Targeting novel sites in DNA gyrase for development of anti-microbials

Design, synthesis and exploration of novel triazinoindoles as potent quorum-sensing inhibitors and radical quenchers

Background: Antimicrobial resistance has become a critical health concern, and quorum-sensing exacerbates the resistance by facilitating cell-to-cell communication within the microbial community, leading to severe pathogenic outbreaks. Methods & results: Novel 1-(2-((5H-[1,2,4]-triazino[5,6-b]indol-3-yl)thio)acetyl)indoline-2,3-diones were synthesized. The title compounds exhibit outstanding anti-quorum-sensing efficacy, and compound 7g demonstrated the maximum proficiency (IC50 = 0.0504 μg/ml). The hybrids displayed potent antioxidant action, and compound 7c showed the highest antioxidant ability (IC50 = 40.71 μg/ml). Molecular docking of the isatin hybrids against DNA gyrase and quorum-sensing receptor CviR validated the observed in vitro findings. The befitting pharmacokinetic profile of the synthesized drug candidates was ascertained through absorption, distribution, metabolism, excretion and toxicity screening. Conclusion: The remarkable biocompetence of the synthesized triazinoindoles may help to combat drug-resistant infections.

Probing Antibacterial and Anticancer Potential of Selenicereus undatus, Pistacia vera L. and Olea europaea L. against Uropathogens, MCF-7 and A2780 Cancer Cells

Urinary tract infection is an infectious disease that requires immediate treatment. It can occur in any age group and involves both genders equally. The present study was to check the resistance of some antibiotics and to assess the antibacterial potential of three extracts of three plants against notorious bacteria involved in urinary tract infections. Along with assessing the antibacterial activity of plant extracts, we checked for the anticancer potential of these extracts against the cancer cell lines MCF-7 and A2780. Cancer is the leading cause of mortality in developed countries. Determinations of total flavonoid content, total phenolic content, total alkaloid content, total tannin content, total carotenoid content, and total steroid content were performed. The disk diffusion method was used to analyze the antibacterial activity of plant extracts. Ethanolic extract of Selenicereus undatus showed sensitivity (25-28 mm) against bacteria, whereas chloroform and hexane extracts showed resistance against all bacteria except Staphylococcus (25 mm). Ethanolic extract of Pistacia vera L. showed sensitivity (22-25 mm) against bacteria, whereas chloroform and hexane extracts showed resistance. Ethanolic extract of Olea europaea L. showed sensitivity (8-16 mm) against all bacteria except Staphylococcus, whereas chloroform and hexane extracts showed resistance. Positive controls showed variable zones of inhibition (2-60 mm), and negative control showed 0-1 mm. The antibiotic resistance was much more prominent in the case of hexane and chloroform extracts of all plants, whereas ethanolic extract showed a sensitivity of bacteria against extracts. Both cell lines, MCF-7 and A2780, displayed decreased live cells when treated with plant extracts.

A Fluorescence-Based, T5 Exonuclease-Amplified DNA Cleavage Assay for Discovering Bacterial DNA Gyrase Poisons

Fluoroquinolones (FQs) are potent antibiotics of clinical significance, known for their unique mechanism of action as gyrase poisons, which stabilize gyrase-DNA cleavage complexes and convert gyrase into a DNA-damaging machinery. Unfortunately, FQ resistance has emerged, and these antibiotics can cause severe side effects. Therefore, discovering novel gyrase poisons with different chemical scaffolds is essential. The challenge lies in efficiently identifying them from compound libraries containing thousands or millions of drug-like compounds, as high-throughput screening (HTS) assays are currently unavailable. Here we report a novel fluorescence-based, T5 exonuclease-amplified DNA cleavage assay for gyrase poison discovery. This assay capitalizes on recent findings showing that multiple gyrase molecules can simultaneously bind to a plasmid DNA molecule, forming multiple gyrase-DNA cleavage complexes on the same plasmid. These gyrase-DNA cleavage complexes, stabilized by a gyrase poison, can be captured using sarkosyl. Proteinase K digestion results in producing small DNA fragments. T5 exonuclease, selectively digesting linear and nicked DNA, can fully digest the fragmented linear DNA molecules and, thus, "amplify" the decrease in fluorescence signal of the DNA cleavage products after SYBR Green staining. This fluorescence-based, T5 exonuclease-amplified DNA cleavage HTS assay is validated using a 50-compound library, making it suitable for screening large compound libraries.

Identification of potential Escherichia coli DNA gyrase B inhibitors targeting antibacterial therapy: an integrated docking and molecular dynamics simulation study

The alarming rise in the rate of antibiotic resistance is a matter of significant concern. DNA gyrase B (GyrB), a critical bacterial enzyme involved in DNA replication, transcription, and recombination, has emerged as a promising target for antibacterial agents. Inhibition of GyrB disrupts bacterial DNA replication, leading to cell death, making it an attractive candidate for antibiotic development. Although several classes of antibiotics targeting GyrB are currently in clinical use, the emergence of antibiotic resistance necessitates the exploration of novel inhibitors. In this study, we aimed to identify potential Escherichia coli GyrB inhibitors from a database of phytoconstituents sourced from Indian medicinal plants. Utilizing virtual screening, we performed a rigorous search to identify compounds with the most promising inhibitory properties against GyrB. Two compounds, namely Zizogenin and Cucurbitacin S, were identified based on their favorable drug likeliness and pharmacokinetic profiles. Employing advanced computational techniques, we analyzed the binding interactions of Zizogenin and Cucurbitacin S with the ATP-binding site of GyrB through molecular docking simulations. Both compounds exhibited robust binding interactions, evidenced by their high docking energy scores. To assess the stability of these interactions, we conducted extensive 100 ns molecular dynamics (MD) simulations, which confirmed the stability of Zizogenin and Cucurbitacin S when bound to GyrB. In conclusion, our study highlights Zizogenin and Cucurbitacin S as promising candidates for potential antibacterial agents targeting GyrB. Experimental validation of these compounds is warranted to further explore their efficacy and potential as novel antibiotics to combat antibiotic-resistant bacteria.Communicated by Ramaswamy H. Sarma.