Metal compounds in cancer chemotherapy

Unprecedented chemical transformation of semicarbazones mediated by Wilkinson's catalyst

para-Nitrobenzaldehyde semicarbazone undergoes an unusual chemical transformation upon reaction with [Rh(PPh(3))(3)Cl] in the presence of trialkyl and dialkylamines (NR(2)R'; R = Et,(i)Pr, (n)Bu; R' = H or R' = R) via dissociation of the C-NH(2) bond and formation of a new C-NR(2) bond (where the NR(2) fragment is provided by the amine). The transformed semicarbazone ligand binds to rhodium as a dianionic C,N,O-donor to afford complexes of type [Rh(PPh(3))(2)(CNO-NR(2))Cl] (CNO-NR(2) = the coordinated semicarbazone ligand). Another group of semicarbazones (viz. salicylaldehyde semicarbazone, 2-hydroxyacetophenone semicarbazone, and 2-hydroxynaphthaldehyde semicarbazone) has also been observed to undergo a similar chemical transformation upon reaction with [Rh(PPh(3))(3)Cl] under similar experimental conditions as before, and these transformed semicarbazones bind to rhodium as dianionic O,N,O-donors affording complexes of the type [Rh(PPh(3))(2)(ONO(n)-NR(2))Cl] (ONO(n)-NR(2) = the coordinated semicarbazone ligand; n = 1-3). The structure of the [Rh(PPh(3))(2)(CNO-NEt(2))Cl] and [Rh(PPh(3))(2)(ONO(2)-NR(2))Cl] complexes has been determined. All the complexes show characteristic (1)H NMR signals. They also show intense absorptions in the visible and ultraviolet region. Cyclic voltammetry on the complexes shows an oxidative response within 0.52-0.97 V versus SCE and a reductive response within -1.00 to -1.27 V versus SCE, where both the responses are believed to be centered on the semicarbazone ligand.

Unprecedented chemical transformation of benzaldehyde semicarbazone mediated by osmium

para-Nitrobenzaldehyde semicarbazone (O(2)N(para)-C(6)H(4)C(H)=N-NH-CO-NH(2)) undergoes unprecedented chemical transformation during its reaction with [Os(PPh(3))(2)(CO)(2)(HCOO)(2)] in different alcoholic (R'OH, R' = CH(2)CH(2)OCH(3), CH(2)CH(3), CH(2)CH(2)CH(3), and CH(2)CH(2)CH(2)CH(3)) solvents whereby the NH(2) group of the semicarbazone ligand is displaced by a OR' group provided by the solvents. The transformed semicarbazone ligand binds to osmium as a bidentate N,O-donor forming five-membered chelate ring to afford complexes of type [Os(PPh(3))(2)(CO)(H)(L-OR')], where L-OR' refers to the transformed semicarbazone ligand. Structure of the [Os(PPh(3))(2)(CO)(H)(L-OCH(2)CH(2)OCH(3))] complex has been determined by X-ray crystallography. All the [Os(PPh(3))(2)(CO)(H)(L-OR')] complexes are diamagnetic and show characteristic (1)H NMR signals. They also show intense absorptions in the visible and ultraviolet region. Cyclic voltammetry on the complexes shows an irreversible oxidative response within 0.69-0.88 V versus SCE.

Lanthanum(IlI) PVC membrane electrodes based on 1,3,5-trithiacyclohexane

Novel plasticized polymeric membrane (PPME) and membrane-coated graphite (MCGE) electrodes based on 1,3,5-trithiacyclohexane for highly selective determination of La3+ ion have been developed. The electrodes exhibit Nernstian responses over very wide concentration ranges (8.0 x 10(-6)-5.0 x 10(-2) M for PPME and 4.0 x 10(-8)-1.0 x 10(-2) M for MCGE). The limit of detections were 5.0 x 10(-6) and 2.0 x 10(-8) M for PPME and MCGE, respectively. The electrodes possess a fast response time of approximately 10 s and can be used for at least 6 months without observing any deviation. The proposed electrodes revealed excellent selectivities for La3+ over a wide variety of alkali, alkaline earth, transition, and heavy metal ions and could be used in a pH range of 5.0-8.0. The practical utility of the electrodes has been demonstrated by their use as indicator electrodes in the potentiometric titration of La3+ ions with EDTA and in determination of F- in some mouthwash preparations.

Synthesis, characterization, and structure of [[PtMe(3)(9-MeA)](3)] (9-MeAH = 9-Methyladenine): a cyclic trimeric platinum(IV) complex with a nucleobase

Reaction of [[PtMe(3)I](4)] with AgOAc in acetone results in formation of trimethylplatinum(IV) acetate (1) that reacts with 9-methyladenine (9-MeAH) in ratio 1:1 with its deprotonation yielding a trimethyl(9-methyladeninato)platinum(IV) complex (2) that was obtained from acetone/diethyl ether as [[PtMe(3)(9-MeA)](3)] x Me(2)CO (2a) and from chloroform/diethyl ether as [[PtMe(3)(9-MeA)](3)] x 1.5Et(2)O x 2H(2)O (2b). Single-crystal X-ray investigations revealed that 2a and 2b in the solid state form cyclic trimeric molecules in which three PtMe(3) moieties are bridged by deprotonated 9-methyladenine ligands in mu-kappa N(1):kappa(2)N(6),N(7) coordination mode. The methyladeninato ligands include angles with the plane defined by the Pt(3) unit between 55.9(3) degrees and 66.6(3) degrees. Thus, the structures of the cyclic trimers resemble hollow truncated cones. Crystals of the acetone solvate 2a consist of stacks of unidirectional trimeric molecules; the solvate acetone molecules lie between the trimers. In the crystals of complex 2b, the trimeric molecules are arranged head-to-head, and the cavity between is filled with four water molecules. Complex 2 was also fully characterized by (1)H, (13)C, and (195)Pt NMR spectroscopies. The existence of the cyclic trimeric structure of complex 2 in acetone solution was confirmed by ESI mass spectrometry exhibiting the protonated trimeric complex [[tMe(3)(9-MeA)]3)H](+) [2 + H](+) (m/z 1165) as base peak. CID experiments of that parent ion showed as main fragmentation processes loss of two methyl ligands (probably as ethane) and cleavage of a methyladenine ligand.

DNA interstrand cross-linking efficiency and cytotoxic activity of novel cadmium(II)-thiocarbodiazone complexes

We have prepared mono- and binuclear complexes of Zn(II) and Cd(II) with bis(2-pyridyl aldehyde) thiocarbodiazone (H(2)L(1)) and bis(methyl 3-pyridyl ketone) thiocarbodiazone (H(2)L(2)). Cytotoxicity data against the ovarian tumor cell line A2780cisR (acquired resistance to cisplatin) indicate that the mononuclear complex Cd/H(2)L(2) (1) and the binuclear complex Cd(2)/H(2)L(1) (4) are able to circumvent cisplatin resistance and that their cytotoxic activity does not substantially vary after depletion of intracellular levels of glutathione. Moreover, DNA binding studies show that complexes 1 and 4 have higher efficiency than cisplatin at forming DNA interstrand cross-links in both naked pBR322 plasmid and A2780cisR cellular DNA. Interestingly, the thiocarbodiazone ligands alone do not show the biological properties of complexes 1 and 4. Altogether these results suggest that DNA interstrand cross-link formation by compounds 1 and 4 might be related with their cytotoxic activity in cisplatin-resistant cells. We think that compounds 1 and 4 may represent a novel structural lead for the development of cadmium cytotoxic agents capable of improving antitumor activity in cisplatin-resistant tumors.

Thiohydrazone copper(II) complexes. The relationship between redox properties and superoxide dismutase mimetic activity

The redox behaviour of copper(II) complexes with the open chain ligand, benzilbisthiosemicarbazone, and the macrocyclic one [3,4,10,11-tetraphenyl-1,2,5,8,9,12,13-octaazacyclotetradeca-7,14- dithione- 2,4,9,11-tetraene] has been explored by cyclic voltammetry. The half-wave potential values for the copper(II)/copper(I) redox couple and the spectral data obtained on dimethylsulfoxide (DMSO) solution agree with the superoxide dismutase (SOD)-mimetic activity of the complexes. The macrocyclic complexes show more positive reduction potential and more activity than the open chain derivatives. From our results it follows that the structure and conformation of ligand has influence on the redox potential of central atom in coordination compound. The changes in the coordination sphere are connected with the change of biological function of compounds represented by SOD-mimic activity. In addition, the L1H6 derivatives show quasireversible waves associated to Cu(II)/Cu(III) process.

Studies of antibacterial activity of binuclear rhodium (II) complexes with heterocyclic nitrogen ligands

Binuclear rhodium (II) complexes, [Rh2(OOCPh)2(phen)2(H2O)2] (OOCPh)2 (1), [Rh2(OOCPh)2(bpy)2(H2O)2] (OOCPh)2 (2), [Rh2(OOCBu(n))2 (bpy)2(H2O)2] (OOCBu(n)2 (3), and [Rh2(OOCPr(n)2 (phen)2(H2O)2] (OOCPr(n)2 (4) (Phen = 1,10-phenanthroline and bpy = 2,2'-bipyridine), have been synthesized and characterized using NMR, IR and electronic spectra. Activity of these compounds against Gram-positive bacteria decreases in the order: 1?2?3 > 4. Complex 1 is active against many Staphylococcus strains resistant to commonly used antibiotics. The complexes 1-4 are much less active agents against Gram-negative bacteria.

Binuclear chloro-bridged palladated and platinated complexes derived from p-isopropylbenzaldehyde thiosemicarbazone with cytotoxicity against cisplatin resistant tumor cell lines

Two novel dimeric chloro-bridged complexes [Pd (p-is. TSCN) (mu-Cl)]2, 2, and [Pt (p-is. TSCN)(mu-Cl)]2, 3, where p-is. TSCN = p-isopropylbenzaldehyde thiosemicarbazone, 1, have been synthesized and characterized by IR and NMR spectroscopy. The in vitro antitumor activity shown by both compounds against several human and murine cell lines sensitive and resistant to the clinically-used drug cisplatin (cis-DDP) suggests that compounds 2 and 3 may be endowed with important anticancer properties. Thus, compounds 2 and 3 not only show IC50 values in the microM range as cis-DDP but also display cytotoxic activity in tumor cell lines resistant to this drug. The analysis of the interaction of these binuclear p-is. TSCN compounds with DNA secondary and tertiary structures indicate that they form DNA interhelical cross-links, a biochemical property that may be involved in their mechanism of action.

Síntese e caracterização de compostos diorganoestânicos com ácido dl-mandélico

Por reação de quantidades eqüimoleculares de R2SnO ou R2SnCl2 (R = -CH3; -C4H9) com ácido dl-mandélico, C6H5CH(OH)COOH, em meio de etanol, foram obtidos novos compostos formulados como [(LR2Sn)2O] [L= C6H5CH(OH)COO-], nos quais o átomo de estanho é pentacoordenado, com o ligante L estabelecendo uma ligação bidentada através dos átomos de oxigênio dos grupos ácido e hidroxila alcoólica. Nas mesmas condições, nenhum produto obtido a partir da reação de (C6H5)2SnO ou (C6H5)2SnCl2 pode ser identificado. No entanto, quando da reação de (C6H5)2SnCl2 com ácido dl-mandélico, em meio de acetonitrila, foi preparado um composto dimérico hexacoordenado formulado como [L(C6H5)2SnCl]2. Este composto não pode ser isolado de forma pura e está misturado com 7% de impurezas não identificadas, cujos parâmetros de interação hiperfina sugerem tratar de estanho tetravalente octaedricamente coordenado por oxigênio. Os compostos obtidos foram caracterizados por determinação de ponto de fusão, microanálise e espectroscopias i.v. e Mössbauer.

Bioorganometallic chemistry--synthesis and antitumor activity of cobalt carbonyl complexes

The interaction of organometallic compounds with biological systems, generally called bioorganometallic chemistry, is receiving increasing interest. We present the first part of our studies concerning the biological activity of organometallic compounds. Several alkyne-cobalt carbonyl complexes inhibited the growth of human melanoma and lung carcinoma cell lines. They are more active than uncomplexed dicobalt octacarbonyl, cobalt chloride, or the free ligand. A significant difference in potency towards the lung carcinoma cell line was observed among the cobalt complexes, indicating that the complexed ligand may influence cytotoxic activity. These results suggest that further exploratory work with such cobalt-alkyne complexes is warranted.

Toward a novel metal-based chemotherapy against tropical diseases. 2. Synthesis and antimalarial activity in vitro and in vivo of new ruthenium- and rhodium-chloroquine complexes

Chloroquine free base (CQ) reacts with [Rh(COD)Cl]2 (COD = 1,5-cyclooctadiene) and RuCl3.-3H2O/Zn to yield Rh(COD)(CQ)Cl (1) and [RuCl2(CQ)]2 (2), respectively. The two novel metal- CQ complexes, which were characterized mainly by 1D and 2D NMR spectroscopy, were tested against Plasmodium berghei. The in vitro activity of 1 was comparable to that of chloroquine diphosphate (CQDP), whereas 2 was about 5 times more active. In in vivo tests at equivalent concentrations of free CQ, CQDP reduced the parasitemia by 55%, while for complexes 1 and 2 the reduction reached 73% and 94%, respectively, without any sign of acute toxicity being observed up to 30 days after treatment. The Ru derivative 2 was further evaluated against two chloroquine-resistant strains of Plasmodium falciparum, and it was found to be 2-5 times more active than CQDP.

Complexes of azathioprine, a biologically active mercaptopurine derivative, with Pt(II), Pd(II), Rh(III), Ru(III) and Ag(I)

In order to possibly elucidate the prevailing factors determining the binding sites in the interactions of azathioprine (AZAH), a biologically active 6-mercaptopurine derivative, with the platinum group and other heavy metals, we probed the binding sites of AZAH with Pt(II), Pd(II), Rh(III), Ru(III), and Ag(I) by using 1H and 195Pt NMR, ESR, and IR spectroscopic techniques as well as magnetic susceptibility measurements and mass spectrometry. The altered coordination behavior of AZAH with respect to the parent 6-mercaptopurine, with sulfur no longer being the primary binding site, was ascertained. In the Pt(II), Rh(III), and Ru(III) complexes, 1H NMR data imply coordination of the metal through the N(3) and N(9) positions of the purine ring, while in the case of the Pt(II) compound, 195Pt NMR data further ascertain AZAH binding in a bridging mode through ring nitrogens. As opposed to the aforementioned metals, in the Pd(II) and Ag(I) compounds, 1H NMR data suggest binding via the N(9) position of deprotonated AZAH. Conductivity measurements for all compounds, except for that of Pt(II), showed a nonelectrolyte behavior in solution; the presence of ionic nitrate in the Pt(II) compound was further ascertained by IR spectroscopy. The coordination sphere of the metal in the cases of the Pt(II) and Pd(II) compounds is completed by ammonia and water molecules, respectively, while in those of the Rh(III) and Ru(III) compounds is completed by chloride bridge. For the Ru(III) compound, the latter is confirmed by magnetic susceptibility measurements.