Synthesis, antimicrobial, and antiviral activities of some new 5-sulphonamido-8-hydroxyquinoline derivatives

Harnessing the Dual Antimicrobial Mechanism of Action with Fe(8-Hydroxyquinoline)3 to Develop a Topical Ointment for Mupirocin-Resistant MRSA Infections

8-Hydroxyquinoline (8-hq) exhibits potent antimicrobial activity against Staphylococcus aureus (SA) bacteria with MIC = 16.0-32.0 µM owing to its ability to chelate metal ions such as Mn²⁺, Zn^2+, and Cu²⁺ to disrupt metal homeostasis in bacterial cells. We demonstrate that Fe(8-hq)₃, the 1:3 complex formed between Fe(III) and 8-hq, can readily transport Fe(III) across the bacterial cell membrane and deliver iron into the bacterial cell, thus, harnessing a dual antimicrobial mechanism of action that combines the bactericidal activity of iron with the metal chelating effect of 8-hq to kill bacteria. As a result, the antimicrobial potency of Fe(8-hq)₃ is significantly enhanced in comparison with 8-hq. Resistance development by SA toward Fe(8-hq)₃ is considerably delayed as compared with ciprofloxacin and 8-hq. Fe(8-hq)₃ can also overcome the 8-hq and mupirocin resistance developed in the SA mutant and MRSA mutant bacteria, respectively. Fe(8-hq)₃ can stimulate M1-like macrophage polarization of RAW 264.7 cells to kill the SA internalized in such macrophages. Fe(8-hq)₃ exhibits a synergistic effect with both ciprofloxacin and imipenem, showing potential for combination therapies with topical and systemic antibiotics for more serious MRSA infections. The in vivo antimicrobial efficacy of a 2% Fe(8-hq)₃ topical ointment is confirmed by the use of a murine model with skin wound infection by bioluminescent SA with a reduction of the bacterial burden by 99 ± 0.5%, indicating that this non-antibiotic iron complex has therapeutic potential for skin and soft tissue infections (SSTIs).

Chloroquine Analogs: An Overview of Natural and Synthetic Quinolines as Broad Spectrum Antiviral Agents

SARS-CoV-2, a positive single-stranded RNA enveloped coronavirus, currently poses a global health threat. Drugs with quinoline scaffolds have been studied to repurpose their useful broad-spectrum properties into treating various diseases, including viruses. Preliminary studies on the quinoline medications, chloroquine and hydroxychloroquine, against SARS-CoV-2, have shown to be a potential area of interest for drug development due to their ability to prevent viral entry, act as anti-inflammatory modulators, and inhibit key enzymes allowing reduced viral infectivity. In addition to Chloroquine and Hydroxychloroquine, we discussed analogs of the drugs to understand the quinoline scaffold's potential antiviral mechanisms. The heterocyclic scaffold of quinoline can be modified in many ways, primarily through the modification of its substituents. We studied these different synthetic derivatives to understand properties that could enhance its antiviral specificity thoroughly. Chloroquine and its analogs can act on various stages of the viral life cycle, pre and post entry. In this study, we reviewed chloroquine and its synthetic and natural analogs for their antiviral properties in a variety of viruses. Furthermore, we reviewed the compound's potential abilities to attenuate symptoms associated with viral infections. Natural compounds that share scaffolding to chloroquine can act as antivirals or attenuate symptoms through the stimulation of the host immune system or reduction of oxidative stress. Furthermore, we discuss perspectives of the drug's repurposing due to its ability to inhibit the beta-hematin formation and to be a Zinc Ionophore.