Antiproliferative, DNA binding, and cleavage properties of dinuclear Co(III) complexes containing the bioactive quinizarin ligand

Coordination compounds of cobalt(II) with carboxylate non-steroidal anti-inflammatory drugs: structure and biological profile

Fourteen cobalt(II) complexes with the non-steroidal anti-inflammatory drugs sodium meclofenamate, tolfenamic acid, mefenamic acid, naproxen, sodium diclofenac, and diflunisal were prepared in the presence or absence of a series of nitrogen-donors (namely imidazole, pyridine, 3-aminopyridine, neocuproine, 2,2'-bipyridine, 1,10-phenanthroline and 2,2'-bipyridylamine) as co-ligands and were characterised by spectroscopic and physicochemical techniques. Single-crystal X-ray crystallography was employed to determine the crystal structure of eight complexes. The biological profile of the complexes was investigated regarding their interaction with serum albumins and DNA, and their antioxidant potency. The interaction of the compounds with calf-thymus DNA takes place via intercalation. The ability of the complexes to cleave pBR322 plasmid DNA at the concentration of 500 μM is rather low. The complexes demonstrated tight and reversible binding to human and bovine serum albumins and the binding site of bovine serum albumin was also examined. In order to assess the antioxidant activity of the compounds, the in vitro scavenging activity towards free radicals, namely 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), and their ability to reduce H2O2 were studied.

Synthesis, characterization, and biological evaluation of novel cobalt(II) complexes with β-diketonates: crystal structure determination, BSA binding properties and molecular docking study

In order to discover a new antibiotic drug with better or similar activity of the already existing drugs, a series of novel cobalt(II) complexes with β-diketonate as ligands is synthesized and tested on four strains of bacteria and four species of fungi. All compounds showed notable antimicrobial activity against all tested strains. More importantly, some cobalt(II) complexes displayed greater activity than ketoconazole. It is important to notice that on the tested strains Mucor mucedo and Penicillium italicum complex 2B showed five times better activity compared to ketoconazole, while complex 2D had two times better activity on Penicillium italicum strain compared to ketoconazole. Moreover, investigations with bovine serum albumin were performed. Investigations showed that the tested complexes have an appropriate affinity for binding to bovine serum albumin. In addition, the molecular docking study was performed to investigate more specifically the sites and binding mode of the tested cobalt(II) complexes with β-diketonate as ligands to bovine serum albumin, tyrosyl-tRNA synthetase, topoisomerase II DNA gyrase, and cytochrome P450 14 alpha-sterol demethylase. In conclusion, all the results indicated the great prospective of the novel cobalt complexes for some potential clinical applications in the future.

Photoactivatable, mitochondria targeting dppz iridium(III) complex selectively interacts and damages mitochondrial DNA in cancer cells

Cyclometalated Ir(III) complex [Ir(L)2(dppz)]PF6 (where L = 1-methyl-2-(thiophen-2-yl)-1H-benzo[d]imidazole and dppz = dipyrido [3,2-a:2',3'-c]phenazine) (Ir1) is potent anticancer agent whose potency can be significantly increased by irradiation with blue light. Structural features of the cyclometalated Ir(III) complex Ir1 investigated in this work, particularly the presence of dppz ligand possessing an extended planar area, suggest that this complex could interact with DNA. Here, we have shown that Ir1 accumulates predominantly in mitochondria of cancer cells where effectively and selectively binds mitochondrial (mt)DNA. Additionally, the results demonstrated that Ir1 effectively suppresses transcription of mitochondria-encoded genes, especially after irradiation, which may further affect mitochondrial (and thus also cellular) functions. The observation that Ir1 binds selectively to mtDNA implies that the mechanism of its biological activity in cancer cells may also be connected with its interaction and damage to mtDNA. Further investigations revealed that Ir1 tightly binds DNA in a cell-free environment, with sequence preference for GC over AT base pairs. Although the dppz ligand itself or as a ligand in structurally similar DNA-intercalating Ru polypyridine complexes based on dppz ligand intercalates into DNA, the DNA binding mode of Ir1 comprises surprisingly a groove binding rather than an intercalation. Also interestingly, after irradiation with visible (blue) light, Ir1 was capable of cleaving DNA, likely due to the production of superoxide anion radical. The results of this study show that mtDNA damage by Ir1 plays a significant role in its mechanism of antitumor efficacy. In addition, the results of this work are consistent with the hypothesis and support the view that targeting the mitochondrial genome is an effective strategy for anticancer (photo)therapy and that the class of photoactivatable dipyridophenazine Ir(III) compounds may represent prospective substances suitable for further testing.

Rational design of an artificial hydrolytic nuclease by introduction of a sodium copper chlorophyllin in L29E myoglobin

Heme proteins have recently emerged as promising artificial metalloenzymes for catalyzing diverse reactions. In this report, L29E Mb, a single mutant of myoglobin (Mb), was reconstituted by replacing the heme with a sodium copper cholorophyllin (CuCP) to form a new green artificial enzyme (named CuCP-L29E Mb). The reconstituted protein CuCP-L29E Mb was found to exhibit hydrolytic DNA cleavage activity, which was not depending on O₂. In addition, Mg²⁺ ion could effectively promote the DNA cleavage activity of CuCP-L29E Mb. Wild-type (WT) Mb reconstituted with CuCP (named CuCP-WT Mb) did not show DNA cleavage activity under the same conditions. This study suggests that both Mg²⁺ and the ligand Glu29 are critical for the nuclease activity and the artificial nuclease of Mg²⁺-CuCP-L29E Mb may have potential applications in the future.

Synthesis, Characterization, and Cytotoxicity of Morpholine-Containing Ruthenium(II) p-Cymene Complexes

Morpholine motif is an important pharmacophore and, depending on the molecular design, may localize in cellular acidic vesicles. To understand the importance of the presence of pendant morpholine in a metal complex, six bidentate N,O-donor ligands with or without a pendant morpholine unit and their corresponding ruthenium(II) p-cymene complexes (1-6) are synthesized, purified, and structurally characterized by various analytical methods including X-ray diffraction. Complexes 2-4 crystallized in the P2₁/c space group, whereas 5 and 6 crystallized in the P1̅ space group. The solution stability studies using ¹H NMR support instantaneous hydrolysis of the native complexes to form monoaquated species in a solution of 3:7 (v/v) dimethyl sulfoxide-d₆ and 20 mM phosphate buffer (pH* 7.4, containing 4 mM NaCl). The monoaquated complexes are stable for at least up to 24 h. The complexes display excellent in vitro antiproliferative activity (IC₅₀ ca. 1-14 μM) in various cancer cell lines, viz., MDA-MB-231, MiaPaCa2, and Hep-G2. The presence of the pendant morpholine does not improve the dose efficacy, but rather, with 2-[[(2,6-dimethylphenyl)imino]methyl]phenol (HL1) and its pendant morpholine analogue (HL3) giving complexes 1 and 3, respectively, the antiproliferative activity was poorer with 3. MDA-MB-231 cells treated with the complexes show that the acidic vesicles remain acidic, but the population of acidic vesicles increases or decreases with time of exposure, as observed from the dispersed red puncta, depending on the complex used. The presence of the 2,6-disubstituted aniline and the naphthyl group seems to improve the antiproliferative dose. The complex treated MDA-MB-231 cells show that cathepsin D, which is otherwise present in the cytosolic lysosomes, translocates to the nucleus as a result of exposure to the complexes. Irrespective of the presence of a morpholine motif, the complexes do not activate caspase-3 to induce apoptosis and seem to favor the necrotic pathway of cell killing.

Effect of the replacement of tripodal 4N donors by two 2N chelators on the redox and cytotoxic activity of maltolato and deferipronato containing Co(III) complexes

Fourteen novel Co^III ternary complexes with the general formula [Co(4N)(2O)]X₂ or [Co(2N)₂(2O)]X₂ where 4N = tris(2-aminoethyl)amine (tren) or tris(2-pyridylmethyl)amine (tpa); 2N = 1,10-phenantroline (phen), 2,2'-bipyridine (bipy), 1,2-diaminoethane (en) or 2-(aminomethyl)pyridine (ampy) and 2O = 1,2-dimethyl-3-hydroxy-4(1H)-pyridinone (dhpH), 3-hydroxy-2-methyl-4-pyrone (maltH) or 2-ethyl-3-hydroxy-4H-pyran-4-one (etmaltH) were synthesized, characterized and their redox features explored. Molecular structure of some selected [Co(2N)₂(2O)](ClO₄)₂ (2N = phen, bipy, en; 2O = dhp, malt) or [Co(4N)(2O)](ClO₄)₂ (4N = tpa; 2O = etmalt) type complexes were assessed by X-ray diffraction and showed the expected octahedral geometry. Replacement of the 4N donor ligands by two 2N donor ligands resulted in the decrease of the cathodic peak potential of the complexes indicating easier reduction and allowing therefore the tailoring of the redox properties of the complexes. Screening of selected compounds against a human derived cancer cell line, HeLa, showed that, unlike the [Co(4N)(2O)]X₂ derivatives, the complexes containing 2N = bipy or phen ligands have better anticancer activity than cisplatin or carboplatin.

Biophysical Characterization and Anticancer Activities of Photosensitive Phytoanthraquinones Represented by Hypericin and Its Model Compounds

Photosensitive compounds found in herbs have been reported in recent years as having a variety of interesting medicinal and biological activities. In this review, we focus on photosensitizers such as hypericin and its model compounds emodin, quinizarin, and danthron, which have antiviral, antifungal, antineoplastic, and antitumor effects. They can be utilized as potential agents in photodynamic therapy, especially in photodynamic therapy (PDT) for cancer. We aimed to give a comprehensive summary of the physical and chemical properties of these interesting molecules, emphasizing their mechanism of action in relation to their different interactions with biomacromolecules, specifically with DNA.

Synthesis, structural determination, in vitro and in silico biological evaluation of divalent or trivalent cobalt complexes with indomethacin

The interaction of cobalt chloride with the non-steroidal anti-inflammatory drug indomethacin (Hindo) led to the formation of the polymeric complex [Co(indo-O)2(H2O)2(μ-Cl)]n·n(MeOH·H2O) bearing one chlorido bridge between the cobalt atoms. The presence of the nitrogen-donor co-ligands 2,2'-bipyridine (bipy), 2,2'-bipyridylamine (bipyam), 1,10-phenanthroline (phen) or 1H-imidazole (Himi) resulted in the isolation of complexes [Co2(μ-indo-O,O')2(indo-O)2(bipy)2(μ-H2O)]·3.3MeOH, [Co(indo-O,O')2(bipyam)]·0.9MeOH·0.2H2O, [Co(indo-O,O')2(phen)] (4) and [Co(indo-O)2(Himi)2] (5), respectively, where the indomethacin ligands were coordinated in diverse manners. The study of the affinity of the complexes for calf-thymus DNA revealed their intercalation between the DNA-bases. The binding of the complexes to albumins was also examined and the corresponding binding constants and binding subdomain were determined. The free radical scavenging activity of the compounds was evaluated towards 1,1-diphenyl-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid). Molecular modeling calculations may usually provide a molecular basis for the understanding of both the impairment of DNA by its binding with the studied complexes and the ability of these compounds to transportation through serum albumin proteins. This study can provide information for the elucidation of the mechanism of action of the compounds in a molecular level.