Synthesis and Characterization of Ruthenium-Paraphenylene-Cyclopentadienyl Full-Sandwich Complexes: Cytotoxic Activity against A549 Lung Cancer Cell Line and DNA Binding Properties

Novel full-sandwich (η5-Cp)-Ru-paraphenylene complexes with the general formula [(η5-Cp)nRu(η6-L)](PF6)n where n = 1-3 and L = biphenyl, p-terphenyl and p-quaterphenyl, were synthesized and characterized by means of spectroscopic and analytical techniques. The structures of the complexes [(η5-Cp)Ru(η6-biphenyl)](PF6) (1), [(η5-Cp)Ru(η6-terphenyl)](PF6) (3) and [(η5-Cp)2Ru(η6-terphenyl)](PF6)2 (4) was determined by X-ray single crystal methods. The interaction of the complexes [(η5-Cp)Ru(η6-quaterphenyl)]Cl, (6)Cl, and [(η5-Cp)2Ru(η6-quaterphenyl)]Cl2, (7)Cl2, with the DNA duplex d(5'-CGCGAATTCGCG-3')2 was studied using NMR techniques. The results showed that both complexes interacted non-specifically with both the minor and major grooves of the helix. Specifically, (6)Cl exhibited partial binding through intercalation between the T7 and T8 bases of the sequence without disrupting the C-G and A-T hydrogen bonds. Fluorometric determination of the complexes' binding constants revealed a significant influence of the number of connected phenyl rings in the paraphenylene ligand (L) on the binding affinity of their complexes with the d(5'-CGCGAATTCGCG-3')2. The complexes (6)Cl and (7)Cl2 were found to be highly cytotoxic against the A549 lung cancer cell line, with complex (6) being more effective than (7) (IC50 for (6)Cl: 17.45 ± 2.1 μΜ, IC50 for (7)Cl2: 65.83 ± 1.8 μΜ) and with a selectivity index (SI) (SI for (6)Cl: 1.1 and SI for (7)Cl2: 4.8).

Synthesis, characterization, interactions with the DNA duplex dodecamer d(5'-CGCGAATTCGCG-3')2 and cytotoxicity of binuclear η6-arene-Ru(II) complexes

The novel binuclear η⁶-arene-Ru(II) complexes with the general formula {[(η⁶-cym)Ru(L)]₂(μ-BL)}(PF₆)₄, and their corresponding water soluble {[(η⁶-cym)Ru(L)]₂(μ-BL)}Cl₄, where cym = p-cymene, L = 2,2'-bipyridine (bpy) and 1,10-phenanthroline (phen), BL = 4,4'-bipyridine (BL-1), 1,2-bis(4-pyridyl)ethane (BL-2) and 1,3-bis(4-pyridyl)propane (BL-3), were synthesized and characterized. The structure of {[(η⁶-cym)Ru(phen)]₂(μ-BL-1)}(PF₆)₄ was determined by X-ray single crystal methods. The interaction of {[(η⁶-cym)Ru(phen)]₂(μ-BL-i)}Cl₄ (i = 1, 2, 3; (4), (5) and (6) correspondingly) with the DNA duplex d(5'-CGCGAATTCGCG-3')₂ was studied by means of NMR techniques and fluorescence titrations. The results show that complex (4) binds with a K_b = 12.133 × 10³ M^-1 through both intercalation and groove binding, while (5) and (6) are groove binders (K_b = 2.333 × 10³ M^-1 and K_b = 3.336 × 10³ M^-1 correspondingly). Comparison with the mononuclear complex [(η⁶-cym)Ru(phen)(py)]²⁺ reveals that it binds to the d(5'-CGCGAATTCGCG-3')₂ with a K_b value two orders of magnitude lower than (4) (K_b = 0.158 × 10³ M^-1), indicating that for the binuclear complexes both ruthenium moieties participate in the binding. The complexes were found to be cytotoxic against the A2780 and A2780 res. cancer cell line with a selectivity index (SI) in the range of 3.0-5.9.

Promising Antifungal and Antibacterial Agents Based on 5-Aryl-2,2'-bipyridines and Their Heteroligand Salicylate Metal Complexes: Synthesis, Bioevaluation, Molecular Docking

A series of new 5-aryl-2,2'-bipyridines and their (polyfluoro)salicylate complexes of Cu(II), Co(II) and Mn(II) were synthesized. Their antimicrobial activity was evaluated in vitro against six strains of Trichophytons, E. floccosum, M. canis, C. ablicans and Gram-negative bacteria N. gonorrhoeae. Among azo-ligands, Ph-bipy and Tol-bipy showed promising antifungal activity (minimum inhibitory concentration (MIC)<0.8-27 μM). Their antifungal action was found can be realized via binding Fe(III) ions. Tol-bipy suppressed growth of Gram-positive bacteria S. aureus, S. aureus MRSA and their monospecies biofilms (MIC 6-16 μM). Using molecular docking, the anti-staphylococcal action mechanism based on the inhibition of S. aureus DNA gyrase GyrB was proposed for the lead compounds. Among metal complexes, Cu(II) and Mn(II) complexes based on tetrafluorosalicylic acid and Tol-bipy or Ph-bipy had the high antifungal activity (MIC<0.24-32 μM). Mn(SalF₄ -2H)₂ (Tol-bipy)₂ ] suppressed the growth of seven Candida strains at MIC 12-24 μM. [Cu(Sal-2H)(Ph-bipy)] and [Cu(SalF₃ -2H)(Ph-bipy)₂ ] showed the promising anti-gonorrhoeae activity (MIC 4.2-5.2 μM). (Cu(SalF_n -2H)(Tol-bipy)₂ ], [Cu(SalF₄ -2H)(Ph-bipy)₂ ] and [Cu(SalF₃ -2H)(Ph-bipy)₂ ]) were found active against the bacteria of S. aureus, S. aureus MRSA and their biofilms (MIC 2.4-41.4 μM). The most active compounds were tested for toxicity in vitro against human embryonic kidney (HEK-293) cells and in vivo experiments with CD-1 mice.

Organotin derivatives of cholic acid induce apoptosis into breast cancer cells and interfere with mitochondrion; Synthesis, characterization and biological evaluation

Organotin(IV) derivatives of cholic acid (CAH) with the formulae R3Sn(CA) (R = Ph- (1), n-Bu- (2)) and R2Sn(CA)2 (R = Ph- (3), n-Bu- (4) and Me- (5)) were synthesized. The compounds were characterized in solid state by melting point, FT-IR, 119Sn Mössbauer, X-ray fluorescence (XRF) spectroscopy and in solution by 1H NMR, UV-Vis spectral data and by Electrospray Ionisation Mass spectrometry (ESI-MS), High Resolution Mass spectrometry (HRMS), and atomic absorption analysis. The in vitro bioactivity of 1-5 against human breast adenocarcinoma cancer cells MCF-7 (positive to hormone receptors) and MDA-MB-231 (negative to hormone receptors) reveal that triorganotin derivatives 1-2 exhibit significantly stronger activity than the corresponding diorganotin ones. Compound 5 is inactive against both cell lines at the concentrations tested. Triorganotins 1-2 inhibit selectively MCF-7 than MDA-MB-231 cells, suggesting hormone mimetic behavior of them. Organotins 1-4 inhibit both cancerous cell lines, stronger than cisplatin which rise up to 55-fold against MCF-7 and 170-fold against MDA-MB-231. The in vitro toxicity of 1-4 was evaluated on normal human fetal lung fibroblast cells (MRC-5), while their genotoxicity in vitro by micronucleus assay (MN). Moreover, the in vivo toxicity of 1-4 was tested by Artemia salina assay and their in vivo genotoxicity with Allium cepa test. The mechanism of action of 1-4 against MCF-7 was clarified in vitro by the means of cell morphology studies, cell cycle arrest, Acridine Orange/Ethidium Bromide (AO/EB) Staining, mitochondrial membrane permeabilization test and by their binding affinity toward the calf thymus (CT) DNA.

Novel silver glycinate conjugate with 3D polymeric intermolecular self-assembly architecture; an antiproliferative agent which induces apoptosis on human breast cancer cells

The new water soluble silver(I) complex of glycine (GlyH) with formula [Ag₃(Gly)₂NO₃]_n (AGGLY) was synthesized. The compound was characterized by melting point (m.p.), Fourier-transform infrared (FT-IR), Ultraviolet-visible (UV-vis) and Nuclear Magnetic Resonance (¹H-,¹³C NMR) spectroscopic techniques and X-ray crystallography. The in vitro cytotoxic activity of AGGLY against human breast adenocarcinoma cell lines: MCF-7 (hormone depended (HD)) and MDA-MB-231 (hormone independent (HI)) was determined. For comparison other adenocarcinoma cells such as human cervical adenocarcinoma (HeLa) cells and lung adenocarcinoma cells (A549) were also screened. AGGLY inhibits both breast cancer cell lines stronger than cisplatin. On the contrary, AGGLY, exhibits lower toxicity against fetal lung fibroblast (MRC-5) cells than cisplatin. Its genotoxicity against MRC-5 cells was detected from the presence or absence of micronucleus using fluorescence microscopy, while the in vivo genotoxicity was evaluated using Allium cepa model. The MCF-7 cells morphology suggests apoptotic pathway for their death. The apoptotic pathway was confirmed by cell cycle arrest, Acridine Orange/Ethidium Bromide (AO/EB) Staining, and permeabilization of the mitochondrial membrane tests. The molecular mechanism of action was further studied by the binding affinity of AGGLY towards the calf thymus (CT) DNA.

Mitochondria- and nucleolus-targeted copper(i) complexes with pyrazole-linked triphenylphosphine moieties for live cell imaging

The labelling and imaging of mitochondria and nucleolus have attracted great attention because of the involvement of these cellular organelles in critical cellular activities. Therefore, a large number of mitochondria- or nucleolus-labelling probes have been developed throughout the world. However, in the current study, we successfully developed two pyrazole-based, copper-linked triphenylphosphine-coupled emissive metallo-complexes (C1 and C2) for the simultaneous visualization of mitochondria and nucleolus in a single run. These complexes were very inexpensive and could be synthesized by a simple one-pot multicomponent reaction scheme. The complexes were very specific, and only a small concentration of 5 μM was found to be sufficient to probe both the organelles efficiently. Additionally, even under a shorter incubation period (half hour), the fluorescence intensity from the cells was appreciable. Also, both the compounds were found to be photostable when torched with 10% of a 100 mW laser for up to 10 min. All these results indicate that both the complexes may contribute towards the future development of cell imaging tools. To the best of our knowledge, this is the first report on the development of multifunctional live cell imaging tools for simultaneous mitochondria and nucleolus imaging and within the shortest incubation time of about 30 minutes.

Nickel and zinc complexes of testosterone N4-substituted thiosemicarbazone: Selective cytotoxicity towards human colorectal carcinoma cell line HCT 116 and their cell death mechanisms

Two new Schiff base ligands (TE and TF) were prepared from conjugation of testosterone with 4-(4-ethylphenyl)-3-thiosemicarbazide and 4-(4-fluorophenyl)-3-thiosemicarbazide, respectively. Their nickel (NE and NF) and zinc (ZE and ZF) complexes were reported. X-ray crystallography revealed a distorted square planar geometry was adopted by NE. The compounds demonstrated excellent selectivity towards the colorectal carcinoma cell line HCT 116 despite their weak preferences towards the prostate cancer cell lines (PC-3 and LNCaP). Against HCT 116, all these compounds were able to arrest cell cycle at G₀/G₁ phase and induce apoptosis via mitochondria-dependent (TE, NE, and TF) and extrinsic apoptotic pathway (ZE, NF, and ZF). Moreover, only ZE was able to act as topoisomease I poison and halt its enzymatic reactions although all compounds presented excellent affinity towards DNA.

Conformational rearrangements of G-quadruplex topology promoted by Cu(II) 12-MCCu(II)PyrAcHA-4 metallacrown

Cu(II) 12-MC_{Cu(II)PyrAcHA}-4 metallacrown was studied by several spectroscopic techniques as an interacting ligand with G-quadruplex DNA structures. Investigations were performed on oligonucleotides bearing human telomeric and protooncogenic c-myc sequences in buffered solution mimicking ionic conditions in cellular environment. The planar square-based Cu(II) 12-MC-4 metallacrown interacts with GQ via an end-stacking mode with 1:1 stoichiometry. Circular dichroism (CD) titration revealed capability of this metallacrown to induce transformation of the GQ hybrid topology into the parallel form. Thermal melting experiment indicated higher thermal stability of both antiparallel (ΔT_m = +15 °C) and parallel (ΔT_m = ≥27 °C) G-quadruplexes in the presence of Cu (II) 12-MC-4. Indirect GQ FID assay let to determine high binding affinity of the Cu(II) 12-MC-4 to antiparallel 22Htel/Na⁺ GQ (K_MC = 3.9 (±0.4) x 10⁶ M^-1). Comparing with lower binding constants previously reported for Ln (III) 15-MC-5 and Sm (III) 12-MC-4, one can conclude that the square planar geometry and the positive charge of metallacrown play an important role in MC/GQ interactions.

A palladium(II) complex with the Schiff base 4-chloro-2-(N-ethyliminomethyl)-phenol: Synthesis, structural characterization, and in vitro and in silico biological activity studies

The synthesis and characterization of the Pd(II) complex of the formula [Pd(L)₂] 1 with the Schiff base 4-chloro-2-(N-ethyliminomethyl)-phenol (HL) as derived in situ via the condensation reaction of 5-chloro-salicylaldehyde and ethylamine was undertaken. The structure of 1 was verified by single-crystal X-ray crystallography. The ability of 1 to interact with calf-thymus (CT) DNA was studied by UV-vis and viscosity experiments, and its ability to displace ethidium bromide (EB) from the DNA-EB conjugate was revealed by fluorescence spectroscopy. It was found that intercalation is the most possible mode of interaction with CT DNA. Additionally, DNA electrophoretic mobility experiments showed that 1 interacts with the plasmid pBluescript SK(+) (pDNA) as proved by the formation of unusual mobility DNA bands and degradation of relaxed pDNA at concentration of 5 mM. The interaction of 1 with human (HSA) and bovine serum albumin (BSA) was monitored revealing its reversible binding to albumins. The complex showed noteworthy antimicrobial activity against one (Bacillus subtilis) of the five tested bacteria. In order to explain the described in vitro activity of the compound, we adopted molecular docking studies on the crystal structure of HSA, BSA, CT DNA and DNA-gyrase. Furthermore, in silico predictive tools have been employed to study the properties of the complex. The in silico studies are adopted on a multitude of proteins involved in cancer growth, as well as prediction of drug-induced changes of gene expression profile, protein- and mRNA-based prediction results, prediction of sites of metabolism, cytotoxicity for cancer cell lines, etc.

Esterification of the free carboxylic group from the lutidinic acid ligand as a tool to improve the cytotoxicity of Ru(ii) complexes

The esterification of the free carboxyl group in ruthenium complexes improves the complex interactions with biomolecules, lipophilicity, and cellular uptake, making them more selective against tumor cells than cisplatin.

Thioether sulfur-bound [Cu2] complexes showing catechol oxidase activity and DNA cleaving behaviour

Ligand backbone alteration leads to different mechanisms for catecholase activity and order of interaction with DNA molecules.

Exploring the effect of substituent in the hydrazone ligand of a family of μ-oxidodivanadium(v) hydrazone complexes on structure, DNA binding and anticancer activity

The reaction of 2-hydroxybenzoylhydrazine (H₂bh) separately with equimolar amounts of [V^IVO(aa)₂] and [V^IVO(ba)₂] in CHCl₃ afforded the complexes [VO₃(HL¹)₂] (1) and [VO₃(HL²)₂] (2) respectively in good to excellent yield ((HL¹)^2- and (HL²)^2- represent respectively the dianionic form of 2-hydroxybenzoylhydrazones of acetylacetone (H₃L¹) and benzoylacetone (H₃L²) (general abbreviation H₃L)). From X-ray structure analysis, the V^V-O-V^V angle was found to be ∼115° and 180° in 1 and 2 respectively. Upon one-electron reduction selectively at one V centre at an appropriate potential, each of 1 and 2 generated mixed-valence [(HL)V^VO-(μ-O)-OV^IV(HL)]^- species 1A and 2A respectively, which showed valence delocalization at room temperature and localization at 77 K, and the V^IV-O-V^V bond angles were calculated to be 177.5° and 180° respectively. The intercalative mode of binding of the two complexes 1 and 2 with CT DNA has been suggested by UV-visible spectroscopy (K_b = 7.31 × 10⁵ M^-1 and 8.71 × 10⁵ M^-1 respectively for 1 and 2), fluorescence spectroscopy (K_sv = 6.85 × 10⁵ M^-1 and 8.53 × 10⁵ M^-1 respectively for 1 and 2) and circular dichroism spectroscopy. Such intercalative mode of binding of these two complexes with CT DNA and HPV DNA has also been confirmed by molecular docking study. Both complexes 1 and 2 exhibited promising anti-cancer activity against SiHa cervical cancer cells with IC₅₀ values of 28 ± 0.5 μM and 25 ± 0.5 μM respectively for 24 h which is significantly better than that of widely used cisplatin (with IC₅₀ value of 63.5 μM). Nuclear staining experiments reveal that these complexes kill the SiHa cells through apoptotic mode. It is interesting to note that these two complexes are non-toxic to normal T293 cell line. Complex 2 showed higher DNA binding ability with CT DNA and HPV DNA as well as better anti-cancer properties towards SiHa cervical cancer cells in comparison to complex 1, a fact which can be explained by considering the lower energy of LUMO (which favours electron transition from DNA to the metal complex) and also the higher surface area of complex 2 in comparison to complex 1 due to the presence of one extra electron-withdrawing phenyl group in the former.

In vitro and in silico study of the biological activity of manganese(III) inverse-[9-MC-3]-metallacrowns and manganese(II) complexes with the anti-inflammatory drugs diclofenac or indomethacin

In the present contribution, the biological properties of four manganese complexes with the non-steroidal anti-inflammatory drugs sodium diclofenac (Nadicl) or indomethacin (Hindo) in the presence or absence of salicylaldoxime (Η₂sao), i.e. [Μn₆(O)₂(dicl)₂(sao)₆(CH₃OH)₆] 1, [Μn₆(O)₂(indo)₂(sao)₆(H₂O)₄], 2, [Μn(dicl)₂(CH₃OH)₄], 3, and [Μn(indo)₂(CH₃OH)₄], 4 are presented. More specifically, the in vitro cytotoxic effects of the complexes were evaluated against three cancer cell lines (HeLa, MCF-7 and A549 cells) as well as their combinatory activity with the well-known chemotherapeutic drugs irinotecan, cisplatin, paclitaxel and 5-fluorouracil. The biological activity of the complexes was investigated in vitro by studying their affinity to calf-thymus DNA and their binding towards bovine or human serum albumin (HSA). Molecular docking simulations on the crystal structure of HSA and human estrogen receptor alpha (hERa) were employed in order to study in silico the ability of the studied complexes to bind to these proteins.

Synthesis, characterization and biological application of 5-quinoline 1,3,5-trisubstituted pyrazole based platinum(ii) complexes

Square planar mononuclear platinum(ii) complexes were synthesized in the presence of neutral bidentate heterocyclic (5-quinoline 1,3,5-tri-substituted pyrazole scaffold) ligands and K2PtCl4 salt. The synthesized compounds were characterized by micro-elemental analysis, FT-IR, UV-vis, 1H NMR, 13C NMR, TGA, mass spectrometry and molar conductivity. Their biological activities were investigated by in vitro brine shrimp lethality bioassay, in vitro antimicrobial study against five different pathogens, in vivo cellular level cytotoxicity against Schizosaccharomyces pombe cells, and in vitro anti-proliferation assay. The binding constant Ksv, Kb, Ka values of the complexes were determined by DNA interaction studies. The gel electrophoresis assay was carried out to examine the effect of the complexes on the DNA nuclease of pUC19 plasmid DNA. The docking energies of the ligands (L1-L5 ) and complexes (I-V) were observed in the range of -265.14 to -284.33 kJ mol-1. The synthesized Pt(ii) complexes (I-V) were screened against the MCF-7 (human breast adenocarcinoma) and HCT-116 (human colon carcinoma) cancer cell lines.

Eco-friendly microwave synthesis of Mg(ii) phenoxy carboxylic acid coordination compounds with specific motifs driven by multiple hydrogen bonding

Four magnesium complexes with specific motifs driven by multiple hydrogen bonding were synthesized by microwave method. The design strategy presented here gave an insight into the further structural prediction of magnesium supramolecular assemblies.

Ni(ii)/Cu(ii)/Zn(ii) 5,5-diethylbarbiturate complexes with 1,10-phenanthroline and 2,2′-dipyridylamine: synthesis, structures, DNA/BSA binding, nuclease activity, molecular docking, cellular uptake, cytotoxicity and the mode of cell death

DNA/BSA binding and anticancer properties of new Ni(ii), Cu(ii) and Zn(ii) 5,5-diethylbarbiturate complexes were evaluated.

Synthesis, crystal structure, DNA-binding and magnetism of copper 15-metallacrown-5 complexes based on glycinehydroxamic acid ligand

Six lanthanide 15-MC-5 complexes based on glycinehydroxamic acid were synthesized. DNA-binding properties of the six complexes with calf thymus DNA were investigated using fluorescence spectroscopy and circular dichroism studies.