New organometallic ruthenium(ii) complexes with purine analogs - a wide perspective on their biological application

Tetranuclear and dinuclear Cu(II) complexes with risedronate as anti-Trypanosoma cruzi and anti-Leishmania mexicana agents. Synthesis, crystal structures, and biological evaluation

The development of new biometal-based complexes containing antiparasitic bioactive ligands is a central field of coordination chemistry that impacts bioinorganic, medicinal, and biological chemistry. Herein, two novel water-soluble polynuclear Cu(II)-complexes with formula [Cu4(4,4'-dmbp)4(μ3-HRis)2Cl2], 1 and [Cu2(5,5'-dmbp)2(μ2-HRis)(H2O)Cl] 2, (4,4'-dmbp = 4,4'-dimethyl-2,2'-bipyridine, 5,5'-dmbp = 5,5'-dimethyl-2,2'-bipyridine, HRis = risedronate), were synthesized by self-assembly solution reactions between the corresponding precursor complexes [Cu2(dmbp)Cl2] and the drug Na2Ris in aqueous media. Both Cu(II)-Ris complexes 1-2 were structurally described by single-crystal X-ray diffraction, characterized by spectroscopic tools (IR-ATR, HRMS, UV-Vis, EPR) and studied as antiparasitic agents against Trypanosoma cruzi causative agent of Chagas disease and Leishmania mexicana that is the etiological agent of cutaneous leishmaniasis. X-ray structural analysis reveals that 1 is an uncommon tetranuclear Cu4 complex where four crystallographically independent units [Cu(4,4'dmbp)]2+ are double-bridged coordinated by two tetra-deprotonated ligands HRis containing the protonated pyridine ring. All Cu(II) centers show a distorted square-based pyramid geometry, and they are coordinated by two bisphosphonate fragments from HRis in a coordination environment μ3 for each one. Crystal analysis of 2 displays a dinuclear Cu2 complex where one ligand HRis coordinated to two different units [Cu(4,4'dmb)]2+ in a μ2 mode, both Cu(II) present distorted square-based pyramid geometry. In general, complexes 1-2 are hydrostable in the millimolar concentration range and present low citotoxicity (<22% on the growth of cancer cell lines and healthy COS-7 cells) similar to the commercial drug, monosodium salt of risedronic acid (NaRis). Complexes 1-2 and NaRis were evaluated in vitro against T. cruzi epimastigotes and L. mexicana promastigotes. Results demonstrated that these Cu-Ris complexes improved the percentages of growth inhibition for T. cruzi. This inhibition ranged from 62-70% at concentrations of 5.0 mM after 24 h and 48 h incubation, compared to those observed for free, which has an inhibition of ∼38%. Under the same concentration at 24 h incubation, complex 1 has a significantly greater inhibition effect against L. mexicana (63%) compared to free NaRis (50%). Reduction in parasite metabolisms and morphological changes included membrane damage, vacuolization, reduction of size and loss of flagellum were also observed. Importantly cytotoxicity to VERO cells was minor with the Cu(II)-Ris complexes compared with NaRis. The molecular docking analysis showed significant affinity towards the enzyme farnesyl diphosphate synthase from T. cruzi (TcFPPS), including simulations of the complexes Cu(II) at the TcFPPS binding site.

An Overview of the Potential Medicinal and Pharmaceutical Properties of Ru(II)/(III) Complexes

This review examines the existing knowledge about Ru(II)/(III) ion complexes with a potential application in medicine or pharmacy, which may offer greater potential in cancer chemotherapy than Pt(II) complexes, which are known to cause many side effects. Hence, much attention has been paid to research on cancer cell lines and clinical trials have been undertaken on ruthenium complexes. In addition to their antitumor activity, ruthenium complexes are under evaluation for other diseases, such as type 2 diabetes, Alzheimer's disease and HIV. Attempts are also being made to evaluate ruthenium complexes as potential photosensitizers with polypyridine ligands for use in cancer chemotherapy. The review also briefly examines theoretical approaches to studying the interactions of Ru(II)/Ru(III) complexes with biological receptors, which can facilitate the rational design of ruthenium-based drugs.

Mechanistic Studies of Arene-Ruthenium(II) Complexes with Carbothioamidopyrazoles as Alternative Cancer Drugs

Arene-ruthenium(II) complexes with carbothioamidopyrazoles at the C-2 and C-5 positions have been recognized as chemotherapeutic agent alternatives to cisplatin and its oxaliplatin analogs. The aim of this study was to continue research on the biological aspect of arene-ruthenium(II) complexes and their anticancer activity. The present paper includes an additional 12 new tumor cells, analyzed by MTT, and employs a series of extended bioassays to better understand their potential mechanism of antitumor activity. The following tests were conducted: membrane permeability studies, intramolecular reactive oxygen and nitrogen species (ROS/RNS) assays, mitochondrial potential changes, DNA analysis by comet assay using the electrophoresis method, measurement of cleaved PARP protein levels, and determination of apoptotic and necrotic cell fractions by fluorescence microscopy. Additionally, the article presents lipophilicity studies based on RP-TLC and molecular docking studies. We hope that the presented data will prove useful in practical treatment, especially for patients with cancer.

New Nucleic Base-Tethered Trithiolato-Bridged Dinuclear Ruthenium(II)-Arene Compounds: Synthesis and Antiparasitic Activity

Aiming toward compounds with improved anti-Toxoplasma activity by exploiting the parasite auxotrophies, a library of nucleobase-tethered trithiolato-bridged dinuclear ruthenium(II)-arene conjugates was synthesized and evaluated. Structural features such as the type of nucleobase and linking unit were progressively modified. For comparison, diruthenium hybrids with other type of molecules were also synthesized and assessed. A total of 37 compounds (diruthenium conjugates and intermediates) were evaluated in a primary screening for in vitro activity against transgenic Toxoplasma gondii tachyzoites constitutively expressing β-galactosidase (T. gondii β-gal) at 0.1 and 1 µM. In parallel, the cytotoxicity in non-infected host cells (human foreskin fibroblasts, HFF) was determined by alamarBlue assay. Twenty compounds strongly impairing parasite proliferation with little effect on HFF viability were subjected to T. gondii β-gal half maximal inhibitory concentration determination (IC₅₀) and their toxicity for HFF was assessed at 2.5 µM. Two promising compounds were identified: 14, ester conjugate with 9-(2-oxyethyl)adenine, and 36, a click conjugate bearing a 2-(4-(hydroxymethyl)-1H-1,2,3-triazol-1-yl)methyl substituent, with IC₅₀ values of 0.059 and 0.111 µM respectively, significantly lower compared to pyrimethamine standard (IC₅₀ = 0.326 µM). Both 14 and 36 exhibited low toxicity against HFF when applied at 2.5 µM and are candidates for potential treatment options in a suitable in vivo model.

Sawhorse-type ruthenium complexes with triazolopyrimidine ligands - what do they represent in terms of cytotoxic and CORM compounds?

Three sawhorse-type ruthenium(I) complexes containing purine analogs such as triazolopyrimidines of the general formula [Ru₂(CO)₄(μ-OOCCH₃)₂(L)₂], where L is 1,2,4-triazolo[1,5-a]pyrimidine (tp for 1), 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp for 2) and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine (dptp for 3), have been synthesized and characterized by elemental analysis, infrared analysis, multinuclear magnetic resonance spectroscopic techniques (¹H, ¹³C, ¹⁵N), and single-crystal X-ray diffraction (for 1 and 2). By assay with myoglobin, the photo-activated CO-releasing molecule (PhotoCORM) character of (1-3) has been confirmed, thus indicating the possibility of use in CO-based therapies. The importance of UV-induced modification has been investigated in the context of anticancer properties. Complexes (1) and (2) have been thoroughly screened for their in vitro cytotoxicity against various cancer cell lines: MCF-7 (breast cancer), HeLa (cervical cancer) and C32 (melanoma), as well as L929 normal fibroblasts in the dark and presence of UV-A light (365 nm). The results were compared with those for cisplatin and two reference ruthenium complexes, namely NAMI-A and KP1019. The most hydrophilic [Ru₂(CO)₄(μ-OOCCH₃)₂(tp)₂] (1) (log P = -1.12) was found to be more cytotoxic than (2), despite the lower cellular uptake measured by ICP-MS toward HeLa cells. Importantly, photo-induced stimulation of cells with (1) resulted in a lower decrease in the viability of L929 normal cells (IC₅₀ = 154.7 ± 6.5 μM) in comparison with HeLa cancer cells (IC₅₀ = 66.7 ± 3.4 μM). The photo-induced stimulation of (1) and (2) increases ROS generation, and their anticancer activity may be a partially ROS-dependent phenomenon.