Palladium(II) salt and complexes of spermidine with a six-member chelate ring. Synthesis, characterization, and initial DNA-binding and antitumor studies

Vibrational microspectroscopy as a tool to unveil new chemotherapeutic strategies against osteosarcoma

Over the years, osteosarcoma therapy has had a significative improvement with the use of a multidrug regime strategy, increasing the survival rates from less than 20 % to circa 70 %. Different types of development of new antineoplastic agents are critical to achieve irreversible damage to cancer cells, while preserving the integrity of their healthy counterparts. In the present study, complexes with two and three Pd(II) centres linked by the biogenic polyamines: spermine (Pd2SpmCl4) and spermidine (Pd3Spd2Cl6) were tested against non-malignant (osteoblasts, HOb) and cancer (osteosarcoma, MG-63) human cell lines. Either alone or in combination according to the EURAMOS-1 protocol, they were used versus cisplatin as a drug reference. By evaluating the cytotoxic effects of both therapeutic approaches (single and drug combination) in HOb and MG-63 cell lines, the selective anti-tumoral potential is assessed. To understand the different treatments at a molecular level, Synchrotron Radiation Fourier Transform Infrared and Raman microspectroscopies were applied. Principal component analysis and hierarchical cluster analysis are applied to the vibrational data, revealing the major metabolic changes caused by each drug, which were found to rely on DNA, lipids, and proteins, acting as biomarkers of drug-to-cell impact. The main changes were observed for the B-DNA native conformation to either Z-DNA (higher in the presence of polynuclear complexes) or A-DNA (preferably after cisplatin exposure). Additionally, a higher effect upon variation in proteins content was detected in drug combination when compared to single drug administration proving the efficacy of the EURAMOS-1 protocol with the new drugs tested.

Pd(II) and Pt(II) Trinuclear Chelates with Spermidine: Selective Anticancer Activity towards TNBC-Sensitive and -Resistant to Cisplatin

Triple-negative breast cancer (TNBC) is one of the most aggressive forms of breast cancer and constitutes 10-20% of all breast cancer cases. Even though platinum-based drugs such as cisplatin and carboplatin are effective in TNBC patients, their toxicity and development of cancer drug resistance often hamper their clinical use. Hence, novel drug entities with improved tolerability and selectivity profiles, as well as the ability to surpass resistance, are needed. The current study focuses on Pd(II) and Pt(II) trinuclear chelates with spermidine (Pd3Spd2 and Pt3Spd2) for evaluating their antineoplastic activity having been assessed towards (i) cisplatin-resistant TNBC cells (MDA-MB-231/R), (ii) cisplatin-sensitive TNBC cells (MDA-MB-231) and (iii) non-cancerous human breast cells (MCF-12A, to assess the cancer selectivity/selectivity index). Additionally, the complexes' ability to overcome acquired resistance (resistance index) was determined. This study revealed that Pd3Spd2 activity greatly exceeds that displayed by its Pt analog. In addition, Pd3Spd2 evidenced a similar antiproliferative activity in both sensitive and resistant TNBC cells (IC50 values 4.65-8.99 µM and 9.24-13.34 µM, respectively), with a resistance index lower than 2.3. Moreover, this Pd compound showed a promising selectivity index ratio: >6.28 for MDA-MB-231 cells and >4.59 for MDA-MB-231/R cells. Altogether, the data presently gathered reveal Pd3Spd2 as a new, promising metal-based anticancer agent, which should be further explored for the treatment of TNBC and its cisplatin-resistant forms.

Impact of the Pd2Spm (Spermine) Complex on the Metabolism of Triple-Negative Breast Cancer Tumors of a Xenograft Mouse Model

The interest in palladium(II) compounds as potential new anticancer drugs has increased in recent years, due to their high toxicity and acquired resistance to platinum(II)-derived agents, namely cisplatin. In fact, palladium complexes with biogenic polyamines (e.g., spermine, Pd₂Spm) have been known to display favorable antineoplastic properties against distinct human breast cancer cell lines. This study describes the in vivo response of triple-negative breast cancer (TNBC) tumors to the Pd₂Spm complex or to cisplatin (reference drug), compared to tumors in vehicle-treated mice. Both polar and lipophilic extracts of tumors, excised from a MDA-MB-231 cell-derived xenograft mouse model, were characterized through nuclear magnetic resonance (NMR) metabolomics. Interestingly, the results show that polar and lipophilic metabolomes clearly exhibit distinct responses for each drug, with polar metabolites showing a stronger impact of the Pd(II)-complex compared to cisplatin, whereas neither drug was observed to significantly affect tumor lipophilic metabolism. Compared to cisplatin, exposure to Pd₂Spm triggered a higher number of, and more marked, variations in some amino acids, nucleotides and derivatives, membrane precursors (choline and phosphoethanolamine), dimethylamine, fumarate and guanidine acetate, a signature that may be relatable to the cytotoxicity and/or mechanism of action of the palladium complex. Putative explanatory biochemical hypotheses are advanced on the role of the new Pd₂Spm complex in TNBC metabolism.

Anticancer activity of palladium-based complexes against triple-negative breast cancer

Treatment of triple-negative breast carcinoma (TNBC) remains an unmet medical need with no targeted therapy available to date. Accounting for 10-30% of all human breast cancer tumors, this mammary carcinoma subtype has a particularly poor prognosis owing to its high metastatic potential, aggressive biology and limited pharmacological treatment options. Platinum chemotherapeutics are the mainstay therapy in patients with TNBC but their clinical use is limited by severe toxicity and acquired resistance. Palladium-based complexes are appealing alternative metal-based drugs because of significant similarities regarding structure and coordination chemistry with the platinum agents. This review summarizes the knowledge gathered so far on 121 Pd(II) complexes, emphasizing their anticancer activity and putative pharmacological targets toward TNBC.

Interactions of diamines with adenosine-5'-triphosphate (ATP) in the systems including copper(II) ions

Interactions were studied in the systems ATP/tn and ATP/Put (tn=1,3-diaminopropane, Put=putrescine) whereas the complexation reactions in ternary systems Cu(II)/ATP/tn and Cu(II)/ATP/Put. Results of the potentiometric and spectroscopic studies evidenced the formation of adducts of the type (ATP)H_x(PA), where PA=diamine. The thermodynamic stability of the complexes and the mode of interactions were determined. On the basis of analysis of changes in the positions of NMR signals, in the pH range of (ATP)H₃(Put) formation, the preferred centres of the interaction between ATP and Put are the endocyclic nitrogen atoms from the nucleotide. On the other hand, the shorter diamine tn in the entire pH range reacts with the phosphate groups from ATP. The positive centres of noncovalent interactions are the protonated NH_x⁺ groups from amines. In both complexes Cu(ATP)H₂(tn) and Cu(ATP)H₃(Put) formed in ternary systems at pH<6.5, the amines are in the outer sphere of coordination with the noncovalent interaction with anchoring Cu(ATP). Only the phosphate groups from the nucleotide take part in metalation. At higher pH in the range of Cu(ATP)(PA) complex formation, significant differences in the reactions of the two amines appear. The shorter one (tn) binds Cu(II) ions with two nitrogen atoms, while putrescine coordinates in the monofunctional mode, which is undoubtedly related to the differences in lengths of methylene chain. This explains the considerable differences in the stability of Cu(ATP)(tn) and Cu(ATP)(Put). In both complexes the nucleotide is coordinated through phosphate groups.

SYNOPSIS

As a result of noncovalent interactions ATP forms molecular complexes with 1,3-diaminopropane and 1,4-diaminobutane (putrescine). Significant differences in the mode of interactions between the two diamines were observed in ATP/diamine binary systems and in ternary systems Cu(II)/ATP/diamine, at high pH.

Platinum and Palladium Polyamine Complexes as Anticancer Agents: The Structural Factor

Since the introduction of cisplatin to oncology in 1978, Pt(II) and Pd(II) compounds have been intensively studied with a view to develop the improved anticancer agents. Polynuclear polyamine complexes, in particular, have attracted special attention, since they were found to yield DNA adducts not available to conventional drugs (through long-distance intra- and interstrand cross-links) and to often circumvent acquired cisplatin resistance. Moreover, the cytotoxic potency of these polyamine-bridged chelates is strictly regulated by their structural characteristics, which renders this series of compounds worth investigating and their synthesis being carefully tailored in order to develop third-generation drugs coupling an increased spectrum of activity to a lower toxicity. The present paper addresses the latest developments in the design of novel antitumor agents based on platinum and palladium, particularly polynuclear chelates with variable length aliphatic polyamines as bridging ligands, highlighting the close relationship between their structural preferences and cytotoxic ability. In particular, studies by vibrational spectroscopy techniques are emphasised, allowing to elucidate the structure-activity relationships (SARs) ruling anticancer activity.

DNA interaction with palladium chelates of biogenic polyamines using atomic force microscopy and voltammetric characterization

The interaction of double-stranded DNA with two polynuclear Pd(II) chelates with the biogenic polyamines spermidine (Spd) and spermine (Spm), Pd(II)-Spd and Pd(II)-Spm, as well as with the free ligands Spd and Spm, was studied using atomic force microscopy (AFM) at a highly oriented pyrolytic graphite (HOPG) surface, voltammetry at a glassy carbon (GC) electrode, and gel electrophoresis. The AFM and voltammetric results showed that the interaction of Spd and Spm with DNA occurred even for a low concentration of polyamines and caused no oxidative damage to DNA. The Pd(II)-Spd and Pd(II)-Spm complexes were found to induce greater morphological changes in the dsDNA conformation, when compared with their ligands. The interaction was specific, inducing distortion and local denaturation of the B-DNA structure with release of some guanine bases. The DNA strands partially opened give rise to palladium intra- and interstrand cross-links, leading to the formation of DNA adducts and aggregates, particularly in the case of the Pd(II)-Spd complex.

Polynuclear palladium complexes with biogenic polyamines: AFM and voltammetric characterization

Polynuclear Pd(II) complexes with biogenic polyamines present great potential clinical importance, due to their antiproliferative and cytotoxic activity coupled to less severe side-effects. The adsorption process and the redox behaviour of two polynuclear palladium chelates with spermine (Spm) and spermidine (Spd), Pd(II)-Spm and Pd(II)-Spd, as well as of their ligands Spm and Spd, were studied using atomic force microscopy (AFM) and voltammetry at highly oriented pyrolytic graphite and glassy carbon electrodes. AFM revealed different adsorption patterns and degree of surface coverage, correlated with the chelate structure, concentration of the solution, applied potential and voltammetric behaviour of the Spm, Spd, Pd(II)-Spm and Pd(II)-Spd systems. The voltammetric study of Spm and Spd showed that these biogenic polyamines undergo an irreversible and pH-dependent oxidation. In acid medium the polyamines are fully protonated, rendering their oxidation more difficult. With increasing pH the oxidation potential for both Spm and Spd is shifted to less positive values, indicating a greater ease of oxidation in alkaline medium. The Pd(II)-Spm and Pd(II)-Spd complexes dissociate at high negative or high positive potentials. The application of a positive potential induced the oxidation of these Pd complexes and the formation of mixed layers of palladium oxides, Spm/Spd and Pd(II)-Spm/Pd(II)-Spd.

Cytotoxic activity of metal complexes of biogenic polyamines: polynuclear platinum(II) chelates

Several polynuclear Pt(II) chelates with biogenic polyamines were synthesized and screened for their potential antiproliferative and cytotoxic activity in different human cancer cell lines. To gather information regarding the structure-activity relationships underlying their biological activity, the complexes studied were designed to differ in geometrical parameters such as the nature of the ligand and the number and chemical environment of the metal centers. Distinct effects were found for different cell lines and different structural characteristics of the complexes; chelates II, III, and IV displayed specificity toward the HeLa and HSC-3 epithelial-type cells, while V, VI, and VII were clearly more effective against the THP-1, MOLT-3, and CCRF-CEM leukemia cell lines. The toxicity of these Pt(II) complexes on noncancer cells was, in all cases, found to be reversed upon drug removal.

Cytotoxic effects of metal complexes of biogenic polyamines. I. Platinum(II) spermidine compounds: prediction of their antitumour activity

Cytotoxicity and cell growth inhibition studies were performed for three distinct polynuclear platinum(II) complexes of spermidine, which showed to have significant cytotoxic and antiproliferative properties on the HeLa cancer cell line. The chemical environment of the metal centres in the drugs, as well as the coordination pattern of the ligand, were found to be strongly determinant of their cytotoxic ability. In the light of the results gathered, the most effective anticancer compound among the ones tested (IC50=5 microM) was found to be the one displaying three difunctional (PtCl2N2) moieties ((PtCl2)3(spd)2). Both the cytotoxic activity and the antiproliferative properties of the complexes studied showed to be irreversible for all the concentrations tested.

Ethylenediamine-palladium(II) complexes with pyridine and its derivatives: synthesis, molecular structure and initial antitumor studies

The synthesis of four mononuclear palladium complexes of general formula [Pd(en)Cl(L)]NO3 (en = ethylenediamine; L = pyridine (I), 4-methylpyridine (II), 4-hydroxypyridine (III) or 4-aminopyridine (IV) has been achieved. The structure of these compounds was studied by elemental analysis, IR, far-IR and 1H NMR; complex I was analyzed by X-ray diffraction. The crystal of [Pd(en)(pyridine)Cl]NO3 is monoclinic, space group P21/c (a = 7.990(2), b = 16.058(3), c = 9.846(2) A, beta = 103.81(3) degrees, Z = 4, R = 0.067, Rw = 0.066). The Pd(II) atom exhibits an approximately square planar coordination with bond lengths in the range 2.017-2.042 A for Pd-N and 2.320 A for Pd-Cl. In order to determine the donor strength of the aromatic pyridine ligands, the stability constants of binary complex ML2+ (M = [Pd(en) (H2O)2]2+; L = pyridine, 4-Me-pyridine, 4-OH-pyridine and 4-NH2-pyridine) were determined by potentiometric pH titration in aqueous solution (T = 25 degrees C, I = 0.1 mol l-1 NaNO3). The results show that the stability constants of the binary complexes systematically increase with increasing pKa of the pyridines. The above four palladium complexes, [Pt(en)(pyridine)Cl]NO3 and cis-diamminedichloroplatinum (II) (cis-DDP) were assayed for cytotoxicity in vitro against the human leukemia cell line HL-60, and compounds I, II, III and cis-DDP show significant cytotoxic activity against HL-60.

Dinuclear palladium(II) complexes containing two monofunctional [Pd(en)(pyridine)Cl]+ units bridged by Se or S. Synthesis, characterization, cytotoxicity and kinetic studies of DNA-binding

Two novel dinuclear palladium(II) complexes, ¿[Pd(en)Cl]2(bpse)¿(NO3)2 (1) and ¿[Pd(en)Cl]2 (bpsu)¿(NO3)2 (2), (where en is ethylenediamine; bpse is bis(3-methyl-4-pyridyl) selenide; bpsu is bis(3-methyl-4-pyridyl) sulfide) have been synthesized. The complexes have been characterized by elemental analysis, IR, 1H NMR, and 13C NMR. They have been assayed for antitumor activity in vitro against the mice leukemia L1210 and the human coloadenocarcinoma HCT8 cell lines. The results show that compound 1 has a lower I.D.50 value against the two cancer cell lines as compared to compound 2; the compounds also shows a lower I.D.50 value than cisplatin against the HCT8 cell line, but a higher I.D.50 value than cisplatin against the L1210 cell line. Binding studies indicate that compound 1 possibly interacts with DNA by a nonintercalative mode. Kinetics of binding of the two compounds to DNA are firstly studied using ethidium bromide as a fluorescence probe with stopped-flow spectrophotometer under pseudo-first-order condition. The stronger binding of two steps in the process of the compounds interacting with DNA are observed, and the Kobs and Ea of binding of the two steps (where Kobs is the observed pseudo-first-order rate constant, Ea is the observed energy of activation) are obtained.

cis-Dichloro(alpha,omega-diamino carboxylate ethyl ester)palladium(II) as Palladium(II) versus Platinum(II) Model Anticancer Drugs: Synthesis, Solution Equilibria of Their Aqua, Hydroxo, and/or Chloro Species, and in Vitro/in Vivo DNA-Binding Properties

cis-Dichloro(d,l-2,3-diaminopropionate ethyl ester)palladium(II), cis-[Pd(Etdap)Cl(2)] (I), and cis-dichloro(d,l-2,4-diaminobutyrate ethyl ester)palladium(II), cis-[Pd(Etdab)Cl(2)] (II), were synthesized and characterized by elemental analysis, IR spectroscopy, and TG-DTA thermal analysis. The equilibrium model and log beta(pqr) constants of hydrolytic species of I and II were also investigated by potentiometric methods (I = 0.15 M (NaClO(4)) and 37 degrees C). Aqueous solutions of cis-[Pd(Etdaa)(H(2)O)(2)](ClO(4))(2) (Etdaa = Etdap (III) or Etdab (IV)) were prepared by stoichiometric reaction of I or II with AgClO(4). Thus, log beta(pqr) of the corresponding cis-aquahydroxo (pqr = 1,0,-1) and di(&mgr;-hydroxo) (pqr = 2,0,-2) species were obtained from E(H(+)) data of alkalimetric titrations of solutions of III or IV. Such constants were then used as fixed values to obtain log beta(pqr)() of chloro-containing species (cis-dichloro (1,2,0), cis-chloroaqua (1,1,0), and cis-chlorohydroxo (1,1,-1)) from E(H(+)) and E(Cl(-)) data pairs simultaneously obtained by titration of solutions of III or IV with NaOH and NaCl. All log beta(pqr) were fitted by the SUPERQUAD program. Appropriate log beta(pqr)() sets give good simulations of experimental titration curves and several species distribution diagrams. In addition the interaction of I and/or II with DNA in vitro and in vivo was studied by various methods. UV spectral data and melting and renaturation curves indicate that both compounds destabilize the DNA helicoidal structure. Compound II disrupts in vivo the structure and transcription process of polytene chromosomes of Drosophila hydei.

Palladium or platinum exacerbates hydroxyl radical mediated DNA damage

Strand breakage of supercoiled pBR322 DNA by a Fenton system is increased in the presence of palladium or platinum (Pt) ions. Neither Pd nor Pt ions can substitute for iron in the Fenton system. We have obtained several lines of evidence that Pd and Pt ions in the presence of a Fenton system can augment the production of OH., as monitored by a spectrophotometric method quantifying hydroxylated salicylate or by a fluorometric method quantifying catechol production. Furthermore, the promoting effect of both metal ions on OH. production was substantiated by the identification of multiple hydroxylated products of salicylate [2,3-dihydroxybenzoate (A), 2,5-dihydroxybenzoate (B), and catechol (C)] using HPLC. The concentrations of A, B, and C produced in the control were 4.5, 8.0, and 2.0 microM, respectively; whereas, their respective concentrations increased to 23.6, 42.0 and 10.0 microM with the addition of Pd ions. The observed phenomenon was further confirmed by the identification of HO-DMPO spin adducts using ESR spectroscopy. Taken together, our data suggest that the mechanism of Pd or Pt ion-mediated exacerbation of DNA damage by a Fenton system is due to the promotion of OH. production by these metal ions.

Cytotoxicity, DNA binding, and reactivity against nucleosides of platinum (II) and (IV) spermine compounds

We describe the synthesis and characterization of a [sperH4][PtCl4]2 salt and of five binuclear platinum (II) and (IV)-spermine compounds of formula [(PtCl2)2(sper)], cis-[(Pt(CH2(COO)2)2(sper)], cis-[(PtCBDCA)2(sper)], (CBDCA = 1,1'-cyclobutanedicarboxylate), cis-trans-cis[(PtCl2(OH)2)2(sper)], and cis-[(PtCl4)2(sper)], respectively. The 1H and 195Pt-NMR analysis of the complexes formed between these compounds and nucleosides indicated that the Pt centers show preferential binding to the N(7) of guanosine and adenosine residues, also being capable of forming bridged structures through the N(7) and N(1). The synthesized Pt-spermine compounds do not form complexes with cytidine residues at 37 degrees C. The circular dichroism, melting, and electrophoretic data of the compounds-DNA complexes show that the Pt(IV)-spermine complexes induce lower DNA conformational changes than their Pt(II) analogs. These results correlate with the IC50 values obtained against MDA-MB 468 and HL-60 human cancer cells which are higher than those of cis-DDP. The [sperH4][PtCl4]2 salt produces a high level of DNA modification and exhibits IC50 values lower than those of cis-DDP.

Cis-Dichloro(diaminosuccinate diethyl ester)palladium (II) as Pd(II)/Pt(II) model compound for DNA-binding and antitumor properties: solution equilibria of their aqua-, hydroxo-, and/or chloro-species

Cis-Dichloro(diaminosuccinic acid)palladium(II), cis-[Pd(H2dasa)Cl2] (I), or cis-dichloro(diaminosuccinate diethyl ester)palladium(II), cis-[Pd(Et2dasa)Cl2] (II) reacts with two equivalents of AgClO4 to give insoluble Pd(dasa) or an aqueous solution of [Pd(Et2dasa) (H2O)2](ClO4)2, respectively. Three solutions of this salt were titrated with NaOH (I = NaClO4 (0.15M),37 degrees C), and 133 E(H+) data (3.5 < or = pH < or = 7) were treated by SUPERQUAD to fit log beta pqr of cis-aquahydroxo-(pqr = 10-1, -5.25(3)) and di-mu-hydroxo-species (20-2, -6.55(1)). At pH > 7 the ester hydrolysis prevents the calculation of log beta 10-2 for the cis-dihydroxo-complex. Another three solutions of such salt were titrated (I = 0.15M (NaClO4), 37 degrees C) with NaOH and NaCl simultaneously using two potentiometric systems (which measure H+ or Cl-). From 147 E(H+) and E(Cl-) data pairs and the above fixed log beta pqr, SUPERQUAD calculations yield log beta pqr for cis-chloro-aqua (pqr = 110, 3.65(1)), cis-chloro-hydroxo (11-1, -2.68 (4)), and cis-dichloro-species (120, 5.86(3)). Simulated and experimental titrations are in good agreement. Circular dichroism spectra of native DNA and drug:DNA complexes suggest that cis-Pd(H2dasa) and cis-Pd(Et2dasa) chelate moieties induce an opening and rotation of the stacked bases in the double helix. This finding is explained by the abundance of each one and of the total neutral and charged species of II in the tested CD solution.

Synthesis, crystal structure, and biological activity of a Pt-dipyridamole salt

In the present paper we present data on the synthesis, crystal structure and biological activity of bis(dipyridamole) tetrachloroplatinate(II).dipyridamole.dihydrate, [dpmH]2 PtCl4.dpm.2H2O. The crystals are Triclinic P1 with a = 11.490(2) A, b = 13.630(2) A, c = 15.81(1) A, a = 100.97(2) degrees, beta = 100.89(3) degrees, gamma = 112.35(1) degrees, Z = 1, M = 1885.9, Dx = 1.46 g/cm3, MoK alpha (lambda = 0.71069 A), mu = 0.0184 mm-1, R = 4.4%, Rw = 5.0%, 3231 (1 > 2 sigma (I)). The structure is stabilized by a hydrogen-bonding network. It was observed that although dpm alone is not able to alter the electrophoretic mobility of pUC8 DNA forms, the synthesized Pt-dpm compound substantially modifies the DNA conformation since it significantly alters the electrophoretic mobility of nicked and closed circular forms of pUC8 DNA. However, the alteration in mobility of pUC8 DNA induced by this compound upon binding is lower than that induced by cis-DDP. The analysis of the antiproliferative activity of the Pt-dpm salt against MDA-MB 468 (breast carcinoma) and HL-60 (leukemia) human cancer cells showed that this compound has ID50 values of 0.87 microM and 0.65 microM, respectively. Interestingly, it was found out that although the dpm molecule does not present any significant antiproliferative activity, the ID50 values of Pt-dpm are about 3-fold and 7-fold lower than those of cis-DDP and K2PtCl4, respectively. Altogether the biological data suggest that in Pt-dpm a synergic effect between cation and anion is produced.

cis-dichloro-palladium(II) complexes with diaminosuccinic acid and its diethyl ester: synthesis, molecular structure, and preliminary DNA-binding and antitumor studies

The reactions of K2PdCl4 with meso-diaminosuccinic acid (H2dasa) in 0.1 M HCl or its diethyl ester dihydrochloride Et2dasa.2HCl in neutralized aqueous solution yield cis-[Pd(H2dasa)Cl2](I) and cis-[Pd(Et2dasa)Cl2](II), respectively. These products were characterized by elemental analysis, IR spectroscopy, and TG-DTA thermal analysis. The crystal of II is monoclinic, space group C2/c (a = 14.292(5), b = 14.636(5), c = 13.435(5) A, beta = 98.08(2) degrees, Z = 8, R = 0.041 and wR = 0.06). The Pd(II) atom exhibits a roughly square planar coordination with two Pd-N bonds (Et2dasa) (2.014(2) and 2.049(7) A) and two cis-imposed Pd-Cl bonds (2.294(2) and 2.303(2) A). Compound I reacts with 2,2'-bipyridine in neutral aqueous solution to give [Pd(2,2'-bipy)(dasa)].3H2O(III) in a process of cis-chloride substitution by 2,2'-bipy as a model N-heterocyclic chelating entity. The molecular and crystal structure of III is also reported. It was observed that both cis-dichloro-Pd(II) complexes having Pd(H2dasa) (acidic) and Pd-(Et2dasa)(esterified) chelate entities induce conformational changes in the covalent closed circular (ccc) form of pUC8 plasmid. Both compounds were assayed for antitumor activity in vitro against MDA-MB 468 and HL-60 human cancer cell lines. The results show that compounds I and II have values of ID50 lower than those of K2PdCl4, and also lower than those of diaminoacid ligands (meso-diaminosuccinic acid and meso-diaminosuccinate diethyl ester). Thus it is likely that the imposed cis-coordination of the chelating H2dasa or Et2dasa to the Pd(II) center increases the biological activity of these palladium(II) complexes.

Platinum (II) and (IV) spermidine complexes. Synthesis, characterization, and biological studies

By reaction of K2PtCl4 with spermidine we have synthesized two tris-platinum covalent compounds of formula (PtI2)3(sper)2 and (PtCl2)3(sper)2, one ionic compound of formula (sperH3)2(PtCl4)3, and another one of a covalent nature of formula (PtCl2sperH)2 (PtCl4) having a partially protonated spermidine residue. Treatment of the tris-platinum compounds with hydrogen peroxide and hydrochloric acid led to the production of two compounds of formula cis-trans-cis-(PtIVCl2(OH)2)3(sper)2 and cis-(PtIVCl4)3(sper)2, respectively. All of them have been characterized by IR and 1H MNR spectroscopy and tested for their ability to interact with pUC8 plasmid DNA by the use of UV, CD, and electrophoretic techniques. The results suggest that all of these compounds modify the secondary structure of the double helix. We observed that the alteration in electrophoretic mobility of nicked and closed circular forms of DNA induced by the Pt(II) complexes is higher than that induced by the Pt(IV) complexes. The synthesized compounds were also assayed for antitumor activity in vitro against breast (MDA-MB468) and leukemia (HL-60) tumor cells. Only three of these complexes may be regarded as potential antitumor agents, since their ID50 values are lower than 10 micrograms/ml.

Palladium (II) compounds of putrescine and spermine. Synthesis, characterization, and DNA-binding and antitumor properties

The reaction of putrescine (Put) with K2PdCl4 and PdCl2 resulted in the synthesis of compounds of formula [PutH2][PdCl4] and [Pd2Cl4(Put)2]. Compounds of formula [PdCl2(SpermH2)][PdCl4] and [Pd2Cl4(Sperm)] have been also synthesized by reaction of spermine (Sperm) with K2PdCl4. The structure of all these compounds has been analyzed by IR and 1H NMR. UV and CD spectroscopic data have shown that all the Pd(II)-polyamine compounds synthesized induce conformational changes in the circular forms of plasmid DNA. Determinations by electrophoresis in agarose gels of the mobility of the DNA in drug:DNA complexes indicated that only the Pd(II)-putrescine compounds have the ability to induce significant conformational changes in the covalently closed circular (ccc) form of the pUC8 plasmid DNA. The Pd(II)-putrescine and Pd(II)-spermine compounds were also assayed for in vitro antiproliferative activity against MDA-MB 468 and HL-60 human cancer cells. The results suggest that the putrescine complexes may be regarded as potential antitumor agents because the ID50 value of all of the Pd(II)-putrescine complexes is twofold lower than the ID50 of cis-DDP. Our data also show that, on the other hand, the Pd(II)-spermine compounds have low antiproliferative activity.

The binding of a complex cobalt ruthenium polyamine by deoxyribonucleic acid and a lipopolysaccharide: a model for a novel class of drugs

In this paper we discuss the following: 1. Synthesis of [Co(H3CsarNHCH2pyRu(NH3)5)] (PF6)5, (CoRu). 2. Interaction of CoRu with calf thymus DNA and with lipopolysaccharide from Escherichia coli C (LPS) has been estimated using the absorption of the complex at 242 and 420 nm. 3. DNA and LPS increase the rate of fall of absorption at 420 nm due to autooxidation of the complex. 4. The fall in absorption of CoRu(II) at 420 nm can be used to give an approximate measure of binding to DNA and to LPS. 5. Both macromolecules are aggregated by CoRu at high concentrations and the cation and macromolecule complex can be removed by low speed centrifugation. 6. The DNA-CoRu complex can also be removed by high speed centrifugation when the cation concentration is too low to cause aggregation (20 microM CoRu/155 microM DNA-P). Absorption of redissolved complex at 420 nm is restored by reduction with ascorbic acid. 7. At saturation the ratio of mole CoRu bound/mole DNA-P is 0.16.