Application of lipase immobilized on a hydrophobic support for the synthesis of aromatic esters.

The present study aimed at preparing three biocatalysts via physical adsorption of lipases from Candida rugosa (CRL), Mucor javanicus, and Candida sp. on a hydrophobic and mesoporous support (Diaion HP-20). These biocatalysts were later applied to the synthesis of aromatic esters of apple peel and citrus (hexyl butyrate), apple and rose (geranyl butyrate), and apricot and pineapple (propyl butyrate). Scanning electron microscopy and gel electrophoresis confirmed a selective adsorption of lipases on Diaion, thus endorsing simultaneous immobilization and purification. Gibbs free energy (∆G) evinced the spontaneity of the process (-17.9 kJ/mol ≤ ∆G ≤ -5.1 kJ/mol). Maximum immobilized protein concentration of 30 mg/g support by CRL. This biocatalyst was the most active in olive oil hydrolysis (hydrolytic activity of 126.0 ± 2.0 U/g) and in the synthesis of aromatic esters. Maximum conversion yield of 89.1% was attained after 150 Min for the synthesis of hexyl butyrate, followed by the synthesis of geranyl butyrate (87.3% after 240 Min) and propyl butyrate (80.0% after 150 Min). CRL immobilized on Diaion retained around 93% of its original activity after six consecutive cycles of 150 Min for the synthesis of hexyl butyrate.

Aromatic compounds produced by endophytic fungi isolated from red alga Asparagopsis taxiformis - Falkenbergia stage.

Endophytic fungi were isolated from red alga Asparagopsis taxiformis - Falkenbergia stage, collected from the Brazilian coast, and were identified as Annulohypoxylon stygium (AT-03) and A. yungensis (AT-06) based on their macro/micromorphological and molecular features. Bioassay-guided fractionation of the EtOAc extract from laboratory cultures of both strains yielded known compounds pyrogallol from A. stygium, (3 R)-scytalone and (3 R,4 R)-4-hydroxy-scytalone from A. yungensis. Pyrogallol was active against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli strains. An inactive fraction from A. stygium afforded two additional compounds, (3 R,4 R)-3,4,5-trihydroxy-1-tetralone and tyrosol. Optically active compounds had their stereochemistry determined by circular dichroism (CD) spectroscopy.

Synthesis, in vitro and in vivo anti-Trypanosoma cruzi and toxicological activities of nitroaromatic Schiff bases.

Chagas disease is a major health problem not only in Latin America but also in Europe and North America due to the spread of this disease into nonendemic areas. In terms of global burden, this major tropical infection is considered to be one of the most neglected diseases, and there are currently only two available chemotherapies: benznidazole and nifurtimox. Unfortunately, although these chemotherapies are beneficial in the acute phase of the disease, benznidazole and nifurtimox lead to significant side effects, including hepatitis and neurotoxicity. Therefore, the search for and development of more effective, safe and inexpensive anti-Trypanosoma cruzi drugs are required. In this work, a series of 10 nitroaromatic Schiff bases bearing different (nitro) aromatic rings-was synthesized. Subsequently, the in vitro and in vivo anti-T. cruzi activities of the Schiff bases were investigated, as well as the in vivo toxicity and the biological effects. The basic structure of the most promising in vivo Schiff base, 10 would be useful in the synthesis of new compounds for Chagas disease treatment.

Fluorinated waste and firefighting activities: biodegradation of hydrocarbons from petrochemical refinery soil co-contaminated with halogenated foams.

Perfluorinated compounds, including fluorotelomers, are important constituents of firefighting foams to extinguish fuel fires in the petrochemical industry, airports, and at fire-training sites. In this study, we monitored the biodegradation process in a co-contamination scenario with monoaromatic hydrocarbons commonly found in fuels (benzene, toluene) and fluorotelomers. The CO2 production rates were evaluated by a factorial design taking into account the effect of seasonality at in situ natural attenuation processes. Headspace analysis by gas chromatography with a thermal conductivity detector (GC-TCD) was applied to detect CO2 production, whereas monoaromatics were analyzed by gas chromatography coupled to mass spectrometry (GC-MS). According to our results, seasonality had a detectable effect during summer, yielding different CO2 production rates. Higher temperatures increased CO2 production rate, while higher concentrations of fluorotelomer inhibited the biodegradation process. On average, benzene and toluene were depleted 17.5 days earlier in control assays without fluorotelomers. Toluene removal efficiency was also notably higher than benzene. The noticeable decrease in degradation rates of monoaromatics was caused by perfluorinated compounds that are possibly linked to metabolic inhibition mechanisms. Fluorotelomer diminished catabolism in all of our batch cultures. In addition to this, an alternative production of by-products could be detected. Thus, we propose that transient components of the benzene and toluene degradation may be differentially formed, causing the benzene, toluene, and perfluorinated co-contaminations to go through switched metabolic stages under the presence of fluoride in a contamination scenario.

Influence of aromatic additives on Bismarck Brown Y dye color removal treatment by Fenton processes.

The influence of diverse aromatic additives on Fenton processes (Fe2+/H2O2, Fe3+/H2O2) has been evaluated by using the Bismarck Brown Y (BBY) di azo dye as target pollutant. Results indicate that all tested Fe3+-reducing additives (gallic, 3,4-dihydroxyphenylacetic, 2,3-dihydroxybenzoic, and 2,5-dihydroxybenzoic acids, catechol, and hydroquinone) exhibited pro-oxidant properties during BBY dye color removal, mainly during Fe3+/H2O2 treatments. For example, in the presence of hydroquinone BBY color removal was increased from 22 to 83% for 60 min through the Fe3+/H2O2 process. The effect of non-reducing additives was less pronounced, among which salicylic and 2,4-dihydroxybenzoic acids were more efficient at removing dye color than benzoic acid and methylene blue. It was suggested that OH radicals may have converted non-reducing additives into Fe3+-reducing intermediates, which had a positive effect on the treatments. On the other hand, antioxidant properties were observed during BBY color removal in the presence of higher concentrations of gallic and salicylic acids. These items of data indicate that a minimum amount of aromatic additive was enough to increase BBY dye color removal by Fenton processes.

Facile Formation of Redox-Active Totally Organic Nanoparticles in Water by In Situ Reduction of Organic Precursors Stabilized through Aromatic-Aromatic Interactions by Aromatic Polyelectrolytes.

The formation of redox-active, totally organic nanoparticles in water is achieved following a strategy similar to that used to form metal nanoparticles. It is based on two fundamental concepts: i) complexation through aromatic-aromatic interactions of a water-soluble precursor aromatic molecule with polyelectrolytes bearing complementary charged aromatic rings, and ii) reduction of the precursor molecule to achieve stabilized nanoparticles. Thus, formazan nanoparticles are synthesized by reduction of a tetrazolium salt with ascorbic acid using polyelectrolytes bearing benzene sulfonate residues of high linear aromatic density, but cannot be formed in the presence of nonaromatic polyelectrolytes. The red colored nanoparticles are efficiently encapsulated in calcium alginate beads, showing macroscopic homogeneity. Bleaching kinetics with chlorine show linear rates on the order of tenths of milli-meters per minute. A linear behavior of the dependence of the rate of bleaching on the chlorine concentration is found, showing the potential of the nanoparticles for chlorine sensing.

Characterization of sulfur and nitrogen compounds in Brazilian petroleum derivatives using ionic liquid capillary columns in comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometric detection.

Diesel and naphtha samples were analyzed using ionic liquid (IL) columns to evaluate the best column set for the investigation of organic sulfur compounds (OSC) and nitrogen(N)-containing compounds analyses with comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry detector (GC×GC/TOFMS). Employing a series of stationary phase sets, namely DB-5MS/DB-17, DB-17/DB-5MS, DB-5MS/IL-59, and IL-59/DB-5MS, the following parameters were systematically evaluated: number of tentatively identified OSC, 2D chromatographic space occupation, number of polyaromatic hydrocarbons (PAH) and OSC co-elutions, and percentage of asymmetric peaks. DB-5MS/IL-59 was chosen for OSC analysis, while IL59/DB-5MS was chosen for nitrogen compounds, as each stationary phase set provided the best chromatographic efficiency for these two classes of compounds, respectively. Most compounds were tentatively identified by Lee and Van den Dool and Kratz retention indexes, and spectra-matching to library. Whenever available, compounds were also positively identified via injection of authentic standards.

Increasing the reaction rate of hydroxynitrile lyase from Hevea brasiliensis toward mandelonitrile by copying active site residues from an esterase that accepts aromatic esters.

The natural substrate of hydroxynitrile lyase from rubber tree (HbHNL, Hevea brasiliensis) is acetone cyanohydrin, but synthetic applications usually involve aromatic cyanohydrins such as mandelonitrile. To increase the activity of HbHNL toward this unnatural substrate, we replaced active site residues in HbHNL with the corresponding ones from esterase SABP2 (salicylic acid binding protein 2). Although this enzyme catalyzes a different reaction (hydrolysis of esters), its natural substrate (methyl salicylate) contains an aromatic ring. Three of the eleven single-amino-acid-substitution variants of HbHNL reacted more rapidly with mandelonitrile. The best was HbHNL-L121Y, with a kcat 4.2 times higher and high enantioselectivity. Site-saturation mutagenesis at position 121 identified three other improved variants. We hypothesize that the smaller active site orients the aromatic substrate more productively.

Minimizing the risk of reporting false aromaticity and antiaromaticity in inorganic heterocycles following magnetic criteria.

Although aromaticity is a concept in chemistry, in the last years, special efforts have been carried out in order to propose theoretical strategies to quantify it as a property of molecular rings. Among them, perhaps the computation of nucleus independent chemical shifts (NICSs) is the most commonly used, since it is possible to calculate it in an easy and fast way with most used quantum chemistry software. However, contradicting assignments of aromaticity by NICS and other methods have been reported in the literature, especially in studies concerning inorganic chemistry. In this Article is proposed a new and simple strategy to use the NICS information to assess aromaticity, identifying the point along the axis perpendicular to the molecular plane where the in-plane component of NICS becomes zero; it is called free of in-plane component NICS (FiPC-NICS). This spatial point is proposed as secure to consider NICS as an aromaticity descriptor; this simple proposal is evaluated in borazine and cyclotriphosphazenes. The results are compared with carefully examined aromatic stabilization energies and magnetically induced current-density analysis.

Emulsifying activity and stability of a non-toxic bioemulsifier synthesized by Microbacterium sp. MC3B-10.

A previously reported bacterial bioemulsifier, here termed microbactan, was further analyzed to characterize its lipid component, molecular weight, ionic character and toxicity, along with its bioemulsifying potential for hydrophobic substrates at a range of temperatures, salinities and pH values. Analyses showed that microbactan is a high molecular weight (700 kDa), non-ionic molecule. Gas chromatography of the lipid fraction revealed the presence of palmitic, stearic, and oleic acids; thus microbactan may be considered a glycolipoprotein. Microbactan emulsified aromatic hydrocarbons and oils to various extents; the highest emulsification index was recorded against motor oil (96%). The stability of the microbactan-motor oil emulsion model reached its highest level (94%) at 50 °C, pH 10 and 3.5% NaCl content. It was not toxic to Artemia salina nauplii. Microbactan is, therefore, a non-toxic and non-ionic bioemulsifier of high molecular weight with affinity for a range of oily substrates. Comparative phylogenetic assessment of the 16S rDNA gene of Microbacterium sp. MC3B-10 with genes derived from other marine Microbacterium species suggested that this genus is well represented in coastal zones. The chemical nature and stability of the bioemulsifier suggest its potential application in bioremediation of marine environments and in cosmetics.

Aromatic-aromatic interactions in proteins: beyond the dimer.

Aromatic residues are key widespread elements of protein structures and have been shown to be important for structure stability, folding, protein-protein recognition, and ligand binding. The interactions of pairs of aromatic residues (aromatic dimers) have been extensively studied in protein structures. Isolated aromatic molecules tend to form higher order clusters, like trimers, tetramers, and pentamers, that adopt particular well-defined structures. Taking this into account, we have surveyed protein structures deposited in the Protein Data Bank in order to find clusters of aromatic residues in proteins larger than dimers and characterized them. Our results show that larger clusters are found in one of every two unique proteins crystallized so far, that the clusters are built adopting the same trimer motifs found for benzene clusters in vacuum, and that they are clearly nonlocal brining primary structure distant sites together. We extensively analyze the trimers and tetramers conformations and found two main cluster types: a symmetric cluster and an extended ladder. Finally, using calmodulin as a test case, we show aromatic clsuters possible role in folding and protein-protein interactions. All together, our study highlights the relevance of aromatic clusters beyond the dimer in protein function, stability, and ligand recognition.

Comparison of QSARs and characterization of structural basis of bioactivity using partial order theory and formal concept analysis: a case study with mutagenicity.

Fifteen quantitative structure-activity relationship (QSAR) models developed by various authors for the prediction of mutagenicity of aromatic and heteroaromatic amines were analyzed and thirteen of them, based on 95 amines, were compared using their respective statistics and order theory (Hasse Diagram Technique, HDT) to obtain an ordering of QSAR models. The technique of Formal Concept Analysis (FCA) was applied to the set of 95 amines to extract concepts and, in general, knowledge about the relationship between structural attributes and mutagenicity. HDT may be useful as a general tool for the comparison of different classes of QSAR models. FCA turns out to be a novel mathematical technique for seeking for relationships between molecular structure and activity.

Therapeutical targeting of nucleic acid-sensing Toll-like receptors prevents experimental cerebral malaria.

Excessive release of proinflammatory cytokines by innate immune cells is an important component of the pathogenic basis of malaria. Proinflammatory cytokines are a direct output of Toll-like receptor (TLR) activation during microbial infection. Thus, interference with TLR function is likely to render a better clinical outcome by preventing their aberrant activation and the excessive release of inflammatory mediators. Herein, we describe the protective effect and mechanism of action of E6446, a synthetic antagonist of nucleic acid-sensing TLRs, on experimental cerebral malaria (ECM) induced by Plasmodium berghei ANKA. We show that in vitro, low doses of E6446 specifically inhibited the activation of human and mouse TLR9. Tenfold higher concentrations of this compound also inhibited the human TLR8 response to single-stranded RNA. In vivo, therapy with E6446 diminished the activation of TLR9 and prevented the exacerbated cytokine response observed during acute Plasmodium infection. Furthermore, severe signs of ECM, such as limb paralysis, brain vascular leak, and death, were all prevented by oral treatment with E6446. Hence, we provide evidence that supports the involvement of nucleic acid-sensing TLRs in malaria pathogenesis and that interference with the activation of these receptors is a promising strategy to prevent deleterious inflammatory responses that mediate pathogenesis and severity of malaria.

Chemical characterization of aromatic compounds in extra heavy gas oil by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry.

Comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS) was used for the characterization of aromatic compounds present in extra heavy gas oil (EHGO) from Brazil. Individual identification of EHGO compounds was successfully achieved in addition to group-type separation on the chromatographic plane. Many aromatic hydrocarbons, especially polycyclic aromatic hydrocarbons and sulfur compounds, were detected and identified, such as chrysenes, phenanthrenes, perylenes, benzonaphthothiophenes and alkylbenzonaphthothiophenes. In addition, triaromatic steroids, methyl-triaromatic steroids, tetrahydrochrysenes and tetraromatic pentacyclic compounds were present in the EHGO aromatic fractions. Considering the roof-tile effect observed for many of these compound classes and the high number of individual compounds identified, GC×GC-TOFMS is an excellent technique to characterize the molecular composition of the aromatic fraction from EHGO samples. Moreover, data processing allowed the quantification of aromatic compounds, in class and individually, using external standards. EHGO data were obtained in µgg(-1), e.g., benzo[a]pyrene were in the range 351 to 1164µgg(-1). Thus, GC×GC-TOFMS was successfully applied in EHGO quantitative analysis.

Aromaticity in cyanuric acid.

This study analyzes the aromatic nature of cyanuric acid (hexahydrotriazine) and some of its derivatives, in terms of aromatic stabilization energy (ASE) and electronic behavior. The simplest molecule (C(3)N(3)O(3)H(3)) is the most aromatic item out of the entire set, but some of the others also display aromatic character. The structure of all the rings is analyzed considering their molecular orbitals as well as studying the inductive effect.

Efficient synthesis of 16 aromatic Morita-Baylis-Hillman adducts: Biological evaluation on Leishmania amazonensis and Leishmania chagasi.

Sixteen aromatic Morita-Baylis-Hillman adducts (MBHA) 1-16 were efficiently synthesized in a one step Morita-Baylis-Hillman reaction (MBHR) involving commercial aldehydes with methyl acrylate or acrylonitrile (81-100% yields) without the formation of side products on DABCO catalysis and at low temperature (0°C). The toxicities of these compounds were assessed against promastigote form of Leishmania amazonensis and Leishmania chagasi. The low synthetic cost of these MBHA, green synthetic protocols, easy one-step synthesis from commercially available and cheap reagents as well as the very good antileishmanial activity obtained for 14 and 16 (IC50 values of 6.88µgmL⁻¹ and 11.06µgmL⁻¹ respectively on L. amazonensis; 9.58µgmL⁻¹ and 14.34µgmL⁻¹ respectively on L. chagasi) indicates that these MBHA can be a novel and promising class of anti-parasitic compounds.

Pattern of volatile aldehydes and aromatic hydrocarbons in the largest urban rainforest in the Americas.

Atmospheric concentrations of aldehydes and monoaromatic hydrocarbons were determined in Tijuca Forest, the largest urban tropical forest in the Americas. The forest is a protected area, surrounded by the city of Rio de Janeiro. Data were also obtained in a commercial and a residential area for comparison. A total of 160 aldehyde samples and 60 BTEX (benzene, toluene, ethyl-benzene and xylenes) samples were collected from four locations between January and August of 2008. The aldehydes were collected using C18 resin cartridges coated with 2,4-dinitrophenylhydrazine and analyzed by high performance liquid chromatography (HPLC) with a diode array UV-Vis detector, while the BTEX samples were collected using tubes of coconut charcoal, which were then extracted with dichloromethane and analyzed by gas chromatography (GC). Within Tijuca Forest, formaldehyde and acetaldehyde levels were in the range of

Heterogeneous CO(2) evolution from oxidation of aromatic carbon-based materials.

Carbon dioxide is one of the main gaseous products in oxidation of carbonaceous materials via both homogeneous and heterogeneous reactions. However, the mechanisms of heterogeneous CO(2) evolution during oxidation of aromatic carbon-based materials are not known in detail. Using density functional theory, a new oxidation mechanism of aromatic hydrocarbons with atomic oxygen was suggested to consist of four main steps, namely, (1) adsorption of oxygen atom, (2) insertion of O atom into the ring, (3) rearrangement to form a five-membered ring and four-membered ring lactone group, and (4) desorption of CO(2). Using naphthoxy radical as a model system, the proposed reaction pathway can explain how some of the experimentally observed CO(2) is formed.

DNA nucleobase synthesis at Titan atmosphere analog by soft X-rays.

Titan, the largest satellite of Saturn, has an atmosphere chiefly made up of N(2) and CH(4) and includes traces of many simple organic compounds. This atmosphere also partly consists of haze and aerosol particles which during the last 4.5 gigayears have been processed by electric discharges, ions, and ionizing photons, being slowly deposited over the Titan surface. In this work, we investigate the possible effects produced by soft X-rays (and secondary electrons) on Titan aerosol analogs in an attempt to simulate some prebiotic photochemistry. The experiments have been performed inside a high vacuum chamber coupled to the soft X-ray spectroscopy beamline at the Brazilian Synchrotron Light Source, Campinas, Brazil. In-situ sample analyses were performed by a Fourier transform infrared spectrometer. The infrared spectra have presented several organic molecules, including nitriles and aromatic CN compounds. After the irradiation, the brownish-orange organic residue (tholin) was analyzed ex-situ by gas chromatographic (GC/MS) and nuclear magnetic resonance ((1)H NMR) techniques, revealing the presence of adenine (C(5)H(5)N(5)), one of the constituents of the DNA molecule. This confirms previous results which showed that the organic chemistry on the Titan surface can be very complex and extremely rich in prebiotic compounds. Molecules like these on the early Earth have found a place to allow life (as we know) to flourish.

N-tert-butyl and N-methyl nitrones derived from aromatic aldehydes inhibit macromolecular permeability increase induced by ischemia/reperfusion in hamsters.

N-alquil nitrones 1c and 3-6 were prepared from aromatic aldehydes and N-tert-butylhydroxylamine or N-methylhydroxylamine in good yields and soft conditions. Their protective effect against microvascular damages caused by ischemia/reperfusion in 'hamster cheek pouch' assay was investigated and compare with that observed for nitrones 1a,b and 2, previously studied. Nitrones 3b, 4b and 4c were the most active ones in inhibiting macromolecular permeability increase induced by ischemia/reperfusion when administered by gavage and intravenous, while 3a and 4a were active only after intravenous administration. N-tert-butylhydroxylamine and Nt-methylhydroxylamine, products of the hydrolysis of these nitrones, were weakly active when administered by gavage or intravenous. Nitrone (4a) was the most potent in inhibiting macromolecular permeability increase induced by histamine. In this case, N-tert-butylhydroxylamine was as active as 4a. The lypophylicity in nitrones, specially in N-methyl nitrones, play an important role on the protective action when compounds were administered by gavage.