Structure and DNA cleavage properties of two copper(ii) complexes of the pyridine-pyrazole-containing ligands mbpzbpy and Hmpzbpya

Study of novel bidentate heterocyclic amine-based metal complexes and their biological activities: cytotoxicity and antimicrobial activity evaluation

Metallic antitumor drugs with heterocyclic ligands, such as novel AMI (amino methyl imidazole) complexes [Pd(AMI)Cl₂](1), [Cu(AMI)L¹](2), and [Cu(AMI)L²·2H₂O](3) where L¹ = oxalate and L² = malonate, were synthesized and characterized. Assessments included elemental analyses, mass spectrometry, Fourier transform-infrared spectroscopy, ultraviolet-visible spectroscopy, and thermal analysis. The cytotoxicity of AMI complexes compared to cisplatin was assessed using MTT (3-[4,5-dimethylthiazol-2-yl] 2,5diphenyl tetrazolium bromide) assay with breast (MCF-7) and cervical (HeLa) cancer cell lines. After treating these cells with the AMI complexes' IC₅₀ values for 48 h, malondialdehyde levels and catalase activity were used to assess oxidative stress, antioxidant activity was evaluated with DPPH radical scavenging method, comet assays assessed DNA damage, and DNA fragmentation was evaluated using the gel electrophoresis. In vitro, antimicrobial activity was assessed using a disc diffusion method. The anticancer activity results showed that IC₅₀ (half-maximal inhibitory concentration) values of complex one, two, and three against MCF-7 and HeLa cancer cells are 0.156 ± 0.0006, 0.125 ± 0.001, 0.277 ± 0.002 μM respectively for MCF-7 cells and 0.222 ± 0.0005, 0.126 ± 0.0009, 0.152 ± 0.001 μM respectively for HeLa cells. Complex two demonstrated strong anticancer activity against MCF-7 and Hela cells. The study of oxidative stress parameters revealed that Malondialdehyde levels increased in cancer cell lines treated with complexes compared to untreated cells. Catalase activity decreased in cells treated with palladium chelate. The DPPH radical scavenging assay results identified that complex one was a more potent antioxidant in MCF-7 and Hela cells than other complexes with SC₅₀ values of 227.5 ± 0.28 and 361 ± 1.2 μL/mL, respectively. The comet assay results showed that complex two caused significant DNA damage in MCF-7 and HeLa cancer cells treated. Antimicrobial assays identified complex three as the most effective. Copper complexes give better antifungal activity against A. flavus than the palladium complex. We conclude that complex two is the most active in both cell types and might be assessed as a clinically useful drug for breast cancer treatment. The significance of the current study is the synthesis of antitumor drugs containing heterocyclic ligands, such as novel AMI complexes, and the study of their biological activities.

Transition metal complexes as self-activating chemical nucleases: proficient DNA cleavage without any exogenous redox agents

Chemical nucleases have found potential applications in the research fields of chemistry, biotechnology and medicine. A variety of metal complexes have been explored as good to outstanding therapeutic agents for DNA cleavage activity most likely via hydrolytic, oxidative or photoinduced cleavage pathways. However, most of these DNA cleaving agents lack their utility in in vivo applications due to their dependence on exogenous oxidants or reductants to achieve successful DNA damage. In view of addressing these issues, the development of metal complexes/organic molecules serving as self-activating chemical nucleases has received growing attention from researchers. In only the last decade, this field has dramatically expanded for the usage of chemical nucleases as therapeutic agents for DNA damage. The present study provides an overview of the opportunities and challenges in the design and development of self-activating chemical nucleases as improved DNA therapeutic candidates in the absence of an external redox agent. The reports on DNA nuclease activity via self-activation, especially with copper, zinc and iron complexes, and their mechanistic investigation have been discussed in this review article.

Cu(II) and Ni(II) Complexes with New Tridentate NNS Thiosemicarbazones: Synthesis, Characterisation, DNA Interaction, and Antibacterial Activity

This paper reports the synthesis and detailed characterisation of copper(II) and nickel(II) complexes with tridentate thiosemicarbazone ligands H 2 L1 and H 2 L2 derived from 2-acetylpyrazine. The ligands and their metal complexes were characterised by different physicochemical techniques, including elemental and thermogravimetric analysis; UV-Vis, IR, 1H-NMR, and 13C-NMR spectroscopy; molar conductance measurements; and mass spectrometry. The crystal structure of the H 2 L1 ligand was determined by single crystal X-ray diffraction studies. The spectral data showed that the thiosemicarbazone behaves as an NNS tridentate ligand through the nitrogen atoms of the azomethine group and pyrazine ring and the sulphur atom of the thioamide group. Elemental and thermal analyses indicated that the obtained metal complexes had a 1 : 1 stoichiometry (metal-ligand). The interactions between these complexes and calf thymus DNA (CT-DNA) were studied by electronic absorption and viscosity measurements. The activities of these compounds against oxidative DNA cleavage were examined by agarose gel electrophoresis. Cu(II) and Ni(II) complexes can wind DNA strands through groove interactions and promote strand breakage of the plasmid pmCherry under oxidative stress conditions. Moreover, all the complexes could interact more strongly with DNA than could with the free ligands. Finally, the antibacterial activities of the ligands and their complexes were determined by in vitro tests against Gram-positive bacterial strains (S. aureus ATCC 25923, L. monocytogenes ATCC 19115, and B. cereus ATCC 10876) and Gram-negative bacterial strains (E. coli ATCC 25922, S. typhimurium ATCC 14028, and K. pneumoniae ATCC BAA-2146) using the broth microdilution method. The metal complexes showed greater antimicrobial activities than the precursor ligands against some of the microorganisms.

A new fluorescence turn-on chemosensor for nanomolar detection of Al3+ constructed from a pyridine–pyrazole system

A pyridine–pyrazole based fluorescence turn-on chemosensor provides access to selective detection of Al³⁺ in solution as well as in HepG2 living cells.

Copper(II) complexes of N3O tripodal ligands appended with pyrene and polyamine groups: Anti-proliferative and nuclease activities

A series of tripodal ligands based on the 2-tert-butyl-4-R-6-phenol was synthesized, where R=aldehyde (HL¹), R=putrescine-pyrene (HL²) and R=putrescine (HL³). A dinucleating ligand wherein a putrescine group connects two tripodal moieties was also prepared (H₂L⁴). The corresponding copper complexes (1, 2, 3, and 4, respectively) were prepared and characterized. We determined the phenol's pKas in the range 2.47-3.93. The DNA binding constants were determined at 6×10⁶, 5.5×10⁵ and 2.7×10⁶ for 2, 3 and 4, respectively. The complexes display a metal-centered reduction wave at E_p^c,red=-0.45 to -0.5V vs. saturated calomel electrode, as well as a ligand-centered oxidation wave above 0.57V at pH7. In the presence of ascorbate they promote an efficient cleavage of DNA, with for example a concentration required to cleave 50% of supercoiled DNA of 1.7μM for 2. The nuclease activity is affected by the nature of the R group: putrescine-pyrene≈bis-ligating>putrescine>aldehyde. The species responsible for strand scission is the hydroxyl radical. The cytotoxicity of the complexes was evaluated on bladder cancer cell lines sensitive or resistant to cis-platin. The IC₅₀ of complexes 2 and 4 span over a short range (1.3-2μM) for the two cell lines. They are lower than those of the other complexes (3.1-9.7μM) and cis-platin. The most active compounds block the cell cycle at the G0/1 phase and promote apoptosis.

Transition-metal norharmane compounds as possible cytotoxic agents: New insights based on a coordination chemistry perspective

New first-row transition-metal compounds with the ligand norharmane (9H-Pyrido[3,4-b]indole; Hnor) are reported. The compounds have the general formula [M(LL)(Hnor)(NO₃)₂](MeOH)_0-1 (M=Co, Ni, Cu, Zn; LL=2,2'-bipyridyl (bpy), 1,10-phenanthroline (phen)) and have been characterized by physical and analytical methods. X-ray structural analysis revealed that the compound of formula [Cu(phen)(Hnor)(NO₃)₂], (1) has a distorted 6-coordinated octahedrally-based geometry, with a planar-based [CuN₃O] core, where Cu-L varies between 1.99 and 2.04Å and two weak axial CuO contacts (2.209 and 2.644Å) from two different nitrates. Based on spectroscopic similarities, the other compounds appear to have the same or very similar coordination geometries. The compounds showed clear cell growth inhibitory effects in two different cancer cell lines in vitro, with the copper and zinc complexes being the most toxic and in fact almost comparable to cisplatin. Flow-cytometry analysis confirmed induction of apoptosis in cancer cells treated with the compounds. Interestingly, co-incubation of the cells with metal complexes and CuCl₂ induced an increase in the cytotoxic effects, most likely due to the conversion of the metal compounds in the corresponding, and most active, copper analogues.

Vanadium(IV) and copper(II) complexes of salicylaldimines and aromatic heterocycles: Cytotoxicity, DNA binding and DNA cleavage properties

Five copper(II) complexes, [Cu(sal-Gly)(bipy)](1), [Cu(sal-Gly)(phen)] (2), [Cu(sal-l-Ala)(phen)] (3), [Cu(sal-D-Ala)(phen)] (4), [Cu(sal-l-Phe)(phen)] (5) and five oxidovanadium(IV) complexes, [V(IV)O(sal-Gly)(bipy)] (6), [V(IV)O(sal-Gly)(phen)] (7), [V(IV)O(sal-l-Phe)(H2O)] (8), [V(IV)O(sal-l-Phe)(bipy)] (9), [V(IV)O(sal-l-Phe)(phen)] (10) (sal=salicylaldehyde, bipy=2,2'-bipyridine, phen=1,10-phenanthroline) were synthesized and characterized, and their interaction with DNA was evaluated by different techniques: gel electrophoresis, fluorescence, UV-visible and circular dichroism spectroscopy. The complexes interact with calf-thymus DNA and efficiently cleave plasmid DNA in the absence (only 2 and 5) and/or presence of additives. The cleavage ability is concentration-dependent as well as metal and ligand-dependent. Moreover, DNA binding experiments show that the phen-containing Cu(II) and V(IV)O compounds display stronger DNA interaction ability than the corresponding bipy analogues. The complexes present cytotoxic activity against human ovarian (A2780) and breast (MCF7) carcinoma cells. Cell-growth inhibition (IC50) of compounds 1, 2 and 5 in human promyelocytic leukemia (HL60) and human cervical cancer (HeLa) cells were also determined. The copper complexes show much higher cytotoxic activity than the corresponding vanadium complexes and the reference drug cisplatin (except for the sal-Gly complexes); namely, the phenanthroline copper complexes 2-5 are ca. 10-fold more cytotoxic than cisplatin and more cytotoxic than their bipyridine analogues.

Significant differences in the biological activity of mononuclear Cu(ii) and Ni(ii) complexes with the polyquinolinyl ligand

The difference in the redox activity of metal ions Cu(ii) and Ni(ii) results in some discrepancy in the biological activity of their complexes.

Synthesis, molecular docking and biological evaluation of new steroidal 4H-pyrans

A series of new steroidal 4H-pyrans (4-6) have been synthesized from steroidal α, β-unsaturated ketones (1-3). The products (4-6) were characterized by IR, (1)H NMR, (13)C NMR, MS and analytical data. The interaction studies of compounds (4-6) with DNA were carried out by employing gel electrophoresis, UV-vis and fluorescence spectroscopy. The gel electrophoresis pattern revealed that compounds (4-6) bind to DNA and also demonstrated that the compound 6 alone or in presence of Cu (II) causes the nicking of supercoiled pBR322. The compounds 4 and 5 bind to DNA preferentially through electrostatic and hydrophobic interactions with Kb values found to be 5.3×10(3) and 3.7×10(3) M(-1), respectively, indicating the higher binding affinity of compound 4 towards DNA. The docking study suggested the intercalation of compounds in between the nucleotide base pairs. The cytotoxicity and genotoxicity of the newly synthesized compounds were checked by MTT and comet assay, respectively during which compound 6 showed potential behaviour.

Highly cytotoxic DNA-interacting copper(ii) coordination compounds

Copper complexes from Schiff-base ligands show high cytotoxicity against diverse cancer cell lines, with IC₅₀ values down to 0.23 μM.

Effect of substituent of terpyridines on the DNA-interaction of polypyridyl ruthenium(II) complexes

An octahedral complexes of ruthenium with 2,9-dimethyl-1,10-phenanthroline (dmphen) and substituted terpyridine have been synthesized. The Ru(II) complexes have been characterized by elemental analyses, thermogravimetric analyses, magnetic moment measurements, FT-IR, electronic, (1)H NMR and FAB mass spectra. The binding strength and mode of interaction of the complexes with Herring Sperm DNA has been investigated using absorption titration and viscosity measurement studies. Results suggest that the substituent on terpyridine ligand affects the binding mode and binding ability of the complexes. Effect of time and ionic strength on DNA cleavage ability of complex has also been studied by gel electrophoresis. Results suggest that more than 200 mM concentration of NaCl decreases the cleavage ability of complex.