DNA binding, prominent photonuclease activity and antibacterial PDT of cobalt(II) complexes of phenanthroline based photosensitizers

Substituted naphthoxy-phthalonitrile derivatives: Synthesis, substituent effects, DFT, TD-DFT Calculations, antimicrobial properties and DNA interaction studies

Herein, substituted-naphthol derivatives 4a-e were synthesized in two steps, namely the Diels Alder cycloaddition and Cu-catalyzed aromatization reactions, respectively. Then, pththalonitrile derivatives 7-12 have been prepared by a nucleophilic displacement reaction of 3-nitrophthalonitrile with the naphthol derivatives 4a-e, 5 and, obtained in excellent yields. Structural characterization of the compounds was identified by different spectroscopic techniques. Antimicrobial properties of the synthesized compounds were determined by the microdilution procedure against Gram-positive, Gram-negative bacteria, and yeast. Furthermore, the DNA interaction of the compounds were determined by gel electrophoresis. One of the most prominent findings is that compounds 9 and 10 have more inhibitory effects on Gram-positive bacteria than Gram-negative bacteria. These compounds especially exhibited the highest antibacterial potency against S. aureus (625 µg/mL) among Gram-positive bacteria. According to the plasmid DNA interaction results, the synthesized compounds caused changes in the structure and mobility of the plasmid DNA. Then, geometry optimizations and frequency calculations were conducted at B3LYP/6-311 G(d,p) level of DFT, and optimized structures were used for further analyses. The NBO results revealed that the π→π * and n→π * interactions were greatly contributed to lowering the stabilization energy of all compounds (7-12). FMO energy analyses showed that compound 9 has the biggest electrodonating power.

Identification of dual-targeted Mycobacterium tuberculosis aminoacyl-tRNA synthetase inhibitors using machine learning

Background: The most serious challenge in the treatment of tuberculosis is the multidrug resistance of Mycobacterium tuberculosis to existing antibiotics. As a strategy to overcome resistance we used a multitarget drug design approach. The purpose of the work was to discover dual-targeted inhibitors of mycobacterial LeuRS and MetRS with machine learning. Methods: The artificial neural networks were built using module nnet from R 3.6.1. The inhibitory activity of compounds toward LeuRS and MetRS was investigated in aminoacylation assays. Results: Using a machine-learning approach, we identified dual-targeted inhibitors of LeuRS and MetRS among 2-(quinolin-2-ylsulfanyl)-acetamide derivatives. The most active compound inhibits MetRS and LeuRS with IC₅₀ values of 33 μm and 23.9 μm, respectively. Conclusion: 2-(Quinolin-2-ylsulfanyl)-acetamide scaffold can be useful for further research.

Macrocyclic "tet a"-Derived Cobalt(III) Complex with a N,N'-Disubstituted Hexadentate Ligand: Crystal Structure, Photonuclease Activity, and as a Photosensitizer

A cobalt(III) complex, [Co(L)]Cl (complex 1, where L = 1,8-[N,N-bis{(3-formyl-2-hydroxy-5-methyl)benzyl}]-1,4,8,11-tetraaza-5,5,7,12,12,14-hexamethylcyclotetradecane) with distorted octahedral geometry has been synthesized and characterized using various spectroscopic techniques. The structure of the ligand has remarkably rich hydrogen intermolecular interactions such as H···H, H···C/C···H, and H···O/O···H that vary with the presence of the metal ion, and the structure of complex 1 has Cl···H interactions; this result has been proved by Hirshfeld surface and two-dimensional (2D) fingerprint maps analyses. The complex exhibits a quasi-reversible Co(III)/Co(II) redox couple with E _1/2 = -0.76 V. Calf thymus DNA (CT DNA) binding abilities of the ligand and complex 1 were confirmed by spectroscopic and electrochemical analyses. According to absorption studies, the ligand and complex 1 bind to CT DNA via intercalative binding mode, with intrinsic binding strengths of 1.41 × 10³ and 8.64 × 10³ M^-1, respectively. A gel electrophoresis assay shows that complex 1 promotes the pUC19 DNA cleavage under dark and light irradiation conditions. Complex 1 has superior antimicrobial activity than the ligand. The cytotoxicity of complex 1 was tested against MDA-MB-231 breast cancer cells with values of IC₅₀ of 1.369 μg mL^-1 in the dark and 0.9034 μg mL^-1 after light irradiation. Besides, cell morphological studies confirmed the morphological changes with AO/EB dual staining, reactive oxygen species (ROS) staining, mitochondria staining, and Hoechst staining on MDA-MB-231 cancer cells by fluorescence microscopy. Complex 1 was found to be a potent antiproliferative agent against MDA-MB-231 cells, and it can induce mitochondrial-mediated and caspase-dependent apoptosis with activation of downregulated caspases. The biotoxicity assay of complex 1 on the development of Artemia nauplii was evaluated at an IC₅₀ value of 200 μg mL^-1 and with excellent biocompatibility.

Antimicrobial Photodynamic Therapy: Latest Developments with a Focus on Combinatory Strategies

Antimicrobial photodynamic therapy (aPDT) has become a fundamental tool in modern therapeutics, notably due to the expanding versatility of photosensitizers (PSs) and the numerous possibilities to combine aPDT with other antimicrobial treatments to combat localized infections. After revisiting the basic principles of aPDT, this review first highlights the current state of the art of curative or preventive aPDT applications with relevant clinical trials. In addition, the most recent developments in photochemistry and photophysics as well as advanced carrier systems in the context of aPDT are provided, with a focus on the latest generations of efficient and versatile PSs and the progress towards hybrid-multicomponent systems. In particular, deeper insight into combinatory aPDT approaches is afforded, involving non-radiative or other light-based modalities. Selected aPDT perspectives are outlined, pointing out new strategies to target and treat microorganisms. Finally, the review works out the evolution of the conceptually simple PDT methodology towards a much more sophisticated, integrated, and innovative technology as an important element of potent antimicrobial strategies.

Discovery of metal-based complexes as promising antimicrobial agents

The antimicrobial resistance (AMR) is an intractable problem for the world. Metal ions are essential for the cell process and biological function in microorganisms. Many metal-based complexes with the potential for releasing ions are more likely to be absorbed for their higher lipid solubility. Hence, this review highlights the clinical potential of organometallic compounds for the treatment of infections caused by bacteria or fungi in recent five years. The common scaffolds, including antimicrobial peptides, N-heterocyclic carbenes, Schiff bases, photosensitive-grand-cycle skeleton structures, aliphatic amines-based ligands, and special metal-based complexes are summarized here. We also discuss their therapeutic targets and the risks that should be paid attention to in the future studies, aiming to provide information for researchers on metal-based complexes as antimicrobial agents and inspire the design and synthesis of new antimicrobial drugs.