Palladium(II) and Platinum(II) Organometallic Complexes with 4,7-dihydro-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine. Antitumor Activity of the Platinum Compounds

First-Row Transition 7-Oxo-5-phenyl-1,2,4-triazolo[1,5-a]pyrimidine Metal Complexes: Antiparasitic Activity and Release Studies

Leishmaniasis and Chagas disease are still considered neglected illnesses due to the lack of investment in research, despite the fact that almost one million new cases are reported every year. Four 7-oxo-5-phenyl-1,2,4-triazolo[1,5-a]pyrimidine (HftpO) first-row transition complexes (Cu, Co, Ni, Zn) have been studied for the first time in vitro against five different species of Leishmania spp. (L. infantum, L. braziliensis, L. donovani, L. peruviana and L. mexicana) as well as Trypanosoma cruzi, showing higher efficacy than the reference commercial drugs. UV and luminescence properties were also evaluated. As a proof of concept, anchoring of a model high-effective-metal complex as an antiparasitic agent on silica nanoparticles was carried out for the first time, and drug-release behaviour was evaluated, assessing this new approach for drug vehiculation.

Homo and heterobimetallic palladium and platinum complexes bearing μ-diphosphane bridges involved in biological studies

Given the increasing reports of well-defined bimetallic molecular complexes as potential anticancer agents in the last decades, along with the prevalence of platinum in anticancer therapy, we report here a detailed survey of bimetallic platinum and palladium complexes investigated as potential anticancer agents. Specifically, we will concentrate on the synthesis, characterisation and biological (anticancer) studies of a sub-class of these agents, namely homo and heterobimetallic complexes bearing a bridging phosphane ligand of the type: [L_nM₁(μ-R₂P(CH₂)_nPR₂)M₂L_m] (where M₁ is platinum or palladium, M₂ is any other transition metal, R = alkyl or aryl substituents, L_n or L_m are co-ligands, n = 1-6). We will review the in vitro and in vivo activities and any mechanistic anticancer studies of these complexes with a view of trying to delineate patterns in biological activity and structure-activity relationships (SAR). We do not include the review of bimetallic complexes in this class that have not undergone any anticancer testing, nor those that have been involved in other biological investigations unrelated to cancer studies.

Solvent induced supramolecular polymorphism in Cu(II) coordination complex built from 1,2,4-triazolo[1,5-a]pyrimidine: Crystal structures and anti-oxidant activity

Two Cu(II) coordination complexes, C1 and C2 of the formula [Cu(4)₂(H₂O)₂], have been prepared by reaction between CuCl₂·2H₂O and 7-ethoxycarbonylmethyl-5-methyl-1,2,4[1,5-a]pyrimidine (L) in a 1:2 M:L molar ratio. The L molecule decomposes during the reaction process into 7-carboxy-5-methyl-[1,2,4]-triazolo[1,5-a]pyrimidine (4) through an intermediate, ethyl 2,2-dihydroxy-2-(5-methyl-[1,2,4]triazolo[1,5-a]pyrimidin-7-yl)acetate (5), which has been isolated and its crystal structure determined by X-ray diffraction. The X-ray analysis of the single crystals of [Cu(4)₂(H₂O)₂] obtained from the slow evaporation of EtOH and MeOH, separately, revealed the formation of "solvent induced" polymorphs C1 and C2, respectively. The primary supramolecular synthon for C1 and C2 are six membered ring, and square shaped hydrogen bonded architecture, respectively. The self-assembly of such synthons resulted in a two dimensional hydrogen bonded sheet supported by OH⋯O interactions. In addition, the antioxidant properties of the ligands and its complexes were evaluated in vitro using 1,1-diphenyl-2-picrylhydrazyl acid, 2,2'-azino-bis (3-ethylbenzothiazoline-6 sulfonic acid radical scavenging methods and ferric reducing antioxidant power.

Palladium(ii) complexes with thiosemicarbazones derived from pyrene as topoisomerase IB inhibitors

New palladium complexes with thiosemicarbazonate ligands derived from pyrene exhibit potent antiproliferative activity against A2780 and cisplatin-resistant A2780Cis human ovarian cancer cells, which is dependent on substituent groups of the thiosemicarbazone ligands. Cellular accumulation and distribution studies confirmed that palladium enters the cell nucleus. DNA and topoisomerase IB studies show that one complex is a potent TopIB inhibitor, with selectivity for cancer versus normal cells.

Cytotoxic Activity of Organotin(IV) Derivatives with Triazolopyrimidine Containing Exocyclic Oxygen Atoms

In this study cytotoxicity of organotin(IV) compounds with 1,2,4-triazolo[1,5-a]pyrimidines, Me3Sn(5tpO) (1), n-Bu3Sn(5tpO) (2), Me3Sn(mtpO) (3), n-Bu3Sn(mtpO) (4), n-Bu3Sn(HtpO2) (5), Ph3Sn(HtpO2) (6) where 5HtpO = 4,5-dihydro-5-oxo-[1,2,4]triazolo-[1,5-a]pyrimidine, HmtpO = 4,7-dihydro-5-methyl-7-oxo-[1,2,4]triazolo-[1,5-a]pyrimidine, and H2tpO2 = 4,5,6,7-tetrahydro-5,7- dioxo-[1,2,4]triazolo-[1,5-a]-pyrimidine, was assessed on three different human tumor cell lines: HCT-116 (colorectal carcinoma), HepG2 (hepatocarcinoma) and MCF-7 (breast cancer). While 1 and 3 were inactive, compounds 2, 4, 5 and 6 inhibited the growth of the three tumor cell lines with IC50 values in the submicromolar range and showed high selectivity indexes towards the tumor cells (SI > 90). The mechanism of cell death triggered by the organotin(IV) derivatives, investigated on HCT-116 cells, was apoptotic, as evident from the externalization of phosphatidylserine to the cell surface, and occurred via the intrinsic pathway with fall of mitochondrial inner membrane potential and production of reactive oxygen species. While compound 6 arrested the cell progression in the G2/M cell cycle phase and increased p53 and p21 levels, compounds 2, 4 and 5 blocked cell duplication in the G1 phase without affecting the expression of either of the two tumor suppressor proteins. Compounds 1 and 2 were also investigated using single crystal X-ray diffraction and found to be, in both cases, coordination polymers forming 1 D chains based on metal-ligand interactions. Interestingly, for n-Bu3Sn(5tpO)(2) H-bonding interactions between 5tpO- ligands belonging to adjacent chains were also detected that resemble the "base-pairing" assembly and could be responsible for the higher biological activity compared to compound 1. In addition, they are the first example of bidentate N(3), O coordination for the 5HtpO ligand on two adjacent metal atoms.

New RuII pincer complexes: synthesis, characterization and biological evaluation for photodynamic therapy

Three new ruthenium(ii) complexes of NCN pincer and phenylcyanamide derivative ligands of the formula [Ru(L)(Ph₂phen)(3,5-(NO₂)₂pcyd)], 1, [Ru(L)(Me₂phen)(3,5-(NO₂)₂pcyd)], 2, and [Ru(L)(Cl₂phen)(3,5-(NO₂)₂pcyd)], 3 (HL: 5-methoxy-1,3-bis(1-methyl-1H-benzo[d]imidazol-2-yl)benzene, 3,5-(NO₂)₂pcyd: 3,5-(NO₂)₂pcyd, Ph₂phen: 4,7-diphenyl-1,10-phenanthroline, Me₂phen: 4,7-dimethyl-1,10-phenanthroline, Cl₂phen: 4,7-dichloro-1,10-phenanthroline) have been synthesized and studied as potential photosensitizers (PSs) in photodynamic therapy (PDT). The complexes exhibited promising ¹O₂ production quantum yields comparable with PSs available on the market. The DNA-binding interactions of the complexes with calf thymus DNA have been studied by absorption, emission, and viscosity measurements. All complexes cleave SC-DNA efficiently on photoactivation at 350 nm with the formation of singlet oxygen (¹O₂) and hydroxyl radicals (˙OH) in type-II and photoredox pathways. Complexes 1-3 showed very good uptake in cervical cancer cells (HeLa). The compounds studied were found to exhibit low toxicity against HeLa cells (IC₅₀ > 300 μM) and, remarkably, on non-cancerous MRC-5 cells (IC₅₀ > 100 μM) in the dark. However, 1 showed very promising behavior with an increment of about 90 times, in its cytotoxicity upon light illumination at 420 nm in addition to very good human plasma stability.

Cycloplatinated(ii) complexes bearing 1,1′-bis(diphenylphosphino)ferrocene ligand: biological evaluation and molecular docking studies

Cycloplatinated(ii) complexes containing dppf ligand were prepared. These complexes exhibited high cytotoxicity and apoptosis-inducing activities to human cancer cell lines.

A novel mesoionic carbene based highly fluorescent Pd(ii) complex as an endoplasmic reticulum tracker in live cells

Synthesis of new organometallic MIC based mononuclear Pd(ii) complex 1, specifically target ER of live cells and have fluorescence recovery after photobleaching (FRAP) property.

Synthesis of novel quinazolin-4(3H)-one derivatives containing the 7-oxo-1,2,4-triazolo[1,5-a]pyrimidine moiety as effective agricultural bactericides against the pathogen Xanthomonas oryzae pv. oryzae

A series of novel quinazolin-4-one derivatives (7a-7n) bearing the 7-oxo-1,2,4-triazolo[1,5-a]pyrimidine moiety were designed, synthesized and evaluated for their inhibition activities against phytopathogenic bacteria and fungi in vitro. All of the target compounds were fully characterized through [Formula: see text] NMR, [Formula: see text] NMR, HRMS and IR spectra. Among these compounds, the structure of compound 7e was unambiguously confirmed via single-crystal X-ray diffraction analysis. The turbidimetric assays indicated that compounds 7b, 7d, 7g, 7k and 7n exhibited much more potent inhibition activities against the pathogen Xanthomonas oryzae pv. oryzae (Xoo), relative to control Bismerthiazol. Moreover, antibacterial activities of compounds 7j, 7k and 7n against the pathogen Xanthomonas axonopodis pv. citri (Xac) were comparable to that of control Bismerthiazol. As for the pathogen Ralstonia solanacearum (Rs), only compounds 7g and 7i demonstrated inhibition activities similar to control Thiadiazole-copper. Moreover, this class of compounds did not display inhibition activity against three fungi tested. The above findings indicated that quinazolin-4-one derivatives containing the 7-oxo-1,2,4-triazolo[1,5-a]pyrimidine moiety have a potential as promising candidates for the development of new and more efficient agricultural bactericides.

Experimental and theoretical investigation of the complexation of 5-methyl-7-isobutyl-1,2,4-triazolo[1,5-a]pyrimidine with platinum(ii) ions

Dichlorido platinum(ii) complexes with 5-methyl-7-isobutyl-1,2,4-triazolo[1,5-a]pyrimidine (ibmtp) were synthesized and characterized by various tools: IR, ¹H, ¹³C, ¹⁵N, ¹⁹⁵Pt NMR and DFT calculations.

Differential cytotoxic activity of a novel palladium-based compound on prostate cell lines, primary prostate epithelial cells and prostate stem cells

The outcome for patients with advanced metastatic and recurrent prostate cancer is still poor. Therefore, new chemotherapeutics are required, especially for killing cancer stem cells that are thought to be responsible for disease recurrence. In this study, we screened the effect of a novel palladium-based anticancer agent (Pd complex) against six different prostate cancer cell lines, and primary cultures from seven Gleason 6/7 prostate cancer, three Gleason 8/9 prostate cancer and four benign prostate hyperplasia patient samples, as well as cancer stem cells selected from primary cultures. MTT and ATP viability assays were used to assess cell growth and flow cytometry to assess cell cycle status. In addition, immunofluorescence was used to detect γH2AX nuclear foci, indicative of DNA damage, and Western blotting to assess the induction of apoptosis and autophagy. The Pd complex showed a powerful growth-inhibitory effect against both cell lines and primary cultures. More importantly, it successfully reduced the viability of cancer stem cells as first reported in this study. The Pd complex induced DNA damage and differentially induced evidence of cell death, as well as autophagy. In conclusion, this novel agent may be promising for use against the bulk of the tumour cell population as well as the prostate cancer stem cells, which are thought to be responsible for the resistance of metastatic prostate cancer to chemotherapy. This study also indicates that the combined use of the Pd complex with an autophagy modulator may be a more promising approach to treat prostate cancer. In addition, the differential effects observed between cell lines and primary cells emphasise the importance of the model used to test novel drugs including its genetic background, and indeed the necessity of using cells cultured from patient samples.

Cancer cell cytotoxicity of cyclometalated compounds obtained with osmium(II) complexes

A library of 29 organoosmium compounds has been built up with known and novel cyclometalated compounds obtained with C-N, N(∧)C(∧)N, and C(∧)N(∧)N ligands. All compounds have been tested for their in vitro cytotoxic properties against A172, a tumor cell line derived from a human glioblastoma, this affording a contrasted picture of the activities of the compounds gathered in this study. Some compounds displayed good to excellent activities, some of them showing IC50 in the nanomolar range. The level of activity was tentatively correlated to several physicochemical properties of the compounds such as their E(0)1/2(Os(III/II)) redox potential and their lipophilicity (log Po/w). A parallel with related ruthenium derivatives was tentatively proposed.

Synthesis of glucopyranosyl Schiff base zinc(II) complexes capable of interacting with mononucleotides, and their DNA-cleavage activities

New glucopyranosyl Schiff base zinc complexes, [Zn(GlcSal)(2) ] (1; GlcSalH=N-(2-deoxy-β-D-glucopyranos-2-yl-salicylaldimine) and [Zn(AcOGlcSal)(2) ] (2; AcOGlcSalH=N-(2-deoxy-β-D-1,3,4,6-tetraacetylglucopyranos-2-yl-salicylaldimine) were synthesized, and characterized by spectral and analytical methods. The interaction between the Zn complexes and mononucleotides was investigated by (1)H-NMR, (31)P-NMR and UV/VIS spectroscopies. Mononucleotides, cytidine 5'-monophosphate (CMP) and uridyl 5'-monophosphate (UMP), interacted with these complexes to form a 1:1 complex with 1 and a 1:2 complex with 2, depending on the presence of the OH group of glucopyranosyl substituents. The DNA-cleavage activities of 1 and 2 were studied using plasmid DNA (pBR322) in a medium of 5 mM Tris·HCl/50 mM NaCl buffer in the presence of H(2)O(2). The DNA-cleavage activity decreased in the order of 2>1>Zn(OAc)(2), indicating the significant promoting effect of the glucopyranosyl Schiff base ligand and the participation of the glucopyranosyl OH groups in the cleavage mechanism. The mechanism of the DNA cleavage by 1 and 2 was investigated by evaluation of the effect of a HO· radical scavenger and a singlet-oxygen ((1)O(2)) quencher under aerobic conditions. The former exhibited little effect, excluding the HO· radical as an active species and supporting the hydrolysis mechanism for the main process of the DNA cleavage. The latter quencher somewhat hindered the cleavage, indicating the partial participation of a (1)O(2) as a competitive active species in the present system.

Organometallic Palladium Complexes with a Water-Soluble Iminophosphorane Ligand as Potential Anticancer Agents

The synthesis and characterization of a new water-soluble iminophosphorane ligand TPA=N-C(O)-2BrC(6)H(4) (C,N-IM; TPA = 1,3,5-triaza-7-phosphaadamantane) 1 is reported. Oxidative addition of 1 to Pd(2)(dba)(3) affords the orthopalladated dimer [Pd(μ-Br){C(6)H(4)(C(O)N=TPA-kC,N)-2}](2) (2) as a mixture of cis and trans isomers (1:1 molar ratio) where the iminophosphorane moeity behaves as a C,N-pincer ligand. By addition of different neutral or monoanionic ligands to 2, the bridging bromide can be cleaved and a variety of hydrophilic or water-soluble mononuclear organometallic palladium(II) complexes of the type [Pd{C(6)H(4)(C(O)N=TPA-kC,N)-2}(L-L)] (L-L = acac (3); S(2)CNMe(2) (4); 4,7-Diphenyl-1,10-phenanthrolinedisulfonic acid disodium salt C(12)H(6)N(2)(C(6)H(4)SO(3)Na)(2) (5)); [Pd{C(6)H(4)(C(O)N=TPA-kC,N)-2}(L)Br] (L = P(mC(6)H(4)SO(3)Na)(3) (6); P(3-Pyridyl)(3) (7)) and, [Pd(C(6)H(4)(C(O)N=TPA)-2}(TPA)(2)Br] (8) are obtained as single isomers. All new complexes were tested as potential anticancer agents and their cytotoxicity properties were evaluated in vitro against human Jurkat-T acute lymphoblastic leukemia cells, normal T-lymphocytes (PBMC) and DU-145 human prostate cancer cells. Compounds [Pd(μ-Br){C(6)H(4)(C(O)N=TPA-kC,N)-2}](2) (2) and [Pd{C(6)H(4)(C(O)N=TPA-kC,N)-2}(acac)] 3 (which has been crystallographically characterized) display the higher cytotoxicity against the above mentioned cancer cell lines while being less toxic to normal T-lymphocytes (peripheral blood mononuclear cells: PBMC). In addition, 3 is very toxic to cisplatin resistant Jurkat shBak indicating a cell death pathway that may be different to that of cisplatin. The interaction of 2 and 3 with plasmid (pBR322) DNA is much weaker than that of cisplatin pointing to an alternative biomolecular target for these cytotoxic compounds. All the compounds show an interaction with human serum albumin (HSA) faster than that of cisplatin.

Platinum(II) complexes with 5,7-disubstituted-1,2,4-triazolo [1,5-a]pyrimidines: spectroscopical characterization and cytotoxic activity in vitro

Complexes of the types: cis-[PtI(2)(dptp)(2)] (1), cis-[PtI(2)(NH(3))(dptp)] (2), trans-[PtI(2)(dptp)(dmso)] (3) and trans-[PtI(2)(dbtp)(dmso)] (4), where dptp=5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine (dptp), dbtp=5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine have been synthesized and characterized by infrared and multinuclear magnetic resonance spectroscopic techniques ((1)H, (13)C, (15)N, (195)Pt). In (195)Pt NMR, the cis-diiodo complexes were observed between -2601 ppm and -3261 ppm, while the trans coordination compounds were found at higher field (ca. -4389 ppm). In all cases significant (15)N NMR shielding (92-95 ppm) were observed for N(3) atom indicating this nitrogen atom as a coordination site. The cis complexes have been assayed for antitumor activity in vitro against two human cell lines: A549 (non-small cell lung carcinoma) and T47D (breast cancer). The results indicate a moderate antiproliferative activity of (2) against human cancer lines.

Cell death-inducing effect of novel palladium(II) and platinum(II) complexes on non-small cell lung cancer cells in vitro

PURPOSE

Treatment for lung cancer is still far from satisfying rates. Therefore, there is a need for novel anticancer agents. For this purpose, novel platinum and palladium complexes {[Pd(sac)(terpy)](sac)·4H(2)O (Complex 1), [Pt(sac)(terpy)](sac)·5H(2)O (Complex 2), [PdCl(terpy)](sac)·2H(2)O (Complex 3), [PtCl(terpy)](sac)·2H(2)O (Complex 4)} have been tested against three different non-small cell lung cancer cell lines (A549, H1299, PC-3).

METHODS

Growth-inhibiting effects have been tested by the MTT and ATP viability assays. Apoptosis has been detected by the caspase-cleaved cytokeratin 18 (M30-antigen) assay. Necrosis has been detected by staining the cells with fluorescent dyes. Mitotic index has been calculated by counting the mitotic figures after staining with hematoxylin.

RESULTS

The complex 3 exhibited significant anti-growth effects, and its anti-growth effect was more powerful than that of cisplatin that is a standard chemotherapeutic agent for this type of cancer. The complexes did not induce apoptosis, while necrosis clearly took place.

CONCLUSIONS

Novel Pd(II) complex ([PdCl(terpy)](sac)·2H(2)O) seems to represent a potentially active drug against non-small cell lung cancer cell lines, and further studies in vivo are warranted.

Platinum(IV) coordination compounds containing 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one as nonleaving ligand. Molecular and cytotoxicity in vitro characterization

Novel platinum(IV) coordination compounds with 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO): cis-trans-[PtCl(2)(OH)(2)(NH(3))(HmtpO)] (1), cis-trans-[PtCl(5)(HmtpO)][(CH(3))(2)NH(2)] (2) have been prepared and structurally characterized by spectroscopic methods ((1)H, IR and X-ray crystallography (2)). The X-ray results indicate that the local geometry around the platinum(IV) centre approximates a typical octahedral arrangement with nitrogen atom N3 of the HmtpO and three chloride atoms in equatorial positions. The remaining two axial positions are occupied by two chlorides. The preliminary assessment of antitumor properties of (1) was performed as an in vitro antiproliferative activity against HL-60 human acute promyelocytic leukemia and HCV29T bladder cancer. The cis-trans-[PtCl(2)(OH)(2)(NH(3))(HmtpO)] (1) exhibits higher cytotoxic activity against HL-60 (IC(50)=6.4 μM) than cisplatin.

In vitro and in vivo antiparasital activity against Trypanosoma cruzi of three novel 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one-based complexes

Conventional reactions of the versatile multidentate ligand 5-methyl-1,2,4-triazolo[1,5-a] pyrimidin-7(4H)-one (HmtpO) with metallic(II) perchlorate salts lead to three novel multidimensional complexes [Cu(HmtpO)(2)(H(2)O)(3)](ClO(4))(2)·H(2)O (1), {[Cu(HmtpO)(2)(H(2)O)(2)](ClO(4))(2) ·2HmtpO}(n) (2) and {[Co(HmtpO)(H(2)O)(3)](ClO(4))(2)·2H(2)O}(n) (3). We have tested the antiparasital activity in vitro and in vivo of the three new complexes against Trypanosoma cruzi showing very promising results and overcoming clearly the reference drug commonly used for the Chagas disease treatment, benznidazole.

Biological activity of three novel complexes with the ligand 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one against Leishmania spp

OBJECTIVES

We report on new 1,2,4-triazolo[1,5-a]pyrimidine complexes that have been developed and examined for both antiproliferative in vitro activity against Leishmania infantum and Leishmania braziliensis, and report their possible mechanism of action on L. infantum and L. braziliensis.

RESULTS

Antileishmanial effects are described for newly synthesized Cu(II) and Co(II) complexes containing 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO) as a ligand. These complexes display a wide structural diversity: (i) mononuclear unit, [Cu(HmtpO)2(H2O)3](ClO4)2·H2O (1); (ii) two-dimensional framework, {[Cu(HmtpO)2(H2O)2](ClO4)(2)·2HmtpO}n (2); and (iii) chains, {[Co(HmtpO)(H2O)3](ClO4)(2)·2H2O}n (3). Compounds 1 and 2 appeared to be the most active against L. infantum (IC50 20.0 and 24.4 μM, respectively), and compounds 1 and 3 the most active against L. braziliensis (IC50 22.1 and 23.5 μM, respectively), with IC50s similar to those of the reference drug, glucantime (18.0 μM for L. infantum and 25.6 μM for L. braziliensis). These compounds were not toxic towards J774.2 macrophages. IC25 decreased infection capacity and severely reduced the multiplication of intracellular amastigotes, following the trend 1>3>2 for L. infantum and 3>1>2 for L. braziliensis. These complexes had an effect on the energy metabolism of the parasites at the level of the NAD+/NADH balance and the organelle membranes, causing their degradation and cell death.

CONCLUSIONS

Cellular proliferation, metabolic and ultrastructural studies showed that the compounds 2>1>3 were highly active against L. infantum and L. braziliensis.