Utilizing coordination chemistry through formation of a CuII-quinalizarin complex to manipulate cell biology: An in vitro, in silico approach.

Quinalizarin, an analogue of anthracycline anticancer agents, is an anticancer agent itself. A CuII complex was prepared and characterized by elemental analysis, UV-Vis & IR spectroscopy, mass spectrometry, EPR and DFT. The intention behind the preparation of the complex was to increase cellular uptake, compare its binding with DNA against that of quinalizarin, modulation of semiquinone formation, realization of human DNA topoisomerase I & human DNA topoisomerase II inhibition and observation of anticancer activity. While the first two attributes of complex formation lead to increased efficacy, decrease in semiquinone generation could results in a compromise with efficacy. Inhibition of human DNA topoisomerase makes up this envisaged compromise in free radical activity since the complex shows remarkable ability to disrupt activities of human DNA topoisomerase I and II. The complex unlike quinalizarin, does not catalyze flow of electrons from NADH to O2 to the extent known for quinalizarin. Hence, decrease in semiquinone or superoxide radical anion could make modified quinalizarin [as CuII complex] less efficient in free radical pathway. However, it would be less cardiotoxic and that would be advantageous to qualify it as a better anticancer agent. Although binding to calf thymus DNA was comparable to quinalizarin, it was weaker than anthracyclines. Low cost of quinalizarin could justify consideration as a substitute for anthracyclines but the study revealed IC50 of quinalizarin/CuII-quinalizarin was much higher than anthracyclines or their complexes. Even then, there is a possibility that CuII-quinalizarin could be an improved and less costly form of quinalizarin as anticancer agent.

Reconstructing dual-phase nanometer scale grains within a pearlitic steel tip in 3D through 4D-scanning precession electron diffraction tomography and automated crystal orientation mapping.

The properties of polycrystalline materials are related to their microstructures and hence a complete description, including size, shape, and orientation of the grains, is necessary to understand the behavior of materials. Here, we use Scanning Precession Electron Diffraction (SPED) in the Transmission Electron Microscope (TEM) combined with a tilt series to reconstruct individual grains in 3D within a polycrystalline dual-phase cold wire-drawn pearlitic steel sample. Nanoscale ferrite grains and intragranular cementite particles were indexed using an Automated Crystallographic Orientation Mapping (ACOM) tool for each tilt dataset. The grain orientations were tracked through the tilt datasets and projections of the individual grains were reconstructed from the diffraction data using an orientation-specific Virtual Dark Field (VDF) approach for tomographic reconstruction. The algorithms used to process and reconstruct such datasets are presented. These algorithms represent an extension to the ACOM approach that may be straightforwardly applied to other multi-phase polycrystalline materials to enable 3D spatial and orientation reconstructions.

A Co(III) Complex of 1-Amino-4-hydroxy-9,10-anthraquinone Exhibits Apoptotic Action against MCF-7 Human Breast Cancer Cells.

A Co(III) complex of 1-amino-4-hydroxy-9,10-anthraquinone (QH) (Scheme-1) having the molecular formula CoQ3 (Scheme-2) was prepared and characterized by elemental analysis, FTIR spectroscopy, UV-vis spectroscopy, fluorescence spectroscopy, and mass spectrometry. In the absence of a single crystal, the energy-optimized molecular structure of CoQ3 was determined by employing computational methods that was validated using spectroscopic evidences, elemental analysis, and mass spectrometry data. The electrochemical properties of the complex were analyzed using cyclic voltammetry and indicate a substantial modification of the electrochemical properties of the parent amino-hydroxy-9,10-anthraquinone. CoQ3 was thereafter tested on MCF-7 human breast cancer cells. The IC50 value for a 24 h incubation was found to be (95 ± 0.05) µg/mL. The study showed that such cancer cells underwent both early and late apoptosis following the interaction with CoQ3.

Free radical induced activity of an anthracycline analogue and its MnII complex on biological targets through in situ electrochemical generation of semiquinone.

Cytotoxicity by anthracycline antibiotics is attributed to several pathways. Important among them are formation of free-radical intermediates. However, their generation makes anthracyclines cardiotoxic which is a concern on their use as anticancer agents. Hence, any change in redox behavior that address cardiotoxicity is welcome. Modulation of redox behavior raises the fear that cytotoxicity could be compromised. Regarding the generation of free radical intermediates on anthracyclines, a lot depends on the surrounding environment (oxic or anoxic), polarity and pH of the medium. In case of anthracyclines, one-electron reduction to semiquinone or two-electron reduction to quinone-dianion are crucial both for cytotoxicity and for cardiotoxic side effects. The disproportion-comproportionation equilibria at play between quinone-dianion, free quinone and semiquinone control biological activity. Whatever is the form of reduction, semiquinones are generated as a consequence of the presence of anthracyclines and these interact with a biological target. Alizarin, a simpler anthracycline analogue and its MnII complex were subjected to electrochemical reduction to realize what happens when anthracyclines are reduced by compounds present in cells as members of the electron transport chain. Glassy carbon electrode maintained at the pre-determined reduction potential of a compound was used for reduction of the compounds. Nucleobases and calf thymus DNA that were maintained in immediate vicinity of such radical generation were used as biological targets. Changes due to the generated species under aerated/de-aerated conditions on nucleobases and on DNA helps one to realize the process by which alizarin and its MnII complex might affect DNA. The study reveals alizarin was more effective on nucleobases than the complex in the free radical pathway. Difference in damage caused by alizarin and the MnII complex on DNA is comparatively less than that observed on nucleobases; the complex makes up for any inefficacy in the free radical pathway by its other attributes.

Utilization of Guanidine-Based Ancillary Ligands in Arene-Ruthenium Complexes for Selective Cytotoxicity.

A family of three water-soluble half-sandwich arene-ruthenium complexes, depicted as C 1 -C 3 , having the general formula [Ru(p-cymene)(L)Cl]Cl has been synthesized, where L represents (1H-benzo[d]imidazol-2-yl)guanidine (L 1 ) or (benzo[d]oxazol-2-yl)guanidine (L 2 ) or (benzo[d]thiazol-2-yl)guanidine (L 3 ). The crystal structure of complex C 3 has been determined. The complexes show several absorption bands in the visible and ultraviolet regions, and they also show prominent emission in the visible region while excited near 400 nm. Studies on the interaction of ligands L 1 -L 3 and complexes C 1 -C 3 with calf thymus DNA reveal that the complexes are better DNA binders than the ligands, which is attributable to the imposed planarity of the ruthenium-bound guanidine-based ligand, enabling it to serve as a better intercalator. Molecular docking studies show that the complexes effectively bind with DNA through electrostatic and H-bonding interactions and partial intercalation of the guanidine-based ligands. Cytotoxicity studies carried out on two carcinoma cell lines (PC3 and A549) and on two non-cancer cell lines (BPH1 and WI-38) show a marked improvement in antitumor activity owing to complex formation, which is attributed to improvement in cellular uptake on complex formation. The C 1 complex is found to exhibit the most prominent activity against the PC3 cell line. Inclusion of the guanidine-based ligands in the half-sandwich ruthenium-arene complexes is found to be effective for displaying selective cytotoxicity to cancer cells and also for convenient tracing of the complexes in cells due to their prominent emissive nature.

Radio-Sensitizing Effects of CuII and ZnII Complexes of Ornidazole: Role of Nitro Radical Anion.

The treatment of malignant cells that are deficient in oxygen due to the insufficient flow of blood is often seen as a major hindrance in radiotherapy. Such cells become radio-resistant because molecular oxygen, the natural and best radio-sensitizer, is depleted. Hence, to compensate this deficiency in oxygen, there is a need for agents that enhance radiation-induced damage of cells (radio-sensitizers) in a manner that normal cells are least affected. Simultaneously, agents capable of showing activity under hypoxic conditions are known as hypoxic cytotoxins that selectively and preferably destroy cells under hypoxic environments. 5-Nitroimidazoles fit both definitions. Their efficiency is based on their ability to generate the nitro radical anion that interacts with the strands of DNA within cells, either damaging or modifying them, leading to cell death. 5-Nitroimidazoles are important radio-pharmaceuticals (radio-sensitizers) in cancer-related treatments where the nitro radical anion has an important role. Since its generation leads to neurotoxic side effects that may be controlled through metal complex formation, this study looks at the possibility of two monomeric complexes of Ornidazole [1-chloro-3-(2-methyl-5-nitro-1H-imidazole-1-yl)propan-2-ol] with CuII and ZnII to be better radio-sensitizers and/or hypoxic cytotoxins than Ornidazole. The study reveals that although there is a decrease in nitro radical anion formation by complexes, such a decrease does not hamper their radio-sensitizing ability. Nucleic acid bases (thymine, cytosine, and adenine) or calf thymus DNA used as targets were irradiated with 60Co γ rays either in the absence or presence of Ornidazole and its monomeric complexes. Radiation-induced damage of nucleic acid bases was followed by high-performance liquid chromatography (HPLC), and modification of calf thymus DNA was followed by ethidium bromide fluorescence. Studies indicate that the complexes were better in performance than Ornidazole. CuII-ornidazole was significantly better than either Ornidazole or ZnII-ornidazole, which is attributed to certain special features of the CuII complex; aspects like having a stable lower oxidation state enable it to participate in Fenton reactions that actively influence radio-sensitization and the ability of the complex to bind effectively to DNA.

Radioprotection of thymine and calf thymus DNA by an azo compound: mechanism of action followed by DPPH radical quenching & ROS depletion in WI 38 lung fibroblast cells.

PURPOSE: To explain the observed radio-protection properties of an azo compound, 2-(2-hydroxyphenylazo)-indole-3∕-acetic acid (HPIA). MATERIALS AND METHODS: Mechanism of radioprotection by HPIA was attempted using the stable free radical 2, 2-diphenyl-1-picrylhydrazyl (DPPH) using UV-Vis and electron paramagnetic resonance (EPR) spectroscopy. The radical destroying ability of HPIA was studied by depletion of reactive oxygen species (ROS) in WI 38 lung fibroblast cells. RESULTS & DISCUSSION: Studies indicate HPIA interacts with radical intermediates formed in solution following irradiation by 60Co γ-rays. As a result, reactive radical intermediates do not cause any damage on chosen substrates like thymine or calf thymus DNA when irradiated in presence of HPIA. The study showed that reactive intermediates not only react with HPIA but that the kinetics of their reaction is definitely faster than their interaction either with thymine or with DNA. Had this not been the case, much more damage would have been observed on chosen substrates following irradiation with 60Co γ-rays, in the presence of HPIA than actually observed in experiments, particularly those that were performed in a relatively high dose. Experiments reveal radiation induced-damage caused to thymine in presence of HPIA was ~ 1 36 to ~ 1 32 times that caused in its absence under different conditions indicating the radio-protection properties of HPIA. In case of calf thymus DNA, damage in presence of HPIA was much lower than in its absence. A fluorometric microplate assay for depletion of ROS by detecting the oxidation of 2',7'-dichlorofluorescin-diacetate (DCF-DA) into the highly fluorescent compound 2',7' dichlorofluorescein (DCF) indicated HPIA brought about a considerable check on ROS-mediated damage to cells by scavenging them right away. CONCLUSION: The study indicates HPIA may be an antioxidant supplement during radiotherapy.

In situ reactivity of electrochemically generated semiquinone on Emodin and its CuII/MnII complexes with pyrimidine based nucleic acid bases and calf thymus DNA: Insight into free radical induced cytotoxicity of anthracyclines.

There is enough proof to believe that free-radical intermediates of anthracycline based anticancer agents are involved in different stages of drug action. Subtle therapeutic differences observed in the actions of different anthracyclines largely influence the mechanism of action of the drugs that distinguish one member from another. Redox properties control biological responses related either to the one-electron quinone/semiquinone couple or the two-electron quinone/quinone-dianion couple. Comproportionation also leads to generation of semiquinone. Hence, whatever the form of reduction of the quinone moiety, a substantial amount of semiquinone is eventually formed in the system. Immediately after formation, there is competition between natural radical-decay pathways and one-electron transfer reactions that generate the superoxide-radical anion. Prototropic properties control rate of radical decay while redox properties control rate of electron transfer to molecular oxygen. In aerated medium, semiquinone-radical anion and superoxide-radical anion co-exist while in de-aerated medium semiquinone-radical anion predominates. All the radicals are damaging to the biological system. Through this study, attempt was made to detect changes induced by the radicals on pyrimidine based nucleic acid bases and calf thymus DNA in aerated and de-aerated (Ar saturated) medium to know the mechanism by which Emodin, its CuII/MnII complexes might affect DNA. Semiquinone-radical anion was generated electrochemically maintaining a glassy carbon electrode at the first reduction potential of each compound. Since the chosen compound (Emodin), its complexes are analogues of anthracyclines, findings on them can be extrapolated to understand the differences in anticancer activity or of adverse drug reactions reported in an innumerable number of clinical studies related to anthracyclines where the difference in structure of different members is due to differences in the relative positioning of hydroxy groups on the hydroxy-9, 10-anthraquinone moiety of anthracyclines. The study helps to realize action of compounds of this class as anticancer agents.

Activity of CoII-Quinalizarin: A Novel Analogue of Anthracycline-Based Anticancer Agents Targets Human DNA Topoisomerase, Whereas Quinalizarin Itself Acts via Formation of Semiquinone on Acute Lymphoblastic Leukemia MOLT-4 and HCT 116 Cells.

Quinalizarin (THAQ), a hydroxy-9,10-anthraquinone analogue of the family of anthracycline anticancer drugs and an inhibitor of protein kinase, was observed for its anticancer activity. Because apart from showing anticancer activity, anthracyclines and their analogues also show cardiotoxic side effects, believed to be addressed through metal complex formation; an effort was made to realize this by preparing a CoII complex of THAQ. The aim of this study was to find out if complex formation leads to a decrease in the generation of intermediates that are responsible for toxic side effects. However, because this also meant that efficacy on cancer cells would be compromised, studies were undertaken on two cancer cell lines, namely, acute lymphoblastic leukemia (ALL) MOLT-4 and HCT116 cells. The complex decreases the flow of electrons from NADH to molecular oxygen (O2) in the presence of NADH dehydrogenase forming less semiquinone than THAQ. It showed increased affinity toward DNA with binding constant values remaining constant over the physiological pH range unlike THAQ (for which decrease in binding constant values with increase in pH was observed). The complex is probably a human DNA topoisomerase I and human DNA topoisomerase II poison acting by stabilizing the covalent topoisomerase-cleaved DNA adduct, a phenomenon not observed for THAQ. Activity of the compounds on cancer cells suggests that THAQ was more effective on ALL MOLT-4 cells, whereas the complex performed better on HCT116 cells. Results suggest that the formation of semiquinone probably dominates the action because of THAQ, whereas the performance of the complex is attributed to increased DNA binding, inhibition of topoisomerase, and so forth. Inspite of a decrease in the generation of superoxide by the complex, it did not hamper efficacy on either cell line, probably compensated by improved DNA binding and inhibition of topoisomerase enzymes which are positive attributes of complex formation. A decrease in superoxide formation suggests that the complex could be less cardiotoxic, thus increasing its therapeutic index.

Role of flupirtine as a preemptive analgesic in patients undergoing laparoscopic cholecystectomy.

BACKGROUND AND AIMS: Postsurgical pain is the leading complaint after laparoscopic cholecystectomy that may delay the postoperative recovery and hence we undertook a prospective randomized trial to analyze the role of flupirtine as a preemptive analgesic for postoperative pain relief in patients undergoing above surgery. MATERIAL AND METHODS: A total of 66 cases were randomly assigned to two groups to receive capsule flupirtine (200 mg) or capsule vitamin B complex administered orally, 2 h before the laparoscopic cholecystectomy surgery. Time to first analgesic requirement, assessment of postoperative pain in terms of visual analog score, and analgesic requirement postoperatively were measured as a primary outcome. RESULTS: Time to first analgesic requirement was significantly prolonged in the flupirtine group as compared with the placebo group. There was significant pain reduction in early postoperative period (up to 4 h), but no changes occurred thereafter. Total analgesic requirement (including rescue analgesia) and side-effects were comparable between the groups except for higher sedation in flupirtine group. CONCLUSIONS: Flupirtine is effective as a preemptive analgesic in providing adequate pain relief during the immediate postoperative period after laparoscopic cholecystectomy surgery. However, continuation of drug therapy postoperatively could possibly delineate its optimal analgesic profile more profoundly.

Peptide Length and Dopa Determine Iron-Mediated Cohesion of Mussel Foot Proteins.

Mussel adhesion to mineral surfaces is widely attributed to 3,4-dihydroxyphenylalanine (Dopa) functionalities in the mussel foot proteins (mfps). Several mfps, however, show a broad range (30-100%) of Tyrosine (Tyr) to Dopa conversion suggesting that Dopa is not the only desirable outcome for adhesion. Here, we used a partial recombinant construct of mussel foot protein-1 (rmfp-1) and short decapeptide dimers with and without Dopa and assessed both their cohesive and adhesive properties on mica using a surface forces apparatus (SFA). Our results demonstrate that at low pH, both the unmodified and Dopa-containing rmfp-1s show similar energies for adhesion to mica and self-self interaction. Cohesion between two Dopa-containing rmfp-1 surfaces can be doubled by Fe3+ chelation, but remains unchanged with unmodified rmfp-1. At the same low pH, the Dopa modified short decapeptide dimer did not show any change in cohesive interactions even with Fe3+. Our results suggest that the most probable intermolecular interactions are those arising from electrostatic (i.e., cation-π) and hydrophobic interactions. We also show that Dopa in a peptide sequence does not by itself mediate Fe3+ bridging interactions between peptide films: peptide length is a crucial enabling factor.

A complex of Co(II) with 2-hydroxyphenyl-azo-2'-naphthol (HPAN) is far less cytotoxic than the parent compound on A549-lung carcinoma and peripheral blood mononuclear cells: Reasons for reduction in cytotoxicity.

Cytotoxic studies using an azo compound HPAN and its Co(II) complex were carried out on non-small lung epithelium carcinoma (A549) cells and peripheral blood mononuclear (PBM) cells. The results obtained suggest that the Co(II) complex is much less toxic toward both cell lines and the decreased toxicity due to the complex was more pronounced with carcinoma A549 cells. An attempt was made to correlate the findings related to cytotoxicity with the interaction of the compounds with DNA using calf thymus DNA as the target. The study was able to conclude that the complex was a relatively weak binder to calf thymus DNA. This information was used to explain the interaction of azo compounds with DNA in peripheral blood mononuclear cells and A549 lung carcinoma cells. It was concluded that the Co(II) complex interacts with DNA to a much lesser extent than HPAN alone. Cyclic voltammetry experiments carried out with HPAN and the Co(II) complex further showed that the presence of the metal ion in the complex prevents reduction of the azo group to such species that are responsible for inducing cytotoxicity. The overall finding was that complex formation with azo compounds might serve as a possible route to curb their toxicities.

Studies on the formation of a complex of Cu(II) with sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate - an analogue of the core unit of anthracycline anticancer drugs and its interaction with calf thymus DNA.

Copper(II) forms a complex with sodium 1,4-dihydroxy-9,10-anthraquinone-2-sulphonate (sodium quinizarin-2-sulphonate, NaQSH(2)), an analogue of the core unit of anthracycline antibiotics used in the treatment of cancer. The 1:2 metal-ligand complex is formed in aqueous solution at neutral and acidic pH while in alkaline pH both 1:1 and 1:2 species are formed. The effective stability constant of the 1:2 metal-ligand complex is 9.64x10(16) while that of the 1:1 metal-ligand complex is 9.4x10(9). The 1:2 complex Cu(NaQSH)(2)(H(2)O)(2) was synthesized and characterized by different techniques in solid state and in solution. The complex Cu(NaQSH)(2)(H(2)O)(2) interacts with calf thymus DNA which was studied by fluorescence spectroscopy. The binding constant and site size for the interaction with DNA were determined.

Four new dinuclear Cu(ii) hydrazone complexes using various organic spacers: syntheses, crystal structures, DNA binding and cleavage studies and selective cell inhibitory effect towards leukemic and normal lymphocytes.

Syntheses and crystal structures of four new hydrazone-based Cu(ii) complexes, [{Cu(L(1))(H(2)O)}(2)(mu-pyraz)](ClO(4))(2) (), [{Cu(L(1))(OClO(3))}(2)(mu-4,4'-bipy)] (), [{Cu(L(2)H)}(mu-pyraz){Cu(L(2)H)(OClO(3))}].(ClO(4)) () and [{Cu(L(2))}(2)(mu-bpe)] () [L(1)H = condensation product of benzhydrazide and pyridine-2-carbaldehyde and L(2)H(2) = condensation product of benzoyl acetone and benzhydrazide], bridged by various organic spacers [pyrazine (pyraz), 4,4'-bipyridine (4,4'-bipy) and 1,2-di(4-pyridyl)ethane (bpe)] are reported in this paper. The single-crystal X-ray crystallographic studies reveal that all are dinuclear units where and form strong intermolecular H-bonding to form sheets of interconnected ions, whereas forms sheets of dinuclear chains through pi-pi interactions; in , molecules are linked only through van der Waals interactions. The variable-temperature magnetic moment studies reveal that and show antiferromagnetic coupling between the Cu(ii) centers at lower temperatures. The binding ability of with calf thymus DNA [CT-DNA] is reported using various spectroscopic studies (UV-Vis titration, circular dichroism and fluorescence). The binding constants of with CT-DNA, as calculated by different methodologies, are of the order of 10(5) M(-1). The mode of interaction between and CT-DNA has been predicted using circular dichroic (CD) spectroscopy, where it has been shown that most probably interacts with DNA via intercalation between the base pairs leading to a change in B-DNA conformation. is also able to cleave supercoiled (SC) plasmid DNA pUC19 in a time and dose dependent manner as demonstrated by agarose gel electrophoresis, and also demonstrates its potential to cleave the SC plasmid DNA via both oxidative and hydrolytic mechanisms. Approximately 50% of leukemic cells are found to be dead when two representative leukemic cell lines are exposed to ( approximately 80 muM) even for 24 h as determined by different cell cytotoxicity assays. Preliminary results also showed that, at 20 muM, could selectively induce apoptosis in leukemic cells without affecting normal lymphocytes.