Search

The present study reports the synthesis and spectroscopic characterization of dinuclear silver(I) complexes, {[Ag(X-O)(phtz-N)]2(µ-phtz-N,N')2} (X = NO3 - (Ag1) and CF3SO3 - (Ag2), and phtz is phthalazine). The interaction of these two complexes with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) was investigated to assess their binding affinity to these biomolecules. The binding constants of complexes Ag1 and Ag2 to BSA are found to be higher than those for ct-DNA, being in accordance with their higher affinity toward the studied protein. The values of partition coefficient (logP) for the investigated complexes indicate higher cellular uptake efficiency of Ag1 than Ag2. The in vivo toxicity of the complexes Ag1 and Ag2 against the model organism, Caenorhabditis elegans, was studied to check their therapeutic potential.

In the present study, a zinc(II) complex with 4-ethynyl-2,2’-bipyridine (ebpy), [Zn(ebpy)Cl2], was synthesized and characterized by spectroscopic (1H-NMR, IR and UV–Vis) methods and molar conductivity measurement. The crystal structure of the [Zn(ebpy)Cl2] complex was determined by single-crystal X-ray diffraction analysis, confirming the bidentate coordination of the ebpy ligand through its two nitrogen atoms, while the remaining two coordination sites are occupied by two chloride ions. With the aim to investigate the reactivity of the synthesized zinc(II) complex toward biologically important molecules, its binding affinity to calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) was studied by fluorescence emission spectroscopy. From the obtained results, it can be concluded that [Zn(ebpy)Cl2] complex binds to bovine serum albumin reversibly, while the combination of ethidium bromide (EthBr) and Hoechst 33258 (2’-(4-hydroxyphenyl)-5-[5-(4-methylpiperazine- 1-yl)benzimidazo-2-yl]-benzimidazole) competitive binding study suggests that this complex interacts with ct-DNA through the minor groove binding, which is in agreement with molecular docking study.

The negative environmental and social impacts of food waste accumulation can be mitigated by utilizing bio-refineries' approach where food waste is revalorized into high-value products, such as prodigiosin (PG), using microbial bioprocesses. The diverse biological activities of PG position it as a promising compound, but its high production cost and promiscuous bioactivity hinder its wide application. Metal ions can modulate the electronic properties of organic molecules, leading to novel mechanisms of action and increased target potency, while metal complex formation can improve the stability, solubility and bioavailability of the parent compound. The objectives of this study were optimizing PG production through bacterial fermentation using food waste, allowing good quantities of the pure natural product for further synthesizing and evaluating copper(II) and zinc(II) complexes with it. Their antimicrobial and anticancer activities were assessed, and their binding affinity toward biologically important molecules, bovine serum albumin (BSA) and DNA was investigated by fluorescence emission spectroscopy and molecular docking. The yield of 83.1 mg/L of pure PG was obtained when processed meat waste at 18 g/L was utilized as the sole fermentation substrate. The obtained complexes CuPG and ZnPG showed high binding affinity towards target site III of BSA, and molecular docking simulations highlighted the affinity of the compounds for DNA minor grooves. [ABSTRACT FROM AUTHOR]

Polynuclear silver(I) complex, [Ag(NO3-O)(2,2'-bq-N,N')]n, was synthesized by the reaction of equimolar amount of silver(I) nitrate and 2,2'-biquinoline (2,2'-bq) in ethanol at room temperature. The characterization of the complex was established on the basis of elemental microanalysis, IR, NMR (1H and 13C) and UV-Vis spectroscopic techniques. The results of spectroscopic analyses revealed that in [Ag(NO3-O)(2,2'-bq-N,N')]n complex, 2,2'-bq ligand behaves as a chelate, while the remaining coordination sites are occupied by the oxygen atoms of two nitrates.

New polynuclear silver(I) complexes, [Ag(CF3SO3)(4,7-phen)(CH3CN)]n (1) and [Ag(PO2F2)(4,7-phen)]n (2), were synthesized by the reaction of 4,7-phenanthroline (4,7-phen) and the corresponding AgX salt (X = CF3SO3 - and PF6 -) in 1:2 mole ratio, respectively, in methanol/acetone (1:1 volume ratio) at room temperature. The characterization of the complexes was established on the basis of elemental microanalysis, IR and NMR (1H and 13C) spectroscopic techniques, while their crystal structures were determined by single-crystal X-ray diffraction analysis. The results of spectroscopic and crystallographic analyses revealed that in these complexes, 4,7-phen behaves as a bridging ligand between two metal ions, while the remaining coordination sites of the Ag(I) ions are occupied by the oxygen atom of CF3SO3 - and an acetonitrile nitrogen atom in 1 or by two oxygen atoms from two PO2F2 -, formed after hydrolysis of PF6 -, in 2. In the solid state, both complexes are coordination polymers in which the geometry around the Ag(I) ions is distorted tetrahedral. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172036]

The aim of this study was to determine whether p-chloroaniline (PCA) is formed in the reactions of sodium hypochlorite (NaOCl) with final rinse chlorhexidine (CHX), QMix (combination of ethylenediaminetetraacetic acid (EDTA), CHX and detergent) and EDTA/CHX solutions by thin-layer chromatography (TLC), proton nuclear magnetic resonance (1H NMR) and infrared (IR) spectroscopy. Commercially available 5.25% NaOCl solution was mixed with 2% CHX and QMix in 1:1 (v/v) ratio at room temperature. Furthermore, 2% CHX was associated with 17% EDTA under the same experimental conditions. The obtained solutions were evaluated qualitatively for color changing, precipitate and/or bubble formation and analyzed by TLC chromatography. The association products were investigated by spectroscopic (1H NMR and IR) methods in order to determine whether they contain PCA. It was found that interactions between NaOCl/CHX and CHX/EDTA led to forming of brown and white precipitate. When NaOCl was mixed with QMix, an orange-brown precipitate was formed. PCA was not detected as a product of the reactions between NaOCl and final rinse solutions of CHX, QMix and EDTA/CHX association.

Inspired by the emergence of resistance to currently available antifungal therapy and by the great potential of metal complexes for the treatment of various diseases, we synthesized three new silver(I) complexes containing clinically used antifungal azoles as ligands, [Ag(ecz)2]SbF6 (1, ecz is econazole), {[Ag(vcz)2]SbF6}n (2, vcz is voriconazole), and [Ag(ctz)2]SbF6 (3, ctz is clotrimazole), and investigated their antimicrobial properties. The synthesized complexes were characterized by mass spectrometry, IR, UV-vis and 1H NMR spectroscopy, cyclic voltammetry, and single-crystal X-ray diffraction analysis. In the mononuclear complexes 1 and 3 with ecz and ctz, respectively, the silver(I) ion has the expected linear geometry, in which the azoles are monodentately coordinated to this metal center through the N3 imidazole nitrogen atom. In contrast, the vcz-containing complex 2 has a polymeric structure in the solid state in which the silver(I) ions are coordinated by four nitrogen atoms in a distorted tetrahedral geometry. DFT calculations were done to predict the most favorable structures of the studied complexes in DMSO solution. All the studied silver(I) complexes have shown excellent antifungal and good to moderate antibacterial activities with minimal inhibitory concentration (MIC) values in the ranges of 0.01–27.1 and 2.61–47.9 μM on the selected panel of fungi and bacteria, respectively. Importantly, the complexes 1–3 have exhibited a significantly improved antifungal activity compared to the free azoles, with the most pronounced effect observed in the case of complex 2 compared to the parent vcz against Candida glabrata with an increase of activity by five orders of magnitude. Moreover, the silver(I)-azole complexes 2 and 3 significantly inhibited the formation of C. albicans hyphae and biofilms at the subinhibitory concentration of 50% MIC. To investigate the impact of the complex 3 more thoroughly on Candida pathogenesis, its effect on the adherence of C. albicans to A549 cells (human adenocarcinoma alveolar basal epithelial cells), as an initial step of the invasion of host cells, was studied. [ABSTRACT FROM AUTHOR]

Three copper(II) complexes, trans-[Cu(1,3-pd)2Cl2]·H2O (Cu1; 1,3-pd is 1,3-propanediamine), trans-[Cu(2,2-diMe-1,3-pd)2Cl2] (Cu2; 2,2-diMe- -1,3-pd is 2,2-dimethyl-1,3-propanediamine) and trans-[Cu(1,3-pnd)2Cl2]·H2O (Cu3; 1,3-pnd is (±)-1,3-pentanediamine), were synthesized and structurally characterized by elemental microanalyses, IR, electronic absorption and reflectance spectroscopy and molar conductivity measurements. The antimicrobial efficiency of the complexes against four clinically relevant microorganisms and their antiproliferative effect on the normal human lung fibroblast cell line MRC-5 were evaluated. Since in many bacteria, pathogenicity is regulated by an intercellular communication process called quorum sensing (QS), the effect of the copper(II) complexes Cu1–3 on bacterial QS was examined. The obtained results showed that these complexes inhibited violacein production in Chromobacterium violaceum CV026, indicating their anti-QS activity via the homoserine lactone (HSL) pathway. Two biosensor strains were used to determine which pathway, C4-HSL (N-butanoylhomoserine lactone) or 3OC12-HSL (N-(3-oxododecanoyl)homoserine lactone), was affected by the copper(II) complexes. The biological activities of the copper(II) complexes were compared with those for the nickel(II) complexes of the general formula trans- -[Ni(L)2(H2O)2]Cl2 (L = 1,3-pd, 2,2-diMe-1,3-pd and 1,3-pnd). [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172036 and Grant no. 173048]

Three diamines, 1,3-propanediamine (1,3-pd), 2,2-dimethyl-1,3-propanediamine (2,2-diMe-1,3-pd) and (±)-1,3-pentanediamine (1,3-pnd), were used for the synthesis of nickel(II) complexes 1–3, respectively, of the general formula [Ni(L)2(H2O)2]Cl2. The stoichiometries of the complexes were confirmed by elemental microanalysis, and their structures were elucidated by spectroscopic (UV–Vis and IR) and molar conductivity measurements. The complexes 1–3, along with NiCl2·6H2O and the diamine ligands, were evaluated against a panel of microbial strains that are associated with skin, wound, urinary tract and nosocomial infections. The obtained results revealed no significant activity of 1–3 against the investigated bacterial strains. On the other hand, they showed good antifungal activity against pathogenic Candida strains, with minimum inhibitory concentration (MIC) values in the range from 15.6 to 62.5 μg mL-1. The best anti-Candida activity was observed for complex 2 against C. parapsilosis, while the least susceptible to the effect of the complexes was C. krusei. The antiproliferative effect on normal human lung fibroblast cell line MRC-5 was also evaluated in order to determine the therapeutic potential of nickel(II) complexes 1–3. These complexes showed lower negative effects on the viability of the MRC-5 cell line than the clinically used nystatin and comparable selectivity indexes to that of this antifungal drug.

Proton NMR spectroscopy and cyclic voltammetry have been applied to study the stability of three gold(III) complexes with L-histidine-containing peptides, [Au(Gly-L-His-N,N’,N’’)Cl]NO3.1.25H2O (Au1), [Au(L-Ala-L-His-N,N’,N’’)Cl]NO3.2.5H2O (Au2) and [Au(Gly-Gly-L-His-N,N’,N’’,N’’’)]Cl.H2O (Au3) under physiologically relevant conditions. It was found that tridentate coordination of Gly-L-His and L-Ala-L-His dipeptides, as well as tetradentate coordination of Gly-Gly-L-His tripeptide in Au1, Au2 and Au3 complexes, respectively, stabilized +3 oxidation state of gold and prevented its reduction to Au(I) and Au(0). No release of the coordinated peptides from Au(III) was observed under these experimental conditions. Considering remarkable stability of Au1, Au2 and Au3 complexes, their cytotoxic activity was evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay toward five human tumor cell lines, MCF-7 (human breast adenocarcinoma), HT-29 (human colon adenocarcinoma), HeLa (human cervix carcinoma), HL-60 (human promyelocytic leukemia), Raji (human Burkitt’s lymphoma) and one human normal cell line MRC-5 (human fetal lung fibroblasts). While the cytotoxic activity of Au1, Au2 and Au3 against investigated human malignant cell lines was strongly cell line dependent, none of these complexes was cytotoxic against normal MRC-5 cell line. This study can contribute to the future development of gold(III)-peptide complexes as potential antitumor agents.