Towards Identification of Essential Structural Elements of Organoruthenium(II)‐Pyrithionato Complexes for Anticancer Activity

Abstract

An organoruthenium(II) complex with pyrithione (2-mercaptopyridine N-oxide) 1a has previously been identified by our group as ac ompound with promising anticancer potential without cytotoxicity towards non-cancerous cells. To expand the rather limited research on compounds of this type, an array of novel chlorido and 1,3,5-triaza-7-phosphaadamantane( pta) organoruthenium(II) complexesw ith methyl-substituted pyrithiones has been prepared. After thorough investigation of the aqueous stability of these complexes, their modeso fa ction have been elucidated at the cellular level.M inor structurala lterations in the rutheni-um-pyrithionato compounds resulted in fine-tuning of their cytotoxicities. The best performing compounds, 1b and 2b, with ac hlorido or pta ligand bound to ruthenium, respectively,and amethyl group at the 3-position of the pyrithione scaffold, have been further investigated. Both compounds trigger early apoptosis, induce the generation of reactive oxygen speciesa nd G1 arrest in A549 cancerc ells, and show no strong interaction with DNA. However,o nly 1b also inhibits thioredoxin reductase.W ound healing assays and mitochondrial function evaluation have revealed differences between these two compounds at the cellular level. Figure 2. Structures of the prepared ligands and reaction path leadingt o the organoruthenium(II) chlorido (1a-e)a nd pta (2a-e)complexes.

Binding Kinetics of Ruthenium Pyrithione Chemotherapeutic Candidates to Human Serum Proteins Studied by HPLC-ICP-MS

“…Importantly, no visible changes for pta complex (2) in 31 P-NMR spectra were monitored ( Figure S3). The obtained data are also in good agreement with previously reported stabilities for such systems [19,21].…”

“…Further, complex (2) binds to HSA with around 50%, whereas its methyl analogue binds to BSA with around 58%. Taken into consideration small structural changes of both pta Ru complexes and both albumins data from these two studies are comparable as well [21]. New findings have again confirmed more in detail that investigated complexes are partly bound to proteins, but they also exist in their free form.…”

“…The equilibrium concentration was obtained 24 h after incubation, with about 50% of complex (2) bound to HSA and another 50% as an unbound drug. These data can be compared with the results of protein binding study described by Kladnik et al [21], where it was investigated the binding of analogous methylsubstituted pyrithione chlorido and pta Ru(II) complexes to BSA. The obtained data reported in this study for chlorido complex (1) are in very good agreement with data obtained for its methylsubstituted pyrithione analogue on BSA, as in both cases complexes are bound to albumins in around 70%.…”

“…They were tested for their cytotoxicities against several cancer cell lines and one normal cell line. Their mode of action was thoroughly assessed through wound healing assay, binding to bovine serum albumin (BSA), induction of apoptosis, cell cycle analysis, DNA interactions, generation of reactive oxygen species (ROS), inhibition of the potential molecular target thioredoxin reductase (TrxR) and mitochondrial function assay [21]. An important step in a drug candidate's characterization is the pharmacological evaluation of its interactions with serum proteins.…”

“…In the investigations of performances of new drug candidates, it is important to elucidate the kinetics of drug bindings to human serum proteins. Therefore, the aim of the present study was to apply the speciation analysis to investigate the kinetics of two prosperous Ru-based anticancer drug candidates in human serum, namely Ru(II) chlorido [(η 6 -p-cymene)Ru(1-hydroxypyridine-2(1H)-thionato)Cl (1) and Ru(II) pta [(η 6 -p-cymene)Ru(1-hydroxypyridine-2(1H)-thionato)pta]PF 6 complex (2), synthesized in Turel group [19,21]. Kladnik et al [21] have already reported some preliminary results on protein binding of analogue methyl-substituted pyrithione Ru(II) chlorido and pta complexes performed on bovine serum albumin (BSA) by atomic absorption spectroscopy.…”