Synthesis and antitumour activity of platinum(II) and platinum(IV) complexes containing ethylenediamine-derived ligands having alcohol, carboxylic acid and acetate substituents. Crystal and molecular structure of [PtL4CL2].H20 where L4 is ethylenediamine-N,N'-diacetate

Platinum Complexes with Edda (Ethylenediamine -N, N - Diacetate) Ligands as Potential Anticancer Agents

The design of platinum based drugs is not a new field of interest. Platinum complexes are widely used as anticancer agents and currently, approximately 30 platinum(II) and platinum(IV) entered into some of the phases of clinical trials. A special place in today’s research belongs to platinum complexes with diammine ligands. A large number of edda (ethylenediamine- N, N’-diacetate)-type ligands and their corresponding metal complexes has been successfully synthesized. This article summarizes recent progress in research on edda-type-platinum complexes. Some of these agents achieves better effect compared to the gold standard (cisplatin). It has been shown that there is a possible relationship between the length of the ligand ester group carbon chain and its cytotoxic effect. In most cases the longer the ester chain is the greater is the antitumor activity. Of particular interest are the noticeable effects of some new platinum compound with edda-type ligand on cell lines that are known to have a high level of cisplatin-resistance. Exanimate complexes appear to have a different mode of mechanism of action compared with cisplatin which includes apoptotic and necrotic cell death. There are indications that further investigations of these compounds may be very useful in overcoming the problems associated global cancer statistic.

Platinum Complexes-Induced Cardiotoxicity of Isolated, Perfused Rat Heart: Comparison of Pt(II) and Pt(IV) Analogues Versus Cisplatin

We have compared the cardiotoxicity of five platinum complexes in a model of isolated rat heart using the Langendorff technique. These effects were assessed via coronary flow (CF) and cardiac functional parameters. cis-Diamminedichloroplatinum(II) (cisplatin, CDDP), dichloro-(1,2-diaminocyclohexane)platinum(II) (Pt((II))DACHCl2), dichloro-(ethylenediamine)platinum(II) (Pt((II))ENCl2), tetrachloro-(1,2-diaminocyclohexane)platinum(IV) (Pt((IV))DACHCl4) and tetrachloro-(ethylenediamine)platinum(IV) (Pt((II))ENCl4) were perfused at increasing concentrations of 10(-8), 10(-7), 10(-6), 10(-5) and 10(-4) M during 30 min. In this paper, we report that cisplatin-induced dose-dependent effects on cardiac contractility and coronary flow both manifested as decrease in cardiac contractile force (dP/dt)max, heart rate and significant reduction in CF. Pt((II))ENCl2, Pt((IV))ENCl2 and Pt((IV))DACHCl4 did induce dose-dependent response only in case of CF. Our results could be also important for better understanding dose-dependent side effects of potential metal-based anticancer drugs.

Oxidative Reactivity and Cytotoxic Properties of a Platinum(II) Complex Prepared by Outer-Sphere Amide Bond Coupling

Benzyl amine was coupled to the dangling carboxylic acid groups of the platinum(II) complex [Pt(edda)Cl₂], where edda = ethylenediamine-N,N'-diacetic acid, to give the diamidetethered complex [Pt(L)Cl₂] (1), where L = ethylenediamine-N,N'-bis(N-benzylacetamide). Complex 1 was oxidized with both PhICl₂ and Br₂. Oxidation with PhICl₂ cleanly afforded the tetrachloride complex, [Pt(L)Cl₄] (2), whereas oxidation with Br₂ gave rise to several mixed halide complexes of the general formula, [Pt(L)Cl_xBr_4-x], where x = 1, 2, or 3. Complexes 1 and 2 were fully characterized by ¹H, ¹³C, and ¹⁹⁵Pt NMR spectroscopy, as well as by ESI-MS. These compounds exist as a mixture of diastereomers that arise from the chirality of the two coordinated nitrogen atoms. Crystal structures of 1, 2, and [Pt(L)Cl_xBr_y] (3) are reported. Although refined as the tetrabromide complex [Pt(L)Br₄], the crystal structure of 3 is a mixture of species with site-occupancy disorder of chloride and bromide ligands. DFT calculations indicate that the two sets of diastereomers of 1 and 2 are effectively thermoneutral, a conclusion that is also supported by the observation of both members of each pair by NMR spectroscopy. The cytotoxicity of 1 and 2 was measured by the MTT assay in HeLa cells and compared to that of cisplatin. Both exhibit IC₅₀ values close to 50 μM and are therefore substantially less toxic than cisplatin, for which the IC₅₀ is 1 μM.

Examination of the effects of oxidation and ring closure on the cytotoxicities of the platinum complexes of N-(2-hydroxyethyl)ethane-1,2-diamine and ethane-1,2-diamine-N,N'-diacetic acid

The crystal structures, electrochemical properties and cytotoxicities of platinum(II) and platinum(IV) complexes of the multidentate ligands N-(2-hydroxyethyl)ethane-1,2-diamine (NNOH) and ethane-1,2-diamine-N,N'-diacetic acid (H(2)enda) are reported. In the platinum(II) state the NNOH and H(2)enda ligands act as bidentate ligands, coordinating through the two amine groups with the hydroxyethyl and carboxylate groups remaining uncoordinated. Oxidation with hydrogen peroxide followed by refluxing yields the ring closed Pt(IV) complexes in which the NNOH and H(2)enda ligands are deprotonated and coordinate via the two amine groups and either the deprotonated alcohol group in the case of NNO or both carboxylato groups in the case of enda. The platinum(IV) complex of NNO is 2- to 5-fold more active against a panel of cisplatin sensitive and resistant human tumour cell lines than is the platinum(II) complex, whereas in the case of enda, the reverse is true. Ring closure to occupy both axial sites apparently leads to deactivation of platinum(IV) complexes, but a single closure does not necessarily do so.

(Aminoethanol)dichloroplatinum(II) complexes: influence of the hydroxyethyl moiety on 5'-GMP and DNA binding, intramolecular stability, the partition coefficient and anticancer activity

The influence of tethered hydroxyl groups on the binding behavior of the three (aminoethanol)dichloroplatinum complexes, dichloro(N,N'-bis(2-hydroxyethyl)ethylenediamine)-platinum(II) (1), dichloro(N-(2-hydroxyethyl)ethylenediamine)platinum(II) (2) and cis-dichlorobis(2-hydroxyethylamine)platinum(II) (3) towards 5'-GMP and DNA was investigated by 1H NMR and r(b) measurements, respectively. At pH 7.2, the sequence of reactivity with 5'-GMP is 1>2>>3. Complex 3 reacts very slowly with 5'-GMP and DNA and the amount and lifetime of the intermediate 5'-GMP monoadduct are much larger than for 1 and 2. At pH 5.5, the reaction of 3 with 5'-GMP is markedly accelerated and very small amounts of monoadduct are observed, indicating a pH-dependent ability of the pendant hydroxyl group to interact with the platinum moiety. In addition, the effect of the hydroxyethyl functionality on octanol/water partitioning and in vitro anticancer activity was studied. No correlation between lipophilicity and anticancer activity was detected. Furthermore, the lipophilicity and anticancer activity could not be directly correlated to 5'-GMP or DNA binding activity.