Synthesis, crystal structures, cytotoxicity and qualitative structure-activity relationship (QSAR) of cis-bis{5-[(E)-2-(aryl)-1-diazenyl]quinolinolato}di-n-butyltin(IV) complexes, (n)Bu2Sn(L)2

Carbohydrate-based heteronuclear complexes as topoisomerase Iα inhibitor: approach toward anticancer chemotherapeutics

Due to the critical role of cellular enzymes necessary for cell proliferation by deciphering topological hurdles in the process of DNA replication, topoisomerases have been one of the major targets in the anticancer drug development area. A need, therefore, arises for new metallodrugs that specifically recognizes DNA and inhibits the activity of topoisomerase enzymes, herein, we report the synthesis and characterization of new metal-based glycoconjugate entities containing heterobimetallic core Cu^II-Sn^IV (1) and Ni^II-Sn^IV (2) derived from N-glycoside ligand (L). The optimized structure of complex 1 and other significant vibrational modes have been explained using dispersion corrected B3LYP/DFT calculations. In vitro DNA binding profile of the L and both the complexes 1 and 2 were done by various biophysical studies. Complex 1 breaks pBR322 DNA via a hydrolytic means which was validated by T4 DNA enzymatic assay. To get a mechanistic insight of mode of action topoisomerase I (Topo I) inhibition assay was carried out. Also, we have taken the help of molecular modeling studies in accordance with experimental findings. In vitro cytotoxicity of the complex 1 was evaluated against a panel of cancer cells which exhibited remarkably good anticancer activity (GI₅₀ values <10 μg/ml). Moreover, intracellular localization of the complex 1 was visualized by confocal microscopy against HeLa cells.

Therapeutic properties of organotin complexes with reference to their structural and environmental features

Organotin complexes are being extensively studied and screened for their therapeutic potential. Although many recent advances and achievements in this field have been made, the exact mode of action of these complexes is yet to be unveiled. In the present review, an attempt has been made to correlate the therapeutic properties of organotin complexes with their structural features and the environment in which these interact with biological systems. The mechanism, various modes of interaction with biological systems, and physiological target sites of organotin complexes have been highlighted as well.

Antitumor activity of di-n-butyl-(2,6-difluorobenzohydroxamato)tin(IV) against human gastric carcinoma SGC-7901 cells via G2/M cell cycle arrest and cell apoptosis

Di-n-butyl-(2,6-difluorobenzohydroxamato)Tin(IV) (DBDFT), a potential antitumor agent against malignancies, exhibited high activities both in vitro and in vivo. Flow cytometric analysis showed that treatment with DBDFT against Human Gastric Carcinoma (SGC-7901) cells induced a concentration and time-dependent cell accumulation in the G2/M phase of the cell cycle with a parallel depletion of the percentage of cells in G0/G1, the cell apoptosis was observed by characteristic morphological changes and AnnexinV/PI dual-immunofluorescence staining. Fluorescence quantitative FQ- PCR and western blot results showed that G2/M-phase arrest was correlated with up-regulation of cyclin dependent kinase inhibitor p21, Chk2 and CyclinB1, whereas the expressions of other G2/M regulatory check-point protein, Cdc2, and feedback loop protein Cdc25C were obviously down-regulated in a p53-independent manner after the SGC-7901 cells were treated with DBDFT (2.5, 5.0, 7.5 µmol·L⁻¹) compared with the control. Furthermore, the up-regulation of Bax and down-regulation of Bcl-2 as well as the activation of caspase-3 were observed, which indicated that DBDFT treatment triggered the mitochondrial apoptotic pathway with an increase of Bax/Bcl-2 ratios, resulting in mitochondrial membrane potential loss and caspase-9 activation in DBDFT treated SGC-7901 cells. In summary, the results illustrated the involvement of multiple signaling pathways targeted by DBDFT in mediating G2/M cell cycle arrest and apoptosis in SGC-7901 cells, which suggested that DBDFT might have therapeutic potential against gastric carcinoma as an effective compound.

Distorted octahedral environments in tricarbonylrhenium(I) complexes of 5-[2-(2,4,6-trimethylphenyl)diazen-1-yl]quinolin-8-olate and 5,7-bis[2-(2-methylphenyl)diazen-1-yl]quinolin-8-olate

The Re(I) centres of two Re(I)-tricarbonyl complexes, viz. tricarbonyl(pyridine-κN){5-[2-(2,4,6-trimethylphenyl)diazen-1-yl]quinolin-8-olato-κ(2)N(1),O}rhenium(I), [Re(C23H21N4O)(CO)3], (I), and {5,7-bis[2-(2-methylphenyl)diazen-1-yl]quinolin-8-olato-κ(2)N(1),O}tricarbonyl(pyridine-κN)rhenium(I), [Re(C28H23N6O)(CO)3], (II), are facially surrounded by three carbonyl ligands, a pyridine ligand and either a 5-[2-(2,4,6-trimethylphenyl)diazen-1-yl]quinolin-8-olate [in (I)] or a 5,7-bis[2-(2-methylphenyl)diazen-1-yl]quinolin-8-olate [in (II)] ligand, in a slightly distorted octahedral environment. The crystal structure of (I) is stabilized by two intermolecular C-H···O interactions and that of (II) is stabilized by three intermolecular C-H···O hydrogen-bonding interactions.

Structural analysis of organometallic compounds with soft ionization mass spectrometry

The analysis of organometallic compounds with mass spectrometry has some special features in comparison with organic and bioorganic compounds. The first step is the choice of a suitable ionization technique, where the electrospray ionization is certainly the best possibility for most classes of organometallic compounds and metal complexes. Some ionization mechanisms of organometallic compounds are comparable to organic molecules, such as protonation/deprotonation, and adduct formation with sodium or potassium ions; however, in many cases, different mechanisms and their combinations complicate the spectra interpretation. Organometallics frequently undergo various types of adduct and polymerization reactions that result in significantly higher masses observed in the spectra in comparison to molecular weights of studied compounds. Metal elements typically have more natural isotopes than common organic elements, which cause characteristic wide distributions of isotopic peaks; for example, tin has ten natural isotopes. The isotopic pattern can be used for the identification of the type and number of metal elements in particular ions. The ionization and fragmentation behavior also depend on the type of metal atom; therefore, our discussion of mass spectra interpretation is divided according to the different type of organometallic compounds. Among various types of mass spectrometers available on the market, trap-based analyzers (linear or spherical ion-traps, Orbitrap) are suitable to study complex fragmentation pathways of organometallic ions and their adducts, whereas high-resolution and high-mass accuracy analyzers (time-of-flight-based analyzers, or Fourier transform-based analyzers-Orbitrap or ion cyclotron resonance mass spectrometers) provide accurate masses applicable for the determination of the elemental composition of individual ions.

Mechanisms by which the antitumor compound di-n-butyl-di-(4-chlorobenzohydroxamato)tin(IV) induces apoptosis and the mitochondrial-mediated signaling pathway in human cancer SGC-7901 cells

The mechanisms by which the strong antitumor diorganotin(IV) compound di-n-butyl-di-(4-chlorobenzohydroxamato)tin(IV) (DBDCT) induces apoptosis of SGC-7901 cells were first investigated. Inhibition of proliferation of four cancer cell lines compared with normal human hepatic L-O2 cells, cancer cell apoptosis, and expression of related mRNA and protein were detected using the methyl thiazolyl tetrazolium (MTT), flow cytometry, reverse transcription polymerase chain reaction (RT-PCR), Western blot, and DNA ladder assays, and electron microscopy and immunocytochemistry. DBDCT decreased cancer cell proliferation rates in a dose- and time-dependent manner and changed the cycle distribution of SGC-7901 cells; the proportion of cells in G(0)-G(1) phase was increased, whereas the numbers in S and G(2)-M phases were decreased. Blockade of the cell cycle was perhaps associated with increased levels of p21, p27, p53 and the decreased level of proliferating cell nuclear antigen (PCNA). Apoptosis was characterized by DNA fragmentation, chromosomal condensation, apoptotic bodies, sub-G(1) peaks, and an increased apoptotic rate, as shown using the annexin V-FITC method. Pretreatment of cells with N-acetylcysteine and caspase-9 inhibitor could reduce growth inhibition and DBDCT-induced apoptosis. The results showed that DBDCT-mediated cell-cycle arrest might occur through the induction of p21 in a p53-dependent manner and that DBDCT induction of the mitochondrial apoptotic signaling pathway is perhaps mediated by increasing Bax/Bcl-2 ratios, which result in the loss of DeltaPsi(m), release of cytochrome c into the cytoplasm, activation of caspase-3 and -9, and increased reactive oxygen species (ROS) generation.