Photocatalytic degradation of organophosphate flame retardant TBEP: kinetics and identification of transformation products by orbitrap mass spectrometry

The photocatalytic degradation of tris (2–butoxyethyl) phosphate (TBEP) flame retardant using visible light response catalysts TiO₂/V₂O₅, (N,F-doped)-TiO₂/V₂O₅, and N-doped-SrTiO₃ has been studied by high-resolution orbitrap mass spectrometry. TBEP degradation followed first-order kinetics with half-life values ranging between 9.8 and 83.5 min. N-doped-SrTiO₃ was the catalyst with better photocatalytic performance while activity for TiO₂/V₂O₅ composites followed the trend: N, F- TiO₂/V₂O₅ > N-TiO₂/V₂O₅> TiO₂/V₂O₅. The identified degradation products (DPs) revealed hydroxylation, further oxidation and dealkylation as major degradation pathways. Based on the identified DPs and scavenging experiments, ^?OH radical-mediated reactions can be considered for the degradation of TBEP using TiO₂ and SrTiO₃-based photocatalytic materials.     

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.     

Carbon-13 solid state NMR investigation and modeling of the morphological reorganization in regenerated cellulose fibres induced by controlled acid hydrolysis

CPMAS carbon-13 NMR has been used to follow structural changes affecting regenerated cellulose fibres during hydrolysis by mineral acids. The C4 envelope of regenerated cellulose was deconvoluted into separate peaks, for ordered (crystal), part-ordered (surface) and disordered (non-crystal) polymer, which allowed calculation of average crystal lateral sizes, in good agreement with WAXD data. A geometrical model has been used to describe recrystallisation at lateral crystal faces, occurring within a disordered boundary surrounding the crystal interior. A one-dimensional relaxation-diffusion model has also been constructed, appropriate to the spinodal structure of lyocell. This has provided estimates of proton T_1ρ relaxation times for pure crystalline (cellulose II) and non-crystalline cellulose, around 24 and 4.5 ms, respectively, at a 45 kHz B₁ field. From the model, crystalline and non-crystalline regions in lyocell are estimated to each be around 2.5 nm thickness for a material of 50% crystallinity, consistent with the 2–3 nm dimensions derived from C4 peak devonvolution.     

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.     

New Pd(II)–mechlorethamine complex: Synthesis,NMR study of hydrolytic activity and in vitro evaluation of antiradical property of new complex and its alkylating precursor

The reaction of PdCl₂ with anticancer-alkylating agent mechlorethamine hydrochloride (CH₃NH(C₂H₄Cl)₂ = HN2 x HCl), in the molar ratio 1:2, affords the complex [CH₃NH(C₂H₄Cl)₂]₂[PdCl₄] ([H2N2]₂[PdCl₄]). Novel Pd(II) complex and the complex precursor mechlorethamine hydrochloride were tested for their antiradical property. Both present weak interaction with 2, 29-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS). Assays with soybean lipoxygenase and with superoxide anion radicals in vitro showed very high radical scavenging activity of the complex, whereas the complex precursor mechlorethamine hydrochloride presents lower inhibition. Hydrolytic activity of new complex with N-acetylhistidylglycine (AcHis–Gly) was also studied. It was established that regioselective cleavage of the amide bond of the investigated dipeptide had occurred after heating at 60 °C and at pH = 1.5 for 36 h.     

Brasilane-type sesquiterpenoids from Laurencia obtusa

[structure: see text] Three novel halogenated rearranged sesquiterpenes (1-3) have been isolated along with brasilenol (4) and epibrasilenol (5) from the organic extract of the red alga Laurencia obtusa, collected at Symi island in the Aegean Sea, Greece. The new metabolites possess the unusual skeleton of brasilane and contain the unprecedented 1,6-epoxy moiety. The structures of the new natural products, as well as their relative stereochemistry, were established by means of spectral data analyses, including two-dimensional NMR experiments along with molecular calculations.     

The effect of ionic and electronic properties of titanium oxide on the electrochemical growth and redox behavior of polyaniline on titanium surfaces

Polyaniline (PANI) was electrodeposited directly from aniline (ANI)-containing sulfuric acid media on Ti|TiO₂ electrodes, which were prepared in ANI-free 0.5 M H₂SO₄ solution by applying suitable anodization conditions in order to control the donor density (N _D) in the oxide layer of a fixed thickness. By using the suggested procedure, reproducible conditions for the cyclic voltammetric growth of PANI on Ti can be achieved, and most importantly, the properties of Ti|TiO₂|PANI electrodes can be modulated to meet the requirements for specific applications. The polymerization rate and the deposited amount of PANI were found to depend strongly on the N _D estimated by Mott-Schottky analysis. The redox behavior of the resulted Ti|TiO₂|PANI electrodes indicated differences in acid solutions as compared with the corresponding behavior of other PANI-modified metal surfaces. Analysis of the anodic and cathodic electrochemical response of the prepared Ti|TiO₂|PANI electrodes discloses the significant role of ionic and electronic properties of the intervening oxide between the metal support and PANI.     

Exploring the 2′-Hydroxy-Chalcone Framework for the Development of Dual Antioxidant and Soybean Lipoxygenase Inhibitory Agents

2′-hydroxy-chalcones are naturally occurring compounds with a wide array of bioactivity. In an effort to delineate the structural features that favor antioxidant and lipoxygenase (LOX) inhibitory activity, the design, synthesis, and bioactivity profile of a series of 2′-hydroxy-chalcones bearing diverse substituents on rings A and B, are presented. Among all the synthesized derivatives, chalcone 4b, bearing two hydroxyl substituents on ring B, was found to possess the best combined activity (82.4% DPPH radical scavenging ability, 82.3% inhibition of lipid peroxidation, and satisfactory LOX inhibition value (IC₅₀ = 70 μM). Chalcone 3c, possessing a methoxymethylene substituent on ring A, and three methoxy groups on ring B, exhibited the most promising LOX inhibitory activity (IC₅₀ = 45 μM). A combination of in silico techniques were utilized in an effort to explore the crucial binding characteristics of the most active compound 3c and its analogue 3b, to LOX. A common H-bond interaction pattern, orienting the hydroxyl and carbonyl groups of the aromatic ring A towards Asp768 and Asn128, respectively, was observed. Regarding the analogue 3c, the bulky (-OMOM) group does not seem to participate in a direct binding, but it induces an orientation capable to form H-bonds between the methoxy groups of the aromatic ring B with Trp130 and Gly247.     

Synthesis of Fused 9,10‐Dihydro‐6H‐Azepino‐ and 9,10‐Dihydro‐6H‐[1,3]Diazepino[1,2‐e]Purines via Ring Closing Metathesis as Antilipid Peroxidation Agents

Ring closing metathesis of 8‐allyl‐9‐butenylpurines or N,9‐diallyl‐N‐methyl‐9H‐purin‐8‐amines with the Grubbs second generation catalyst resulted in fused 9,10‐dihydro‐6H‐azepino[1,2‐e]purines or 9,10‐dihydro‐6H‐[1,3]diazepino[1,2‐e]purines, respectively. The 8‐allyl‐9‐butenylpurines were prepared from 8‐bromo‐9‐butenylpurines after Stille coupling with allyltributyltin. The N,9‐diallyl‐N‐methyl‐9H‐purin‐8‐amines were synthesized from 9‐allyl‐8‐bromopurines after treatment with allylamine in H₂O under MW irradiation, followed by methylation with MeI in KOH. The new compounds were tested as inhibitors of lipid peroxidation. 6‐Methyl‐4‐(morpholin‐4‐yl)‐7,10‐dihydro‐6H‐[1,3]diazepino[1,2‐e]purine presents interesting results and could serve as a lead compound.