Recent advances on non-steroidal anti-inflammatory drugs, NSAIDs: Organotin complexes of NSAIDs

An overview is given of the results of organotin-NSAIDs interactions. Several organotin complexes with NSAIDs, derivatives of the carboxylic acid family and oxicam family, have been synthesized and characterized by spectroscopy and X-ray crystallography at the University of Ioannina. Results concerning the biological activity of these organotin complexes will be referred.     

Organotin complexes of pyruvic acid thiosemicarbazone: Synthesis,crystal structures and antiproliferative activity of neutral and cationic diorganotin complexes

The synthesis and spectral characterization of novel neutral and cationic organotin complexes with pyruvic acid thiosemicarbazone, H₂pt (1), [SnPh₂(pt)] (2), [SnMe₂(Hpt)(H₂O)]Cl (3) and [SnPh₂(Hpt)(H₂O)]Cl (4) are reported. The crystal structure of the complexes [SnPh₂(pt)] (2) and [SnMe₂(Hpt)(H₂O)]Cl (3) have been solved by single-crystal X-ray diffraction. The crystal structure of complex 2 showed that the ligand is doubly deprotonated at the oxygen and amide nitrogen atoms and is coordinated to the SnPh₂ fragment via two five-membered chelate rings. The monomers of 2 are linked through intermolecular hydrogen bonds of C−H–O type and through π−π intermolecular interactions. The crystal structure of [SnMe₂(Hpt)(H₂O)]Cl (3) showed that the ligand is mono-deprotonated at the oxygen atom and is coordinated to the SnMe₂ fragment via two five-membered chelate rings. The counter ion chloride is participated in intermolecular hydrogen bonds. An extended network of intermolecular hydrogen bonds leads to aggregation and a supramolecular assembly. The IR and NMR spectroscopic data of the complexes are reported. The in vitro cytotoxic activity has been evaluated against the cells of three human cancer cell lines: MCF-7 (human breast cancer cell line), T-24 (bladder cancer cell line), A-549(non-small cell lung carcinoma) and a mouse L-929 (a fibroblast-like cell line cloned from strain L). The most active of all was found the diorganotin complex 2. The cytotoxic activity shown by these compounds against all these cancer cell lines indicates that coupling of 1 with R₂Sn(IV) metal center result in metallic complexes with important biological properties and remarkable cytotoxic activity, since they are display IC₅₀ values in a μM range the same or better to that of the antitumor drug cisplatin. Compound 2 is considered as agent with potential antitumor activity, and can therefore be candidate for further stages of screening in vitro and/or in vivo.     

Sample pretreatment method for the determination of polychlorinated biphenyls in bird livers using ultrasonic extraction followed by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A simple and reliable sample methodology based on simultaneous ultrasonic extraction, sulfuric acid clean-up and headspace solid-phase microextraction (SPME)-gas chromatography-mass spectrometry has been developed as an advantageous analytical tool for the determination of seven polychlorinated biphenyl congeners in bird livers at low levels. The influence of several parameters on the efficiency of the proposed method was systematically investigated. The clean-up efficiency of sulfuric acid treatment was tested and compared with those of column chromatography (Flosiril, silica gel and alumina) and solid-phase extraction (SPE) (Supelclean ENVI-Carb cartridge) procedures. The use of sulfuric acid in the clean-up step prior to headspace solid-phase microextraction analysis allows the removal of interfering matrix compounds present in the liver extracts that would otherwise cause severe ionization suppression of the polychlorinated biphenyls (PCBs) during the ionization process. The optimized method had good linearity (R2>0.99) over the range studied (5-500 ng/g wet weight) and showed satisfactory level of precision, with RSD values lower than 10.6%. The obtained relative recoveries ranged between 63 and 94%. The limits of detection (0.06-0.63 ng/g wet weight) were low enough to check for harmful levels of polychlorinated biphenyls in biological samples, and were well below most of the restrictive limits established by European Union regulations. The method was found to be reliable under the operational conditions proposed and was applied successfully to the analysis of individual polychlorinated biphenyls in liver tissues. The results obtained from five bird species from Greece revealed the presence of the target compounds in all samples analyzed, at levels ranging between 0.54 and 39.45 ng/g wet weight.     

FTIR spectroscopic characterization of Nafion®–polyaniline composite films employed for the corrosion control of stainless steel

Nafion®–polyaniline (PAn) composite films deposited by a two-step process on a stainless steel (SS) substrate were characterized in this study using Fourier transform infrared (FTIR) spectroscopy under various conditions employed to evaluate their anticorrosion properties. The SS|Nafion® electrode was first prepared by placing a certain amount of Nafion® on the SS substrate, and then polymerization of aniline was carried out potentiodynamically on the SS|Nafion® electrode. The SS|Nafion®–PAn electrodes subjected to both potentiodynamic polarization and open-circuit conditions in sulfuric acid solutions without and with chlorides appeared to have distinct differences in their FTIR spectra. It is proposed that under the electrochemical conditions used in this study, the PAn is mostly formed inside the Nafion® membrane with a high proportion of oligomers influencing the ionic transport through the membrane. The inhibition of pitting corrosion arises primarily from the enhanced permselectivity of the composite film due to the Nafion® membrane that prevents chloride transport. An essential beneficial effect comes also from the PAn redox properties on the growth of the passive oxide film. Even under severe corrosion conditions, Nafion®–PAn films retain their redox activity and chemical stability, whereas the membrane crystallinity seems to be enhanced.

     

Synthesis and biological evaluation of several 3‐(coumarin‐4‐yl)tetrahydroisoxazole and 3‐(coumarin‐4‐yl)dihydropyrazole derivatives

A series of novel 3‐(coumarin‐4‐yl)tetrahydroisoxazoles 5a,b, 7, 9 and 3‐(coumarin‐4‐yl)dihydropyra‐zoles 13a‐d, 14,15a,b were synthesized from coumarin‐4‐carboxaldehyde 1 via the intermediate N‐methyl nitrone 3 and N‐phenyl or N‐methyl hydrazones 11a,b . These coumarin derivatives were isolated, characterized and evaluated in vitro for their ability to inhibit trypsin, β‐glucuronidase, soybean lipoxygenase and to interact with the stable radical 1,1‐diphenyl‐2‐picrylhydrazyl. The compounds were tested in vivo as anti‐inflammatory agents in the rat carrageenin paw edema assay. Compound 15a seems to be a lead molecule to be modified in order to improve the lipoxygenase inhibition. The results are discussed in terms of structural characteristics.     

Chemiluminescence reactions with cationic, neutral, and anionic ruthenium(II) complexes containing 2,2′-bipyridine and bathophenanthroline disulfonate ligands

Ruthenium complexes containing 4,7-diphenyl-1,10-phenanthroline disulfonate (bathophenanthroline disulfonate; BPS) ligands, Ru(BPS)₃⁴⁻, Ru(BPS)₂(bipy)²⁻ and Ru(BPS)(bipy)₂, were compared to tris(2,2′-bipyridine)ruthenium(II) (Ru(bipy)₃²⁺), including examination of the wavelengths of maximum absorption and corrected emission intensity, photoluminescence quantum yield, stability of their oxidised ruthenium(III) form, and relative chemiluminescence intensities and signal-to-blank ratios with cerium(IV) sulfate and six analytes (codeine, morphine cocaine, potassium oxalate, furosemide and hydrochlorothiazide) in acidic aqueous solution. The presence of BPS ligands in the complex increased the photoluminescence quantum yield, but decreased the stability of the oxidised form of the reagent. In contrast to previous evidence showing much greater electrochemiluminescence intensities using Ru(BPS)₂(bipy)²⁻ and Ru(BPS)(bipy)₂, these complexes did not provide superior chemiluminescence signals than their homoleptic analogues.     

FTIR spectroscopic characterization of Nafion®–polyaniline composite films employed for the corrosion control of stainless steel

Nafion?–polyaniline (PAn) composite films deposited by a two-step process on a stainless steel (SS) substrate were characterized in this study using Fourier transform infrared (FTIR) spectroscopy under various conditions employed to evaluate their anticorrosion properties. The SS|Nafion? electrode was first prepared by placing a certain amount of Nafion? on the SS substrate, and then polymerization of aniline was carried out potentiodynamically on the SS|Nafion? electrode. The SS|Nafion?–PAn electrodes subjected to both potentiodynamic polarization and open-circuit conditions in sulfuric acid solutions without and with chlorides appeared to have distinct differences in their FTIR spectra. It is proposed that under the electrochemical conditions used in this study, the PAn is mostly formed inside the Nafion? membrane with a high proportion of oligomers influencing the ionic transport through the membrane. The inhibition of pitting corrosion arises primarily from the enhanced permselectivity of the composite film due to the Nafion? membrane that prevents chloride transport. An essential beneficial effect comes also from the PAn redox properties on the growth of the passive oxide film. Even under severe corrosion conditions, Nafion???/em>PAn films retain their redox activity and chemical stability, whereas the membrane crystallinity seems to be enhanced.     

Fluorescence of the DNA double helices (dAdT)n.(dAdT)n studied by femtosecond spectroscopy

Polymeric and oligomeric DNA helices, poly(dAdT).poly(dAdT) and (dAdT)(10).(dAdT)(10), composed of 200-400 and 20 adenine-thymine base pairs, respectively, are studied by fluorescence upconversion. Fluorescence decays, anisotropy decays and time-resolved spectra, obtained for this alternating base sequence, are compared with those determined previously for the homopolymeric sequence (dA)(n).(dT)(n). It is shown that identical fluorescence decays may correspond to quite different anisotropy decays and vice versa, both varying with the emission wavelength, the base sequence and the duplex size. Our observations cannot be explained in terms of monomer and excimer emission exclusively, as concluded in the past on the basis of steady-state measurements. Excitons also contribute to the fluorescence. These are rapidly trapped by excimers, characterized by long-lived weak emission.