Electronic and Magnetic Interactions in 6-Oxoverdazyl Diradicals: Connection through N(1) vs C(3) Revisited.

Four isomeric di-6-oxoverdazyl diradicals connected at their N(1) or C(3) positions with either 1,3- or 1,4-phenylene linkers were obtained and characterized by spectroscopic, electrochemical, magnetic, and structural methods. These results were compared to those for the corresponding 6-oxoverdazyl monoradicals. UV-vis spectroscopy demonstrated that only the N(1)-connected para-through-benzene diradical has a distinct spectrum with significant bathochromic and hypsochromic shifts relative to the remaining species. Electrochemical analysis revealed two one-electron reduction processes in all diradiacals, while only the N(1)-connected para-through-benzene diradical exhibits two one-electron oxidation processes separated by 0.10 V. Variable temperature EPR measurements in polystyrene solid solutions gave negative mean exchange interaction energies J for all diradicals, suggesting the dominance of conformers with significant intramolecular antiferromagnetic interactions for the meta-through-benzene isomers. DFT calculations predict a small preference for the triplet state with the ΔES-T of about 0.25 kcal mol-1 for both meta-through-benzene connected diradicals.

Physicochemical and in vitro cytotoxicity studies of inclusion complex between gemcitabine and cucurbit[7]uril host.

Gemcitabine, a cytostatic drug from the pyrimidine antimetabolite group, exhibits limited storage stability and numerous side effects during therapy. One of the strategies to improve the effectiveness of therapy with such drugs is the use of supramolecular nano-containers, including dendrimers and macrocyclic compounds. The ability of gemcitabine to attach a proton in an aqueous environment necessitates the search for a carrier that is well-tolerated by an organism and capable of supramolecular binding of a ligand (drug) in a cationic form. In the current study a promising strategy was tested for using cucurbituril Q7 to bind gemcitabine cations for its efficient intracellular delivery on three selected cancer cell lines (MOLT4, THP-1 and U937). Based on physicochemical studies (equilibrium dialysis, UV and 1H NMR titrations, DOSY 1H NMR measurements, DSC calorimetry) and cytotoxicity tests on cells with a free and blocked hENT1 transporter, the conclusion was drawn about the binding and penetration of the cucurbituril-drug complex into cancer cells.

In vitro SOD-like activity of mono- and di-copper complexes with a phosphonate substituted SALAN-type ligand.

SALEN- and SALAN-based complexes with catalytically active metal centers are very promising small molecules to be utilized as part of antioxidant therapies. Here we discuss a modified SALAN-type molecule armed with two phosphonate groups that significantly increase its water solubility and aid to furnish mono- or dinuclear complexes with Cu2+ ions. The regulation of the SOD-mimicking (i.e., catalytic) disproportionation reaction of the superoxide radical anion (O2•-) at pH ~7.5 could be achieved by adjusting the metal-to-ligand stoichiometry as confirmed by McCord-Fridovich and pulse radiolysis tests. The higher antioxidant activity of the dicopper complex can be explained by the better access of O2•- to the copper centers and their more positive Cu(II)/Cu(I) redox potential. Simultaneously the analysis of in vitro effect on cells morphology indicates that cytotoxicity is also affected by the metal-to-ligand ratio, however, the active complex molecules do not show notable cytotoxicity that, together with the observed SOD-like activities, makes them potential candidates for antioxidant therapies.

A potential CARB-pharmacophore for antineoplastic activity: part 1.

Diverse functionalized representatives of various classes of sugars, such as thio-, anhydro-, and sulfamido-sugars and myo-inositol oxide, were synthesized and assessed for cytotoxicity against human cancer cell lines (A549, LoVo, MCF-7 and HeLa). The inositol oxide (4) was more active against MCF-7 cells (i.e., an estrogen-dependent breast cancer line), whereas all 3 sulfur-containing compounds showed strongest activity against A549 cells (i.e., a lung adenocarcinoma line). We propose to use a concept of functional 'CARB-pharmacophores' when evaluating a potential for the compounds' general antineoplastic activity. Future studies will determine the reasons for cell-type specificity of these compounds. The thio-sugar motif appears to be a promising lead for future developments.