Three-ring, branched cyclam derivatives and their interaction with nickel(ii), copper(ii), zinc(ii) and cadmium(ii)

Carbohydrate-conjugate heterobimetallic complexes: synthesis, DNA binding studies, artificial nuclease activity and in vitro cytotoxicity

New carbohydrate-conjugated heterobimetallic complexes [C(32)H(62)N(10)O(8)NiSn(2)Cl(4)]Cl(2)(1) and [C(32)H(62)N(10)O(8)CuSn(2)Cl(4)]Cl(2) (2) were synthesized and characterized by spectroscopic (IR, (1)H, (13)C, and (119)Sn NMR, EPR, UV-vis, ESI-MS) and analytical methods. The interaction studies of 2 with CT DNA were studied by using various biophysical techniques, which showed high binding affinity of 2 toward CT DNA. The extent of interaction was further confirmed by the interaction of 2 with the nucleotides viz.; 5'-AMP, 5'-CMP, 5'-GMP, and 5'-TMP, by absorption titration. (1)H, (31)P, (119)Sn NMR spectroscopy further validated the interaction mode of 2 with 5'-GMP. The electrophoresis pattern observed for 2 with supercoiled pBR322 DNA, exhibited significantly good nuclease activity following oxidative pathway. The preferential selectivity of 2 toward the major groove was observed on interaction of 2 with pBR322 DNA, in the presence of standard groove binders viz.; DAPI and methyl green. Additionally, in vitro antitumor activity of 2 was evaluated on a panel of human cancer cell lines, exhibiting remarkable cytotoxicity activity against Colo205 (colon) and MCF7 (breast) cell lines with GI(50) values <10 μg/mL.

Synthesis and enantiopreferential DNA-binding profile of late 3d transition metal R- and S-enantiomeric complexes derived from N,N-bis-(1-benzyl-2-ethoxyethane): Validation of R-enantiomer of copper(II) complex as a human topoisomerase II inhibitor

To evaluate the biological preference of chiral drug candidates for molecular target DNA, new potential metal-based chemotherapeutic agents 1-3 (a and b) of late 3d transition metals Ni(II), Cu(II), and Zn(II), respectively, derived from (R)- and (S)-2-amino-2-phenylethanol with CH(2) CH(2)  linker were synthesized and thoroughly characterized. Interaction studies of 1-3 (a and b) with calf thymus DNA in Tris buffer were studied by electronic absorption titrations, luminescence titrations, cyclic voltammetry, and circular dichroism. The results reveal that the extent of DNA binding of R-enantiomer of copper 1a was highest in comparison to rest of the complexes via electrostatic interaction mode. The nuclease activity of 1(a and b) with supercoiled pBR322 DNA was further examined by gel electrophoresis, which reveals that complex 1a exhibits a remarkable DNA cleavage activity (concentration dependent) with pBR322DNA, and the cleavage activity of both enantiomers of complex 1 was significantly enhanced in the presence of activators. The activating efficiency follows the order Asc > H(2) O(2) > MPA for 1a, and reverse order was observed for 1b, because of the differences in enantioselectivity and conformation. Further, it was observed that cleavage reaction involves singlet oxygen species and superoxide radicals via oxidative cleavage mechanism. In addition, complex 1a exhibits significant inhibitory effects on the topoisomerase II (topo II) activity at a very low concentration ∼24 μM, which suggest that complex 1a is indeed catalytic inhibitor or (poison) of human topo II.

Synthesis of carbohydrate-conjugate heterobimetallic Cu(II)-Sn(2)(IV) and Zn(II)-Sn(2)(IV) complexes; their interactions with CT DNA and nucleotides; DNA cleavage, in-vitro cytotoxicity

The new heterobimetallic Ni(II)-Sn(2)(IV) (1), Cu(II)-Sn(2)(IV) (2) and Zn(II)-Sn(2)(IV) (3) complexes, containing D-glucosamine, 1,8-diamino-3,6-diazaoctane and imidazole were isolated and characterized by spectral and analytical methods. The proposed geometry of Ni(II) and Cu(II) in 1 and 2 was square pyramidal, Zn(II) in 3 exhibited tetrahedral while Sn(IV) exhibits hexacoordinate environment, respectively. The X-ray powder diffraction (XRPD) confirmed the amorphous nature of all the complexes. The interaction studies of 2 and 3 with CT DNA were carried out by various biophysical techniques to show the mode of binding. The interaction of 2 and 3 with nucleotides viz 5'-GMP and 5'-TMP, respectively were further confirmed by (1)H, (31)P and (119)Sn NMR spectroscopy. The complex 2 exhibited effective cleavage activity with pBR322 DNA. Furthermore, the cytotoxicity of 2 was examined on a panel of human tumor cell lines of different histological origins and showed good activity against Colo205 and A2780 (GI50 < 10 μg/ml).

Synthesis and biophysical studies of bis-macrocyclic cobalt/copper(II) complexes having a pyridine spacer with CT DNA and 5'-GMP

New bis-macrocyclic complexes of Co(III), 1, Ni(II), 2, and Cu(II), 3, containing pyridyl bridges between 13-membered macrocyclic subunits, have been synthesized via an in situ one-pot template condensation reaction (IOPTCR). The proposed structures of these new dinuclear complexes are consistent with the data obtained from elemental analysis, molar conductance, IR, EPR, UV/VIS, (1)H- and 13C-NMR, and ESI-MS. The complexes 2 and 3 possess square-planar geometry with four secondary N-atoms coordinated to the metal ion, while complex 1 reveals octahedral geometry in solution due to coordinated H(2)O molecules. DNA-Binding properties of the complexes 1 and 3 were investigated by absorption and emission titrations, cyclic voltammetry, and viscosity measurements. Complexes 1 and 3 are strong DNA binders with binding constants, K(b), of 1.64 x 10(5) and 2.05 x 10(5) M(-1), respectively. Hyperchromism, decrease in emission intensity of DNA-bound ethidium bromide (EB), and changes observed in the viscosity and cyclic voltammograms in the presence of added metal complexes reveals that the complexes bind to DNA predominantly by electrostatic attraction, substantiated by absorption titration with 5'-GMP.

Synthesis of new heterometallic macromolecules: their DNA binding, cleavage activity and in vitro model electrochemotherapy study

The homodinuclear C(16)H(30)N(8)O(5)Sn(2)Cl(4) (1), heterotetranuclear C(16)H(38)N(8)O(9)Sn(2)Cu(2)Cl(8) (2) and C(16)H(38)N(8)O(9)Sn(2)Mn(2)Cl(8) (3) macrocyclic complexes were synthesized and characterized by elemental analysis, spectroscopic techniques and molar conductance measurements. The interaction studies of 1-3 with calf thymus DNA (CT-DNA) were carried out by UV-vis titration, fluorescence, cyclic voltammetry and viscosity measurements. These results were further authenticated by carrying out interaction studies of 1-3 with plasmid pBR322 DNA employing gel electrophoresis. To overcome the dose resistance, auto toxicity of the drugs, a model study based on electrochemotherapy (ECT) was carried out and the results were compared in the presence and in the absence of the applied electrical potential.

Macrocyclic Ligand Design. A Large Covalently-Linked Ring System Incorporating Four Cyclam Units and its Interaction with Nickel(II), Copper(II), Zinc(II), and Cadmium(II)

A cyclic, tetra-linked macrocyclic species incorporating four 1,4,8,11-tetraazacyclotetradecane (cyclam) subunits has been synthesized employing Boc amine-group protecting chemistry coupled with high dilution conditions for the cyclization step. A series of 4:1 (metal:ligand (M:L)) complexes with nickel(ii), copper(ii), zinc(ii), and cadmium(ii) has been synthesized. Visible spectophotometric (including spectrophotometric titration), EPR, NMR, and electrochemical studies are reported for individual complexes and are in general accord with similar 4:1 (M:L) coordination behaviour occurring in both the solid state and in solution. The study makes available an example of a new category of large cyclic receptors whose cavity can be tuned electronically through variation of the metal centres incorporated in the cavity walls.

Chiral and Achiral Macrocyclic Copper(II) Complexes: Synthesis, Characterization, and Comparative Binding Studies with Calf-Thymus DNA

The new chiral macrocyclic complexes [1,2-bis(1H-benzimidazol-2-yl)-1-(1,8-dihydro-1,3,5,8,10,12-hexaazacyclotetradecane)-2-hydroxyethanolate] copper(II) and -nickel(II) perchlorate, 3 and 4, respectively, were synthesized by the reaction of 1,2-bis(1H-benzimidazol-2-yl)ethane-1,2-diol (L) and (1,8-dihydro-1,3,5,8,10,12-hexaazacyclotetradecane)copper(II) and -nickel(II) diperchlorate complexes, 1 and 2, respectively. All complexes were characterized by various spectroscopic techniques. Molar-conductance measurements showed that all of the complexes are ionic in nature. In complexes 3 and 4, the metal center is encapsulated by the ligand L in a pentacoordinated environment. The optical-rotation values ([alpha](D)) of 3 and 4 at 25 degrees indicate that the complexes are chiral. Absorption- and fluorescence-spectral studies, cyclic voltammetry, and viscosity measurements have been carried out to assess the comparative binding of complexes 1 and 3 with calf thymus (CT)-DNA. Analysis of the results suggests that the new chiral complex 3 binds to CT-DNA through a partial intercalation mode that is different from the binding mode of parent achiral complex 1. The complexes 1 and 3 bind to CT-DNA with binding constants K(b) of 2.7 x 10(4) and 6.6 x 10(4) M(-1), respectively. Circular-dichroism (CD) studies have been further employed to ascertain the binding mode of complex 3, which is consistent with the other spectral studies.

Synthesis and Characterization of a New Macrocyclic Copper(II) Complex with anN-Glycosidic Pendant Arm:in vitro Cytotoxicity and Binding Studies with Calf-Thymus DNA

The new macrocyclic complex 2-amino-2-deoxy-N-[2-(1,3,5,8,11-pentaazacyclotridecan-3-yl)ethyl]-beta-D-glucopyranosylamine copper(II) dichloride (1a) was prepared and thoroughly characterized by various techniques. Molar-conductance measurements showed that 1a (and its Ni analogue 1b) are ionic in nature. On the basis of spectroscopic data, both complexes were assigned a square-planar geometry, and found to be highly stabile and hydrolytically robust in H2O over a wide range of pH, as confirmed by cyclic voltammetry (CV). The Cu(II) complex 1a was found to bind to CT-DNA, with a binding constant Kb of 2.4x10(3) M(-1), as derived by UV/VIS titration, and confirmed by CV, circular dichroism (CD), and viscosity measurements. DNA binding seems to occur mostly via H-bonding. In an in vitro antitumor MTT assay, 1a exhibited significant anticancer activity against the SY5Y and PC-12 cell lines, with an estimated IC50 value in the micromolar range for SYSY, similar to the standard drug 5-fluorouracil.

Mononuclear and Trinuclear Palladium(II) Complexes of Single- and Three-Ring Benzyl- or Xylyl-Substituted Cyclam Derivatives

A selection of 1 : 1 (palladium/ligand) complexes of cyclam derivatives incorporating from one to three N-benzyl groups has been synthesized. Related 3 : 1 species of two symmetrically branched, tri-cyclam species incorporating 1,3,5-‘tribenzyl’ or phloroglucinol cores are also reported. The X-ray crystal structures of the palladium complexes of two isomeric forms of the N,N′-dibenzylated (single-ring) macrocycle have been determined. In each complex the palladium ion occupies the N4-plane of the respective macrocycles in a square planar arrangement, with each complex cation adopting a stable trans-III configuration.