxide releasing molecules of the fac-[Re(CO)3(N-N)L]+ family

The toxicity profile of fac-[Re(CO)3(N-N)L]+ complexes against microbial and tumoral cells has been extensively studied, primarily focusing on modifications to the bidentate diimine (N-N) ligand. However, less attention has been paid to modifications of the axial ligand L, which is perpendicular to the Re-N-N plane. This study reveals that the high toxicity of the fac-[Re(CO)3(bpy)(Ctz)]+ complex may be attributed to the structural effect of the trityl (CPh3) group present in clotrimazole, as removal of phenyl rings causes a significant decrease in the activity against Staphylococcus aureus (S. aureus). Moreover, substitution of the 1-tritylimidazole ligand by the structurally related ligands PPh3 and PCy3 maintains similarly high activity levels. These findings contribute to understanding the interactions of toxic complexes with bacterial membranes, suggesting that the ligand structures play a crucial role in inhibiting cell wall synthesis processes, potentially including Lipid II synthesis. Compounds with Ph3E (E = C-imidazole; P) groups also showed to be 10 times more toxic than cisplatin against three mammalian cell lines (IC50: 2-4 μM). In contrast, the analogue 1-benzylimidazole and 1-tert-butylimidazole derivatives were as toxic as cisplatin. We observed that the decomposition of the [Re(I)(CO)3] fragment inside mammalian cell lines liberates CO, which is expected to exert biological effects. Therefore, compounds of this family possessing the structural motif Ph3E seem to combine high antimicrobial and antitumoral activities, the latter being much higher than that of cisplatin.

Silver Nanoparticles Encapped by Dihydromyricetin: Optimization of Green Synthesis, Characterization, Toxicity, and Anti-MRSA Infection Activities for Zebrafish (Danio rerio)

To achieve the environmentally friendly and rapid green synthesis of efficient and stable AgNPs for drug-resistant bacterial infection, this study optimized the green synthesis process of silver nanoparticles (AgNPs) using Dihydromyricetin (DMY). Then, we assessed the impact of AgNPs on zebrafish embryo development, as well as their therapeutic efficacy on zebrafish infected with Methicillin-resistant Staphylococcus aureus (MRSA). Transmission electron microscopy (TEM) and dynamic light-scattering (DLS) analyses revealed that AgNPs possessed an average size of 23.6 nm, a polymer dispersity index (PDI) of 0.197 ± 0.0196, and a zeta potential of -18.1 ± 1.18 mV. Compared to other published green synthesis products, the optimized DMY-AgNPs exhibited smaller sizes, narrower size distributions, and enhanced stability. Furthermore, the minimum concentration of DMY-AgNPs required to affect zebrafish hatching and survival was determined to be 25.0 μg/mL, indicating the low toxicity of DMY-AgNPs. Following a 5-day feeding regimen with DMY-AgNP-containing food, significant improvements were observed in the recovery of the gills, intestines, and livers in MRSA-infected zebrafish. These results suggested that optimized DMY-AgNPs hold promise for application in aquacultures and offer potential for further clinical use against drug-resistant bacteria.

Diving into drug-screening: zebrafish embryos as an in vivo platform for antimicrobial drug discovery and assessment

The rise of multidrug-resistant bacteria underlines the need for innovative treatments, yet the introduction of new drugs has stagnated despite numerous antimicrobial discoveries. A major hurdle is a poor correlation between promising in vitro data and in vivo efficacy in animal models, which is essential for clinical development. Early in vivo testing is hindered by the expense and complexity of existing animal models. Therefore, there is a pressing need for cost-effective, rapid preclinical models with high translational value. To overcome these challenges, zebrafish embryos have emerged as an attractive model for infectious disease studies, offering advantages such as ethical alignment, rapid development, ease of maintenance, and genetic manipulability. The zebrafish embryo infection model, involving microinjection or immersion of pathogens and potential antibiotic hit compounds, provides a promising solution for early-stage drug screening. It offers a cost-effective and rapid means of assessing the efficacy, toxicity and mechanism of action of compounds in a whole-organism context. This review discusses the experimental design of this model, but also its benefits and challenges. Additionally, it highlights recently identified compounds in the zebrafish embryo infection model and discusses the relevance of the model in predicting the compound's clinical potential.

Discovery of antibacterial manganese(i) tricarbonyl complexes through combinatorial chemistry

The continuous rise of antimicrobial resistance is a serious threat to human health and already causing hundreds of thousands of deaths each year. While natural products and synthetic organic small molecules have provided the majority of our current antibiotic arsenal, they are falling short in providing new drugs with novel modes of action able to treat multidrug resistant bacteria. Metal complexes have recently shown promising results as antimicrobial agents, but the number of studied compounds is still vanishingly small, making it difficult to identify promising compound classes or elucidate structure-activity relationships. To accelerate the pace of discovery we have applied a combinatorial chemistry approach to the synthesis of metalloantibiotics. Utilizing robust Schiff-base chemistry and combining 7 picolinaldehydes with 10 aniline derivatives, and 6 axial ligands, either imidazole/pyridine-based or solvent, we have prepared a library of 420 novel manganese tricarbonyl complexes. All compounds were evaluated for their antibacterial properties and 10 lead compounds were identified, re-synthesised and fully characterised. All 10 compounds showed high and broad activity against Gram-positive bacteria. The best manganese complex displayed low toxicity against human cells with a therapeutic index of >100. In initial mode of action studies, we show that it targets the bacterial membrane without inducing pore formation or depolarisation. Instead, it releases its carbon monoxide ligands around the membrane and inhibits the bacterial respiratory chain. This work demonstrates that large numbers of metal complexes can be accessed through combinatorial synthesis and evaluated for their antibacterial potential, allowing for the rapid identification of promising metalloantibiotic lead compounds.

Detection of Methicillin-Resistant Staphylococcus Aureus using vancomycin conjugated silica-based fluorescent nanoprobe

Methicillin-Resistant Staphylococcus Aureus (MRSA) is a worldwide major pathogenic bacteria that has emerged over the past three decades as the leading cause of nosocomial and community-acquired infections. Biosensors can provide rapid, sensitive, and selective detection of the presence and number of bacteria in various environments. Herein, a novel fluorescence nanoprobe was designed as a biosensor for MRSA detection using dye-incorporated silica nanoparticles (FSiNP). Based on the results of specific surface area analysis using the Brauner Emmett-Teller (BET) method, the surface area of the nanoparticles was obtained at 377.127 m2/g, and the X-ray diffraction (XRD) analysis confirmed that it was in the amorphous phase. Vancomycin, as the bioreceptor, was immobilized on the silica surface through a hydrosilylation reaction, generating the biosensing platform FSiNP-Van. Each modification step was corroborated by the Fourier Transform Infra-Red (FTIR) spectroscopy. The sensing principle was based on the fluorescence-quenching mechanism of FSiNP-Van at 515 nm obtaining a rapid response time of 20 min. The FSiNP-Van nanoprobe provided a wide linear concentration range of 10-106 CFU/mL with a limit of MRSA detection calculated at 1 CFU/mL. The fluorescent nanoprobe demonstrated here is expected to find applications in point-of-care (POC) diagnostics to detect the presence of MRSA bacteria.

3-Substituted Coumarins Inhibit NorA and MepA Efflux Pumps of Staphylococcus aureus

Coumarins are compounds with scientifically proven antibacterial properties, and modifications to the chemical structure are known to improve their effects. This information is even more relevant with the unbridled advances of antibiotic resistance, where Staphylococcus aureus and its efflux pumps play a prominent role. The study's objective was to evaluate the potential of synthetic coumarins with different substitutions in the C-3 position as possible inhibitors of the NorA and MepA efflux pumps of S. aureus. For this evaluation, the following steps took place: (i) the determination of the minimum inhibitory concentration (MIC); (ii) the association of coumarins with fluoroquinolones and ethidium bromide (EtBr); (iii) the assessment of the effect on EtBr fluorescence emission; (iv) molecular docking; and (v) an analysis of the effect on membrane permeability. Coumarins reduced the MICs of fluoroquinolones and EtBr between 50% and 87.5%. Coumarin C1 increased EtBr fluorescence emission between 20 and 40% by reinforcing the evidence of efflux inhibition. The molecular docking results demonstrated that coumarins have an affinity with efflux pumps and establish mainly hydrogen bonds and hydrophobic interactions. Furthermore, C1 did not change the permeability of the membrane. Therefore, we conclude that these 3-substituted coumarins act as inhibitors of the NorA and MepA efflux pumps of S. aureus.

Recent advances in the development of metal complexes as antibacterial agents with metal-specific modes of action

The mounting burden of antimicrobial resistance (AMR) is one of the most concerning threats to public health worldwide. With low economic incentives and a dwindling supply of new drugs in clinical pipelines, more innovative approaches to novel drug design and development are desperately required. Metal-based compounds are rapidly emerging as an alternative to organic drugs, as they have the ability to kill pathogens via metal-specific modes of action. We herein review recent advances in metal-based antibacterial agents, including metal complexes, metal ions and catalytic metallodrugs. The review concludes with a perspective on the rational design of metal-based antibiotics, and how we can exploit their unique properties to tackle AMR.

Conjugated carbon monoxide-releasing molecules have broad-spectrum antimicrobial activity

Aim: To test the antimicrobial effect of carbon monoxide-releasing molecules (CORMs) conjugated with azoles on different microorganisms. Methods & results: We used broth microdilution, checkerboard and cytotoxicity assays, as well as imaging, fluorescence and bioluminescence experiments to study [Re(CO)3(2,2'-bipyridyl)(Ctz)]+ (also known as ReBpyCtz). ReBpyCtz exhibits a low minimum inhibitory concentration value, increases the intracellular formation of reactive oxygen species and causes significant alterations on Staphylococcus aureus's membrane. ReBpyCtz is active against fungi, having a more prolonged fungicidal effect on Candida glabrata than clotrimazole and is selectively active on blood-stage malaria parasites, at a concentration that is not toxic to kidney epithelial cells. Conclusion: Conjugated CORMs have the potential to be active against different types of pathogens, thus constituting a promising class of broad-spectrum antimicrobials.

Metal-Organic Framework-Based Nanomedicines for the Treatment of Intracellular Bacterial Infections

Metal-organic frameworks (MOFs) are a highly versatile class of ordered porous materials, which hold great promise for different biomedical applications, including antibacterial therapy. In light of the antibacterial effects, these nanomaterials can be attractive for several reasons. First, MOFs exhibit a high loading capacity for numerous antibacterial drugs, including antibiotics, photosensitizers, and/or photothermal molecules. The inherent micro- or meso-porosity of MOF structures enables their use as nanocarriers for simultaneous encapsulation of multiple drugs resulting in a combined therapeutic effect. In addition to being encapsulated into an MOF's pores, antibacterial agents can sometimes be directly incorporated into an MOF skeleton as organic linkers. Next, MOFs contain coordinated metal ions in their structure. Incorporation of Fe2/3+, Cu2+, Zn2+, Co2+, and Ag+ can significantly increase the innate cytotoxicity of these materials for bacteria and cause a synergistic effect. Finally, abundance of functional groups enables modifying the external surface of MOF particles with stealth coating and ligand moieties for improved drug delivery. To date, there are a number of MOF-based nanomedicines available for the treatment of bacterial infections. This review is focused on biomedical consideration of MOF nano-formulations designed for the therapy of intracellular infections such as Staphylococcus aureus, Mycobacterium tuberculosis, and Chlamydia trachomatis. Increasing knowledge about the ability of MOF nanoparticles to accumulate in a pathogen intracellular niche in the host cells provides an excellent opportunity to use MOF-based nanomedicines for the eradication of persistent infections. Here, we discuss advantages and current limitations of MOFs, their clinical significance, and their prospects for the treatment of the mentioned infections.

Synthesis and anti-proliferative activity of dehydroabietinol derivatives bearing a triazole moiety

In search of more efficacious antitumor agents, a series of novel dehydroabietinol derivatives containing a triazole moiety was synthesized, and evaluated for cytotoxicity against four human cancer cell lines. Many exhibited superior cytotoxic profiles compared to the parent molecule, dehydroabietic acid. In particular, compounds 5g, 5i and 5j exhibited promising cytotoxicity with IC50 values ranging from 4.84 to 9.62 μM against all the test cell lines. Cell clone formation and migration tests of compound 5g showed that it not only effectively inhibited the formation of MGC-803 cell colonies but also inhibited the MGC-803 cell migration and invasion. Additionally, the preliminary pharmacological mechanism indicated compound 5g induced apoptosis, arrested the mitotic process at the G0/G1 phase of the cell cycle, reduced the mitochondrial membrane potential, and increased the intracellular ROS and Ca2+ levels.

Computer-Aided Drug Design and Synthesis of Rhenium Clotrimazole Antimicrobial Agents

In the context of the global health issue caused by the growing occurrence of antimicrobial resistance (AMR), the need for novel antimicrobial agents is becoming alarming. Inorganic and organometallic complexes represent a relatively untapped source of antibiotics. Here, we report a computer-aided drug design (CADD) based on a 'scaffold-hopping' approach for the synthesis and antibacterial evaluation of fac-Re(I) tricarbonyl complexes bearing clotrimazole (ctz) as a monodentate ligand. The prepared molecules were selected following a pre-screening in silico analysis according to modification of the 2,2'-bipyridine (bpy) ligand in the coordination sphere of the complexes. CADD pointed to chiral 4,5-pinene and 5,6-pinene bipyridine derivatives as the most promising candidates. The corresponding complexes were synthesized, tested toward methicillin-sensitive and -resistant S. aureus strains, and the obtained results evaluated with regard to their binding affinity with a homology model of the S. aureus MurG enzyme. Overall, the title species revealed very similar minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values as those of the reference compound used as the scaffold in our approach. The obtained docking scores advocate the viability of 'scaffold-hopping' for de novo design, a potential strategy for more cost- and time-efficient discovery of new antibiotics.

Metals to combat antimicrobial resistance

Bacteria, similar to most organisms, have a love-hate relationship with metals: a specific metal may be essential for survival yet toxic in certain forms and concentrations. Metal ions have a long history of antimicrobial activity and have received increasing attention in recent years owing to the rise of antimicrobial resistance. The search for antibacterial agents now encompasses metal ions, nanoparticles and metal complexes with antimicrobial activity ('metalloantibiotics'). Although yet to be advanced to the clinic, metalloantibiotics are a vast and underexplored group of compounds that could lead to a much-needed new class of antibiotics. This Review summarizes recent developments in this growing field, focusing on advances in the development of metalloantibiotics, in particular, those for which the mechanism of action has been investigated. We also provide an overview of alternative uses of metal complexes to combat bacterial infections, including antimicrobial photodynamic therapy and radionuclide diagnosis of bacterial infections.

Exploring the in vitro anticancer activities of Re(I) picolinic acid and its fluorinated complex derivatives on lung cancer cells: a structural study

Fifteen rhenium(I) tricarbonyl complexes of the form fac-[Re(N,O')(CO)₃(X)], where N,O'-bidentate ligand = 2-picolinic acid (Pico); 3,5-difluoropyridine-2-carboxylic acid (Dfpc); 3-trifluoromethyl-pyridine-2-carboxylic acid (Tfpc) and X = H₂O; pyrazole (Pz); pyridine (Py); imidazole (Im); and methanol (CH₃OH) were synthesized using the '2 + 1' mixed ligand approach with an average yield of 84%. The complexes were characterized using the following spectroscopic techniques: IR, ¹H and ¹³C NMR, UV/Vis, and single-crystal X-ray diffraction. The effect of the fluorine atoms on the backbone of the N,O'-bidentate ligand was investigated and a trend was noticed in the carbonyl stretching frequencies: with Pico < Tfpc < Dfpc. The in vitro biological screening on Vero (healthy mammalian), HeLa (cervical carcinoma) and A549 (lung cancer) cells revealed one toxic complex, fac-[Re(Pico)(CO)₃(H₂O)], with respective LC₅₀ values of 9.0 ± 0.9, 15.8 ± 4.9 (SI = 0.570) and 20.9 ± 0.8 (SI = 0.430) μg/mL. As a result, it can be used as a positive control drug of toxicity.

Coumarin Triazoles as Potential Antimicrobial Agents

Currently, in hospitals and community health centers, microbial infections are highly common diseases and are a leading cause of death worldwide. Antibiotics are generally used to fight microbial infections; however, because of the abuse of antibiotics, microbes have become increasingly more resistant to most of them. Therefore, medicinal chemists are constantly searching for new or improved alternatives to combat microbial infections. Coumarin triazole derivatives displayed a variety of therapeutic applications, such as antimicrobial, antioxidant, and anticancer activities. This review summarizes the advances of coumarin triazole derivatives as potential antimicrobial agents covering articles published from 2006 to 2022.

3-(3-Bromophenyl)-7-acetoxycoumarin

In natural product synthesis, the procurement of easily accessible starting materials is crucial. Chromenones and their subclass, coumarins, are a wide family of small, oxygen-containing aromatic heterocycles. Phenylcoumarins offer a particularly excellent starting point for a diverse chemical space of natural products, and thus are excellent staring materials for more complex natural products. Herein, we report an efficient synthesis of an easily accessible 3-phenylcoumarin bearing two orthogonally substitutable groups, bromine, and an acetyl-protected phenylic hydroxyl group.

(E)-3-(2-(4-methylthiazol-2-yl)hydrazineylidene)chromane-2,4-dione

(E)-3-(2-(4-methylthiazol-2-yl)hydrazineylidene)chromane-2,4-dione was synthesized for the first time and the compound was characterized by 1H and 13C spectroscopy, IR spectroscopy, and UV-Vis. The chemical structure and isomeric configuration of the molecule were confirmed by single-crystal X-ray diffraction.

Discovery of New Anti-MRSA Agents Based on Phenoxyethanol and Its Mechanism

Methicillin-resistant Staphylococcus aureus (MRSA) poses a severe threat to public health and safety. The discovery and development of novel anti-MRSA drugs with a new mode of action are a challenge. In this study, a class of novel aryloxyethyl propiolates and their homologues as anti-MRSA agents have been designed and synthesized based on phenoxyethanol, of which compound II-39 showed high inhibitory activity against MRSA with an MIC of 0.78 μg/mL and an MBC of 3.13 μg/mL, which was better than that of vancomycin. Compound II-39 could destroy the cell wall and cell membrane, inhibited the formation of a biofilm, and bound to the DNA of MRSA through the electrostatic and groove interaction. Proteomic and metabolomic studies revealed that compound II-39 affected multiple intracellular metabolic pathways of MRSA. Notably, compound II-39 could effectively inhibit the expression of CrtPQMN proteins and block the biosynthesis of virulence factor (staphyloxanthin). Thus, aryloxyethyl propiolates and their homologues are promising anti-MRSA agents with multiple targets.

Metal Complexes as Antifungals? From a Crowd-Sourced Compound Library to the First In Vivo Experiments

There are currently fewer than 10 antifungal drugs in clinical development, but new fungal strains that are resistant to most current antifungals are spreading rapidly across the world. To prevent a second resistance crisis, new classes of antifungal drugs are urgently needed. Metal complexes have proven to be promising candidates for novel antibiotics, but so far, few compounds have been explored for their potential application as antifungal agents. In this work, we report the evaluation of 1039 metal-containing compounds that were screened by the Community for Open Antimicrobial Drug Discovery (CO-ADD). We show that 20.9% of all metal compounds tested have antimicrobial activity against two representative Candida and Cryptococcus strains compared with only 1.1% of the >300,000 purely organic molecules tested through CO-ADD. We identified 90 metal compounds (8.7%) that show antifungal activity while not displaying any cytotoxicity against mammalian cell lines or hemolytic properties at similar concentrations. The structures of 21 metal complexes that display high antifungal activity (MIC ≤1.25 μM) are discussed and evaluated further against a broad panel of yeasts. Most of these have not been previously tested for antifungal activity. Eleven of these metal complexes were tested for toxicity in the Galleria mellonella moth larva model, revealing that only one compound showed signs of toxicity at the highest injected concentration. Lastly, we demonstrated that the organo-Pt(II) cyclooctadiene complex Pt1 significantly reduces fungal load in an in vivo G. mellonella infection model. These findings showcase that the structural and chemical diversity of metal-based compounds can be an invaluable tool in the development of new drugs against infectious diseases.

The combination of diethyldithiocarbamate and copper ions is active against Staphylococcus aureus and Staphylococcus epidermidis biofilms in vitro and in vivo

Staphylococcus aureus and Staphylococcus epidermidis are associated with life-threatening infections. Despite the best medical care, these infections frequently occur due to antibiotic resistance and the formation of biofilms of these two bacteria (i.e., clusters of bacteria embedded in a matrix). As a consequence, there is an urgent need for effective anti-biofilm treatments. Here, we describe the antibacterial properties of a combination treatment of diethyldithiocarbamate (DDC) and copper ions (Cu²⁺) and their low toxicity in vitro and in vivo. The antibacterial activity of DDC and Cu²⁺ was assessed in vitro against both planktonic and biofilm cultures of S. aureus and S. epidermidis using viability assays, microscopy, and attachment assays. Cytotoxicity of DDC and Cu²⁺ (DDC-Cu²⁺) was determined using a human fibroblast cell line. In vivo antimicrobial activity and toxicity were monitored in Galleria mellonella larvae. DDC-Cu²⁺ concentrations of 8 μg/ml DDC and 32 μg/ml Cu²⁺ resulted in over 80% MRSA and S. epidermidis biofilm killing, showed synergistic and additive effects in both planktonic and biofilm cultures of S. aureus and S. epidermidis, and synergized multiple antibiotics. DDC-Cu²⁺ inhibited MRSA and S. epidermidis attachment and biofilm formation in the xCELLigence and Bioflux systems. In vitro and in vivo toxicity of DDC, Cu²⁺ and DDC-Cu²⁺ resulted in > 70% fibroblast viability and > 90% G. mellonella survival. Treatment with DDC-Cu²⁺ significantly increased the survival of infected larvae (87% survival of infected, treated larvae vs. 47% survival of infected, untreated larvae, p < 0.001). Therefore, DDC-Cu²⁺ is a promising new antimicrobial with activity against planktonic and biofilm cultures of S. epidermidis and S. aureus and low cytotoxicity in vitro. This gives us high confidence to progress to mammalian animal studies, testing the antimicrobial efficacy and safety of DDC-Cu²⁺.

Antimicrobial Activity of Rhenium Di- and Tricarbonyl Diimine Complexes: Insights on Membrane-Bound S. aureus Protein Binding

Antimicrobial resistance is one of the major human health threats, with significant impacts on the global economy. Antibiotics are becoming increasingly ineffective as drug-resistance spreads, imposing an urgent need for new and innovative antimicrobial agents. Metal complexes are an untapped source of antimicrobial potential. Rhenium complexes, amongst others, are particularly attractive due to their low in vivo toxicity and high antimicrobial activity, but little is known about their targets and mechanism of action. In this study, a series of rhenium di- and tricarbonyl diimine complexes were prepared and evaluated for their antimicrobial potential against eight different microorganisms comprising Gram-negative and -positive bacteria. Our data showed that none of the Re dicarbonyl or neutral tricarbonyl species have either bactericidal or bacteriostatic potential. In order to identify possible targets of the molecules, and thus possibly understand the observed differences in the antimicrobial efficacy of the molecules, we computationally evaluated the binding affinity of active and inactive complexes against structurally characterized membrane-bound S. aureus proteins. The computational analysis indicates two possible major targets for this class of compounds, namely lipoteichoic acids flippase (LtaA) and lipoprotein signal peptidase II (LspA). Our results, consistent with the published in vitro studies, will be useful for the future design of rhenium tricarbonyl diimine-based antibiotics.

Rhenium(I) derivatives of aminoquinoline and imidazolopiperidine-based ligands: Synthesis, in vitro and in silico biological evaluation against Plasmodium falciparum

A small library of aminoquinoline and imidazolopiperidine (IMP)-based ligands, containing the 1,2,3-triazole moiety, and their corresponding tricarbonyl rhenium complexes were synthesised and their inhibitory activities evaluated against the chloroquine-sensitive (CQS) and multidrug-resistant (MDR) strains (NF54 and K1, respectively) of P. falciparum. The quinoline-based compounds (L1, L2, ReL1, and ReL2) were at least six-fold more potent than their IMP-based counterparts (L3, L4, ReL3, and ReL4) against both strains of P. falciparum, with the most promising compound (L1) displaying activity comparable to chloroquine diphosphate (CQDP) in the MDR strain. Additionally, all of the synthesised compounds have resistance indices less than CQDP. To gain insight into a possible mechanism of action, in silico hemozoin docking simulations were performed. These studies proposed that the tested compounds may act via hemozoin inhibition, as the new aminoquinoline-derivatives, with the exception of complex ReL2 (binding affinity: -12.62 kcal/mol), showed higher binding affinities than the reference drug chloroquine (CQ, -13.56 kcal/mol). Furthermore, the ligands exhibited superior binding affinity relative to their corresponding Re(I) complexes, which is reflected in their antiplasmodial activity.

Synthesis and anti-microbial activity of a new series of bis(diphosphine) rhenium(V) dioxo complexes

Rhenium-based metallodrugs have recently been highlighted as promising candidates for new antibiotics to combat multi-drug resistant (MDR) pathogens. A new class of rhenium(V) dioxo complexes were prepared from readily accessible diphosphine ligands, and have been shown to possess potent activity against Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) alongside low human cell toxicity.

Synergetic Antimicrobial Activity and Mechanism of Clotrimazole-Linked CO-Releasing Molecules

Several metal-based carbon monoxide-releasing molecules (CORMs) are active CO donors with established antibacterial activity. Among them, CORM conjugates with azole antibiotics of type [Mn(CO)₃(2,2′-bipyridyl)(azole)]⁺ display important synergies against several microbes. We carried out a structure–activity relationship study based upon the lead structure of [Mn(CO)₃(Bpy)(Ctz)]⁺ by producing clotrimazole (Ctz) conjugates with varying metal and ligands. We concluded that the nature of the bidentate ligand strongly influences the bactericidal activity, with the substitution of bipyridyl by small bicyclic ligands leading to highly active clotrimazole conjugates. On the contrary, the metal did not influence the activity. We found that conjugate [Re(CO)₃(Bpy)(Ctz)]⁺ is more than the sum of its parts: while precursor [Re(CO)₃(Bpy)Br] has no antibacterial activity and clotrimazole shows only moderate minimal inhibitory concentrations, the potency of [Re(CO)₃(Bpy)(Ctz)]⁺ is one order of magnitude higher than that of clotrimazole, and the spectrum of bacterial target species includes Gram-positive and Gram-negative bacteria. The addition of [Re(CO)₃(Bpy)(Ctz)]⁺ to Staphylococcus aureus causes a general impact on the membrane topology, has inhibitory effects on peptidoglycan biosynthesis, and affects energy functions. The mechanism of action of this kind of CORM conjugates involves a sequence of events initiated by membrane insertion, followed by membrane disorganization, inhibition of peptidoglycan synthesis, CO release, and break down of the membrane potential. These results suggest that conjugation of CORMs to known antibiotics may produce useful structures with synergistic effects that increase the conjugate’s activity relative to that of the antibiotic alone.

Van-mediated self-aggregating photothermal agents combined with multifunctional magnetic nickel oxide nanoparticles for precise elimination of bacterial infections

Building a novel and efficient photothermal antibacterial nanoplatform is a promising strategy for precise bacterial elimination. Herein, a nanocomposite NiO NPs@AuNPs@Van (NAV) for selective MRSA removal was constructed by electrostatic self-assembly of highly photothermal magnetic NiO NPs and vancomycin (Van)-modified gold nanoparticles (AuNPs). In the presence of MRSA and under NIR irradiation, Van-mediated AuNPs can self-aggregate on MRSA surface, generating photothermal effect in situ and killing 99.6% MRSA in conjunction with magnetic NiO NPs. Additionally, the photothermal efficiency can be improved by magnetic enrichment due to the excellent magnetism of NAV, thereby enhancing the bactericidal effect at a lower experimental dose. In vitro antibacterial experiments and full-thickness skin wound healing test demonstrated that this combination therapy could effectively accelerate wound healing in MRSA-infected mice, increase collagen coverage, reduce IL-6 and TNF-α content, and upregulate VEGF expression. Biological safety experiments confirmed that NAV has good biocompatibility in vivo and in vitro. Overall, this work reveals a new type of nanocomposite with enhanced photothermal antibacterial activity as a potential nano-antibacterial agent for treating bacteria-infected wounds.

Novel Quorum Quenching YtnP Lactonase From Bacillus paralicheniformis Reduces Pseudomonas aeruginosa Virulence and Increases Antibiotic Efficacy in vivo

Bacterial infections have become increasingly difficult to treat due to the occurrence of antibiotic-resistant strains. A promising strategy to increase the efficacy of therapy is to combine antibacterials with agents that decrease pathogen virulence via the modulation of the quorum sensing (QS). Lactonases inhibit acylated homoserine lactone (AHL)-mediated QS in Gram-negative bacteria, including the leading nosocomial pathogen Pseudomonas aeruginosa. Here we describe the characteristics of heterologously expressed YtnP lactonase from Bacillus paralicheniformis ZP1 (YtnP-ZP1) isolated from agricultural soil using the culture enrichment method. Purified YtnP-ZP1 hydrolyzed different AHLs with preference to substrates with long acyl residues as evaluated in assays with biosensors and HPLC. The enzyme showed good thermostability and activity in a wide temperature range. YtnP-ZP1 in 50 μg mL^-1 concentration reduced the amount of P. aeruginosa-produced long-chain AHLs by 85%, while it hydrolyzed 50% of short-chain AHLs. Incubation of P. aeruginosa PAO1 with YtnP-ZP1 reduced its swarming motility and elastolytic activity without bactericidal effect. YtnP-ZP1 caused the inhibition of biofilm formation and disintegration of mature biofilms in P. aeruginosa PAO1 and multiresistant clinical strain BR5H that was visualized by crystal violet staining. The treatment with YtnP-ZP1 in concentrations higher than 25 μg mL^-1 improved the survival of P. aeruginosa PAO1-infected zebrafish (Danio rerio), rescuing 80% of embryos, while in combination with tobramycin or gentamicin survival rate increased to 100%. The treatment of P. aeruginosa PAO1 biofilms on infected zebrafish tail wounds with 50 μg mL^-1 YtnP-ZP1 and 2 × MIC tobramycin led to infection clearing in 2 days. The extensive toxicity studies proved YtnP-ZP1 was non-toxic to human cells and zebrafish. In conclusion, novel YtnP-ZP1 lactonase with its effective anti-virulence activity could be used to increase the efficacy of clinically approved antibiotics in clearing both systemic and biofilm-associated P. aeruginosa infections.

Persulfate-nitrogen doped graphene mixture as an oxidant for the synthesis of 3-nitro-4-aryl-2H-chromen-2-ones from aryl alkynoate esters and nitrite

A series of 3-nitro-4-aryl-2H-chromen-2-ones in good yields have directly been obtained from aryl alkynoate esters and nitrite by employing a mixture of K₂S₂O₈-nitrogen doped graphene as an oxidant in a watery medium at room temperature. A plausible mechanism for the reaction is also reported. It reveals that the product is formed through a cascade of nitro radical addition, spirocyclization, and ester migration. When compared to known methods for the synthesis of 3-nitro-4-aryl-2H-chromen-2-ones from aryl alkynoate esters, this protocol is environmentally friendly, sustainable, practical and energy efficient and does not use a harmful nitro source. Furthermore, nitrogen doped graphene used in this approach can be easily recovered and reused at least four times without losing its activity.

Crystal and molecular structures of fac-[Re(Bid)(PPh3)(CO)3] [Bid is tropolone (TropH) and tribromotropolone (TropBr3H)]

Two rhenium complexes, namely, fac-tricarbonyl(triphenylphosphane-κP)(tropolonato-κ2O,O')rhenium(I), [Re(C7H5O2)(C18H15P)(CO)3] or fac-[Re(Trop)(PPh3)(CO)3] (1), and fac-tricarbonyl(3,5,7-tribromotropolonato-κ2O,O')(triphenylphosphane-κP)rhenium(I), [Re(C7H2Br3O2)(C18H15P)(CO)3] or fac-[Re(TropBr3)(PPh3)(CO)3] (2) (TropH is tropolone and and TropBr3H is tribromotropolone), were synthesized and their crystal and molecular structures confirmed by single-crystal X-ray diffraction. Both crystallized in the space group P-1 and display an array of inter- and intramolecular interactions which were confirmed by solid-state 13C NMR spectroscopy using cross polarization magic angle spinning (CPMAS) techniques, as well as Hirshfeld surface analysis. The slightly longer Re-P distance of 1 [2.4987 (5) versus 2.4799 (11) Å for 1 and 2, respectively] suggests stronger back donation from the carbonyl groups in the former case, possibly due to the stronger electron-donating ability of the unsubstituted tropolonate ring system. However, this is not supported in the Re-CO bond distances of 1 and 2.

Oxadiazon Derivatives Elicit Potent Intracellular Growth Inhibition against Toxoplasma gondii by Disrupting Heme Biosynthesis

Infections of Toxoplasma gondii can cause severe and sometimes fatal diseases in immunocompromised individuals. The de novo heme biosynthesis pathway is required for intracellular growth and pathogenesis, making it an appealing therapeutic target. We synthesized a small library of derivatives of the herbicide oxadiazon, a known inhibitor of the penultimate reaction within the heme biosynthesis pathway in plants, catalyzed by protoporphyrinogen oxidase (PPO). Seven of the 18 analogs exhibit potent intracellular growth inhibition of wild-type T. gondii (IC50 = 1 to 2.4 μM). An assay of the compounds against Toxoplasma PPO knockout and complementation strains confirmed the mode of action to be due to the potent inhibition of PPO. The most potent compounds have no detectable cytotoxicity against human foreskin fibroblast cells up to 100 μM. This study suggests that oxadiazon derivatives may represent a new molecular scaffold for the effective treatment of T. gondii infections.

Antibacterial activity and mechanism of chloroform fraction from aqueous extract of mugwort leaves (Artemisia argyi L.) against Staphylococcus aureus

In this work, the antibacterial activity and mechanism of chloroform fraction obtained from aqueous extract of mugwort leaves against Staphylococcus aureus were investigated. The extract showed obvious antibacterial activity against S. aureus which the minimum inhibitory concentration and minimum bactericidal concentration were determined to be 3·0 and 6·0 mg ml^-1 respectively. The mechanism study suggested that the extract could destroy the integrity of the S. aureus cell walls and increase the permeability of cell membrane in a certain concentration, but it could not kill S. aureus in a short time. Instead, the extract could make bacteria in a state of apoptosis for a long time, interfere with the normal physiological metabolism of bacteria, and eventually make bacteria die, which was confirm by scanning electronic microscope.

Anticancer and Antibiotic Rhenium Tri- and Dicarbonyl Complexes: Current Research and Future Perspectives

Organometallic compounds are increasingly recognized as promising anticancer and antibiotic drug candidates. Among the transition metal ions investigated for these purposes, rhenium occupies a special role. Its tri- and dicarbonyl complexes, in particular, attract continuous attention due to their relative ease of preparation, stability and unique photophysical and luminescent properties that allow the combination of diagnostic and therapeutic purposes, thereby permitting, e.g., molecules to be tracked within cells. In this review, we discuss the anticancer and antibiotic properties of rhenium tri- and dicarbonyl complexes described in the last seven years, mainly in terms of their structural variations and in vitro efficacy. Given the abundant literature available, the focus is initially directed on tricarbonyl complexes of rhenium. Dicarbonyl species of the metal ion, which are slowly gaining momentum, are discussed in the second part in terms of future perspective for the possible developments in the field.

Indole-containing arene-ruthenium complexes with broad spectrum activity against antibiotic-resistant bacteria

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A new family of indole-containing arene ruthenium organometallic compounds are active against several bacterial species and drug resistant strains

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Bactericidal activity observed against various Gram negative, Gram positive and acid-fast bacteria, demonstrating broad-spectrum inhibitory activity

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Compound series exhibits low toxicity against human cells

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Shows considerable promise as next generation antibiotics

Antimicrobial resistant (AMR) bacteria are emerging and spreading globally, threatening our ability to treat common infectious diseases. The development of new classes of antibiotics able to kill or inhibit the growth of such AMR bacteria through novel mechanisms of action is therefore urgently needed. Here, a new family of indole-containing arene ruthenium organometallic compounds are screened against several bacterial species and drug resistant strains. The most active complex [(p-cym)Ru(O-cyclohexyl-1H-indole-2-carbothioate)Cl] (3) shows growth inhibition and bactericidal activity against different organisms (Acinetobacter baumannii, Mycobacterium abscessus, Mycobacterium tuberculosis, Staphylococcus aureus, Salmonella enterica serovar Typhi and Escherichia coli), demonstrating broad-spectrum inhibitory activity. Importantly, this compound series exhibits low toxicity against human cells. Owing to the novelty of the antibiotic family, their moderate cytotoxicity, and their inhibitory activity against Gram positive, Gram negative and acid-fast, antibiotic resistant microorganisms, this series shows significant promise for further development.

Combatting AMR: A molecular approach to the discovery of potent and non-toxic rhenium complexes active against C. albicans-MRSA co-infection

Antimicrobial resistance (AMR) is a major emerging threat to public health, causing serious issues in the successful prevention and treatment of persistent diseases. While the problem escalates, lack of financial incentive has lead major pharmaceutical companies to interrupt their antibiotic drug discovery programs. The World Health Organisation (WHO) has called for novel solutions outside the traditional development pathway, with emphasis on new classes of active compounds with non-classical mechanisms of action. Metal complexes are an untapped source of antibiotic potential owing to unique modes of action and a wider range of three-dimensional geometries as compared to purely organic compounds. In this study, we present the antimicrobial and antifungal efficacy of a family of rhenium tricarbonyl diimine complexes with varying ligands, charge and lipophilicity. Our study allowed the identification of potent and non-toxic complexes active in vivo against S. aureus infections at MIC doses as low as 300 ng/mL, as well as against C. albicans-MRSA mixed co-infection. The compounds are capable of suppressing the C. albicans morphogenetic yeast-to-hyphal transition, eradicating fungal-S. aureus co-infection, while showing no sign of cardio-, hepato-, hematotoxiciy or teratogenicity.

The role of substituted pyridine Schiff bases as ancillary ligands in the optical properties of a new series of fac-rhenium(i) tricarbonyl complexes: a theoretical view

Over the last few years, luminescent Re(i) tricarbonyl complexes have been increasingly proposed as fluorophores suitable for fluorescence microscopy to visualize biological structures and cells. In this sense, incorporating an asymmetrical pyridine Schiff base (PSB) as the ancillary ligand strongly modifies the staining and luminescent properties of Re(i) tricarbonyl complexes. In this work, we analyzed two series of Re(i) tricarbonyl complexes with their respective PSB ligands: (1) fac-[Re(CO)3(2,2'-bpy)(PSB)]1+ and (2) fac-[Re(CO)3(4,4'-bis(ethoxycarbonyl)-2,2'-bpy)(PSB)]1+, where the PSB exhibits substitutions at positions 4 or 6 in the phenolic ring with methyl or halogen substituents. Thus, we performed computational relativistic DFT and TDDFT studies to determine their optical properties. The ten complexes analyzed showed absorption in the visible light range. Furthermore, our analyses, including zero-field splitting (ZFS), allowed us to determine that the low-lying excited state locates below the 3LLCT states. Interestingly, seven of the ten analyzed complexes, whose corresponding PSB harbors an intramolecular hydrogen bond (IHB), exhibited luminescent emission that could be suitable for biological purposes: large Stokes shift, emission in the range 600-700 nm and τ in the order of 10-2 to 10-3 s. Conversely, the three complexes lacking the IHB due to two halogen substituents in the corresponding PSB showed a predicted emission with the lowest triplet excited state energy entering the NIR region. The main differences in the complexes' photophysical behavior have been explained by the energy gap law and time-resolved luminescence. These results emphasize the importance of choosing suitable substituents at the 4 and 6 positions in the phenolic ring of the PSB, which determine the presence of the IHB since they modulate the luminescence properties of the Re(i) core. Therefore, this study could predict Re(i) tricarbonyl complexes' properties, considering the desired emission features for biological and other applications.

3-Phenylcoumarins as a Privileged Scaffold in Medicinal Chemistry: The Landmarks of the Past Decade

3-Phenylcoumarins are a family of heterocyclic molecules that are widely used in both organic and medicinal chemistry. In this overview, research on this scaffold, since 2010, is included and discussed, focusing on aspects related to its natural origin, synthetic procedures and pharmacological applications. This review paper is based on the most relevant literature related to the role of 3-phenylcoumarins in the design of new drug candidates. The references presented in this review have been collected from multiple electronic databases, including SciFinder, Pubmed and Mendeley.

Platinum Cyclooctadiene Complexes with Activity against Gram-positive Bacteria

Antimicrobial resistance is a looming health crisis, and it is becoming increasingly clear that organic chemistry alone is not sufficient to continue to provide the world with novel and effective antibiotics. Recently there has been an increased number of reports describing promising antimicrobial properties of metal-containing compounds. Platinum complexes are well known in the field of inorganic medicinal chemistry for their tremendous success as anticancer agents. Here we report on the promising antibacterial properties of platinum cyclooctadiene (COD) complexes. Amongst the 15 compounds studied, the simplest compounds Pt(COD)X2 (X=Cl, I, Pt1 and Pt2) showed excellent activity against a panel of Gram-positive bacteria including vancomycin and methicillin resistant Staphylococcus aureus. Additionally, the lead compounds show no toxicity against mammalian cells or haemolytic properties at the highest tested concentrations, indicating that the observed activity is specific against bacteria. Finally, these compounds showed no toxicity against Galleria mellonella at the highest measured concentrations. However, preliminary efficacy studies in the same animal model found no decrease in bacterial load upon treatment with Pt1 and Pt2. Serum exchange studies suggest that these compounds exhibit high serum binding which reduces their bioavailability in vivo, mandating alternative administration routes such as e. g. topical application.

Efficient Direct Nitrosylation of α-Diimine Rhenium Tricarbonyl Complexes to Structurally Nearly Identical Higher Charge Congeners Activable towards Photo-CO Release

The reaction of rhenium α-diimine (N-N) tricarbonyl complexes with nitrosonium tetrafluoroborate yields the corresponding dicarbonyl-nitrosyl [Re(CO)2(NO)(N-N)X]+ species (where X = halide). The complexes, accessible in a single step in good yield, are structurally nearly identical higher charge congeners of the tricarbonyl molecules. Substitution chemistry aimed at the realization of equivalent dicationic species (intended for applications as potential antimicrobial agents), revealed that the reactivity of metal ion in [Re(CO)2(NO)(N-N)X]+ is that of a hard Re acid, probably due to the stronger π-acceptor properties of NO+ as compared to those of CO. The metal ion thus shows great affinity for π-basic ligands, which are consequently difficult to replace by, e.g., σ-donor or weak π-acids like pyridine. Attempts of direct nitrosylation of α-diimine fac-[Re(CO)3]+ complexes bearing π-basic OR-type ligands gave the [Re(CO)2(NO)(N-N)(BF4)][BF4] salt as the only product in good yield, featuring a stable Re-FBF3 bond. The solid state crystal structure of nearly all molecules presented could be elucidated. A fundamental consequence of the chemistry of [Re(CO)2(NO)(N-N)X]+ complexes, it that the same can be photo-activated towards CO release and represent an entirely new class of photoCORMs.

Coumarins as Tool Compounds to Aid the Discovery of Selective Function Modulators of Steroid Hormone Binding Proteins

Steroid hormones play an essential role in a wide variety of actions in the body, such as in metabolism, inflammation, initiating and maintaining sexual differentiation and reproduction, immune functions, and stress response. Androgen, aromatase, and sulfatase pathway enzymes and nuclear receptors are responsible for steroid biosynthesis and sensing steroid hormones. Changes in steroid homeostasis are associated with many endocrine diseases. Thus, the discovery and development of novel drug candidates require a detailed understanding of the small molecule structure–activity relationship with enzymes and receptors participating in steroid hormone synthesis, signaling, and metabolism. Here, we show that simple coumarin derivatives can be employed to build cost-efficiently a set of molecules that derive essential features that enable easy discovery of selective and high-affinity molecules to target proteins. In addition, these compounds are also potent tool molecules to study the metabolism of any small molecule.

Zebrafish: An Attractive Model to Study Staphylococcus aureus Infection and Its Use as a Drug Discovery Tool

Non-mammalian in vivo disease models are particularly popular in early drug discovery. Zebrafish (Danio rerio) is an attractive vertebrate model, the success of which is driven by several advantages, such as the optical transparency of larvae, the small and completely sequenced genome, the small size of embryos and larvae enabling high-throughput screening, and low costs. In this review, we highlight zebrafish models of Staphyloccoccus aureus infection, which are used in drug discovery and for studying disease pathogenesis and virulence. Further, these infection models are discussed in the context of other relevant zebrafish models for pharmacological and toxicological studies as part of early drug profiling. In addition, we examine key differences to commonly applied models of S.aureus infection based on invertebrate organisms, and we compare their frequency of use in academic research covering the period of January 2011 to January 2021.

Design, synthesis and biological evaluation of novel pleuromutilin derivatives as potent anti-MRSA agents targeting the 50S ribosome

A series of novel pleuromutilin derivatives were designed and synthesized with 1,2,4-triazole as the linker connected to benzoyl chloride analogues under mild conditions. The in vitro antibacterial activities of the synthesized derivatives against four strains of Staphylococcus aureus (MRSA ATCC 43300, ATCC 29213, AD3 and 144) were tested by the broth dilution method. Most of the synthesized derivatives displayed potent activities, and 22-(3-amino-2-(4-methyl-benzoyl)-1,2,4-triazole-5-yl)-thioacetyl)-22-deoxypleuromutilin (compound 12) was found to be the most active antibacterial derivative against MRSA (MIC = 0.125 μg/mL). Furthermore, the time-kill curves showed compound 12 had a certain inhibitory effect against MRSA in vitro. The in vivo antibacterial activity of compound 12 was further evaluated using MRSA infected murine thigh model. Compound 12 exhibited superior antibacterial efficacy than tiamulin. It was also found that compound 12 had no significant inhibitory effect on the proliferation of RAW264.7 cells. Compound 12 was further evaluated in CYP450 inhibition assay and showed moderate inhibitory effect on CYP3A4 (IC50 = 3.95 μM). Moreover, seven candidate compounds showed different affinities with the 50S ribosome by SPR measurement. Subsequently, binding of compound 12 and 20 to the 50S ribosome was further investigated by molecular modeling. Three strong hydrogen bonds were formed through the interaction of compound 12 and 20 with 50S ribosome. The binding free energy of compound 12 and 20 with the ribosome was calculated to be -10.7 kcal/mol and -11.66 kcal/mol, respectively.

Aerobically stable and substitutionally labile α-diimine rhenium dicarbonyl complexes

New synthetic routes to aerobically stable and substitutionally labile α-diimine rhenium(i) dicarbonyl complexes are described. The molecules are prepared in high yield from the cis–cis–trans-[Re(CO)₂(^tBu₂bpy)Br₂]⁻ anion (2, where ^tBu₂bpy is 4,4′-di-tert-butyl-2,2′-bipyridine), which can be isolated from the one electron reduction of the corresponding 17-electron complex (1). Compound 2 is stable in the solid state, but in solution it is oxidized by molecular oxygen back to 1. Replacement of a single bromide of 2 by σ-donor monodentate ligands (Ls) yields stable neutral 18-electron cis–cis–trans-[Re(CO)₂(^tBu₂bpy)Br(L)] species. In coordinating solvents like methanol the halide is replaced giving the corresponding solvated cations. [Re(CO)₂(^tBu₂bpy)Br(L)] species can be further reacted with Ls to prepare stable cis–cis–trans-[Re(CO)₂(^tBu₂bpy)(L)₂]⁺ complexes in good yield. Ligand substitution of Re(i) complexes proceeds via pentacoordinate intermediates capable of Berry pseudorotation. In addition to the cis–cis–trans-complexes, cis–cis–cis- (all cis) isomers are also formed. In particular, cis–cis–trans-[Re(CO)₂(^tBu₂bpy)(L)₂]⁺ complexes establish an equilibrium with all cis isomers in solution. The solid state crystal structure of nearly all molecules presented could be elucidated. The molecules adopt a slightly distorted octahedral geometry. In comparison to similar fac-[Re(CO)₃]⁺complexes, Re(i) diacarbonyl species are characterized by a bend (ca. 7°) of the axial ligands towards the α-diimine unit. [Re(CO)₂(^tBu₂bpy)Br₂]⁻ and [Re(CO)₂(^tBu₂bpy)Br(L)] complexes may be considered as synthons for the preparation of a variety of new stable diamagnetic dicarbonyl rhenium cis-[Re(CO)₂]⁺ complexes, offering a convenient entry in the chemistry of the core.

New synthetic routes to aerobically stable and substitutionally labile α-diimine rhenium(i) dicarbonyl complexes offer a convenient entry in the chemistry of the cis-[Re(CO)₂]⁺ core.

Trending Topics on Coumarin and Its Derivatives in 2020

Coumarins are naturally occurring molecules with a versatile range of activities. Their structural and physicochemical characteristics make them a privileged scaffold in medicinal chemistry and chemical biology. Many research articles and reviews compile information on this important family of compounds. In this overview, the most recent research papers and reviews from 2020 are organized and analyzed, and a discussion on these data is included. Multiple electronic databases were scanned, including SciFinder, Mendeley, and PubMed, the latter being the main source of information. Particular attention was paid to the potential of coumarins as an important scaffold in drug design, as well as fluorescent probes for decaging of prodrugs, metal detection, and diagnostic purposes. Herein we do an analysis of the trending topics related to coumarin and its derivatives in the broad field of drug discovery.

Design, synthesis, antibacterial activity evaluation and molecular modeling studies of new sulfonamides containing a sulfathiazole moiety

Molecular modifications on sulfathiazole to overcome sulfonamide resistance: the discovery of selective antibacterial agents against Staphylococcus aureus.

Potentials of nanotechnology in treatment of methicillin-resistant Staphylococcus aureus

Abuse of antibiotics has led to the emergence of drug-resistant pathogens. Methicillin-resistant Staphylococcus aureus (MRSA) was reported just two years after the clinical use of methicillin, which can cause severe infections with high morbidity and mortality in both community and hospital. The treatment of MRSA infection is greatly challenging since it has developed the resistance to almost all types of antibiotics. As such, it is of great significance and importance to develop novel therapeutic approaches. The fast development of nanotechnology provides a promising solution to this dilemma. Functional nanomaterials and nanoparticles can act either as drug carriers or as antibacterial agents for antibacterial therapy. Herein, we aim to provide a comprehensive understanding of the drug resistance mechanisms of MRSA and discuss the potential applications of some functionalized nanomaterials in anti-MRSA therapy. Also, the concerns and possible solutions for the nanomaterials-based anti-MRSA therapy are discussed.