Role of the (pseudo)halido ligand in ruthenium(II) p-cymene α-amino acid complexes in speciation, protein reactivity and cytotoxicity

The reactions of the dimeric complexes [RuX2(η6-p-cymene)]2 (X = Br, I, SCN) with L-proline (ProH) and trans-4-hydroxy-L-proline (HypH), in methanol in the presence of NaOH, afforded [RuX(κ2N,O-Pro)(η6-p-cymene)] (X = Br, 1b; I, 1c; SCN, 1d) and [RuX(κ2N,O-Hyp)(η6-p-cymene)] (X = Br, 2b; I, 2c; SCN, 2d), respectively. Alternatively, the one-pot, sequential addition of the appropriate α-amino carboxylate and X- salt to [RuCl2(η6-p-cymene)]2 led to [RuX(κ2N,O-Pro)(η6-p-cymene)] (X = N3, 1e; NO2, 1f; CN 1g) and [Ru(N3)(κ2N,O-Hyp)(η6-p-cymene)] (2e). Complexes [Ru(κ3N,O,O'-O2CCH(NH2)(R)O)(η6-p-cymene)] (R = CH2, 3h; R = CHMe, 4h; R = CH2CH2, 5h) were prepared from the reaction of [RuCl2(η6-p-cymene)]2 with the appropriate α-amino acid and NaOH in refluxing isopropanol. Treatment of the L-serine (SerH2) derivative [RuCl(κ2N,O-SerH)(η6-p-cymene)] (3a) with 1,3,5-triaza-7-phosphaadamantane (PTA) in water at reflux produced [Ru(κ2N,O-Ser)(κP-PTA)(η6-p-cymene)]Cl ([3i]Cl). The products were isolated in good to excellent yields, and were characterized by elemental analysis, IR and multinuclear NMR spectroscopy. The structures of 1f and 2b-e were ascertained by X-ray diffraction studies. The behaviour of the complexes in water and cell culture medium was investigated by multinuclear NMR and UV-Vis spectroscopy, revealing a considerable influence of the monodentate ligand on the aqueous chemistry. Complexes 1d-e, 2d-e, 3h, 4h and [3i]Cl, showing substantial inertness in aqueous media, were assessed for their cytotoxicity towards A2780 and A2780cisR cancer cell lines and the noncancerous HEK 293T cell line. A selection of compounds was also investigated for Ru uptake in A2780 cells and interactions with cytochrome c as a model protein. Combined, these studies provide insights into the previously debated role of the 'leaving' ligand on the biological activity of Ru(II) arene α-amino acid complexes.

An overview of hydroxypyranone and hydroxypyridinone as privileged scaffolds for novel drug discovery

Hydroxypyranone and hydroxypyridinone are important oxygen-containing or nitrogen-containing heterocyclic nucleus and attracted increasing attention in medicinal chemistry and drug discovery over the past decade. Previous literature reports revealed that hydroxypyranone and hydroxypyridinone derivatives exhibit a wide range of pharmacological activities such as antibacterial, antifungal, antiviral, anticancer, anti-inflammatory, antioxidant, anticonvulsant, and anti-diabetic activities. In this review, we systematically summarized the literature reported biological activities of hydroxypyranone and hydroxypyridinone derivatives. In particular, we focus on their biological activity, structure-activity relationship (SAR), mechanism of action, and interaction mechanisms with the target. The collected information is expected to provide rational guidance for the development of clinically useful agents from these pharmacophores.

Inhibition of the p53/hDM2 protein-protein interaction by cyclometallated iridium(III) compounds

Inactivation of the p53 transcription factor by mutation or other mechanisms is a frequent event in tumorigenesis. One of the major endogenous negative regulators of p53 in humans is hDM2, a ubiquitin E3 ligase that binds to p53 causing proteasomal p53 degradation. In this work, a library of organometallic iridium(III) compounds were synthesized and evaluated for their ability to disrupt the p53/hDM2 protein-protein interaction. The novel cyclometallated iridium(III) compound 1 [Ir(eppy)₂(dcphen)](PF₆) (where eppy = 2-(4-ethylphenyl)pyridine and dcphen = 4, 7-dichloro-1, 10-phenanthroline) blocked the interaction of p53/hDM2 in human amelanotic melanoma cells. Finally, 1 exhibited anti-proliferative activity and induced apoptosis in cancer cell lines consistent with inhibition of the p53/hDM2 interaction. Compound 1 represents the first reported organometallic p53/hDM2 protein-protein interaction inhibitor.

Ru(ii)-(PTA) and -mPTA complexes with N2-donor ligands bipyridyl and phenanthroline and their antiproliferative activities on human multiple myeloma cell lines

A series of novel ruthenium(ii) 2,2'-bipyridyl (bpy) and 1,10-phenanthroline (phen) derivatives containing PTA (1,3,5-triaza-7-phosphaadamantane) or mPTA (N-methyl-1,3,5-triaza-7-phosphaadamantane cation) have been synthesized and fully characterized. Three types of complexes have been obtained, neutral [Ru(N-N)(PTA)₂Cl₂] (1, N-N = bpy and 4, N-N = phen), monocationic [Ru(N-N)(PTA)₃Cl][Cl] (2, N-N = bpy and 5, N-N = phen) and dicationic [Ru(N-N)(mPTA)Cl₂][BF₄]₂ (3, N-N = bpy and 6, N-N = phen). The solid-state structures of four complexes have been determined by single-crystal X-ray diffraction. The cytotoxicity of the complexes has been evaluated in vitro against U266 and RPMI human multiple myeloma cells.

Ruthenium arene complexes with triphenylphosphane ligands: cytotoxicity towards pancreatic cancer cells, interaction with model proteins, and effect of ethacrynic acid substitution

The anticancer behaviour of Ru arene complexes can be tuned by an appropriate choice of the site and linkage of the bioactive group to the phosphane ligand.

Mass Spectrometry Uncovers Molecular Reactivities of Coordination and Organometallic Gold(III) Drug Candidates in Competitive Experiments That Correlate with Their Biological Effects

The reactivity of three cytotoxic organometallic gold(III) complexes with cyclometalated C,N,N and C,N ligands (either six- or five-membered metallacycles), as well as that of two representative gold(III) complexes with N-donor ligands, with biological nucleophiles has been studied by ESI-MS on ion trap and time-of-flight instruments. Specifically, the gold compounds were reacted with mixtures of nucleophiles containing l-histidine (imine), l-methionine (thioether), l-cysteine (thiol), l-glutamic acid (carboxylic acid), methylseleno-l-cysteine (selenoether), and in situ generated seleno-l-cysteine (selenol) to judge the preference of the gold compounds for binding to selenium-containing amino acid residues. Moreover, the gold compounds' reactivity was studied with proteins and nucleic acid building blocks. These experiments revealed profound differences between the coordination and organometallic families and even within the family of organometallics, which allowed insights to be gained into the compounds mechanisms of action. In particular, interactions with seleno-l-cysteine appear to reflect well the compounds' inhibition properties of the seleno-enzyme thioredoxin reductase and to a certain extent their antiproliferative effects in vitro. Therefore, mass spectrometry is successfully applied for linking the molecular reactivity and target preferences of metal-based drug candidates to their biological effects. Finally, this experimental setup is applicable to any other metallodrug that undergoes ligand substitution reactions and/or redox changes as part of its mechanism of action.