The variable chelating behavior of 3-methoxysalicylaldehyde-4(N)-substituted thiosemicarbazones was observed in equimolar reactions with [PdCl2(PPh3)2]. The new complexes were characterized by various analytical, spectroscopic techniques (mass, 1H-NMR, absorption, IR). All the new complexes were structurally characterized by single crystal X-ray diffraction. Crystallographic results showed that the ligands H2L1and H2L4 are coordinated as binegative tridentate ONS donor ligands in the complexes 1 and 4 by forming six and five member rings. However, the ligands H2L2 and H2L3 bound to palladium in 2 and 3 as uninegative bidentate NS donors by forming a five member chelate ring. From this study, it was found that the substitution on terminal 4(N)- nitrogen may have an influence on the chelating ability of thiosemicarbazone. The presence of hydrogen bonding in 2 and 3 might be responsible for preventing the coordination of phenolic oxygen to the metal ion. The interaction of the complexes with calf-thymus DNA (CT-DNA) has been explored by absorption and emission titration methods. Based on the observations, an electrostatic binding mode of DNA has been proposed. The protein binding studies were monitored by quenching of tryptophan and tyrosine residues in the presence of complexes using Lysozyme as model protein. Antibacterial activity studies of the complexes have been screened against pathogenic bacteria such as Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa.MIC50 values of the complexes showed that they exhibited significant activity against the pathogens and among them, 3 exhibited higher activity. Further, anticancer activity of the complexes on the lung cancer cell line A549 has also been studied.

Influence of terminal substitution on structural, DNA, Protein binding, anticancer and antibacterial activities of palladium(II) complexes containing 3-methoxy salicylaldehyde-4(N) substituted thiosemicarbazones

A series of new 6-methoxy-2-oxo-1,2-dihydroquinoline-3-carbaldehyde 4N-substituted thiosemicarbazone ligands (H2L1–H2L5) and their corresponding palladium(II) complexes [Pd(L1)(PPh3)] (1), [Pd(L2)(PPh3)] (2), [Pd(HL3)(PPh3)]Cl (3), [Pd(L4)(PPh3)] (4) and [Pd(L5)(PPh3)] (5), have been synthesized in order to evaluate the effect of terminal N-substitution in thiosemicarbazone moiety on coordination behaviour and biological activity. The new ligands and their corresponding complexes were characterized by analytical and various spectral techniques. The molecular structure of the complexes 2–5 were characterized by single crystal X-ray diffraction studies which revealed that the ligands H2L2, H2L4 and H2L5 are coordinated to palladium(II) as binegative tridentate (ONS2−) by forming six and five member rings whereas, the ligand H2L3 coordinated to Pd(II) as uninegative tridentate (ONS−). The interactions of the new complexes with calf thymus DNA (CT-DNA) have been evaluated by absorption and ethidium bromide (EB) competitive studies which revealed that complexes 1–5 could interact with CT-DNA through intercalation. Further, the interactions of the complexes with bovine serum albumin (BSA) were also investigated using UV-visible, fluorescence and synchronous fluorescence spectroscopic methods, which showed that the new complexes could bind strongly with BSA. Antioxidant studies showed that all the complexes have a strong antioxidant activity against 2-2′-diphenyl-1-picrylhydrazyl (DPPH) radical and 2,2′-azino-3-ethylbenzthiazoline-6-sulfonic acid diammonium salt (ABTS) cation radical. In addition, in vitro cytotoxicity of the complexes against human lung cancer (A549) cell line was assayed which showed that 4 has higher cytotoxic activity than the rest of the complexes and cisplatin.

Mixed ligand palladium(II) complexes of 6-methoxy-2-oxo-1,2-dihydroquinoline-3-carbaldehyde 4N-substituted thiosemicarbazones with triphenylphosphine co-ligand: synthesis, crystal structure and biological properties.

Since the initial discovery of applications of platinum complexes in the clinical treatment of many kinds of cancers, the efficiency of platinum complexes in inhibiting the proliferation of various types of tumors surprised researchers working on the development of anticancer drugs. Meanwhile, despite the potent clinical treatment patients get from platinum complexes, there are also disadvantages including limited solubility in aqueous media and side effects like ototoxicity, myelosuppression, nephrotoxicity, and poor selectivity toward healthy cells. For this reason, efforts have been made to search for novel solutions. Non-platinum complexes (like Fe, Pd, Ru, Cu, Bi, Zn, etc.) were found with potential anticancer activities. We here review the properties of five metal complexes as anticancer agents and make comparisons among them in biological features and cytotoxic activity. Seeking the interrelation between microstructure and mechanism of anticancer, we hope this review provides distinct insig...

Review: recent advances and future development of metal complexes as anticancer agents

Microwave-assisted synthesis of arene ruthenium(II) complexes that induce S-phase arrest in cancer cells by DNA damage-mediated p53 phosphorylation.

Evaluation of DNA binding, antioxidant and cytotoxic activity of mononuclear Co(III) complexes of 2-oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde thiosemicarbazones.

A novel microwave-assisted synthetic method has been used to synthesise a series of mixed ligand ruthenium(II) compounds containing diimine as well as bidentate thiosemicarbazone ligands. The compounds contain the diimine 1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy) and the thiosemicarbazone is derived from 9-anthraldehyde. Based on elemental analyses and spectroscopic data, the compounds are best formulated as [(phen)2Ru(thiosemicarbazone)](PF6)2 and [(phen)2Ru(thiosemicarbazone)](PF6)2 where thiosemicarbazone = 9-anthraldehydethiosemicarbazone, 9-anthraldehyde-N(4)-methylthiosemicarbazone, and 9-anthraldehyde-N(4)-ethylthiosemicarbazone. Fluorescence competition studies with ethidium bromide, along with viscometric measurements suggests that the complexes bind calf thymus DNA (CTDNA) relatively strongly via an intercalative mode possibly involving the aromatic rings of the diimine ligands. The complexes show good cytotoxic profiles against MCF-7 and MDA-MB-231 (breast adenocarcinoma) as well as HCT 116 and HT-29 (colorectal carcinoma) cell lines.

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Microwave synthesis of mixed ligand diimine–thiosemicarbazone complexes of ruthenium(II): biophysical reactivity and cytotoxicity

(E)-2-(2-hydroxybenzylideneamino)phenolato-2,2-diphenyl-6-aza-1,3-dioxa-2-stanna-[d,h]dibenzocyclononene, [Sn(Ph2SB)] (compound 1, where Ph2SB=(E)2-(2-hydroxybenzylideneamino)phenolato Schiff base) and two novel compounds, [[SnPh2(F-azoSB)] (compound 2, where F-azoSB=4-((E)-(4-fluorophenyl) diazenyl)-2-((E)-(2-hydroxyphenylimino)methyl)phenolato Schiff base), [[SnPh2(sulf-azoSB)]0.125CHCl3 (compound 3, where sulfamerazineazosalSB=4-((E)(4-hydroxy-3-((E)-(2-hydroxyphenylimino)methyl)phenyl)diazenyl)-N-(4-methylpyrimidin-2-yl) benzenesulfonamide Schiff base), and the control compound, cisplatin (compound 4) were analysed to comparatively determine their effect on cancer cell growth. Anti-cancer properties of compounds 1-4 were examined using glioblastoma (U-1242 MG), colorectal (HT-29 and HCT-116), and skin (A431) human cancer cell lines. With regards to human glioblastoma cells, compounds 1 and 3 demonstrated anti-proliferative capacity in the cell line tested. Specifically, compounds 1 and 3 inhibited cell proliferation by 50% at concentrations between 10 and 50 μM. With respect to colon cancer cell lines, the IC50 values for compounds 1-3 ranged from 3.04 ± 0.98 to 104.51 ± 13.87 μM. In the case of HCT-116, this translates to a 3to 73-fold inhibitory effect of compounds 1-3 over cisplatin. In all cell lines tested, the chemo-effect was more pronounced with compounds 1-3 than with the control (compound 4); demonstrating that these azo-containing Sn(IV) complexes were more potent than compound 4. The overall effect of compounds 1-3 in the induction of appotosis and the inhibition of proliferation have defined an essential role for these compounds in chemotherapy. Correspondence to: Alvin A Holder, Department of Chemistry and Biochemistry, Old Dominion University, 4541 Hampton Boulevard, Norfolk, VA 23529, USA, Tel: 757-683-7102, Fax: 757-683-4628, E-mail: aholder@odu.edu

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Lesley C. Lewis-Alleyne

Papers

Microwave synthesis of mixed ligand diimine–thiosemicarbazone complexes of ruthenium(II): biophysical reactivity and cytotoxicity

An in vitro study on the effect of synthesized tin(IV) complexes on glioblastoma, colorectal, and skin cancer cell lines