Multi-target antibacterial mechanism of ruthenium polypyridine complexes with anthraquinone groups against Staphylococcus aureus

Copper(II) carboxylate complexes inhibit Staphylococcus aureus biofilm formation by targeting extracellular proteins

Three copper(II) complexes of diphenyl acetic acid (DPAA) pyridine (py), 2,2΄-dipyridylamine (dpa), and 4,7-diphenyl, 1,10-phenanthroline (di-phen), [Cu₂(DPAA)₄(py)2] (Cu-1), [Cu(DPAA)₂(dpa)] (Cu-2), and [Cu₂(DPAA)₄(di-phen)₂] (Cu-3) were synthesized and characterized. Their antibacterial activities were evalvated. The minimum inhibitory concentrations (MIC) of these complexes against six tested microbial strains ranged from 1 to 128 μg/mL, and that of vancomycin antibiotic ranged from 0.5 to 2 μg/mL. The bactericidal effects of Cu-1, Cu-2 and Cu-3 and vancomycin against Staphylococcus aureus (S. aureus) were determined by colony count assay. Cu-1, Cu-2, and vancomycin showed relatively weaker antibiofilm formation activities; however, Cu-3 showed enhanced activity against S. aureus proliferation and biofilm formation as confirmed by microscopic analysis. In antibiofilm assays, Cu-1, Cu-2 and Cu-3 demonstrated high inhibition ability (23-75 %), of mature biofilm formation at concentrations of 5 to 15 μg/mL, and vancomycin at 15 μg/mL inhibited only 47 %. Cu-3 also effectively killed S. aureus within biofilms at doses up to 2 × MIC μg/mL. Further analysis of extracellular proteins (ECPs) expression revealed, that Cu-3 had significant potential in suppressing ECPs production. Molecular docking (MD) studies with biofilm associated protein (Bap) and SARS-CoV-2 receptors showed high interactions by several bonding types, where Cu-2 found as potent antiviral agent. Collectively, these findings highlighted the copper complexes potential in antibacterial applications, with Cu-3 emerging as a potent candidate for S. aureus biofilm inhibition.

Eradication of Antibiotic-Resistant Gram-Positive Bacteria and Biofilms by Rationally Designed AIE-Active Iridium(III) Complexes Derived from Cyclometalating 2-Phenylquinoline and Ancillary Bipyridyl Ligands

Antibiotic resistance caused by Gram-positive bacteria is a growing global human health threat. Selective discrimination and eradication of Gram-positive bacteria and their biofilms is challenging. Therapeutic strategies with multiple modes of action are urgently needed to address the increase in Gram-positive bacteria-resistant nosocomial infections. In this work, we have presented rationally designed aggregation-induced emission (AIE)-active cationic cyclometalated iridium(III) complexes derived from 2-phenylquinoline and 2,2'-bipyridine ligands for Gram-positive antibacterial studies. The AIE properties of these complexes were exploited for selective discrimination between Gram-positive and Gram-negative bacteria. These complexes displayed good antimicrobial activity against critical Gram-positive ESKAPE pathogens with minimum inhibitory concentrations in the low micromolar range but were inactive against Gram-negative pathogens. Importantly, the complexes can inhibit biofilm formation and eradicate bacteria from mature biofilms, which are major causes of persistent infections and antibiotic resistance and are more difficult to eliminate. In addition, these complexes showed low hemolytic activity against mammalian cells and a high therapeutic index, indicating good selectivity. Interestingly, the complexes kill bacteria through a variety of modes of mechanism, including ROS generation, cell membrane disruption, and depolarization and the loss of bacterial membrane integrity. These findings offer opportunities for designing metal AIEgens to treat Gram-positive bacterial infections effectively.

Targeting bacterial efflux pump effectively enhances the efficacy of Ru-based antibacterial agents against Gram-negative pathogen

The rise of antibiotic resistance has posed a great threat to human's life, thus develop novel antibacterial agents is urgently needed. It worthies to noted that Ru-based antibacterial agents often showed robust potency against Gram-positive pathogens, disrupted bacterial membrane and avoided bacterial resistance, making they promising antibiotic candidates. However, they are generally less active when applied to negative pathogens. To address this problem, a Ru-based metalloantibiotic (RuN) modified with a nitrothiophene moiety, which can target bacterial efflux pump, was designed and evaluated in this work. A series of assays demonstrated that RuN not only fully retained the advantages of Ru-based agents, such as destroyed bacterial membrane and induced reactive oxygen species production, but also can targeted bacterial efflux pumps. Of course, these properties make it effective in killing both Gram-positive and negative pathogens, its MIC values against Staphylococcus aureus and Escherichia coli lies at 3.125 and 6.25 μg/mL, respectively. Importantly, RuN also showed low toxicity and has robust anti-infective potency in two animal infection models. Together, our results paved an alternative way to enhance the anti-infective efficacy of Ru-based agents against resistant negative bacteria.

Development of Cyclometalated Iridium(III) Complexes of 2-Phenylbenzimidazole and Bipyridine Ligands for Selective Elimination of Gram-Positive Bacteria

Herein, we have reported a series of cationic aggregation-induced emission (AIE) active iridium(III) complexes (Ir1-Ir5) of the type [Ir(C N)2(N N)]Cl, wherein C N is a cyclometalating 2-phenylbenzimidazole ligand with varying alkyl chain lengths and N N is a 2,2'-bipyridine ligand attached to bis-polyethylene glycol chains, for the treatment of bacterial infections. The AIE phenomenon of the complexes leveraged for detecting bacteria by fluorescence microscopy imaging that displayed a strong red emission in Gram-positive bacteria. The antibacterial activity of the complexes assessed against Gram-positive methicillin-sensitive S. aureus, methicillin-resistant S. aureus, E. faecium and E. faecalis and Gram-negative E. coli and P. aeruginosa bacteria of clinical interest. The complexes Ir2-Ir4 exerted potent antibacterial activity towards Gram-positive strains with low minimum inhibitory concentrations (MICs) values in the range of 1-9 μM, which is comparable to clinically approved antibiotic vancomycin. In contrast, these complexes were found to be inactive towards Gram-negative bacterial strains (MICs >100 μM). The mechanism of antibacterial activity of the complexes implies that ROS generation, membrane depolarization and rupture are responsible for bacterial cell death. Further, the complexes Ir1-Ir3 were found to be low-toxic against human red blood cells and human embryonic kidney (HEK293) cells, indicating their potential for use as antibacterial agents.

Synthesis of a New Series of Anthraquinone-Linked Cyclopentanone Derivatives: Investigating the Antioxidant, Antibacterial, Cytotoxic and Tyrosinase Inhibitory Activities of the Mushroom Tyrosinase Enzyme Using Molecular Docking

Purpose

New bioactive anthraquinone derivatives are investigated for antibacterial, tyrosinase inhibitory, antioxidant cytotoxic activity, and molecular docking.

Methods

The compounds were produced using the grindstone method, yielding 69 to 89%. These compounds were analyzed using IR, 1H, and 13C NMR and elemental and mass spectral methods. Additionally, the antibacterial, antioxidant, and tyrosinase inhibitory activities of all the synthesised compounds were evaluated.

Results

Compound 2 showed remarkable tyrosinase inhibition activity, with an (IC50: 13.45 µg/mL), compared to kojic acid (IC50: 19.40 µg/mL). It also exhibited moderate antioxidant and antibacterial activities with respect to the references BHT and ampicillin, respectively. Kinetic analysis revealed that the tyrosinase inhibitory activity of compound 2 was non-competitive and competitive, whereas that of compound 1 was low. All compounds (1-8) were significantly less active than doxorubicin (LC50: 0.74±0.01μg/mL). However, compound 2 affinity for the 2Y9X protein was lower than kojic acid, with a lower docking score (-8.6 kcal/mol compared to (-4.7 kcal/mol), making it more effective.

Conclusion

All synthesized compounds displayed remarkable antibacterial, tyrosinase inhibitory, antioxidant, and cytotoxic activities, with compound 2 showing exceptional potency as a multitarget agent. Anthraquinone substituent groups may offer the potential for the development of treatments. The derivatives were synthesized using the grindstone method, and their antibacterial, antioxidant, tyrosinase inhibitory, and cytotoxic activities were inspected. Molecular docking and molecular dynamics simulations were performed using compound 2 and kojic acid to validate the results and confirm the stability of the compounds.

Gaafar AR, Gurusamy R, Akbar I. Synthesis of anthraquinone-connected coumarin derivatives via grindstone method and their evaluation of antibacterial, antioxidant, tyrosinase inhibitory activities with molecular docking, and DFT calculation studies

Anthraquinones and coumarins have excellent pharmacological activities and are an important class of natural plant metabolites with various biological activities. In this study, anthraquinone-9,10-dione and coumarin derivatives were combined to develop a novel anthraquinone-connected coumarin-derivative sequence. The synthesised novel anthraquinone-connected coumarin derivatives (1a-t) were screened for in vitro antibacterial, antioxidant, and tyrosinase inhibitory activities. The antibacterial activities of the synthesised compounds (1a-t) were tested against both gram-positive and gram-negative bacteria. Specifically, compound 1t was more active against E. aerogenes than ciprofloxacin. With regard to antioxidant activity, compound 1o (50.68 % at 100 μg/mL) was highly active compared to the other compounds, whereas it was less active than the standard BHT (76.74 % at 100 μg/mL). In terms of compound 1r (9.31 ± 0.45 μg/mL) was highly active against tyrosinase inhibitory activity compared with kojic acid (10.42 ± 0.98 μg/mL). In the molecular docking study, compound 1r had a higher docking score (-8.8 kcal mol-1) than kojic acid (-1.7 kcal mol-1). DFT calculations were performed to determine the energy gap of highly active compound 1r (ΔE = 0.11) and weakly active compound 1a (ΔE = 0.12). In this study, we found that every molecule displayed significant antibacterial, antioxidant, and tyrosinase inhibitory properties. Based on these reports, compounds 1r and 1t may act as multi-target agents.

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.