Studies on antibacterial mechanisms of copper complexes with 1,10-phenanthroline and amino acid on Escherichia coli

Antimicrobial and antifungal activities of bifunctional cooper(ii) complexes with non-steroidal anti-inflammatory drugs, flufenamic, mefenamic and tolfenamic acids and 1,10-phenanthroline

Cooper(ii) complexes represent a promising group of compounds with antimicrobial and antifungal properties. In the present work, a series of Cu(ii) complexes containing the non-steroidal anti-inflammatory drugs, tolfenamic acid, mefenamic acid and flufenamic acid as their redox-cycling functionalities, and 1,10-phenanthroline as an intercalating component, has been studied. The antibacterial activities of all three complexes, [Cu(tolf-O,O′)2(phen)] (1), [Cu(mef-O,O′)2(phen)] (2) and [Cu(fluf-O,O′)2(phen)] (3), were tested against the prokaryotic model organisms Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) and their antifungal activities were evaluated towards the yeast, Saccharomyces cerevisiae (S. cerevisiae). The antibacterial activity of both strains has been compared with the antibiotic Neomycin. The calculated IC50 values revealed slight differences in the antibacterial activities of the complexes in the order 1 ∼ 3 > 2. The most profound growth inhibition of E. coli was observed, at its highest concentration, for the complex 1, which contains chlorine atoms in the ligand environment. The trend obtained from IC50 values is generally in agreement with the determined MIC values. Similarly, the complex 1 showed the greatest growth inhibition of the yeast S. cerevisiae and the overall antifungal activities of the Cu(ii) complexes were found to follow the order 1 > 3 ≫ 2. However, for complex 2, even at the highest concentration tested (150 μM), a 50% decrease in yeast growth was not achieved. It appears that the most potent antimicrobial and antifungal Cu(ii) complexes are those containing halogenated NSAIDs. The mechanisms by which Cu(ii) complexes cause antibacterial and antifungal activities can be understood on the basis of redox-cycling reactions between cupric and cuprous species which lead to the formation of free radicals. The higher efficacy of the Cu(ii) complexes against bacterial cells may be due to an absence of membrane-protected nuclear DNA, meaning that on entering a cell, they can interact directly with its DNA. Contrastingly, for the complexes to interact with the DNA in yeast cells, they must first penetrate through the nuclear membrane.

Ternary copper(II) complex of 5-hydroxytryptophan and 1,10-phenanthroline with several pharmacological properties and an adequate safety profile

We report the synthesis and biological evaluation of a ternary copper complex, [Cu(5HTP)(phen)(H₂O)](NO₃).2H₂O, with the antioxidant agent 5-hydroxytryptophan (5-HTP) and phenanthroline (phen, added to improve its lipophilicity and membrane transport). The crystal structure of the complex was determined by X-ray diffraction methods. The complex showed antioxidant, antimicrobial, antitumor and antimetastatic properties with an adequate safety profile. The interaction of the metal with phen promotes cellular copper accumulation and cytotoxicity on human lung A549 cell line (IC₅₀ = 3.6 μM). Furthermore, the viability of the normal human fetal lung fibroblast cell line (MRC-5) is not altered by the complex. An oxidative stress mechanism for the anticancer effect has been determined: cellular increase of reactive oxygen species (ROS), decrease of the glutathione (GSH) and oxidized GSH (GSSG) ratio and alteration of the mitochondrial potential. The complex also displays antimetastatic activities with inhibition of cell adhesion, invasion and migration. It has not mutagenic behavior and no toxicity on Artemia salina indicating its potential to act as an effective and safety antimicrobial and antitumor drug.

Cobalt, nickel and copper complexes with glycinamide: structural insights and magnetic properties

Ten new compounds of Co, Ni and Cu with glycinamide (HL = glycinamide): [Co(H₂O)₂(HL)₂]Cl₂ (1a), [Co(H₂O)₂(HL)₂]Br_1.06Cl_0.94 (1b), [Co(H₂O)₂(HL)₂]I₂ (1c), [Ni(H₂O)₂(HL)₂]Cl₂ (2a), [Ni(H₂O)₂(HL)₂]Br_0.94Cl_1.06 (2b), [Ni(H₂O)₂(HL)₂]I₂ (low and room temperature polymorph, 2c_LT and 2c_RT), [CuCl₂(HL)₂] (3a), [CuBr_1.3Cl_0.7(HL)₂] (3b) and {[Cu(HL)₂]₂[Cu₂I₆]}_n (3c), as well as glycinamide hydroiodide (H₂LI) and a new polymorph of glycinamide hydrochloride (β-H₂LCl) were prepared and characterized by single-crystal X-ray diffraction, infrared spectroscopy, thermal analysis (TG/DTA) and ESR spectroscopy. 1a, 1b, 2a and 2b are isostructural, as well as 1c and 2c_RT, while the Cu compounds (3a–c) have entirely different molecular structures. All investigated compounds are mononuclear with exception of the 1D coordination polymer 3c. Compound 3c contains copper ions in the mixed oxidation state Cu(i) and Cu(ii) with interesting magnetic properties. Paramagnetic behaviour was found in 1a, 1b, 3a and 3b. Temperature induced polymorphic transformation was observed in 2c. Compounds 1a and 3a showed moderate antiproliferative activity and selectivity toward the human breast tumor cell line MCF-7.

We report the crystal structures and magnetic properties of nine mononuclear complexes and one 1D coordination polymer containing Cu^II/Cu^I ions.

Dual Mechanism of Action of 5-Nitro-1,10-Phenanthroline against Mycobacterium tuberculosis

New chemotherapeutic agents with novel mechanisms of action are urgently required to combat the challenge imposed by the emergence of drug-resistant mycobacteria. In this study, a phenotypic whole-cell screen identified 5-nitro-1,10-phenanthroline (5NP) as a lead compound. 5NP-resistant isolates harbored mutations that were mapped to fbiB and were also resistant to the bicyclic nitroimidazole PA-824. Mechanistic studies confirmed that 5NP is activated in an F₄₂₀-dependent manner, resulting in the formation of 1,10-phenanthroline and 1,10-phenanthrolin-5-amine as major metabolites in bacteria. Interestingly, 5NP also killed naturally resistant intracellular bacteria by inducing autophagy in macrophages. Structure-activity relationship studies revealed the essentiality of the nitro group for in vitro activity, and an analog, 3-methyl-6-nitro-1,10-phenanthroline, that had improved in vitro activity and in vivo efficacy in mice compared with that of 5NP was designed. These findings demonstrate that, in addition to a direct mechanism of action against Mycobacterium tuberculosis, 5NP also modulates the host machinery to kill intracellular pathogens.

Combinatorial phenotypic screen uncovers unrecognized family of extended thiourea inhibitors with copper-dependent anti-staphylococcal activity

The continuous rise of multi-drug resistant pathogenic bacteria has become a significant challenge for the health care system. In particular, novel drugs to treat infections of methicillin-resistant Staphylococcus aureus strains (MRSA) are needed, but traditional drug discovery campaigns have largely failed to deliver clinically suitable antibiotics. More than simply new drugs, new drug discovery approaches are needed to combat bacterial resistance. The recently described phenomenon of copper-dependent inhibitors has galvanized research exploring the use of metal-coordinating molecules to harness copper's natural antibacterial properties for therapeutic purposes. Here, we describe the results of the first concerted screening effort to identify copper-dependent inhibitors of Staphylococcus aureus. A standard library of 10 000 compounds was assayed for anti-staphylococcal activity, with hits defined as those compounds with a strict copper-dependent inhibitory activity. A total of 53 copper-dependent hit molecules were uncovered, similar to the copper independent hit rate of a traditionally executed campaign conducted in parallel on the same library. Most prominent was a hit family with an extended thiourea core structure, termed the NNSN motif. This motif resulted in copper-dependent and copper-specific S. aureus inhibition, while simultaneously being well tolerated by eukaryotic cells. Importantly, we could demonstrate that copper binding by the NNSN motif is highly unusual and likely responsible for the promising biological qualities of these compounds. A subsequent chemoinformatic meta-analysis of the ChEMBL chemical database confirmed the NNSNs as an unrecognized staphylococcal inhibitor, despite the family's presence in many chemical screening libraries. Thus, our copper-biased screen has proven able to discover inhibitors within previously screened libraries, offering a mechanism to reinvigorate exhausted molecular collections.

Binary and ternary new water soluble copper(II) complexes of l-tyrosine and substituted 1,10-phenanthrolines: effect of substitution on DNA interactions and cytotoxicities

Binary and ternary water soluble copper(II) complexes - [Cu(nphen)2(H2O)](NO3)2·H2O (1), [Cu(phen)2(H2O)](NO3)2 (2), [Cu(nphen)(l-tyr)(H2O)]NO3·2H2O (3), [Cu(phen)(tyr)(H2O)] NO3·2H2O (4) - and diquarternary salts of nphen and phen (nphen=5-nitro-1,10-phenanthroline, phen=1,10-phenanthroline and tyr=l-tyrosine) have been synthesized and characterized by CHN analysis, (1)H NMR, (13)C NMR and IR spectroscopy, thermal analysis and single crystal X-ray diffraction techniques. The CT-DNA binding properties of these compounds have been investigated by thermal denaturation measurements, absorption and emission spectroscopy. The supercoiled pUC19 plasmid DNA cleavage activity of these compounds has been explored by agarose gel electrophoresis. The cytotoxicity of these compounds against MCF-7, Caco-2, A549 cancer cells and BEAS-2B healthy cells was also studied by using XTT method. The complexes 1-4 exhibit significant high cytotoxicity with low IC50 values in compared with cisplatin. The effect of the substituents of phen and coordinated amino acid in the above complexes are presented and discussed.

Cytotoxicity of sulfurous acid on cell membrane and bioactivity of Nitrosomonas europaea

Nitrosomonas europaea, an ammonia oxidizing bacterium, was chosen as a research model to study the alteration of cell membrane in the presence of sulfurous acid and biodegradation of acetochlor. Significant changes of the outer cell membrane were observed in the presence of sulfurous acid using scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM). The fluorescence polarization has shown a significant decrease in membrane fluidity and the increase of permeability of cell membrane. Lysozyme experiment show the cell becomes easily influenced by substance in medium. Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) measurements show considerable amount of Ca(2+) and Mg(2+) in the supernatant from the sulfurous acid exposed cells. Sulfurous acid treatment enhanced the ability of N. europaea to degrade acetochlor. On this basis, it can be concluded that the increased cell permeability is favor for the absorbability of nutrition. As a result, N. europaea grows faster and the biodegradation efficiency was improved.

A high-throughput small-molecule screen to identify a novel chemical inhibitor of Clostridium difficile

Clostridium difficile, a highly drug-resistant Gram-positive, spore-forming bacterium, remains a leading cause of hospital-acquired diarrhoea and antibiotic-associated colitis. Clinically, only a handful of antibiotics are used for treating C. difficile infection (CDI), suggesting a necessity for the development of new treatment options. Here we performed a high-throughput screen of 2000 drug-like compounds for inhibition of C. difficile. From this screen, one compound, 5-nitro-1,10-phenanthroline (5-NP), showed potent bactericidal effects in vitro. In addition, this compound displayed high potency towards other Clostridium spp. as well as Mycobacterium bovis but not towards other tested Gram-positive and Gram-negative bacteria. Furthermore, we show that this inhibition may proceed through a metal chelation-dependent mechanism. More importantly, preliminary evidence suggests moderate efficacy for this compound in treating CDI in a murine infection model. These results present a possible basis for the further development of this compound as an antibiotic treatment for CDI.