Palladium(II) complexes with N,N'-dialkyl-1,10-phenanthroline-2,9-dimathanamine: synthesis, characterization and cytotoxic activity

Schiff Base Complexes with Covalently Anchored Luminophores: Self-Enhanced Electrochemiluminescence Detection of Neomycin

A novel electrochemiluminescence (ECL) amplification strategy was established aiming to overcome the inherent shortcomings of the current oxygen (O₂) coreactant ECL systems. Macrocyclic Schiff base Fe complexes were rationally designed as a novel integrated ECL emitter by iminium linkage between N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and 1,10-phenanthroline-2,9-dicarbaldehyde (PDL) and postmetalation of the macrocyclic Schiff base. Covalently combining luminophore ABEI with a catalytic center endowed the novel ECL emitter with both remarkable redox electrocatalytic properties and significantly enhanced ECL efficiency. The high content of ferrous iron and the dominantly active low-spin Fe state greatly contributed to the inherent catalytic activity for O₂ activation. The rational modification of luminophore optimized the spatial distribution and simultaneously shortened the species transport distance of coreactant radicals generated in situ from dissolved O₂, resulting in significantly self-enhanced ECL efficiency. Neomycin, which posed a growing threat to aquatic biodiversity and environmental safety, as the model antibiotic was successfully detected with a detection limit of 0.21 pM (S/N = 3), clarifying a promising application prospect of this new luminophore-embedded ECL amplification strategy in biological analysis and environmental monitoring.

Effect of chalcogen bonding interactions on molecular structures; theoretical and crystallographic studies on two palladium(ii) acetate complexes

New palladium complexes, [Pd(L)(OAc))], have been synthesized. The complexes and their ligand have been characterized by X-ray crystal structure analysis. Interestingly, the molecular structures of the two complexes are stabilized by S⋯O chalcogen bonds.

DNA-and BSA-Binding Studies of Dinuclear Palladium(II) Complexes with 1,5-Naphtiridine Bridging Ligands

The interactions of metal complexes with important biomolecules such as deoxyribonucleic acid (DNA) or bovine serum albumin (BSA) are responsible for their antitumor activity due to different modes of interaction with DNA and their transport through the blood system to cells and tissues via serum albumin. Therefore, the dinuclear palladium(II) complexes, [{Pd(en)Cl}2(μ-1,5- nphe)](NO3)2 (Pd1) and [{Pd(1,3-pd)Cl}2(μ-1,5-nphe)](NO3)2 (Pd2) (en is ethylenediamine, 1,3-pd is 1,3-propylenediamine and 1,5-nphe is the bridging 1,5-naphthyridine ligand) were synthesized and characterized by different spectroscopic methods. The UV-Vis and fluorescence emission spectroscopy were applied for evaluation of binding modes of Pd1 and Pd2 complexes to DNA as well as their interaction with BSA. The emission spectra indicate that the investigated Pd1 and Pd2 complexes can displace the ethidium bromide intercalator from DNA/EtBr molecules and act as intercalators showing strong interactions with DNA. The fluorescence intensity showes that Pd1 and Pd2 complexes can bind to BSA and then be transported to the cell.

Synthesis of novel 1,10-phenanthroline-2,9-bis-α-amino acid conjugates

Starting from 2,9-dimethyl-1,10-phenanthroline, the syntheses of eight novel 1,10-phenanthroline-2,9-bis-α-aminoacid conjugates (α-amino acids: DL-Ala, L-Val, L-Phe, L-His, L-Ile, L-Met, L-Glu, L-Asp) are described in detail.

Palladium Complexes of N,N'-Bis(2-aminoethyl)oxamide (H2L): Structural (PdIIL, PdII2L2, and PdIVLCl2), Electrochemical, Dynamic 1H NMR, and Cytotoxicity Studies

The monomeric (PdL·2H₂O) and dimeric (Pd₂L₂·7H₂O) palladium(II) complexes of N,N'-bis(2-aminoethyl)oxamide (H₂L) were isolated, and their structures were established by single-crystal X-ray diffraction. Both compounds display identical cis-(2N_amide + 2N_amine) coordination environments of the metal ion. The dimer, representing a combination of two PdL species with an open lateral chelate ring, has an "open clamshell"-like structure. The intramolecular metal-metal separation in Pd₂L₂ (3.215 Å) is slightly shorter than the sum of the van der Waals radii of the palladium(II) atoms. The dimeric complex is relatively stable to dissociation, and its spectral features in aqueous solutions have been compared to those of the monomeric complex. A ¹H NMR spectroscopic study revealed the presence of the dynamic conformational exchange process assigned to a turning of the dimeric molecule "inside out" with an activation energy of 65 kJ/mol. Cyclic voltammetry of PdL in perchlorate-, chloride-, and sulfate-containing electrolytes revealed two-electron oxidation of the palladium center. For the dimeric complex similar, though irreversible, oxidation to the palladium(IV) state was observed in NaCl electrolyte. At the same time, in NaClO₄ or Na₂SO₄ solutions oxidation of Pd₂L₂ occurs in two distinct steps. The first step is quasi-reversible and can be assigned to the formation of species in an intermediate Pd^IIIPd^III state. Monomeric palladium(IV) complex Pd^IVLCl₂ was generated via chemical oxidation of Pd^IIL by peroxodisulfate in the presence of chloride ions and structurally characterized. The related M^IIL complexes (M = Pd, Ni, Cu) showed low cytotoxicity in human cancer cell lines AGS (gastric adenocarcinoma) and HCT116 (colorectal carcinoma) with IC₅₀ values from 204 to 525 μM, while the proligand H₂L was devoid of antiproliferative activity (IC₅₀ > 1000 μM).

Cytotoxic and apoptotic effects of the combination of palladium (II) 5,5-diethylbarbiturate complex with bis(2-pyridylmethyl)amine and curcumin on non small lung cancer cell lines

Metal-based chemotherapeutics such as cisplatin are widely used treatment of lung cancer which is the major cause of cancer-related mortality worldwide. Recent studies demonstrated that novel metal-based compounds have strong cytotoxic activity in a similar way as cisplatin. Therefore, metal-based compounds have been synthesized and investigated in order to determine their cytotoxic activities. It has been also reported curcumin, which has been derived from turmeric plant, has powerful cytotoxic effect on various cancer cell lines. In the light of these data, it has been investigated the cytotoxic effects of combination of curcumin (0.78-100μM) and palladium (II) 5,5-diethylbarbiturate complex with bis(2-pyridylmethyl)amine [Pd(II) complex] (0.39-50μM) against non small lung cancer cell lines, A549 and H1299. It has been found that combination of Pd(II) complex and curcumin enhanced the cytotoxic activity and apoptotic cell death at 48h, compared to single use of each agent, only in H1299 cell line (combination index <1). Apoptosis was evident by annexin v staining positivity, increased caspase 3/7 activity and the presence of pyknotic nuclei. Pro-apoptotic genes of TNFRSF10A and HRK were found to be involved in apoptotic cell death. In conclusion, the application of this combination may be regarded as a novel and effective approach for the treatment of lung cancer due to its promising cytotoxic and apoptotic effect.

2,2'- bipyridine coplanar with coordination square of Pd(II) nonyldithiocarbamato antitumor complex interacting with DNA in two distinct steps

Cisplatin is one of the most effective chemotherapy drugs, and has been widely employed for more than four decades in the treatment of different forms of human tumors. In recent years, various examples of metal complex-based compounds have been used for medicinal purposes. In this context, the novel palladium(II) complex, [Pd(non-dtc)(bpy)]NO₃, (non-dtc = nonyldithiocarbamate and bpy = 2,2'- bipyridine) has been synthesized and characterized by means of elemental analysis, conductivity measurements, FT-IR, ¹H NMR, ¹³C NMR, and electronic spectroscopy studies. The 50% cytotoxic concentrations (Ic₅₀) of this Pd(II) complex (0.53 mM) and cisplatin (154 mM) against human cell tumor line (K562) indicates its interaction with DNA of cancer cell at quite low concentration. Thus, binding characteristics of this compound to calf thymus DNA (CT-DNA) has been investigated by UV-vis absorption spectroscopy and fluorescence spectra. The exciting observation of this work in the UV-visible studies was that the Pd(II) complex exhibit two or more types of interaction with CT-DNA. Such properties have rarely been observed in the literature. This complex cooperatively binds with DNA and denatures it too. Fluorescence studies proved the intercalation mode of binding and the other modes seems to be hydrophobic and electrostatic interactions. Binding parameters and thermodynamics of the interaction with CT-DNA are also described. Finally, multifunctional interactions of [Pd(non-dtc)(bpy)]NO₃ make it suitable to interact with DNA of cancer cell at quite low concentration and if it is used as anticancer agent, very low doses will be needed which may have fewer side effects.

New mixed ligand palladium(II) complexes based on the antiepileptic drug sodium valproate and bioactive nitrogen-donor ligands: synthesis, structural characterization, binding interactions with DNA and BSA, in vitro cytotoxicity studies and DFT calculations

The complexes [Pd(valp)2(imidazole)2] (1), [Pd(valp)2(pyrazine)2] (2) (valp is sodium valproate) have been synthesized and characterized using IR, (1)H NMR, (13)C{(1)H} NMR and UV-Vis spectrometry. The interaction of complexes with CT-DNA has been investigated using spectroscopic tools and viscosity measurement. In each case, the association constant (Kb) was deduced from the absorption spectral study and the number of binding sites (n) and the binding constant (K) were calculated from relevant fluorescence quenching data. As a result, a non-covalent interaction between the metal complex and DNA was suggested, which could be assigned to an intercalative binding. In addition, the interaction of 1 and 2 was ventured with bovine serum albumin (BSA) with the help of absorption and fluorescence spectroscopy measurements. Through these techniques, the apparent association constant (Kapp) and the binding constant (K) could be calculated for each complex. Evaluation of cytotoxic activity of the complexes against four different cancer cell lines proved that the complexes exhibited cytotoxic specificity and significant cancer cell inhibitory rate. Moreover, density functional theory (DFT) calculations were employed to provide more evidence about the observed data. The majority of trans isomers were supported not only by energies, but also by the similarity of its calculated IR frequencies, UV adsorptions and NMR chemical shifts to the experimental values.

Investigation of the Effects of Various Cyclodextrins on the Stabilisation of Human Serum Albumin by a Spectroscopic Method

The binding parameters between cyclodextrins (CDs) and human serum albumin (HSA) were investigated by isothermal titration calorimetry (ITC), fluorescence quenching, and UV-vis absorption spectroscopy at 300 K in 50 mM phosphate buffer solution. Among the various CDs investigated, β-CD has the greater ability to decrease the aggregation of HSA and the results indicated that the inhibition order is γ-CD < α-CD < β-CD. The obtained heats for HSA+CDs interactions were reported and analysed in terms of the extended solvation model, which was used to reproduce the enthalpies of HSA interactions with CDs over a broad range of complex concentrations. The binding constant and thermodynamic parameters were obtained. These suggested that the binding reaction was driven by both enthalpy and entropy, and electrostatic interactions played a major role in the stabilising of HSA. The parameters and reflected the net effect of β-CD on the HSA stability at low and high cyclodextrin concentrations, respectively. The positive values for indicated that β-CD stabilises the HSA structure at low concentrations. The UV absorption intensity of theses complexes increased and a slight red shift was observed in the absorbance wavelength with increasing the CD concentration. The fluorescence intensity of HSA decreased regularly and a slight blue shift was observed for the emission wavelength with increasing CD concentration. The results indicate that the CD complex could quench the fluorescence of HSA and changes the microenvironment of the tryptophan residue.

Cytotoxic Effects of Newly Synthesized Palladium(II) Complexes of Diethyldithiocarbamate on Gastrointestinal Cancer Cell Lines

As a part of a drug development program to discover novel therapeutic and more effective palladium (Pd) based anticancer drugs, a series of water-soluble Pd complexes have been synthesized by interaction between [Pd (phen)(H₂O)₂(NO₃)₂] and alkylenebisdithiocarbamate(al-bis-dtc) disodium salts. This study was undertaken to examine the possible cytotoxic effect of three novel complexes (0.125–64 µg/mL) on human gastric carcinoma (AGS), esophageal squamous cell carcinoma (Kyse-30), and hepatocellular carcinoma (HepG2) cell lines. The cytotoxicity was examined using cell proliferation and acridine orange/ethidium bromide (AO/EB) assay. In order to examine the effects of new Pd(II) complexes on cell cycle status, we performed cell cycle analysis. The complexes were found to have completely lethal effects on the cell lines, and the half maximal inhibitory concentration (IC50) values obtained for the cell lines were much lower in comparison with cisplatin. We demonstrated that the three new Pd(II) complexes are able to induce G2/M phase arrest in AGS and HepG2; in addition, the Pd(II) complexes caused an S phase arrest in Kyse-30 cell line. Our results indicate that newly synthesized Pd(II) complexes may provide a novel class of chemopreventive compounds for anticancer therapy.

Investigation of the pharmacological profiles of dinuclear metal complexes as novel, potent and selective cytotoxic agents against ras-transformed cells

Around the world scientists try to design successful cures against still incurable diseases, especially cancers. New targets for prevention and new agents for therapy need to be identified. We synthesized novel metal complexes [Au(L1)(L2)Pt]Cl2 and [Ru(L1)2(L2)Pt]Cl2 for determining their cytotoxic and apoptotic effects. The complexes are synthesized by using 1,8-diaminonaphthalene (L1), and bis-1,4-di[([1,10]phenanthroline-5-il)aminomethyl]cyclohexane (L2) as ligands. This is the first study to examine these metals and these molecules in cancer treatment. We elucidated the effects of test compounds with embryonic rat fibroblast-like cells (F2408) and H-ras oncogene activated embryonic rat fibroblast-like cancer cells (5RP7). Results showed that our complexes are more effective than cisplatin to kill ras-transformed cells. Although the [Au(L1)(L2)Pt]Cl2 compound showed a cytotoxic potency higher than [Ru(L1)2(L2)Pt]Cl2 against cancer cells, it proved to be almost five times less effective in decreasing cell viability over healthy cells. Au(III) compound selectively targets the cancer cells but not the healthy cells.

Anti-cancer palladium complexes: a focus on PdX2L2, palladacycles and related complexes

Much success has been achieved with platinum-based chemotherapeutic agents, i.e. through interactions with DNA. The long-term application of Pt complexes is thwarted by issues, leading scientists to examine other metals such as palladium which could exhibit complementary modes of action (given emphasis wherever known). Over the last 10 years several research groups have focused on the application of an eclectic array of palladium complexes (of the type PdX2L2, palladacycles and related structures) as potential anti-cancer agents. This review therefore provides readers with an up to date account of the advances that have taken place over the past several decades.

Synthesis, characterization, and cytotoxicity studies of a novel palladium(II) complex and evaluation of DNA-binding aspects

A new water-soluble palladium(II) complex, [Pd(bpy)(pyr-Ac]NO₃ in which bpy = 2,2'-bipyridine and pyr-Ac is 1-pyrrolacetato, has been synthesized and characterized by spectroscopic methods (¹H NMR, FT-IR, and UV-Vis), molar conductivity measurements, and elemental analysis. The results obtained from elemental analysis and conductivity measurements confirmed the stoichiometry of ligand and its complex while the characteristic peaks in UV-Vis and FT-IR and resonance peaks in (¹H NMR spectra confirmed the formation of ligand frameworks around the palladium ion. The 50% cytotoxic concentration (Ic₅₀) of new synthesized Pd(II) complex was determined by using MTT assay against human breast cancer cell line, T47D. The interaction between the Pd(II) complex with calf thymus DNA was studied at different temperatures by using absorption spectroscopy, fluorescence titration spectra, ethidium bromide displacement, and gel chromatography studies. The results obtained by absorption spectroscopy revealed that the Pd(II) complex can bind to DNA cooperatively at low concentrations. Several binding parameters in the above interaction were calculated by the fluorescence quenching method. The quenching mechanism was suggested to be the static quenching. The thermodynamic parameters: enthalpy change (ΔH °), entropy change (ΔS °), and Gibbs free energy (ΔG °), showed that van der Waals and hydrogen binding are predominant intermolecular forces between Pd(II) complex and DNA. These results were also consistent with the results obtained from Scatchard's plots.

Study of Metal-1,10-Phenanthroline Complex Equilibria by Potentiometric Measurements

The interaction of Sc(III), Y(III), and La(III) ions with 1,10-phenanthroline (Phen) has been investigated, using the potentiometric method at 25   and  M KNO3. Collected potentiometric data were processed by the “BEST” software program to establish the complexation model for each system. SPE software program was used to evaluate the concentration distributions of the species formed in solution. The stability constants for the binary complexes increased as the ionic radii of the metal cations decreased.

Studies on the cytotoxic, apoptotic and antitumoral effects of Au(III) and Pt(II) complexes of 1, 10-phenanthroline on V79 379A and A549 cell lines

In the present study, Au(III) and Pt(II) complexes of 1, 10-phenanthroline (phen) were synthesized and used as the test compounds. The structure elucidation of the synthesized compounds was performed by IR, (1)H-NMR and MASS spectroscopic data and the results of elemental analyses. The cytotoxic and apoptotic effects of test compounds were elucidated on V79 379A (Chinese hamster lung fibroblast like) and A549 (human lung carcinoma epithelial like) cell lines. Cytotoxicity was measured with MTT assay and antitumoral effect was determined by colony forming ability methods. In addition, nuclear fragmentation and activation of apoptotic enzyme (caspase-3) and DAPI staining were used to detect the apoptotic effect of the compounds. All the test compounds induced time and concentration-dependent cytotoxic and antitumoral effects. Significant increases in the levels of apoptosis were observed with increasing exposure concentration.

Design, synthesis, and biological evaluation of a new palladium(II) complex: beta-lactoglobulin and K562 as targets

A water-soluble Pd(II) complex (2,2'-bipyridinglycinato Pd(II) nitrate) has been synthesized and characterized. The effect of synthesized complex on the carrier model protein structure and cell proliferation was investigated. Whey carrier protein beta-lactoglobulin-B (BLG-B) and chronic myelogenous leukemia cell line K562 were the targets. Fluorescence and CD instruments were used to assess effect of the complex on the protein structure at different temperatures. Growth inhibitory and apoptotic effect of the Pd(II) complex toward the cancer cells was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry. This complex exhibited potent cytotoxic properties against chronic myelogenous leukemia cell line K562. The cells showed different sensitivity to complex. Cytotoxic studies shown that Pd(II) complex induced apoptosis of K562 cells in a concentration and time dependent manner. Then, it might be concluded that Pd(II) complex is a promising antiproliferative agent and should execute its biological effects by inducing apoptosis. Results of fluorescence studies revealed that Pd(II) complex can quench the intrinsic fluorescence emission of the protein at different temperatures. The far- and near-UV CD studies displayed that the Pd(II) complex induces changes in the secondary and tertiary structures of BLG-B at different temperatures. The biological significance of this work is evident since BLG serves as a carrier molecule for several antitumor compounds. Therefore, the interaction of the Pd(II) complex (with antitumor activity) can provide useful information to better design metal anticancer complexes with fewer side effects.

Cytotoxicity and effects of 1,10-phenanthroline and 5-amino-1,10-phenanthroline derivatives on some immunocompetent cells

The biological activity of previously synthesized compounds [(phen)(3)(H(+))(2)(NO(3)(-))(2) (1), Pd(5-NH(2)-phen)(2)(NO(3))(2) (2) and Pd(phen)(2)(NO(3))(2)(H(2)O) (3)] was investigated in vivo. The three compounds did not show any histological alterations in the observed lung, liver, spleen and lymph nodes of White Wistar rats. The propidium iodine staining did not discover any cytotoxic effect of the tested derivatives. The tests for immunological response predominantly showed stimulation of the antibody-producing B-cells and lower or no stimulation of the T-cells. The LIF-test showed better stimulation of all lymphocytes with 1, followed by 2 and 3. Substance 3 showed highest stimulating effect on B-cell blood lymphocytes in all doses (maximum in the lowest dose), whereas the impact of 2 is weaker and that of 1 is the weakest. The T-cell immune response after treatment with substance 1 is best influenced by dose of 1mg in the spleen cell-fraction, followed by 3 (5 mg).

Binding Properties of a New Anti-tumor Component (2,2′-bipyridin octylglycinato Pd(II) nitrate) with Bovine β-lactoglobulin-A and -B

An new water soluble palladium (II) complex of formula [Pd(bpy)(Oct-Gly)]NO(3), (where bpy is 2,2'-bipyridine and Oct-Gly is octylglycine) have been synthesised. The Pd(II) complex has been characterized by elemental analysis and conductivity measurements as well as spectroscopic methods such as infrared, (1)H NMR, and ultraviolet-visible. The interaction between the new Pd(II)-complex (2,2'-bipyridin octylglycinato Pd(II) nitrate), an anti-tumor component, with beta-lactoglobulin-A and -B (BLG-A and -B) was studied by fluorescence spectroscopy and far and near-UV circular dichroism (CD) spectrophotometric techniques. A strong fluorescence quenching interaction of Pd(II) complex with BLG-A and -B was observed. The quenching constant was determined using the modified Stern-Volmer equation. The calculated binding constants of Pd(II) complex with BLG-A and -B were 0.51 and 0.28 (x 10(6) M(-1)) and the corresponding average number of binding sites were 2.8 and 1.5, respectively. Far-UV CD studies showed that the Pd(II) complex can significantly change the secondary structure of BLG-A and -B via an increase in the content of alpha-helix structure, which stabilizes the secondary structure of the proteins. Near-UV CD data clearly indicate the alteration in the tertiary structure of BLG-A and -B due to the interaction with Pd(II) complex. Pd(II) complex can change and stabilize both the secondary and tertiary structures of BLG-A more than BLG-B. These conformational changes may be considered to be a deleterious effect of the designed ligand on the protein structures. The difference in the interaction properties observed for BLG-A and -B with Pd(II) complex is due to the difference in the amino acid sequences between these two variants.

Synthesis, cytotoxic effect, and structure-activity relationship of Pd(II) complexes with coumarin derivatives

We report the influence of the substituent at the N atom of the ligands on the synthesis, biological activity, and stability of Pd(II) complexes of the general formula PdL(2). The compounds adopt a cis or trans configuration with respect to the substituent at the nitrogen atom. Sterically hindered substituents promote the formation of trans isomers, whereas when the nitrogen atom is unsubstituted, cis isomers are formed. The compounds were characterized by elemental analysis, infrared and 1H NMR spectroscopies, and electrospray mass spectrometry. The complexes were also studied using X-ray diffraction and computational DFT methods. Both complexes cis-3a and trans-3c exhibit square-planar geometries around the Pd(II) atom. The cytotoxic effects of these complexes were examined on two human leukemia cell lines, HL-60 and NALM-6. Pd complex cis-3a showed significant cytotoxic activity. The effects exhibited by this complex were comparable to those reported for carboplatin. Loigand 2a was not cytotoxic. Computational analysis carried out at the PB/B3LYP/LACVP**//mPW1PW91/LanL2DZ level showed excellent correlation between the energy difference of the cis and trans isomers and the cytotoxic activity, rendering computations a useful predictive tool for the design of new drugs.

Curcumin and cyclopalladated complexes: a recipe for bifunctional biomaterials

The first examples of binuclear and mononuclear ortho-palladated complexes based on a functionalized 2-phenylquinoline ligand have been synthesized and fully characterized. Conjugating cyclopalladated fragments to curcumin family biologically active beta-diketones gives in one single molecule two different functionalities. The structural variations based on the curcuminoid structure have been tested for their in vitro cytotoxic activity. The activity of complexes comprised of a cyclopalladated fragment conjugated to functionalized bioactive ligands, represents the potential of organometallic systems in generating new bifunctional biomaterials.

Spectroscopic and cytotoxic studies of the novel designed palladium(II) complexes: β-Lactoglobulin and K562 as the targets

Since palladium complexes have been reported to show fewer side effects relative to other heavy metal anticancer compounds, in this study a new class of four structurally related anticancer Pd(II) complexes including 2,2'-bipyridin-n-butyl dithiocarbamato Pd(II) nitrate (Com-1), 2,2'-bipyridin-n-hexyl dithiocarbamato Pd(II) nitrate (Com-2), 2,2'-bipyridin glycinato Pd(II) nitrate (Com-3) and 2,2'-bipyridin octylglycinato Pd(II) nitrate (Com-4) was designed. The effect of four synthesized ligands on the protein structure and cell proliferation were investigated. Whey carrier proteins beta-lactoglobulin-A and-B (BLG-A and-B) and chronic myelogenous leukemia cell line K562 were the targets. Fluorescence and CD instruments were used to assess effect of the ligands on the protein structure. Growth inhibitory effect of the Pd(II) complexes towards the cancer cells was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Results of fluorescence studies revealed that the complexes had no dithiocarbamate moiety (compounds 3 and 4) could quench the intrinsic fluorescence emission of the proteins at lower concentrations than those had such moiety (compounds 1 and 2). The far-UV-CD studies revealed that the regular secondary structure of BLG-A and -B did not show any noticeable alteration upon interaction with different of Pd(II)-complexes. The results of cell proliferation assay also displayed that Com-1 and Com-2 had more growth inhibitory activity against K562, than Com-3 and Com-4. Our results suggested that addition of dithiocarbamate moiety to structure of Pd(II) complexes probably has important role to improve the antiproliferative properties of the anticancer ligands and fewer effects on the carrier protein structure.

Copper(II) complexes of 1,10-phenanthroline-derived ligands: studies on DNA binding properties and nuclease activity

A series of copper(II) complexes of the type [Cu(L)]2+, where L = N,N'-dialkyl-1,10-phenanthroline-2,9-dimethanamine and R = methyl (L1), n-propyl (L2), isopropyl (L3), sec-butyl (L4), or tert-butyl (L5) group, have been synthesized. The interaction of the complexes with DNA has been studied by DNA fiber electron paramagnetic resonance (EPR) spectroscopy, emission, viscosity and electrochemical measurements and agarose gel electrophoresis. In the X-ray crystal structure of [Cu(HL2)Cl2]NO3, copper(II) is coordinated to two ring nitrogens and one of the two secondary amine nitrogens of the side chains and two chloride ions as well and the coordination geometry is best described as trigonal bipyramidal distorted square based pyramidal (TBDSBP). Electronic and EPR spectral studies reveal that all the complexes in aqueous solution around pH 7 possess CuN3O2 rather than CuN4O chromophore with one of the alkylamino side chain not involved in coordination. The structures of the complexes in aqueous solution around pH 7 change from distorted tetragonal to trigonal bipyramidal as the size of the alkyl group is increased. The observed changes in the physicochemical features of the complexes on binding to DNA suggest that the complexes, except [Cu(L5)]2+, bind to DNA with partial intercalation of the derivatised phen ring in between the DNA base pairs. Electrochemical studies reveal that the complexes prefer to bind to DNA in Cu(II) rather than Cu(I) oxidation state. Interestingly, [Cu(L5)]2+ shows the highest DNA cleavage activity among all the present copper(II) complexes suggesting that the bulky N-tert-butyl group plays an important role in modifying the coordination environment around the copper(II) center, the Cu(II)/Cu(I) redox potential and hence the formation of activated oxidant responsible for the cleavage. These results were compared with those for bis(1,10-phenanthroline)copper(II), [Cu(phen)2]2+.

Effect of charge and surface area on the cytotoxicity of cationic metallointercalation reagents

Reaction of a series of nitrogen donor ligands (1-phenylpyrazoles, 2-phenylpyridine, benzo[h]quinoline, 1-(2′-pyridyl)indole, 1-phenylindazole, and 2-phenylindazole) with palladium(II) and platinum(II) salts gave complexes where ortho-metallation had occurred resulting in bidentate binding to the metal centres through N and C atoms. These cyclometallated products were isolated as µ-chloro dimers. Subsequent treatment of these µ-chloro dimers with chelating diamines such as 1,2-ethanediamine converted them into 14 cationic (1+) complexes. Analogous coordination mixed ligand complexes (charge 2+) were prepared by reaction of dichloro(1,2-ethanediamine-N,N′)palladium(II) with aromatic diamines such as 2-(1′-pyrazolyl)pyridine, 2,2′-bipyridine, and 1,10-phenanthroline. The complexes exhibited growth inhibitory activity against L1210 mouse leukæmia cells in vitro over a wide concentration range; in general, the cyclometallated complexes were more active than the mixed ligand complexes, although one cyclometallated organoplatinum complex was less active than the mixed ligand analogue. Substitution around the periphery of the aromatic ligands also resulted in increased activity. One complex, derived from 1-(2'-pyridyl)indole, was tested in vivo and showed no significant antitumour inhibition against P388 leukæmia at doses below toxic levels. Key words: anticancer, metallointercalator, cyclometallation, palladium, platinum, cytotoxicity.