From Antibacterial to Antifungal: Structure, Safety, and Serum Albumin Binding of Zn(II)-Nalidixate Complexes with Phenanthroline and Bipyridine.

Design of a bioactive nickel(II) complex based on a hydrazone Schiff base ligand: Synthesis, structural characterization and antimicrobial investigations

A novel hydrazone Schiff base ligand (H3L) and its nickel(II) complex were synthesized and fully characterized using a range of spectroscopic techniques. The antibacterial activities of both compounds were evaluated against Gram-positive and Gram-negative bacterial strains by means of the agar diffusion method, minimum inhibitory concentration (MIC) assays, and minimum bactericidal concentration (MBC) assays. The nickel complex exhibited significantly enhanced antibacterial activity compared to the free ligand, an improvement that may be attributed to the chelation effect and the increased lipophilicity of the complex. The present work aimed to synthesize a novel hydrazone Schiff base ligand and its nickel(II) complex, characterize their structures, and evaluate their antibacterial activities against selected pathogenic bacterial strains. The ligand (H3L) crystallizes in the monoclinic system in the space group C2/c, with unit cell parameters a = 21.0113(2) Å, b = 6.9353(4) Å, c = 21.3996(9) Å, α = 90°, β = 104.202(2)°, γ = 90°.

Synthesis, characterization, antimicrobial, antibiofilm, and molecular docking studies of Cu(II) and Zn(II) Schiff base complexes derived from L-tyrosine and indole-3-carboxaldehyde

Schiff bases and their metal complexes have garnered significant interest as antimicrobial agents, particularly in addressing antimicrobial resistance (AMR). Schiff base-derived metal complexes constitute an important class of compounds that exhibit exceptional biological activity and are therefore promising candidates for drug development, especially in view of the growing threat of AMR and microbial biofilms. This study reports the synthesis and characterization of Cu(II) and Zn(II) complexes, and a Schiff base ligand derived from indole-3-carboxaldehyde and L-tyrosine. The structures of the ligand and its complexes were confirmed using IR, electronic, and NMR spectroscopy. Based on the experimental results, the Cu(II) and Zn(II) complexes were assigned square planar and tetrahedral geometries, respectively. The antimicrobial efficacy of the complexes was evaluated using disc diffusion and minimum inhibitory concentration (MIC) assays. Antibiofilm investigations and fluorescence microscopy revealed that both complexes were effective against P. aeruginosa biofilms, with the Cu(II) complex demonstrating notably greater activity than the Zn(II) complex. Computational studies were performed for target prediction and revealed strong binding affinities with specific P. aeruginosa proteins (PelA, LpxC, AlgL, ExoS, and PslG), thereby supporting the observed biological activity of the synthesized complexes. These synthesized Schiff base complexes efficiently disrupted biofilms, providing a promising approach for managing chronic infections associated with resistant bacteria.

Synthesis, structural elucidation, antimicrobial performance, and DNA-binding behavior of a new N2O2 tetradentate schiff base and its transition metal and uranyl complexes

A new tetradentate N2O2 Schiff base ligand derived from 2,6-diaminopyridine and 2,4-dihydroxybenzaldehyde was synthesized and used to prepare its Cu(II), Co(II), Ni(II), Mn(II), and UO2 (II) complexes. The ligand and complexes were fully characterized by elemental analysis, FT-IR, UV–Vis, 1H/13C NMR, ESR, mass spectrometry, powder X-ray diffraction, magnetic measurements, and thermal (TGA/DTA) analyses. Spectroscopic data confirm coordination through azomethine nitrogen and phenolic oxygen atoms, leading to predominantly octahedral geometries for the transition metal complexes, while the uranyl complex retains a hexagonal-planar O=U=O environment. Thermal studies reveal enhanced stability of the metal complexes compared to the free ligand. The antimicrobial activity was evaluated against Bacillus subtilis, Enterobacter aerogenes, Aspergillus niger, and Candida albicans using inhibition zone, minimum inhibitory concentration, and minimum microbicidal concentration assays. The Co(II) and Mn(II) complexes exhibit superior antibacterial performance, whereas the UO2 (II) complex shows remarkable antifungal activity. DNA-binding studies with calf thymus DNA indicate intercalative binding, with the Mn(II) complex displaying the highest intrinsic binding constant (Kb = 7.28 × 105 M−1). The results demonstrate a clear correlation between metal coordination, structural features, DNA affinity, and biological activity. These findings highlight the potential of N2O2 Schiff base metal complexes as promising multifunctional antimicrobial agents with structure-dependent biological properties.

Green synthesis of tetrahydropyridine-3-carboxylate derivatives and evaluation of antimicrobial and antimalarial activities supported by molecular docking, POM studies, and drug-likeness analysis

A series of novel haloarene-decorated tetrahydropyridine derivatives B(1a–1f) were synthesized via a simple, environmentally benign one-pot multicomponent reaction employing ethanol as a green solvent and [Et₃NH][HSO₄] as a Brønsted acid ionic liquid catalyst. The reaction utilized methyl acetoacetate (1 mmol), substituted aromatic aldehydes (2 mmol), and substituted anilines (2 mmol) at 60 °C to afford the desired compounds. All compounds were evaluated for their in vitro antimicrobial activity against three fungal strains (Candida albicans, Aspergillus niger, and Aspergillus clavatus), two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and two Gram-positive bacteria (Staphylococcus aureus and Streptococcus pyogenes), using the serial broth dilution method. Additionally, their antimalarial potential was assessed against chloroquine- and quinine-sensitive 3D7 and multidrug-resistant Dd2 strains of Plasmodium falciparum. Among the synthesized derivatives, compounds B1a, B1b, and B1b exhibited the most potent antimicrobial and antimalarial activities. Molecular docking studies revealed that compound B1f showed the highest binding affinity toward S. aureus nucleoside diphosphate kinase, with a predicted free binding energy of − 913 kcal/mol. Pharmacological profiling suggested favorable drug-like properties and non-toxic behavior. These findings highlight haloarene-decorated tetrahydropyridine derivatives as promising dual-action candidates with potential to combat both bacterial and malarial infections.

Synthesis, antibacterial, and antibiofilm activities of an adenosine-benzoic acid conjugate against Streptococcus mutans and Escherichia coli: insights from molecular docking.

Molecular docking results provided a molecular basis for the conjugate's interaction with target proteins (PDB IDs: 4LFU and 4TQX), suggesting its potential as a quorum-sensing modulator.

Pharmacological potential of the marine peptide cyclo(L-phenylalanyl-L-prolyl) against both multidrug-resistant, gram-negative Acinetobacter baumannii and gram-positive Staphylococcus aureus: structure – activity relationship, computational and experimental studies