Mechanochemical Preparation, Solid-State Characterization, and Antimicrobial Performance of Copper and Silver Nitrate Coordination Polymers with L- and DL-Arginine and Histidine

The antimicrobial activity of the novel coordination polymers obtained by co-crystallizing the amino acids arginine or histidine, as both enantiopure L and racemic DL forms, with the salts Cu(NO3)2 and AgNO3 has been investigated to explore the effect of chirality in the cases of enantiopure and racemic forms. The compounds [Cu·AA·(NO3)2]CPs and [Ag·AA·NO3]CPs (AA = L-Arg, DL-Arg, L-His, DL-His) were prepared by mechanochemical, slurry, and solution methods and characterized by X-ray single-crystal and powder diffraction in the cases of the copper coordination polymers, and by powder diffraction and by solid-state NMR spectroscopy in the cases of the silver compounds. The two pairs of coordination polymers, [Cu·L-Arg·(NO3)2·H2O]CP and [Cu·DL-Arg·(NO3)2·H2O]CP, and [Cu·L-Hys·(NO3)2·H2O]CP and [Cu·DL-His·(NO3)2·H2O]CP, have been shown to be isostructural in spite of the different chirality of the amino acid ligands. A similar structural analogy could be established for the silver complexes on the basis of SSNMR. The activity against the bacterial pathogens Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus was assessed by carrying out disk diffusion assays on lysogeny agar media showing that, while there is no significant effect arising from the use of enantiopure or chiral amino acids, the coordination polymers exert an appreciable antimicrobial activity comparable, when not superior, to that of the metal salts alone.

Transition metal(II) complexes with the non–steroidal anti–inflammatory drug oxaprozin: Characterization and biological profile

A series of copper(II), nickel(II) and cobalt(II) complexes with the non-steroidal anti-inflammatory drug oxaprozin (Hoxa) have been synthesized and characterized by diverse techniques. The crystal structures of two copper(II) complexes, namely the dinuclear complex [Cu₂(oxa)₄(DMF)₂] (1) and the polymeric complex {[Cu₂(oxa)₄]·2MeOH·0.5MeOH}₂ (12) were determined by single-crystal X-ray diffraction studies. In order to evaluate in vitro the antioxidant activity of the resultant complexes, their scavenging ability towards 1,1-diphenyl-picrylhydrazyl (DPPH), hydroxyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals was investigated revealing their high effectiveness against these radicals. The binding of the complexes to bovine serum albumin and human serum albumin was examined and the corresponding determined albumin-binding constants showed a tight and reversible interaction. The interaction of the complexes with calf-thymus DNA was monitored by diverse techniques including UV-vis spectroscopy, cyclic voltammetry, DNA-viscosity measurements and competitive studies with ethidium bromide. Intercalation may be proposed as the most possible DNA-interaction mode of the complexes.

Copper(II) Complexes of 5-Fluoro-Salicylaldehyde: Synthesis, Characterization, Antioxidant Properties, Interaction with DNA and Serum Albumins

The synthesis, characterization and biological profile (antioxidant capacity, interaction with calf-thymus DNA and serum albumins) of five neutral copper(II) complexes of 5-fluoro-salicylaldehyde in the absence or presence of the N,N'-donor co-ligands 2,2'-bipyridylamine, 2,9-dimethyl-1,10-phenanthroline, 1,10-phenanthroline and 2,2'-bipyridine are presented herein. The compounds were characterized by physicochemical and spectroscopic techniques. The crystal structures of four complexes were determined by single-crystal X-ray crystallography. The ability of the complexes to scavenge 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radicals and to reduce H₂O₂ was investigated in order to evaluate their antioxidant activity. The interaction of the compounds with calf-thymus DNA possibly takes place via intercalation as suggested by UV-vis spectroscopy and DNA-viscosity titration studies and via competitive studies with ethidium bromide. The affinity of the complexes with bovine and human serum albumins was examined by fluorescence emission spectroscopy revealing the tight and reversible binding of the complexes with the albumins.

Copper(ii) complexes with terpene derivatives of ethylenediamine: synthesis, and antibacterial, antifungal and antioxidant activity

The synthesis of new chiral copper(ii) complexes with terpene derivatives of ethylenediamine and the results of studying their antibacterial, antifungal and antioxidant activity in vitro are discussed. All studied copper complexes (1–4) showed significantly higher antifungal activity against the strains of C. albicans, S. salmonicolor and P. notatum compared to the activity of the clinical antifungal drug amphotericin. High antibacterial activity of copper complexes with terpene derivatives of ethylenediamine was revealed against the S. aureus (MRSA) strain, which is resistant to the reference antibiotic ciprofloxacin. Using various test systems, a comparative assessment of the antioxidant activity (AOA) of the synthesized copper complexes and the ligands was carried out. The salen-type complex 4, which has the highest AOA in the model of initiated oxidation of a substrate containing animal lipids, was superior to other copper complexes in the ability to protect erythrocytes under conditions of H₂O₂-induced hemolysis.

The synthesis of new chiral copper(ii) complexes with terpene derivatives of ethylenediamine and the results of studying their antibacterial, antifungal and antioxidant activity in vitro are discussed.

A Ternary Copper (II) Complex with 4-Fluorophenoxyacetic Acid Hydrazide in Combination with Antibiotics Exhibits Positive Synergistic Effect against Salmonella Typhimurium

Salmonella spp. continues to figure prominently in world epidemiological registries as one of the leading causes of bacterial foodborne disease. We characterised 43 Brazilian lineages of Salmonella Typhimurium (ST) strains, characterized drug resistance patterns, tested copper (II) complex as control options, and proposed effective antimicrobial measures. The minimum inhibitory concentration was evaluated for seven antimicrobials, isolated and combined with the copper (II) complex [Cu(4-FH)(phen)(ClO₄)₂] (4-FH = 4-fluorophenoxyacetic acid hydrazide and phen = 1,10-phenanthroline), known as DRI-12, in planktonic and sessile ST. In parallel, 42 resistance genes were screened (PCR/microarray). All strains were multidrug resistant (MDR). Resistance to carbapenems and polymyxins (86 and 88%, respectively) have drawn attention to the emergence of the problem in Brazil, and resistance is observed also to CIP and CFT (42 and 67%, respectively), the drugs of choice in treatment. Resistance to beta-lactams was associated with the genes bla_TEM/bla_CTX-M in 39% of the strains. Lower concentrations of DRI-12 (62.7 mg/L, or 100 μM) controlled planktonic and sessile ST in relation to AMP/SUL/TET and AMP/SUL/TET/COL, respectively. The synergistic effect provided by DRI-12 was significant for COL/CFT and COL/AMP in planktonic and sessile ST, respectively, and represents promising alternatives for the control of MDR ST.

Transition Metal Complexes of 4-Aminoantipyrine Derivatives and Their Antimicrobial Applications

Transition metal complexes of 4-aminoantipyrine derivatives have been gaining great interest due to their rich coordination chemistry and potential applications in the field of pharmaceutical science. The presence of a free amine and a cyclic ketone functionality makes 4-aminoantipyrine an attractive amphoteric substrate for Schiff base formation. Varieties of aldehydes/ketones or amines of versatile steric, electronic and functional nature could be condensed with the 4-aminoantipyrine motif to obtain the ligand systems of multi-denticity and diverse coordination behaviour. The transition metal complexes obtained from these ligand systems exhibit unique structural and functional properties. This review compiles the important transition metal complexes developed from the Schiff base derivatives of 4-aminoantipyrine, and their utility as antibacterial and antifungal agents. Rationale of the strategies involved in the development of highly potential antimicrobial agents is discussed.