Synthesis, spectral and structural characterization and biological activity of Cu(II) complexes with 4-(diethylamino)salicylaldehyde and α-diimines

Synthesis of a novel Cu/DPA-MOF/OP/CS hydrogel with high capability in antimicrobial studies

Today, with the indiscriminate use of antibiotics, we face the resistance of some bacterial strains against some antibiotics. Therefore, it is essential to report and synthesize new compounds with antimicrobial properties. A novel copper/dipicolinic acid-metal-organic framework cross-linked oxidized pectin and chitosan (Cu/DPA-MOF/OP/CS) hydrogel polymer was synthesized under environmental conditions with the controllable process, which uses biodegradable polymer compounds such as pectin and chitosan in its structure. The efficient physicochemical features of the synthesized Cu/DPA-MOF/OP/CS hydrogel using SEM, FT-IR, TGA, BET, XRD, and EDS/mapping were identified and confirmed. The newly synthesized Cu/DPA-MOF/OP/CS hydrogel showed activity against Gram-positive and Gram-negative bacterial strains and fungal species, and significant antibacterial and antifungal properties were observed. In antibacterial activity, the MIC against Gram-positive species was in the range of 16-128 mg/mL, the MIC against Gram-negative species was in the range of 64-256 mg/mL, and the MIC against fungal species was in the range of 128-512 mg/mL. In antimicrobial evaluations, in addition to the MIC test, the MBC test, the MFC test, and the IZD test were performed, and the results were reported. The results were compared with commercial antibiotics in the market. Development of novel nanostructures based on hydrogel polymers with distinctive functionality can affect the performance of these nanostructures in different areas.

Manganese(II) complexes of substituted salicylaldehydes and α-diimines: Synthesis, characterization and biological activity

The interaction of Mn⁺² with substituted salicylaldehydes (X-saloH) led to the formation of five manganese(II) complexes formulated as [Μn(X-salo)₂(MeOH)₂]. When the reactions took place in the presence of an α-diimine such as 2,2'-bipyridine, 1,10-phenanthroline or 2,2'-bipyridylamine, five manganese(II) complexes of the formula [Mn(X-salo)₂(α-diimine)] were isolated. The characterization of the complexes was accomplished by various spectroscopic techniques and single-crystal X-ray crystallography. The antioxidant activity of the compounds was evaluated via the scavenging of 1,1-diphenyl-picrylhydrazyl, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl free radicals. The antibacterial activity of the complexes was tested in vitro against Staphylococcus aureus and Xanthomonas campestris bacterial strains and was found moderate. Diverse techniques were employed to examine the interaction of the complexes with calf-thymus DNA which showed intercalation as the most possible interaction mode. The affinity of the complexes for bovine serum albumin was investigated by fluorescence emission spectroscopy and the binding constants were determined.

Zinc(II) complexes of 3,5-dibromo-salicylaldehyde and α-diimines: Synthesis, characterization and in vitro and in silico biological profile

The synthesis of five neutral zinc(II) complexes of 3,5-dibromo-salicyladehyde (3,5-diBr-saloH) in the presence of nitrogen-donor co-ligands 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (neoc), or 2,2'-bipyridylamine (bipyam) was undertaken and complexes [Zn(3,5-diBr-salo)₂(H₂O)₂] (1), [Zn(3,5-diBr-salo)₂(bipy)] (2), [Zn(3,5-diBr-salo)₂(phen)]^.3,5-diBr-saloΗ (3), [Zn(3,5-diBr-salo)₂(neoc)] (4) and [Zn(3,5-diBr-salo)₂(bipyam)] (5) were characterized by various techniques. The crystal structures of complexes 3 and 5 were determined by X-ray crystallography, revealing the co-existence of two different coordination modes of 3,5-diBr-salo^- ligands. The new complexes show selective in vitro antibacterial activity against two Gram-positive and two Gram-negative bacterial strains. The complexes may scavenge 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radicals and reduce H₂O₂. The complexes may intercalate in-between the calf-thymus DNA-bases and have exhibited low-to-moderate ability to cleave supercoiled circular pBR322 plasmid DNA. The complexes may bind tightly and reversibly to bovine and human serum albumins. In order to explain the in vitro activity of the compounds, molecular docking studies were adopted on the crystal structure of calf-thymus DNA, human and bovine serum albumin, Escherichia coli and Staphylococcus aureus DNA-gyrase, 5-lipoxygenase, and 5-lipoxygenase activating protein. The employed in silico studies aimed to explore the ability of the compounds to bind to these target biomacromolecules, establishing a possible mechanism of action and were in accordance with the in vitro studies.

Recent developments of metal-based compounds against fungal pathogens

This review provides insight into the rapidly expanding field of metal-based antifungal agents. In recent decades, the antibacterial resistance crisis has caused reflection on many aspects of public health where weaknesses in our medicinal arsenal may potentially be present - including in the treatment of fungal infections, particularly in the immunocompromised and those with underlying health conditions where mortality rates can exceed 50%. Combination of organic moieties with known antifungal properties and metal ions can lead to increased bioavailability, uptake and efficacy. Development of such organometallic drugs may alleviate pressure on existing antifungal medications. Prodigious antimicrobial moieties such as azoles, Schiff bases, thiosemicarbazones and others reported herein lend themselves easily to the coordination of a host of metal ions, which can vastly improve the biocidal activity of the parent ligand, thereby extending the library of antifungal drugs available to medical professionals for treatment of an increasing incidence of fungal infections. Overall, this review shows the impressive but somewhat unexploited potential of metal-based compounds to treat fungal infections.

Effects of cellulose/salicylaldehyde thiosemicarbazone complexes on PVA based hydrogels: Portable, reusable, and high-precision luminescence sensing of Cu2

Novel portable, high-precision, and reusable fluorescent polyvinyl alcohol (PVA)-borax hydrogel sensors were prepared to detect Cu²⁺ in aqueous environment. A TEMPO-oxidized cellulose nanofibers/salicylaldehyde thiosemicarbazone (TOCN/ST) complex was further incorporated into the PVA-borax matrix. The in situ polymerization of TOCN/ST complex enhanced the mechanical properties of the hydrogels and improved the accuracy of detection. The resultant hydrogels were thermo reversible, and it converted to the liquid state during heating, which could greatly reduce the deviations caused in the detection of solid sensors. After cooling, the hydrogel could transform into the solid condition, which was easily portable. The sensor induced a significant luminescence quenching to the Cu²⁺ at 485 nm, with a detection limit of 0.086 μM. In the presence of ethylenediaminetetraacetic acid disodium, Cu²⁺ were tightly seized, causing the liberation of TOCN/ST complex and thus, a reversible "ON-OFF-ON" fluorescence behavior was displayed. The fluorescence intensity was maintained at 82 % after 10 uses, and the mechanical strength was maintained at 85 % after 3 uses. The anti-bacterial activity test also confirmed the TOCN/ST complex was extremely potent in suppressing the growth and reproduction of Escherichia coli. The proposed hydrogel provides a new insight into the detection of Cu²⁺ in aqueous environments.