Studies on activities, cell up take and DNA binding of four multinuclear complexes of the form: [{trans-PtCl(NH3)2}2μ-{trans-Pd(NH3)2-(H2N(CH2)nNH2)2}]Cl4 where n=4–7

Potent cyclometallated Pd(II) antitumor complexes bearing α-amino acids: synthesis, structural characterization, DNA/BSA binding, cytotoxicity and molecular dynamics simulation

A rational approach was adopted to design high-potential metal-based antitumor agents. A series of organometallic Pd(ii) complexes with a general formula of [Pd{κ2(C,C)-[(C6H4-2)PPh2]CH(CO)C6H4Ph-4}{κ2(N,O)}] (N,O = alanine (Pd-A), valine (Pd-V), leucine (Pd-L), l-isoleucine (Pd-I) and phenylalanine (Pd-F)) were prepared by cyclopalladation of the phosphorus ylide, bridge cleavage reaction and subsequent chelation of natural α-amino acids. The complexes were fully identified using IR and multinuclear 1H, 13C, 31P NMR spectroscopic methods. X-ray crystallography exhibited that the Pd(ii) atom is located in a slightly distorted square-planar environment surrounded by C,C-orthometallated phosphorus ylide as well as NO-pendant amino acid functionality. In vitro cytotoxicity evaluation of new cyclometallated Pd(ii) complexes toward a human leukemia (K562) cancer cell line indicated promising results. The highest cytotoxic activity was discovered in the case of phenylalanine (CH2C6H5). IC50 values of this complex on a panel of human tumor cell lines representative of liver (HepG2), breast (SKBR-3), and ovarian (A2780-Resistance/Sensitive) cancers also indicated promising antitumor effects in comparison with standard cisplatin. The binding interaction ability of the phenylalanine-containing orthopalladated complex, as the most efficient compound, with calf-thymus deoxyribonucleic acid (CT-DNA) and bovine serum albumin (BSA) was investigated. UV-Vis spectroscopy, competitive emission titration, and circular dichroism (CD) techniques demonstrated the intercalative binding of the Pd(ii) complex with DNA. Molecular docking studies also fully agreed with the experimental data. Examination of the reactivity towards the protein BSA revealed that the static quenching mechanism of BSA intrinsic fluorescence by the Pd(ii) complex with a binding constant (Kb) of ∼105 is indicative of the high affinity of the complex. The competitive binding experiment using site markers with definite binding sites demonstrated that the hydrophobic cavities of site I (subdomain IIA) are responsible for the bimolecular interaction between protein BSA and the complex. Molecular docking studies effectively confirmed the significance of hydrophobic interactions in Pd(ii)-BSA binding. The results of this study could greatly contribute to exploring new potent metal-based anticancer drugs.

Synthesis and spectroscopic properties of (N/O) mono- and dispirocyclotriphosphazene derivatives with benzyl pendant arms: study of biological activity

The Cl replacement reactions of hexachlorocyclotriphosphazene (trimer; N 3 P 3 Cl 6 ) with sodium (N-benzyl)- aminopropanoxides (1 and 2) produced monospiro- (3 and 4), cis-, and trans-dispirocyclotriphosphazenes (13-16). The monospiro tetrakis-aminocyclotriphosphazenes (5-12) were obtained by the Cl substitutions of 3 and 4 with different secondary amines. The cis- (13 and 14) and trans-dispirophosphazenes (15 and 16) possessed 2 chiral P centers, and they were able to present meso and racemic forms, respectively. Moreover, the structures of compounds 5 and 14 were designated using X-ray data. The absolute configuration of compound 14 was found as SR in the solid state. Analytical and spectroscopic data of the phosphazenes were consistent with their suggested structures. Antimicrobial activities of the benzyl-pendant-armed cyclotriphosphazenes were scrutinized against G(+) and G(-) bacteria and yeast strains. The bacterium most affected by the synthesized compounds was Pseudomonas aeruginosa . Minimum inhibitory concentrations and minimal bacterial concentrations were in the range of 125-500 μM. Interactions between the phosphazenes (3-12 and 15) and plasmid DNA were studied with agarose gel electrophoresis. The phosphazene- DNA interaction studies of the cyclotriphosphazenes revealed that phosphazenes 3, 4, and 15 had a substantial effect on supercoiled DNA by cleavage of the double helix.

New bimetallic palladium(ii) and platinum(ii) complexes: studies of the nucleophilic substitution reactions, interactions with CT-DNA, bovine serum albumin and cytotoxic activity

Nucleophilic substitution reactions, interactions with CT-DNA, bovine serum albumin and cytotoxic activity of new bimetallic Pt(ii) and Pd(ii) complexes.

Synthesis and activity of three new trinuclear platinums with cis-geometry for terminal metal centres

BACKGROUND

As compared to cisplatin, trinuclear platinum compounds such as BBR3464 and DH6Cl have an altered spectrum of activity possibly because they form long-range adducts with DNA as against mainly intrastrand 1,2-bifunctional adducts formed by cisplatin and its analogues. Because of the labilizing effect associated with the trans-geometry, the compounds are expected to break down inside the cell thus serving to reduce the number of long-range adducts formed. In contrast, trinuclear platinum complexes with cis-geometry for the terminal metal centres would be less subject to such breakdown and hence may produce a greater number of long-range inter- and intrastrand adducts with the DNA. This paper describes the synthesis and activity against human ovarian tumour models of of three new trinuclear platinum complexes with cis-geometry for terminal platinum centres, coded as QH4, QH7 and QH8. The paper also describes cellular accumulation of platinum, level of drug-DNA binding, and nature of interaction of the compounds with pBR322 plasmid DNA.

RESULTS

Methods of synthesis, elemental analysis, spectral studies and molar conductivity measurements provide support to the suggested structures of the compounds. QH4 and QH8 are found to be more cytotoxic than cisplatin against the parental A2780 cell line; QH8 is more active than cisplatin against the resistant A2780cisR and A2780ZD0473R cell lines as well. The least compound QH7 shows a greater activity against the resistant cell lines than the parental cell line; it is most damaging to pBR322 plasmid DNA and most able to induce changes in DNA conformation. The variations in activity of the compounds, changes in intracellular drug accumulation and levels of Pt-DNA binding with the changes in number of planaramine ligands bound to central platinum and the length of the linking diamines, can be seen (1) to illustrate structure-activity relationships and (2) to highlight that the relationship between antitumour activity and interaction with cellular platinophiles including DNA can be quite complex as the cell death is carried out by downstream processes in the cell cycle where many proteins are involved.

CONCLUSION

Among the three designed trinuclear platinum complexes with cis-geometry for the terminal metal centres, the most active compound QH8 is found to be more active than cisplatin against the parental A2780 and the resistant A2780cisR and A2780ZD0473R cell lines.

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.

Platinum and Palladium Polyamine Complexes as Anticancer Agents: The Structural Factor

Since the introduction of cisplatin to oncology in 1978, Pt(II) and Pd(II) compounds have been intensively studied with a view to develop the improved anticancer agents. Polynuclear polyamine complexes, in particular, have attracted special attention, since they were found to yield DNA adducts not available to conventional drugs (through long-distance intra- and interstrand cross-links) and to often circumvent acquired cisplatin resistance. Moreover, the cytotoxic potency of these polyamine-bridged chelates is strictly regulated by their structural characteristics, which renders this series of compounds worth investigating and their synthesis being carefully tailored in order to develop third-generation drugs coupling an increased spectrum of activity to a lower toxicity. The present paper addresses the latest developments in the design of novel antitumor agents based on platinum and palladium, particularly polynuclear chelates with variable length aliphatic polyamines as bridging ligands, highlighting the close relationship between their structural preferences and cytotoxic ability. In particular, studies by vibrational spectroscopy techniques are emphasised, allowing to elucidate the structure-activity relationships (SARs) ruling anticancer activity.

trans-Bis(3-hy-droxy-pyridine-κN)diiodidoplatinum(II) dimethyl sulfoxide disolvate

In the title compound, [PtI₂(C₅H₅NO)₂]·2(CH₃)₂SO, the Pt^II ion lies on an inversion center and is coordinated in a slightly distorted square-planar environment by two trans iodide ligands and two pyridine N atoms. In the crystal, complex mol­ecules and solvent dimethyl sulfoxide mol­ecules are linked by inter­molecular O—H⋯O hydrogen bonds.

Synthesis, characterization, activities, cell uptake and DNA binding of trinuclear complex: [{trans-PtCl(NH3)}2μ-{trans-Pt(NH3)(2-hydroxypyridine)-(H2N(CH2)6NH2)2]Cl4

The trinuclear complex: [{trans-PtCl(NH(3))}(2)mu-{trans-Pt(NH(3))(2-hydroxypyridine)-(H(2)N(CH(2))(6)NH(2))(2)]Cl(4) (code named CH9) has been synthesized and characterized. The activity of the compound against human ovarian cancer cell lines: A2780, A2780(cisR) and A2780(ZD0473R), cell up take, level of binding with DNA and nature of its interaction with pBR322 plasmid DNA have been determined. Although the compound is found to be less active (about a half time as active as cisplatin) against the parent ovary cell line A2780, it is found to be more active than cisplatin against resistant cell lines: A2780(cisR) (3.6 times more) and A2780(ZD0473R) (3.4 times more). The higher activity of CH9 against the resistant cell lines suggests that the compound has been able to overcome multiple mechanisms of resistance operating in A2780(cisR) and A2780(ZD0473R) cell lines. Like other multicentered complexes, the compound is believed to form a range of interstrand GG adducts with duplex DNA that induces permanent global changes in the DNA conformation. This binding is different from that of cisplatin and ZD0473 that form mainly intrastrand adducts, inducing a local kink in a DNA strand. Increasing prevention of BamH1 digestion of form I and form II pBR322 plasmid DNA with the increase in concentration of CH9 provides support to the idea that global changes in DNA conformation are induced as a result of its interaction with the compound.