Synthesis and Assessment of Antibacterial Activities of Ruthenium(III) Mixed Ligand Complexes Containing 1,10-Phenanthroline and Guanide

Synthesis, structural investigations, and in vitro biological activity of Co(II) and Fe(III) mixed ligand complexes of 1,10-phenanthroline and 2,2'-bipyridine

Herein, we report, four new mixed ligand complexes of Cobalt(II) and Iron(III), viz., [Co(L₁ )(L₂ )(H₂ O)₂ ]Cl₂ (1), [Co(L₁ )(L₂ )(L₃ )(H₂ O)]Cl₂ (2), [Fe(L₁ )(L₂ )(H₂ O)₂ ]Cl₃ (3), and [Fe(L₁ )(L₂ )(L₃ )(H₂ O)]Cl₃ (4), where L₁  = 1,10-phenanthroline (C₁₂ H₈ N₂ ), L₂  = 2,2'-bipyridine (C₁₀ H₈ N₂ ), and L₃  = acetamide (C₂ H₅ NO)). They were synthesized and characterized using spectroscopic analysis (ESI-MS, ICP-OES, FT-IR, and UV-Vis), elemental analysis, melting point determination, and conductance measurement. The in vitro antibacterial activity was tested on two Gram-positive Staphylococcus aureus (S. aureus) and Streptococcus pyogenes (S. pyogenes) and two Gram-negative Escherichia coli (E. Coli)and Klebsiella pneumoniae (K. pneumoniae) bacteria using the disc diffusion method. Based on the analytical and spectroscopic data, octahedral geometries are assigned to the complexes. Co(II) complexes were found more active against K. pneumoniae than the corresponding Fe(III) complexes which indicated that antibacterial activities of metal complexes have tuned with the nature of the metal. The results provide an insight to design and readily prepare task-specific metal-based drugs for interaction with particular bacterial strains.

Organic-inorganic hybrid salt and mixed ligand Cr(III) complexes containing the natural flavonoid chrysin: Synthesis, characterization, computational, and biological studies

Organic-inorganic hybrid salt and mixed ligand Cr(III) complexes (Cr1 and Cr2) containing the natural flavonoid chrysin were synthesized. The metal complexes were characterized using UV-Vis, Fourier-transform infrared, MS, SEM-EDX, XRD, and molar conductance measurements. Based on experimental and DFT/TD-DFT calculations, octahedral geometries for the synthesized complexes were suggested. The powder XRD analysis confirms that the synthesized complexes were polycrystalline, with orthorhombic and monoclinic crystal systems having average crystallite sizes of 21.453 and 19.600 nm, percent crystallinities of 51% and 31.37%, and dislocation densities of 2.324 × 10^-3 and 2.603 × 10^-3 nm^-2 for Cr1 and Cr2, respectively. The complexes were subjected to cytotoxicity, antibacterial, and antioxidant studies. The in vitro biological studies were supported with quantum chemical and molecular docking computational studies. Cr1 showed significant cytotoxicity to the MCF-7 cell line, with an IC₅₀ value of 8.08 μM compared to 30.85 μM for Cr2 and 18.62 μM for cisplatin. Cr2 showed better antibacterial activity than Cr1. The higher E _HOMO (-5.959 eV) and dipole moment (10.838 Debye) values of Cr2 obtained from the quantum chemical calculations support the observed in vitro antibacterial activities. The overall results indicated that Cr1 is a promising cytotoxic drug candidate.

Synthesis of a novel diaquabis(1,10-phenanthroline)copper(II)chloride complex and its voltammetric application for detection of amoxicillin in pharmaceutical and biological samples

A one step facile synthesis of the novel diaquabis(1,10-phenanthroline)copper(II)chloride (A₂P₂CuC) complex is demonstrated. Cyclic voltammetric and electrochemical impedance spectroscopic results revealed potentiodynamic deposition of a conductive electroactive poly(A₂P₂CuC) film on the glassy carbon electrode surface increasing its effective surface area. In contrast to the unmodified glassy carbon electrode, appearance of an oxidative peak at a reduced potential with over two fold current for amoxicillin at poly(A₂P₂CuC)/GCE demonstrated its electrocatalytic property attributed to reduce charge transfer resistance and the improved surface area of the electrode surface. Better correlation of the oxidative peak current with square root of scan rate (R² = 0.99779) than with scan rate (R² = 0.96953) supplemented by slope of 0.58 for log(current) versus log(scan rate) confirmed diffusion controlled irreversible oxidation of amoxicillin. At optimized solution and SWV parameters, current response of poly(A₂P₂CuC)/GCE showed linear dependence on concentration of amoxicillin (2.0–100.0 μM) with LoD 0.0115 μM. While no amoxicillin was detected in the human blood serum sample, an amount 89.40–100.55% of the nominal level was detected in the analyzed eight tablet brands. Spike recovery in tablet samples (98.90–101.95%) and blood serum sample (102.20–101.37%); interference with an error (%RSD) of 0.00–4.51% in tablet and 0.00–2.10% in serum samples; excellent stability and reproducible results, added with the wide dynamic range and low LoD validated the method for amoxicillin determination in pharmaceutical formulations and human urine samples.

Synthesis and characterization of novel metal complexes with new azo-schiff base ligand derived from sulfa drug and toxicological studies of its complexes as antibacterial

The New Azo- Schiff base ligand [4-((E)-(2-hydroxyphenyl)diazenyl)-3-(((1E,2E)-2-((2-((E)-(2-hydroxyphenyl)diazenyl)-5-(N-(pyrimidin-2-yl)sulfamoyl)phenyl)imino)-1,2-diphenylethylidene )amino)-N-(pyrimidin-2-yl)benzenesulfonamide] (4HDPS) was primed. Three chelate complexes have correspondingly been equipped by reacting this ligand (4HDPS) with the metal ions Co (II), Ni (II) and Cu (II). (UV-Vis) electronic spectra of complexes showed bathchromic shift, as compared with that of free ligand .The Mass Spectrum and 1HNMR Spectrum of the free ligand has been taken   and the FTIR spectrums of the Ligand and its chelating complexes have been investigated. This may specify that coordination among the metal ions and the equipped ligand takes place .The conductivity and magnetic measurements, Elemental micro analysis and the percentage of metal ions were determined. Based on these consequences, the proposed geometrical structures of the equipped complexes of Co(II),Ni(II) and Cu(II).ions are octahedral  with mole ratio (M:L) was (1:1) for all prepared complexes while the conductivity measurements shows non – electrical properties. The final stage involved the study of the biological activity of prepared component to two type of pathogenic bacteria: (G+) Staph. Aureus and Escherichia coli (G-) using Well diffusion methods .Three different concentration were tested (100, 500, 1000) ppm in Ethanol Absolute (99%) as a solvent.

Antibacterial Activity of 2-Picolyl-polypyridyl-Based Ruthenium (II/III) Complexes on Non-Drug-Resistant and Drug-Resistant Bacteria

A new hexadentate 2-picolyl-polypyridyl-based ligand (4, 4'-(butane-1, 4-diylbis(oxy))bis(N, N-bis(pyridin-2-ylmethyl)aniline)) (2BUT) (1) and its corresponding Ru(II/III) complexes were synthesized and characterized, followed by assessment of their possible bioactive properties towards drug-resistant and non-drug-resistant bacteria. Spectroscopic characterization of the ligand was done using proton NMR, FTIR, and ESI-MS, which showed that the ligand was successfully synthesized. The Ru(II/III) complexes were characterized by FTIR, UV/Vis, elemental analysis, proton NMR, ESI-MS, and magnetic susceptibility studies. The analysis of ESI-MS data of the complexes showed that they were successfully synthesized. Empirical formulae derived from elemental analysis of the complexes also indicated successful synthesis and relative purity of the complexes. The important functional groups of the ligands could be observed after complexation using FTIR. Magnetic susceptibility data and electronic spectra indicated that both complexes adopt a low spin configuration. The disc diffusion assay was used to test the compounds for antibiotic activity on two bacteria species and their drug-resistant counterparts. The compounds displayed antibiotic activity towards the two non-drug-resistant bacteria. As for the drug-resistant organisms, only [Ru₂(2BUT)(DMF)₂(DPA)₂](BH₄)₄3 and 2, 2-dipyridylamine inhibited the growth of MRSA. Gel electrophoresis DNA cleavage studies showed that the ligands had no DNA cleaving properties while all the complexes denatured the bacterial DNA. Therefore, the complexes may have DNA nuclease activity towards the bacterial genomic material.

Bis(bipyridine)ruthenium(II) Ferrocenyl β-Diketonate Complexes: Exhibiting Nanomolar Potency against Human Cancer Cell Lines

The synthesis and characterization of new bis(bipyridine)ruthenium(II) ferrocenyl β-diketonate complexes, [(bpy)2 Ru(Fc-acac)][PF6 ] (bpy=2,2'-bipyridine; Fc-acac=functionalized ferrocenyl β-diketonate ligand) are reported. Alongside clinical platinum drugs, these bimetallic ruthenium-iron complexes have been screened for their cytotoxicity against MIA PaCa-2 (human pancreatic carcinoma), HCT116 p53+/+ (human colon carcinoma, p53-wild type) and ARPE-19 (human retinal pigment epithelial) cell lines. With the exception of one complex, the library exhibit nanomolar potency against cancerous cell lines, and their relative potencies are up to 40x, 400x and 72x more cytotoxic than cisplatin, carboplatin and oxaliplatin, respectively. Under hypoxic conditions, the complexes remain cytotoxic (sub-micromolar range), highlighting their potential in targeting hypoxic tumor regions. The Comet assay was used to determine their ability to damage DNA, and results show dose dependent damage which correlates well with the cytotoxicity results. Their potential to treat bacterial and fungal strains has been determined, and highlight complexes have selective growth inhibition of up to 87-100 % against Staphylococcus aureus and Candida albicans.

Polymeric ruthenium precursor as a photoactivated antimicrobial agent

Ruthenium coordination compounds have demonstrated a promising anticancer and antibacterial activity, but their poor water solubility and low stability under physiological conditions may limit their therapeutic applications. Physical encapsulation or covalent conjugation with polymers may overcome these drawbacks, but generally involve multistep reactions and purification processes. In this work, the antibacterial activity of the polymeric precursor dicarbonyldichlororuthenium (II) [Ru(CO)₂Cl₂]_n has been studied against Escherichia coli and Staphylococcus aureus. This Ru-carbonyl precursor shows minimum inhibitory concentration at nanogram per millilitre, which renders it a novel antimicrobial polymer without any organic ligands. Besides, [Ru(CO)₂Cl₂]_n antimicrobial activity is markedly boosted under photoirradiation, which can be ascribed to the enhanced generation of reactive oxygen species under UV irradiation. [Ru(CO)₂Cl₂]_n has been able to inhibit bacterial growth via the disruption of bacterial membranes and triggering upregulation of stress responses as shown in microscopic measurements. The activity of polymeric ruthenium as an antibacterial material is significant even at 6.6 ng/mL while remaining biocompatible to the mammalian cells at much higher concentrations. This study proves that this simple precursor, [Ru(CO)₂Cl₂]_n, can be used as an antimicrobial compound with high activity and a low toxicity profile in the context of need for new antimicrobial agents to fight bacterial infections.

Evaluation of substituent bioactivity and anion impact of linear and T-shaped silver(i) pyridinyl complexes as potential antiproliferative, antioxidant, antimicrobial agents and DNA- and BSA-binders

The impact of ligand substituents and anion variation on the bio-activity of pyridinyl Ag(I) complexes was evaluated. The complexes showed potential therapeutic ability with notable anticancer, antioxidant, and antimicrobial activities.

Mono and binuclear cobalt(II) mixed ligand complexes containing 1,10-phenanthroline and adenine using 1,3-diaminopropane as a spacer: synthesis, characterization, and antibacterial activity investigations

Background

Coordination compounds, in particular cobalt(II) mixed ligand complexes containing 1,10-phenantroline, have drawn the attention of many investigators as some of them are showing antimicrobial activities.

Result

Herein, we report three novel mixed ligand complexes of cobalt(II) having the formulae [Co(L1)2(H2O)2]Cl2, [Co(L1)2(L2)(H2O)]Cl2 and [Co2(L1)4(L2)2(L3)]Cl4 (L1 = 1,10-phenanthroline, L2 = adenine, L3 = 1,3-diaminepropane) were synthesized and characterized by elemental analysis, conductivity measurement, infrared, and UV-Vis spectroscopic techniques. Octahedral geometries are proposed to all the complexes. In vitro antibacterial activities of the ligands, salt, and metal complexes were tested on four pathogenic bacteria (Staphylococcus aureus, Salmonella typhus, Escherichia coli, and Staphylococcus epidermis) using disc diffusion method.

Conclusions

It is interesting to note that the newly synthesized cobalt(II) complexes are active against gram negative bacteria (Escherichia coli and Klebsiella pneumoniae) even though cobalt(II) complexes are well known for their activity against gram positive bacteria.

Cytotoxic and apoptotic effects of ternary silver(i) complexes bearing 2-formylpyridine thiosemicarbazones and 1,10-phenanthroline

New silver(i) compounds containing 2-formylpyridine-N(4)-R-thiosemicarbazones and 1,10-phenanthroline (phen) were synthesized and characterized by spectroscopic techniques (IR and NMR), elemental analysis, ESI-MS and molar conductance measurements. In these complexes, both phen and thiosemicarbazone ligands are coordinated in a chelating bidentate fashion. Compounds 1-3 not only showed good in vitro antiproliferative activity against human lung (A549) and breast tumor cells (MDA-MB-231 and MCF-7), with IC50 values ranging from 1.49 to 20.90 μM, but were also demonstrated to be less toxic towards human breast non-tumor cells (MCF-10A). Cellular uptake studies indicated that compounds 1-3 were taken up by the MDA-MB-231 cells in 6 hours. Cell death assays in the MDA-MB-231 cells were conducted with compound 1 aiming to evaluate its effects on cell morphology, induction of apoptosis, the cell cycle, reactive oxygen species (ROS) formation and mitochondrial membrane potential (Δψm). Compound 1 caused morphological changes, such as cell shrinkage and rounding, increased the sub-G1 phase population, and induced apoptotic cell death, ROS formation and loss of mitochondrial membrane potential (Δψm). DNA binding results revealed that 1 interacted with the ct-DNA minor groove. Complexes 1-3 also exhibited good in vitro activity against M. tuberculosis H37Rv, with MIC values ranging from 3.37 to 4.65 μM.

Resistance of Gram-Negative Bacteria to Current Antibacterial Agents and Approaches to Resolve It

Antimicrobial resistance represents an enormous global health crisis and one of the most serious threats humans face today. Some bacterial strains have acquired resistance to nearly all antibiotics. Therefore, new antibacterial agents are crucially needed to overcome resistant bacteria. In 2017, the World Health Organization (WHO) has published a list of antibiotic-resistant priority pathogens, pathogens which present a great threat to humans and to which new antibiotics are urgently needed the list is categorized according to the urgency of need for new antibiotics as critical, high, and medium priority, in order to guide and promote research and development of new antibiotics. The majority of the WHO list is Gram-negative bacterial pathogens. Due to their distinctive structure, Gram-negative bacteria are more resistant than Gram-positive bacteria, and cause significant morbidity and mortality worldwide. Several strategies have been reported to fight and control resistant Gram-negative bacteria, like the development of antimicrobial auxiliary agents, structural modification of existing antibiotics, and research into and the study of chemical structures with new mechanisms of action and novel targets that resistant bacteria are sensitive to. Research efforts have been made to meet the urgent need for new treatments; some have succeeded to yield activity against resistant Gram-negative bacteria by deactivating the mechanism of resistance, like the action of the β-lactamase Inhibitor antibiotic adjuvants. Another promising trend was by referring to nature to develop naturally derived agents with antibacterial activity on novel targets, agents such as bacteriophages, DCAP(2-((3-(3,6-dichloro-9H-carbazol-9-yl)-2-hydroxypropyl)amino)-2(hydroxymethyl)propane1,3-diol, Odilorhabdins (ODLs), peptidic benzimidazoles, quorum sensing (QS) inhibitors, and metal-based antibacterial agents.

Synthesis, Structural Characterization and Antimicrobial Evaluation of Ruthenium Complexes with Heteroaromatic Carboxylic Acids

The antibacterial and antibiofilm activities of two new ruthenium complexes against E. coli, S. aureus, P. aeruginosa PAO1 (laboratory strain) and P. aeruginosa LES B58 (clinical strain) were evaluated. Complexes, mer-[Ru^III (2-bimc)₃ ] ⋅ H₂ O (1) and cis-[Ru^IV Cl₂ (2,3-pydcH)₂ ] ⋅ 4H₂ O (2), were obtained using aromatic carboxylic acid ligands, namely, 1H-benzimidazole-2-carboxylic acid (2-bimcH) and pyridine-2,3-dicarboxylic acid (2,3-pydcH₂ ). Compounds were physicochemically characterized using X-ray diffraction, Hirshfeld surface analysis, IR and UV/VIS spectroscopies, as well as magnetic and electrochemical measurements. Structural characterization revealed that Ru(III) and Ru(IV) ions in the complexes adopt a distorted octahedral geometry. The intermolecular classical and weak hydrogen bonds, and π⋅⋅⋅π contacts significantly contribute to structure stabilization, leading to the formation of a supramolecular assembly. Biological studies have shown that the Ru complexes inhibit the growth of bacteria and biofilm formation by the tested strains and the complexes seem to be a potential as antimicrobial agents.

A benzimidazole-based ruthenium(IV) complex inhibits Pseudomonas aeruginosa biofilm formation by interacting with siderophores and the cell envelope, and inducing oxidative stress

Pseudomonas aeruginosa biofilm-associated infections are a serious medical problem, and new compounds and therapies acting through novel mechanisms are much needed. Herein, the authors report a ruthenium(IV) complex that reduces P. aeruginosa PAO1 biofilm formation by 84%, and alters biofilm morphology and the living-to-dead cell ratio at 1 mM concentration. Including the compound in the culture medium altered the pigments secreted by PAO1, and fluorescence spectra revealed a decrease in pyoverdine. Scanning electron microscopy showed that the ruthenium complex did not penetrate the bacterial cell wall, but accumulated on external cell structures. Fluorescence quenching experiments indicated strong binding of the ruthenium complex to both plasmid DNA and bovine serum albumin. Formamidopyrimidine DNA N-glycosylase (Fpg) protein digestion of plasmid DNA isolated after ruthenium(IV) complex treatment revealed the generation of oxidative stress, which was further proved by the observed upregulation of catalase and superoxide dismutase gene expression.

Synthesis of N-Tetradecyl-1,10-phenathrolinium-Based New Salts for Biological Applications

New organic salts were synthesized by quaternizing 1,10-phenanthroline using 1-bromotetradecane. The first step yielded an organic salt of formula [C₂₆H₃₇N₂]Br. Anion exchange reaction using Li[(CF₃SO₂)₂N] resulted in a more stable salt of formula [C₂₆H₃₇N₂][(CF₃SO₂)₂N]. The organic salts were investigated by spectrometry (¹H, ¹³C, ¹⁹F NMR, X-ray photoelectron spectroscopy (XPS), UV-Vis, and matrix-assisted laser desorption/ionization mass spectroscopy (MALDI MS), CHNSBr elemental analysis, and thermal analysis (TGA and DSC). The thermal characterization showed the melting and decomposition points of [C₂₆H₃₇N₂][(CF₃SO₂)₂N] to be 48°C and 290°C, respectively, which indicates it is an ionic liquid with large liquidus range. The biological activities of the salts were investigated against two Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) and two Gram-negative (Escherichia coli and Klebsiella pneumoniae) bacteria, and they are found to be active against all of them. They were compared with [Cu(1,10-phenanthroline)₂Cl]Cl. They are found more active against the Gram-negative bacteria. The salts demonstrated minimum inhibitory concentration as low as 50 µg/L. These results suggest the synthesized salts can be considered as a better alternative to certain transition metal complex drugs. This minimizes the concern of introducing metal ions into the organism.