Synthesis, spectral study and cytotoxicity of platinum(II) complexes with 2,9-disubstituted-6-benzylaminopurines

Evaluation of in vitro cytotoxicity of 6-benzylaminopurine carboplatin derivatives against human cancer cell lines and primary human hepatocytes

A series of seven platinum(II) cyclobutane-1,1-dicarboxylato (cbdc) complexes {[Pt(cbdc)(L(n))(2)], 1-7}, derived from carboplatin by a substitution of two NH(3) molecules for two 2,6,9-trisubstituted 6-benzylaminopurine-based N-donor ligands (L(n)), was studied by the MTT assay for their in vitro cytotoxic activity against seven human cancer cell lines, i.e. lung carcinoma (A549), cervix epithelioid carcinoma (HeLa), osteosarcoma (HOS), malignant melanoma (G361), breast adenocarcinoma (MCF7), ovarian carcinoma (A2780) and its cisplatin-resistant analogue (A2780cis), and against two primary cultures of human hepatocytes (LH31 and LH32). The prepared complexes were cytotoxic against several cancer cells, in some cases even more than cisplatin. The best results were achieved for complexes 1 (IC(50)=17.4 ± 2.0 μM) and 2 (IC(50)=14.8 ± 2.1 μΜ) against HOS cells, 1 (IC(50)=15.1 ± 6.8 μM), 2 (IC(50)=13.6 ± 5.2 μM) and 6 (IC(50)=19.0 ± 6.6 μM) against MCF7, 6 (IC(50)=6.4 ± 0.1 μM) against A2780, and 1-6 (IC(50)=15.6 ± 4.0, 12.9 ± 3.7, 15.8 ± 3.8, 16.6 ± 5.5, 22.1 ± 2.5, and 5.6 ± 1.7 μM, respectively) against A2780cis. Viability of human hepatocytes was not declined by the tested complexes up to the concentration of 50 μM (for 1, 3-7) and 20 μM (for 2; caused by lower solubility of this complex).

Roscovitine-based CDK inhibitors acting as N-donor ligands in the platinum(II) oxalato complexes: preparation, characterization and in vitro cytotoxicity

The reactions of potassium bis(oxalato)platinate dihydrate with two molar equivalents of the potent adenine-based cyclin-dependent kinase inhibitor 2-(1-ethyl-2-hydroxyethylamino)-N6-(benzyl)-9-isopropyladenine (Roscovitine; Ros) and its benzyl-substituted analogues, i.e. 2-(1-ethyl-2-hydroxyethylamino)-N6-(2-methoxybenzyl)-9-isopropyladenine (2OMeRos), 2-(1-ethyl-2-hydroxyethylamino)-N6-(3-methoxybenzyl)-9-isopropyladenine (3OMeRos) and 2-(1-ethyl-2-hydroxyethylamino)-N6-(4-methoxybenzyl)-9-isopropyladenine (4OMeRos), were performed and the [Pt(ox)(Ros)(2)].(3/4)H(2)O (1), [Pt(ox)(2OMeRos)(2)].H(2)O (2), [Pt(ox)(3OMeRos)(2)].(1/2)H(2)O (3) and [Pt(ox)(4OMeRos)(2)].(3/4)H(2)O (4) platinum(II) oxalato complexes were obtained. The methods of the elemental analysis, IR, Raman and NMR spectroscopy, ESI + mass spectrometry, molar conductivity measurement and TG/DTA thermal analysis were performed to characterize the obtained products. The complexes 1-4 involve tetracoordinated central Pt(II) atom with one bidentate-coordinated oxalate dianion (ox) and two monodentate adenine-based molecules (nRos), thus giving the square-planar geometry around the metal centre with a PtN(2)O(2) donor set. In vitro cytotoxic activity of the complexes against ovarian carcinoma (A2780), cisplatin resistant ovarian carcinoma (A2780cis), malignant melanoma (G-361), lung carcinoma (A549), cervix epitheloid carcinoma (HeLa), breast adenocarcinoma (MCF7) and osteosarcoma (HOS) human cancer cell lines was evaluated. All the tested complexes exceeded the in vitro cytotoxicity of cisplatin and oxaliplatin against HeLa, A2780cis and, except for 2, also against HOS cancer cells. The complex 1 was also tested for its cytotoxicity in primary cultures of human hepatocytes and it was not found to be hepatotoxic up to the concentration of 50.0 microM.

Platinum(II) oxalato complexes with adenine-based carrier ligands showing significant in vitro antitumor activity

[Pt(L)(2)(ox)] (1), [Pt(2-OMeL)(2)(ox)] (2), [Pt(3-OMeL)(2)(ox)] (3), [Pt(2,3-diOMeL)(2)(ox)] (4), [Pt(2,4-diOMeL)(2)(ox)] (5), [Pt(3,4-diOMeL)(2)(ox)] (6) and [Pt(3,5-diOMeL)(2)(ox)].4H(2)O (7) platinum(II) oxalato (ox) complexes were synthesized using the reaction of potassium bis(oxalato)platinate(II) dihydrate with 2-chloro-N6-(benzyl)-9-isopropyladenine or its benzyl-substituted analogues (nL). The complexes 1-7, which represent the first platinum(II) oxalato complexes involving adenine-based ligands, were fully characterized by various physical methods including multinuclear and two dimensional NMR spectroscopy. A single-crystal X-ray analysis of [Pt(2,4-diOMeL)(2)(ox)].2DMF (5.2DMF; DMF=N,N'-dimethylformamide), proved the slightly distorted square-planar geometry in the vicinity of the Pt(II) ion with one bidentate-coordinated oxalate dianion and two adenine derivatives (nL) coordinated to the Pt(II) centre through the N7 atom of an adenine moiety, thereby giving a PtN(2)O(2) donor set. In vitro cytotoxicity of the prepared complexes was tested by an MTT assay against osteosarcoma (HOS) and breast adenocarcinoma (MCF7) human cancer cell lines. The best results were achieved for the complexes 2 and 5 in the case of both cell lines, whose IC(50) values equalled 3.6+/-1.0, and 4.3+/-2.1microM (for 2), and 5.4+/-3.8, and 3.6+/-2.1microM (for 5), respectively. The IC(50) equals 9.2+/-1.5microM against MCF7 cells in the case of 1. The in vitro cytotoxicity of the mentioned complexes significantly exceeded commercially used platinum-based anticancer drugs cisplatin (34.2+/-6.4microM and 19.6+/-4.3microM) and oxaliplatin (>50.0microM for both cancer cell lines).

Cytotoxic activities, cellular uptake, gene regulation, and optical imaging of novel platinum(II) complexes

A new class of platinum(II) coordination complexes and their dye tagged conjugates has been synthesized from N-substituted diaminocyclohexane ligands. The in vitro anticancer activities of the platinum compounds have been validated against the breast cancer cell-line MCF-7 and the normal cell-line MCF-10A via sulforhodamine B and colony formation assay. The platinum compounds and the corresponding metal-free ligands exhibited higher drug efficiencies than cisplatin and oxaliplatin against MCF-7 cells. Cellular uptake and DNA-bound Pt were demonstrated by atomic absorption spectroscopy. The platinum complexes displayed increased cellular accumulation and DNA binding as compared with cisplatin. Real-time reverse transcription polymerase chain reaction assay was employed to investigate drug effects on mRNA expression in MCF-7 cells. The results indicated that the study compounds are effective in regulating cyclin D1, Bcl-2, and p53 genes; yet, oxaliplatin is less effective in manipulating those genes. The luminescent probe that was integrated into the platinum complexes made it possible to monitor cellular drug distribution using optical imaging. Targeting of tumor cell nuclei by the study compounds was confirmed by confocal microscopy. Taken together, these new platinum(II)-based antitumor agents are different from marketed platinum drugs in several critical aspects and could have potential in cancer therapy.

Synthesis, characterization and assessment of the cytotoxic properties of cis and trans-[Pd(L)2Cl2] complexes involving 6-benzylamino-9-isopropylpurine derivatives

A series of square-planar Pd(II) complexes of the composition cis-[Pd(L(n))(2)Cl(2)] {L(1)=2-chloro-6-benzylamino-9-isopropylpurine (1), L(2)=2-chloro-6-[(4-methoxybenzyl)amino]-9-isopropylpurine (2), L(3)=2-chloro-6-[(2-methoxybenzyl)amino]-9-isopropylpurine (3) and 2-[(chloropropyl)amino]-6-benzylamino-9-isopropylpurine (6)} has been synthesized by the reaction of PdCl(2) with L(n) in a 1:2 molar ratio. In contrast, the same reaction followed by recrystallization of the product from N,N'-dimethylformamide (DMF) leads to trans-[Pd(L(n))(2)Cl(2)] x nDMF {L(3), n=0 (4), n=1(4( *)DMF); L(4)=2-chloro-6-[(2,3-dimethoxybenzyl)-amino]-9-isopropylpurine, n=0 (5), n=1.5 (5( *)DMF). The compounds have been characterized by elemental analyses, conductivity measurements, electrospray mass spectra in the positive ion mode (ES+MS), FTIR, (1)H and (13)C NMR spectra, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Moreover, the complexes 2 and 6 have been also investigated by (15)N NMR spectroscopy. The molecular structures of L(5), {(H(2+)L(5))(Cl(-))(2)} x H(2)O, i.e. the protonated form of L(5), trans-[Pd(L(3))(2)Cl(2)] (4) and trans-[Pd(L(4))(2)Cl(2)] (5) have been determined by single crystal X-ray analysis. NMR data and X-ray structures revealed that the organic molecules are coordinated to Pd via N7 atom of a purine moiety. All the complexes and the corresponding ligands have been tested in vitro for their cytotoxicity against four human cancer cell lines: breast adenocarcinoma (MCF7), malignant melanoma (G361), chronic myelogenous leukaemia (K562) and osteogenic sarcoma (HOS). Promising in vitro cytotoxic effect has been found for cis-[Pd(L(2))(2)Cl(2)] (2), having the IC(50) values of 12, 10, 25, and 14 microM against MCF7, G361, K562, and HOS, respectively, and for trans-[Pd(L(3))(2)Cl(2)].DMF (4) with the IC(50) value of 15 microM against G361.