Chiral ruthenium complexes induce apoptosis of tumor cell and interact with bovine serum albumin

New Heteroleptic Ruthenium(II) Complexes with Sulfamethoxypyridazine and Diimines as Potential Antitumor Agents

Two new complexes of Ru(II) with mixed ligands were prepared: [Ru(bpy)₂smp](PF₆) (1) and [Ru(phen)₂smp](PF₆) (2), in which smp = sulfamethoxypyridazine; bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline. The complexes have been characterized by elemental and conductivity analyses; infrared, NMR, and electrospray ionization mass spectroscopies; and X-ray diffraction of single crystal. Structural analyses reveal a distorted octahedral geometry around Ru(II) that is bound to two bpy (in 1) or two phen (in 2) via their two heterocyclic nitrogens and to two nitrogen atoms from sulfamethoxypyridazine—one of the methoxypyridazine ring and the sulfonamidic nitrogen, which is deprotonated. Both complexes inhibit the growth of chronic myelogenous leukemia cells. The interaction of the complexes with bovine serum albumin and DNA is described. DNA footprinting using an oligonucleotide as substrate showed the complexes’ preference for thymine base rich sites. It is worth notifying that the complexes interact with the Src homology SH3 domain of the Abl tyrosine kinase protein. Abl protein is involved in signal transduction and implicated in the development of chronic myelogenous leukemia. Nuclear magnetic resonance (NMR) studies of the interaction of complex 2 with the Abl-SH3 domain showed that the most affected residues were T79, G97, W99, and Y115.

Ruthenium (II) complexes interact with human serum albumin and induce apoptosis of tumor cells

The interaction of ruthenium (II) complex [Ru(bpy)2(mal)](2+) (RBM) and [Ru(phen)2(mal)](2+) (RPM) (bpy = 2, 2-bipyridine, phen = 1,10-phenanthroline, mal = malonyl carboxylate) with human serum albumin (HSA) has been investigated by using fluorescence, UV absorption and circular dichroism (CD) spectroscopy approaches. A strong fluorescence quenching reaction of complexes to HSA was observed and the quenching mechanism was suggested as static quenching according to the Stern-Volmer (S-V) equation. The number of binding sites n and observed binding constant Kb was measured by fluorescence quenching method. The thermodynamic parameters ΔH, ΔS, and ΔG at different temperatures were calculated and the results indicate the binding reaction is mainly entropy-driven and Vander Waals force played a major role in the reaction. The result of CD showed that the secondary structure of HSA molecules was changed in the presence of the ruthenium (II) complexes. Furthermore, the cell viability of ruthenium (II) complexes was evaluated by MTT and complex RPM has shown significant higher anticancer potency than RBM against all the cell lines screened. RPM showed a significant antitumor activity through induction of apoptosis in A549 cells.

Chiral-auxiliary-mediated asymmetric synthesis of ruthenium polypyridyl complexes

An octahedral metal complex with 6 different monodentate ligands can form 15 diastereomers as pairs of enantiomers. As a result, the elaborate stereochemistry of octahedral coordination geometries provides tremendous opportunities in the fields of catalysis, the materials sciences, and the life sciences. The demand for enantiomerically pure coordination complexes for tasks related to the selective molecular recognition of biomacromolecules led us to develop synthetic methods to control the absolute stereochemistry at octahedral metal centers. A few years ago our laboratory therefore embarked on a project exploring new and general synthetic strategies for the asymmetric synthesis of inert octahedral transition metal complexes. We initially used the example of thermally inert ruthenium polypyridyl complexes and developed a family of chiral bidentate ligands, including salicyloxazolines, (mercaptophenyl)oxazolines, sulfinylphenols, N-acetylsulfinamides, a phosphinohydroxybinaphthyl, and even the amino acid proline to serve as chiral auxiliaries for asymmetric coordination chemistry. All these chiral auxiliaries strongly coordinate to ruthenium(II) in a bidentate, deprotonated fashion, allowing them to control the absolute metal-centered configuration in the course of subsequent ligand exchange reactions. Finally, we can remove them from the metal without any loss of chiral information and without leaving a chemical trace. A key feature of these chiral auxiliary ligands is their switchable binding strength. A chelate effect ensures that the chiral ligands coordinate very tightly to the metal center, placing their carbon-based, sulfur-based, or axial chirality in a well-defined position close to the metal center to efficiently establish the absolute metal-centered configuration. At the same time a coordinating phenolate, carboximidate, carboxylate, or thiophenolate moiety makes the coordination reversible by weakening the binding strength through protonation or methylation. Following this strategy, we synthesized a large number of homoleptic, bis-heteroleptic, and tris-heteroleptic ruthenium polypyridyl complexes in an asymmetric fashion with enantiomeric ratios that routinely reached or exceeded 96:4. Our approach should serve as a blueprint for the asymmetric synthesis of different classes of ruthenium complexes and chiral coordination complexes of other metals.