Catalytic Performance in Nitroarene Reduction of Nanocatalyst Based on Noble Metal Nanoparticles Supported on Polymer/s-Layer Protein Hybrids.

We present a novel bionanocatalyst fabricated by the adsorption-reduction of metal ions on a polyurethane/S-layer protein biotemplate. The bioinspired support was obtained by the adsorption of S-layer proteins (isolated from Lentilactobacillus kefiri) on polyurethane particles. Silver and platinum nanoparticles were well-loaded on the surface of the support after the combination with metallic salts and reduction with H2 at room temperature. Transmission electron microscopy analysis revealed the strawberry-like morphology of the bionanocatalysts with a particle size, dn, of 2.39 nm for platinum and 9.60 nm for silver. Both systems catalyzed the hydrogenation of p-nitrophenol to p-aminophenol with high efficiency in water at mild conditions in the presence of NaBH4. Three different amounts of bionanocatalyst were tested, and in all cases, conversions between 97 and 99% were observed. The catalysts displayed excellent recyclability over ten cycles, and no extensive damage in their nanostructure was noted after them. The bionanocatalysts were stable during their production, storage, and use, thanks to the fact that the biosupport provides an effective driving force in the formation and stabilization of the metallic nanoparticles. The successful bioinspired production strategy and the good catalytic ability of the systems are encouraging in the search for nontoxic, simple, clean, and eco-friendly procedures for the synthesis and exploitation of nanostructures.

Diethylamino hydroxybenzoyl hexyl benzoate (DHHB) as additive to the UV filter avobenzone in cosmetic sunscreen formulations - Evaluation of the photochemical behavior and photostabilizing effect.

The aim of the present study was to investigate the photochemical behavior of DHHB and its photostabilizing effect on avobenzone (AVO) in different sunscreen formulations. The formulations were subjected to photostability studies by HPLC and spectrophotometry. In vitro phototoxicity was assessed using 3T3 fibroblast cultures. The mechanism of interaction between DHHB and AVO was investigated by steady state and time-resolved fluorescence spectroscopy. All formulations provided ultra-protection against UVA radiation. HPLC results demonstrated that DHHB did not present a photostabilizing effect on AVO. Fluorescence spectroscopy showed that AVO and DHHB interact by a static quenching mechanism and DHHB did not affect the AVO excited state lifetime. In addition, the energy transfer by Förster mechanism (FRET), which is the most often mechanism responsible for singlet-singlet quenching, is unlikely in this work. These results suggest why DHHB did not work as a photostabilizer on AVO singlet excited state. Phototoxicity results demonstrated that combinations containing DHHB (C2) did not show a phototoxic potential. Finally, although DHHB was considered to be photostable for all formulations studied (F2 and F3) it did not increase the photostability of AVO (F3). Thus, we suggested that formulations containing DHHB (F2) should be considered more advantageous than formulations containing AVO and AVO/DHHB (F1 and F3 respectively).

Design and evaluation of 4-aminophenol and salicylate derivatives as free-radical scavenger.

This theoretical and experimental study describes the design and evaluation of the free-radical scavenging effect for the molecular association of 4-aminophenol and salicylate derivatives. For this purpose, we employed theoretical methods for the selection of antioxidant drugs and the rapid methods of evaluation: the 1,1-diphenyl-2-picrylhydrazyl radical and the thiobarbituric acid reactive substances in the lipid peroxidation initiated by Fe(2+) and ascorbic acid in human erythrocytes. The associate derivatives exhibited a more potent inhibition than the salicylic acid, while the benzoyl compound exhibited a more potent inhibition than paracetamol. The molecular parameters related to the electron distribution and structure (ionization potential and energy of the highest occupied molecular orbital) correlated very well with the antioxidant action of the compounds studied here in different tests.

Venezuelines A-G, new phenoxazine-based alkaloids and aminophenols from Streptomyces venezuelae and the regulation of gene target Nur77.

Five new phenoxazine-based alkaloids venezuelines A-E (1-5) and two new aminophenols venezuelines F-G (6-7), as well as three known analogues exfoliazone, chandrananimycin D and carboxyexfoliazone were isolated from the fermentation broth of the marine-derived bacterium Streptomyces venezuelae. The structures of new compounds were determined on the basis of extensive spectroscopic analysis. The cytotoxic activity of these compounds against a panel of tumor cell lines were tested, while the regulation of gene target Nur77 of 2 and exfoliazone (8) were evaluated.

A greener and highly sensitive flow-based procedure for carbaryl determination exploiting long pathlength spectrophotometry and photochemical waste degradation.

An environmentally friendly analytical procedure with high sensitivity for determination of carbaryl pesticide in natural waters was developed. The flow system was designed with solenoid micro-pumps in order to improve mixing conditions and minimize reagent consumption as well as waste generation. A long pathlength (100 cm) flow cell based on a liquid core waveguide (LCW) was employed to increase the sensitivity in detection of the indophenol formed from the reaction between carbaryl and p-aminophenol (PAP). A clean-up step based on cloud-point extraction was explored to remove the interfering organic matter, avoiding the use of toxic organic solvents. A linear response was observed within the range 5-200 microg L(-1) and the detection limit, coefficient of variation and sampling rate were estimated as 1.7 microg L(-1) (99.7% confidence level), 0.7% (n=20) and 55 determinations per hour, respectively. The reagents consumption was 1.9 microg of PAP and 5.7 microg of potassium metaperiodate, with volume of 2.6 mL of effluent per determination. The proposed procedure was selective for the determination of carbaryl, without interference from other carbamate pesticides. Recoveries within 84% and 104% were estimated for carbaryl spiked to water samples and the results obtained were also in agreement with those found by a batch spectrophotometric procedure at the 95% confidence level. The waste of the analytical procedure was treated with potassium persulphate and ultraviolet irradiation, yielding a colorless residue and a decrease of 94% of total organic carbon. In addition, the residue after treatment was not toxic for Vibrio fischeri bacteria.

One-pot, Pd-catalyzed synthesis of trans-dihydrobenzofurans from o-aminophenols.

An efficient and facile synthesis of trans-dihydrobenzofurans has been accomplished from o-aminophenols and phenylpropenes via a novel (one-pot) diastereoselective Pd-catalyzed oxyarylation reaction. The development and optimization of this method is described.

Integrated microfluidic magnetic immunosensor for quantification of human serum IgG antibodies to Helicobacter pylori.

In this paper, we have developed and characterized a microfluidic magnetic immunosensor coupled to a gold electrode for the rapid and sensitive quantification of human serum IgG antibodies to Helicobacter pylori. This microorganism cause peptic ulcers and chronic gastritis, affecting around the 10% of the world population. The sensor was completely automated and the antibodies detection in serum samples was carried out using a non-competitive immunoassay based on the use of purified H. pylori antigens that are immobilized on magnetic microspheres 3-aminopropyl-modified. The magnetic microbeads were injected into microchannel devices and manipulated for an external removable magnet. The IgG antibodies in human serum sample are allowed to react immunologically with the immobilized antigens, and the bounded antibodies are quantified by alkaline phosphatase (AP) enzyme-labeled second antibodies specific to human IgG. The p-aminophenyl phosphate (p-APP) was converted to p-aminophenol (p-AP) by AP and an electroactive product was detected on gold layer electrode at 0.250V. The response current obtained from the product of enzymatic reaction is directly proportional to the activity of the enzyme and, consequently, to the amount of IgG antibodies to H. pylori in serum samples. The electrochemical detection can be done within 1min and total assay time was 25min. The calculated detection limits for electrochemical detection and the ELISA procedure were 0.37 and 2.1UmL(-1), respectively, and the within- and between-assay coefficients of variation were below 5%. Our results indicate the potential usefulness of our fabricated microbiochip for the early assessment of human serum immunoglobulin G (IgG) antibodies to H. pylori.

A catalytically active molecularly imprinted polymer that mimics peroxidase based on hemin: application to the determination of p-aminophenol.

Despite the increasing number of applications of molecularly imprinted polymers (MIP) in analytical chemistry, the synthesis of polymers with hemin introduced as the catalytic center to mimic the active site of peroxidase remains as a challenge. In the current work, a new type of molecularly imprinted polymer (MIP) was synthesized with 4-aminophenol (4-APh) as the template and two monomers: hemin, which acts as the catalytic center, and methacrylic acid (MAA), which is used to build the active sites. This work shows that MIP successfully mimics peroxidase. For this purpose, a flow injection analysis system coupled to an amperometric detector was investigated through multivariate analysis. The determination of 4-APh was not affected by the equimolar presence of structurally similar phenol compounds, including catechol, 4-chloro-3-methylphenol, 2-aminophenol, guaiachol, chloroguaiachol and 2-cresol, thus highlighting the good performance of the imprinted polymer. Under the optimized experimental conditions, an analytical curve covering a wide linear response range from 0.8 up to 500 micromol L(-1) (r > 0.999) was obtained, and the method gave satisfactory precisions (n = 8), as evaluated via the relative standard deviation (RSD), of 4.1 and 3.2% for solutions of 4-APh of 50 and 500 micromol L(-1), respectively. Recoveries of 96-111% from water samples (tap water and river water) spiked with 4-APh were achieved, thus illustrating the accuracy of the proposed system.

Synthesis and characterization of di-phenyl-tin(IV)-salicyliden-ortho-aminophenols: analysis of in vitro antitumor/antioxidant activities and molecular structures.

The one pot reactions carried among salicylaldehyde 1, ortho-aminophenols 2a-2g, and di-phenyl-tin(IV) oxide 3 led to seven di-phenyl-tin(IV) compounds 4a-4g in good yields (97-83%). All compounds were analyzed by IR, 1H, 13C, 119Sn NMR spectroscopy, mass spectrometry and elemental analyses; furthermore, in the case of compounds 4b, 4c, 4e and 4g by X-ray diffraction. Compounds 4a-4g were tested in vitro against six human tumor cell lines U251, PC-3, K-562, HCT-15, MCF-7 and SKLU-1 to assess their in vitro antitumor activity. The results suggest biological specificity towards U251, MCF-7 and SKLU-1 cells at doses below 2.5 microM, which are lower than cis-platin IC50's in the three cell lines. Since the inhibitory concentration values for the series were alike to Ph(2)SnCl(2) is feasible that only the Ph(2)Sn moiety is responsible for those activities, further experiments are under research. Besides, 4a-4g were tested for their antioxidant efficiency in rat brain homogenate showing that 4g is more active (IC50=3.01 microM) than the flavone quercetin (natural antioxidant, IC50=4.11 microM) on inhibition of thiobarbituric acid reactive substances (TBARS). The TBARS activity (IC50) correlates with the ortho-aminophenol substitutions and a linear combination among sigma Hammett, one bond tin coupling constants and tin chemical shifts against the measured IC(50-TBARS) was found. This correlation gave basis that the implied molecular variables can become trackers for the calculation of TBARS inhibitory concentrations in similar systems. Moreover, there seemed to be an inverse structure-response behavior among activities, since the 4g derivative is the less active compound for cytotoxic assays meanwhile it is the best in antioxidant tests.

Electron paramagnetic resonance analyses of biotransformation reactions with cytochrome P-450 immobilized on mesoporous molecular sieves.

Mobil Crystalline Material (MCM-41) can be used for the immobilization of enzymes and the investigation of electron transfer in biological systems. Electron transfer between MCM-41 with aluminum (Al-MCM-41) and cytochrome P-450 (CYP2B4) was observed using electron paramagnetic resonance (EPR). When CYP2B4 was immobilized by adsorption, it catalyzed the conversion of aniline to p-aminophenol. The electron transfer was evidenced when the signal with a g value (also called g-factor or spectroscopic manifestation of the magnetic moment) of 1.98 increased at the same time that the signal with a g value 2.24 decreased due to the addition of NADPH to CYP2B4 immobilized on Al-MCM-41, indicating that FeIII was reduced to FeII. Therefore, it is possible that Al-MCM-41 participates in the electron transfer process in biological systems.

Removal of p-aminophenol and p-nitrophenol from aqueous solution through adsorption on antimony, cadmium, and zirconium ferrocyanides.

Adsorptive interaction of p-aminophenol and p-nitrophenol in the concentration range 10(-4)-10(-5) M and at room temperature (30+/-1 degrees C) was studied with antimony, cadmium, and zirconium ferrocyanides. The interaction followed the Langmuir type of adsorption in general. The p-nitrophenol was found to have greater affinity for the antimony, cadmium, and zirconium ferrocyanides then the p-aminophenol.

Reversible and irreversible inhibitory activity of succinic and maleic acid derivatives on acetylcholinesterase.

Aryl succinic and maleic acid derivatives are potent inhibitors of bovine acetylcholinesterase in vitro. Succinic acid aminophenol derivatives 1b-e and 2b-d act as reversible inhibitors of acetylcholinesterase, while maleic acid aminophenol derivatives 3b-d and 4c-e act as choline subsite-directed irreversible inhibitors, detected by dialysis in the presence of edrophonium. Linear relationships between the logarithm of the velocity of hydrolysis of acetylcholine plotted against the time of incubation at several different inhibitor concentrations were determined. The K(i) for reversible competitive inhibitors was determined. For irreversible inhibitors the K(i) for the dissociation constant of the enzyme-inhibitor complex at the beginning of the recognition process was also determined as well as the inactivation constant of the enzyme-inhibitor adduct formation k(+2) and the bimolecular inhibition constant k(i) for the inhibition of acetylcholinesterase by aminophenol derivatives 3b-d and 4c-e. The conclusions of this study can be summarized as follows for both families: (a) the aromatic moiety played a critical role in the recognition of the active site; (b) in case of the reversible inhibitor, when the ester function took the place of the hydroxyl fragment, there was an important increase in the affinity; and (c) the distance between phenolic hydroxyl and nitrogen was critical because the inhibition is ortho<