Anticancer activities of manganese-based photoactivatable CO-releasing complexes (PhotoCORMs) with benzimidazole derivative ligands

Carbon monoxide is an important signaling molecule which is produced by heme oxygenase-1. CO shows antiproliferative activity against cancer cells; hence, activation of HO-1 is a significant inhibition strategy against tumor formation and survival of cancer cells. In this work, manganese-based CO-releasing molecules (CORMs) were designed and synthesized to inhibit breast cancer cell proliferation. Human invasive ductal breast cancer cells (MCF-7) were treated with the synthesized CORMs to investigate the effect of the complexes on breast cancer survival under UV light. In vitro experiments indicated that the complexes inhibited breast cancer cell proliferation, and further, the antiproliferative effects were increased under UV light. Thus, these novel CORMs may provide a drug template for the treatment of invasive ductal breast cancer.     

Synthesis,structures and magnetic properties of two 2D → 3D entangled Cobalt(II) coordination polymers

Two Co(II) coordination polymers, namely Co(HBTC)(4-bpdb)·H₂O (1) and Co(HBTC)(3-bpdb)·H₂O (2) (H₃BTC = 1,3,5-benzenetricarboxylic acid, 4-bpdb = 1,4-bis-(4-pyridyl)-2,3-diaza-1,3-butadiene, 3-bpdb = 1,4-bis(3-pyridyl)-2,3-diaza-1,3- butadiene), have been hydrothermally synthesized and characterized both structurally and magnetically. Compound 1 exhibits a (2D → 3D) polythreaded architecture. It is assembled from HBTC^2? ligands to form a 2D puckered (4,4) layer plus 4-bpdb ligands which are orientated above and below each layer. The structure of compound 2 consists of a 2D (3,5) wavelike sheet constructed from HBTC^2? anions and 3-bpdb spacers. The uncoordinated carboxyl groups of the HBTC^2? ligands protrude from both sides of the wavelike sheet to form a 2D → 3D interdigitated motif. The magnetic properties of both compounds are also investigated, indicating antiferromagnetic interactions between the adjacent metal centers.     

Synthesis,characterization and antitumor activity of palladium(II) complexes of imidazolidine-2-thione

Complexes of the type cis-[PdX₂(imzt)(PPh₃)] {imzt = imidazolidine-2-thione; PPh₃ = triphenylphosphine; X = Cl (1), Br (2), I (3), SCN (4)} have been synthesized and characterized by elemental analyses, molar conductance, IR and ¹H NMR spectroscopies. The complex 1·MeOH was obtained from the reaction of [PdCl₂(CH₃CN)₂], imidazolidine-2-thione and triphenylphosphine in CHCl₃/CH₃OH. Complexes 2·MeOH, 3 and 4 were prepared by metathesis of the chlorido ligands in 1 with bromide, iodide and thiocyanate, respectively. Elemental analyses showed good agreement with the expected mononuclear compositions, while the molar conductivities of the complexes in DMF were consistent with their nonelectrolytic nature. NMR spectra confirmed coordination of the imidazolidine-2-thione and triphenylphosphine ligands. Single-crystal X-ray diffraction determination of 1·CH₃OH showed that the coordination geometry around Pd^II is nearly square planar, with the chlorido ligands in a cis configuration. All four complexes have been tested in vitro by XTT assay for their cytotoxicity against human glioblastoma cell line (U87MG). The binding of 1 with guanosine was studied by ¹H NMR spectroscopy, revealing that the coordination takes place via N7.     

Syntheses,crystal structures,electrochemical and photocatalytic properties of two mixed-ligand cobalt(II) coordination polymers based on flexible bis(2-methylbenzimidazole) dicarboxylic acid ligands

Two Co(II) coordination polymers (CPs), namely [Co(L)(tp)] _n (1) and [Co(L)_0.5(tbip)·H₂O] _n (2), (L = 1,6-bis(2-methylbenzimidazolyl) hexane, H₂tp = terephthalic acid, H₂tbip = 5-tert-butyl isophthalic acid), were hydrothermally synthesized and characterized by physicochemical and spectroscopic methods. CP 1 possesses a 2D (4,4) corrugated layer structure, which further extends into a 3D supramolecular framework by π–π stacking interactions, while CP 2 has a 1D ladder-like chain structure and combines into a 2D layer via O–H?O hydrogen-bonding interactions. The thermal stabilities, luminescence and electrochemical properties of both CPs, as well as photocatalytic activities for the decomposition of methylene blue, were presented. The photocatalytic mechanism was investigated by introducing t-butyl alcohol, EDTA-2Na and benzoquinone as ?OH, (hole)⁺ and ·O^2? scavengers, respectively.     

Encapsulation of RNA by negatively charged human serum albumin via physical interactions

Human serum albumin (HSA) is the most abundant plasma protein and has an inherent ability to target tumor cells. It is an excellent candidate for drug delivery. However, HSA cannot form complex with DNA or RNA, because it is negatively charged under physiological conditions. In this work, we reported a simple method to prepare HSA/RNA nanoparticles mainly by physical interaction. Firstly, the solution pH is adjusted to 4.0, under which condition HSA is positively charged. It forms complex with RNA via electrostatic interaction. The solution is then heated at 75 oC for 15 min to stabilize the structure and the size of the formed complex. The HSA/RNA nanoparticle prepared by this method has a diameter about 110 nm and a narrow distribution. It is also stable for days under physiological conditions. Cellular essays demonstrate that these particles exhibit a high cellular uptake efficiency and non-toxicity to HeLa cells.     

Comparison of methods to estimate the free energy of solvation:Importance in the modulation of the affinity of 3-benzazepines for the D1receptor

We computed the free energy of solvation for a series of ions and neutral molecules using two different continuum approaches. First, we used the AM1–SM1 technique, where the AM1 Fock matrix is modified to include a generalized Born contribution. Second, we applied the DelPhi approach, where the electrostatic component of the free energy of solvation is evaluated by resolving the Poisson–Boltzman equation by a finite difference method. Both methods appear equally reliable for ionic systems. For neutral compounds, AM1–SM1 performs better than DelPhi; however, the differences become less pronounced for compounds with larger free energies of solvation. In parallel, both methods were applied to study the influence of the solvation process in the overall drug receptor interaction for a series of closely related ligands for the D₁ dopamine receptor. An inverse linear relationship was found between the free energy of solvation and the logarithm of the affinity of the ligands; nevertheless, electrostatic properties are likely to modulate affinity as well. © 1993 John Wiley & Sons, Inc.     

The electrochemical reduction of perezone in the presence of benzoic acid in acetonitrile

An electrochemical study using transient techniques of a quinone-type natural product, perezone, has been performed in acetonitrile and in the presence of benzoic acid. Using linear sweep voltametry and single potential step chronoamperometry, it was possible to establish that the reduction mechanism of perezone involves a monoelectronic charge-transfer step, followed by a protonation step and homogeneous charge transfer due to disproportionation of the protonated intermediate. The mechanism for the homogeneous charge-transfer step was found to be of the type DISP1 (disproportionation order one) from the results of double potential step chronoamperometry experiments. The occurrence of the DISP1 mechanism was provoked by the mildly acidic medium used in this study.     

Synthesis of 2,3,8,9-tetramethoxy-11-phenyl-5,6-dihydrodibenz[2,3;7,8]indolizine

2,3,8,9-Tetramethoxy-11-phenyldibenz[2,3;7,8]indolizine was obtainedinhighyieldfrom (6,7-dimethoxyisoquinolin-1-yl)-(3,4-dimethylphenyl)phenylcarbinol by cyclization in the presence of formic acid. The behavior of (6,7-dimethoxyisoquinolin-1-yl)-(3,4-dimethoxyphenyl)methylcarbinol and (6,7-dimethoxyisoquinolin-1-yl-(3,4-dimethoxyphenyl)carbinol was studied under these same conditions. 2,3,7,8-Tetramethoxy-11-phenyl-5,6-dihydrodibenz[2,3;7,8]indolizine was obtained by hydrogenation on rhenium heptasulfide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1233–1238, September, 1993.     

On the origin of changes in topicity observed in Diels–Alder reactions catalyzed by Ti–TADDOLates

New C₂ symmetric TADDOLs containing different groups at the 2-position of the dioxolane ring have been prepared. The Ti catalysts derived from these have been studied in the Diels–Alder reaction of cyclopentadiene and (E)-2-butenoyl-1,3-oxazolidin-2-one. Substituents at the C-2 position of the dioxolane ring can play an important role in determining the selectivity as well as the nature of the major isomer. This effect is more important for TADDOLs containing bulky aromatic groups such as 3,5-dimethylphenyl- or 1-naphthyl at the -positions. Experimental evidence supports the hypothesis that π–π interactions between aromatic groups at the C-2 and the ones at the -positions are critical in this respect.