Innovative flow-through reaction system for the sustainable production of phenolic monomers from lignocellulose catalyzed by supported Mo2C.

Molybdenum carbide supported on activated carbon (ß-Mo2C/AC) has been tested as catalyst in the reductive catalytic fractionation (RCF) of lignocellulosic biomass both in batch and in Flow-Through (FT) reaction systems. High phenolic monomer yields (34 wt.%) and selectivity to monomers with reduced side alkyl chains (up to 80 wt.%) could be achieved in batch in the presence of hydrogen. FT-RCF were made with no hydrogen feed, thus via transfer hydrogenation from ethanol. Similar selectivity could be attained in FT-RCF using high catalyst/biomass ratios (0.6) and high molybdenum loading (35 wt.%) in the catalyst, although selectivity decreased with lower catalyst/biomass ratios or molybdenum contents. Regardless of these parameters, high delignification of the lignocellulosic biomass and similar monomer yields were observed in the FT mode (13-15 wt.%) while preserving the holocellulose fractions in the delignified pulp. FT-RCF system outperforms the batch reaction mode in the absence of hydrogen, both in terms of activity and selectivity to reduced monomers that is attributed to the two-step non-equilibrium processes and the removal of diffusional limitations that occur in the FT mode. Even though some molybdenum leaching was detected, the catalytic performance could be maintained with negligible loss of activity or selectivity for 15 consecutive runs.

A new oxidative pathway of nitric oxide production from oximes in plants.

Nitric oxide (NO) is an essential reactive oxygen species and a signal molecule in plants. Although several studies have proposed the occurrence of oxidative NO production, only reductive routes for NO production, such as the nitrate (NO-3) -upper-reductase pathway, have been evidenced to date in land plants. However, plants grown axenically with ammonium as the sole source of nitrogen exhibit contents of nitrite and NO3-, evidencing the existence of a metabolic pathway for oxidative production of NO. We hypothesized that oximes, such as indole-3-acetaldoxime (IAOx), a precursor to indole-3-acetic acid, are intermediate oxidation products in NO synthesis. We detected the production of NO from IAOx and other oximes catalyzed by peroxidase (POD) enzyme using both 4-amino-5-methylamino-2',7'-difluorescein fluorescence and chemiluminescence. Flavins stimulated the reaction, while superoxide dismutase inhibited it. Interestingly, mouse NO synthase can also use IAOx to produce NO at a lower rate than POD. We provided a full mechanism for POD-dependent NO production from IAOx consistent with the experimental data and supported by density functional theory calculations. We showed that the addition of IAOx to extracts from Medicago truncatula increased the in vitro production of NO, while in vivo supplementation of IAOx and other oximes increased the number of lateral roots, as shown for NO donors, and a more than 10-fold increase in IAOx dehydratase expression. Furthermore, we found that in vivo supplementation of IAOx increased NO production in Arabidopsis thaliana wild-type plants, while prx33-34 mutant plants, defective in POD33-34, had reduced production. Our data show that the release of NO by IAOx, as well as its auxinic effect, explain the superroot phenotype. Collectively, our study reveals that plants produce NO utilizing diverse molecules such as oximes, POD, and flavins, which are widely distributed in the plant kingdom, thus introducing a long-awaited oxidative pathway to NO production in plants. This knowledge has essential implications for understanding signaling in biological systems.

The importance of the urea cycle and its relationships to polyamine metabolism during ammonium stress in Medicago truncatula.

The ornithine-urea cycle (urea cycle) makes a significant contribution to the metabolic responses of lower photosynthetic eukaryotes to episodes of high nitrogen availability. In this study, we compared the role of the plant urea cycle and its relationships to polyamine metabolism in ammonium-fed and nitrate-fed Medicago truncatula plants. High ammonium resulted in the accumulation of ammonium and pathway intermediates, particularly glutamine, arginine, ornithine, and putrescine. Arginine decarboxylase activity was decreased in roots, suggesting that the ornithine decarboxylase-dependent production of putrescine was important in situations of ammonium stress. The activity of copper amine oxidase, which releases ammonium from putrescine, was significantly decreased in both shoots and roots. In addition, physiological concentrations of ammonium inhibited copper amine oxidase activity in in vitro assays, supporting the conclusion that high ammonium accumulation favors putrescine synthesis. Moreover, early supplementation of plants with putrescine avoided ammonium toxicity. The levels of transcripts encoding urea-cycle-related proteins were increased and transcripts involved in polyamine catabolism were decreased under high ammonium concentrations. We conclude that the urea cycle and associated polyamine metabolism function as important protective mechanisms limiting ammonium toxicity in M. truncatula. These findings demonstrate the relevance of the urea cycle to polyamine metabolism in higher plants.

Extraction of Phenolic Compounds from Populus Salicaceae Bark.

Lignocellulosic residues have the potential for obtaining high value-added products that could be better valorized if biorefinery strategies are adopted. The debarking of short-rotation crops yields important amounts of residues that are currently underexploited as low-grade fuel and could be a renewable source of phenolic compounds and other important phytochemicals. The isolation of these compounds can be carried out by different methods, but for attaining an integral valorization of barks, a preliminary extraction step for phytochemicals should be included. Using optimized extraction methods based on Soxhlet extraction can be effective for the isolation of phenolic compounds with antioxidant properties. In this study, poplar bark (Populus Salicaceae) was used to obtain a series of extracts using five different solvents in a sequential extraction of 24 h each in a Soxhlet extractor. Selected solvents were put in contact with the bark sample raffinate following an increasing order of polarity: n-hexane, dichloromethane, ethyl acetate, methanol, and water. The oily residues of the extracts obtained after each extraction were further subjected to flash chromatography, and the fractions obtained were characterized by gas chromatography coupled with mass spectrometry (GC-MS). The total phenolic content (TPC) was determined using the Folin-Ciocalteu method, and the antioxidant activity (AOA) of the samples was evaluated in their reaction with the free radical 2,2-Diphenyl-picrylhydrazyl (DPPH method). Polar solvents allowed for higher individual extraction yields, with overall extraction yields at around 23% (dry, ash-free basis). Different compounds were identified, including hydrolyzable tannins, phenolic monomers such as catechol and vanillin, pentoses and hexoses, and other organic compounds such as long-chain alkanes, alcohols, and carboxylic acids, among others. An excellent correlation was found between TPC and antioxidant activity for the samples analyzed. The fractions obtained using methanol showed the highest phenolic content (608 µg of gallic acid equivalent (GAE)/mg) and the greatest antioxidant activity.

Production of Aromatic Compounds by Catalytic Depolymerization of Technical and Downstream Biorefinery Lignins.

Lignocellulosic materials are promising alternatives to non-renewable fossil sources when producing aromatic compounds. Lignins from Populus salicaceae. Pinus radiata and Pinus pinaster from industrial wastes and biorefinery effluents were isolated and characterized. Lignin was depolymerized using homogenous (NaOH) and heterogeneous (Ni-, Cu- or Ni-Cu-hydrotalcites) base catalysis and catalytic hydrogenolysis using Ru/C. When homogeneous base catalyzed depolymerization (BCD) and Ru/C hydrogenolysis were combined on poplar lignin, the aromatics amount was ca. 11 wt.%. Monomer distributions changed depending on the feedstock and the reaction conditions. Aqueous NaOH produced cleavage of the alkyl side chain that was preserved when using modified hydrotalcite catalysts or Ru/C-catalyzed hydrogenolysis in ethanol. Depolymerization using hydrotalcite catalysts in ethanol produced monomers bearing carbonyl groups on the alkyl side chain. The analysis of the reaction mixtures was done by size exclusion chromatography (SEC) and diffusion ordered nuclear magnetic resonance spectroscopy (DOSY NMR). 31P NMR and heteronuclear single quantum coherence spectroscopy (HSQC) were also used in this study. The content in poly-(hydroxy)-aromatic ethers in the reaction mixtures decreased upon thermal treatments in ethanol. It was concluded that thermo-solvolysis is key in lignin depolymerization, and that the synergistic effect of Ni and Cu provided monomers with oxidized alkyl side chains.

IAOx induces the SUR phenotype and differential signalling from IAA under different types of nitrogen nutrition in Medicago truncatula roots.

Indole-3-acetaldoxime (IAOx) is a particularly relevant molecule as an intermediate in the pathway for tryptophan-dependent auxin biosynthesis. The role of IAOx in growth-signalling and root phenotype is poorly studied in cruciferous plants and mostly unknown in non-cruciferous plants. We synthesized IAOx and applied it to M. truncatula plants grown axenically with NO3-, NH4+ or urea as the sole nitrogen source. During 14 days of growth, we demonstrated that IAOx induced an increase in the number of lateral roots, especially under NH4+ nutrition, while elongation of the main root was inhibited. This phenotype is similar to the phenotype known as "superroot" previously described in SUR1- and SUR2-defective Arabidopsis mutants. The effect of IAOx, IAA or the combination of both on the root phenotype was different and dependent on the type of N-nutrition. Our results also showed the endogenous importance of IAOx in a legume plant in relation to IAA metabolism, and suggested IAOx long-distance transport depending on the nitrogen source provided. Finally, our results point out to CYP71A as the major responsible enzymes for IAA synthesis from IAOx, while they exclude indole-3-acetaldehyde oxidases.

Pretreatment and enzymatic hydrolysis for the efficient production of glucose and furfural from wheat straw, pine and poplar chips.

A flexible approach to a two-step Biorefinery for the production of glucose and furfural from three different feedstocks is presented. Pretreatment conditions were selected to drive the production towards the generation of glucose or furfural. Harsh pretreatment conditions produced solids with highly accessible glycan contents for the enzymatic hydrolysis with 100% glucose yields when wheat straw or poplar chips were used as feedstock. Mild conditions afforded xylan-rich hydrolysates that could be efficiently transformed to furfural, either under conventional or microwave heating in biphasic media. Yields for the transformation of xylan from feedstocks ranged between 45% and 90% depending on the feedstock, the thermal pretreatment and the cyclodehydration conditions. Up to 12.6 kg of glucose and materials and 2.5 kg of furfural can be produced starting from 50 kg of biomass. A new analytical methodology based on 13C NMR that provided good quality analytical results is also presented.

Synthesis and Leishmanicidal Activity of Novel Urea, Thiourea, and Selenourea Derivatives of Diselenides.

A novel series of thirty-one N-substituted urea, thiourea, and selenourea derivatives containing diphenyldiselenide entities were synthesized, fully characterized by spectroscopic and analytical methods, and screened for their in vitro leishmanicidal activities. The cytotoxic activity of these derivatives was tested against Leishmania infantum axenic amastigotes, and selectivity was assessed in human THP-1 cells. Thirteen of the synthesized compounds showed a significant antileishmanial activity, with 50% effective concentration (EC50) values lower than that for the reference drug miltefosine (EC50, 2.84 µM). In addition, the derivatives 9, 11, 42, and 47, with EC50 between 1.1 and 1.95 µM, also displayed excellent selectivity (selectivity index ranged from 12.4 to 22.7) and were tested against infected macrophages. Compound 11, a derivative with a cyclohexyl chain, exhibited the highest activity against intracellular amastigotes, with EC50 values similar to those observed for the standard drug edelfosine. Structure-activity relationship analyses revealed that N-aliphatic substitution in urea and selenourea is recommended for the leishmanicidal activity of these analogs. Preliminary studies of the mechanism of action for the hit compounds was carried out by measuring their ability to inhibit trypanothione reductase. Even though the obtained results suggest that this enzyme is not the target for most of these derivatives, their activity comparable to that of the standards and lack of toxicity in THP-1 cells highlight the potential of these compounds to be optimized for leishmaniasis treatment.

Validation of a questionnaire about the perception of occupational biohazard in Spanish companies.

OBJECTIVES: The aim of this work was to develop, validate and test a new questionnaire to assess the biological risk in workers with intentional or unintentional exposure to biological agents. METHODS: A questionnaire including 34 questions was developed to study the perception of workers against occupational biohazard. Content Validity Index (CVI) and Content Validity Ratio (CVR) were calculated for the analysis of content validity. A pilot study was carried out with 60 workers from 17 companies performing analysis of Cronbach's α to assess the internal consistency or reliability. RESULTS: A total of 518 workers from 51 Spanish companies in which there is exposure to biological agents participated in the study yielding a response rate of 90%. The final questionnaire obtained a Cronbach's α > 0.759 with a stable test-retest result. The questionnaire validation demonstrates that it could be used to evaluate the biological risks and help the prevention of occupational accidents and diseases. DISCUSSION: This study has validated the need to evaluate worker's perception against occupational risks, as well as the application of prevention methods and protective equipment. It is a first step towards developing an occupational biohazards assessment method including all the requirements set by the European Health and Safety Strategy 2013-2020.

¿Seguridad biológica o bioseguridad laboral? / Occupational biosecurity or occupational biosafety?

No disponible

Diferencias de protección frente al riesgo biológico laboral en función del tamaño de la empresa / Differences of occupational biohazard protection risk in relation to company size

Objetivo Obtener información sobre el nivel de exposición y protección de los trabajadores a los agentes biológicos laborales, en el sector sanitario, granjas, industria cárnica, laboratorios, plantas de tratamiento de residuos, industria alimentaria y centros veterinarios valorando sus diferencias en relación al tamaño de la empresa. Método Se realizó un estudio en el que participaron 590 trabajadores pertenecientes a 59 empresas españolas en las que se pasó un cuestionario inicial con 3 preguntas dirigidas a las empresas contestadas por los responsables de prevención y otro cuestionario con 34 preguntas para ser contestado por los trabajadores expuestos. Se realizó una validación mediante análisis del alfa de Cronbach global del segundo cuestionario para valorar la consistencia interna y fiabilidad de los cuestionarios. Resultados La muestra definitiva obtenida fue de 518 trabajadores de 51 empresas en las que existía exposición a agentes biológicos. El cuestionario obtuvo un alfa de Cronbach superior a 0,7. Se encontraron diferencias significativas en la gestión del riesgo biológico laboral en función del tamaño de la empresa (p-valor<0,05). Conclusiones Los resultados obtenidos ofrecieron una adecuada consistencia interna del cuestionario. Por otro lado la exposición laboral a agentes biológicos es un factor que debe tenerse en cuenta puesto que no está desarrollada por completo porque tanto las empresas como los profesionales de la prevención no tienen herramientas disponibles que permitan su fácil realización y por lo tanto la gestión de los riesgos biológicos general no es adecuada.(AU)

Objective To obtain information on the level of exposure and protection of workers to biological agents working in the health sector, farms, meat industry, laboratories, sewage treatment plants, food industry and veterinary centers, valuing their differences in relation to the size of the company. Method A study in which 590 workers belonging to 59 Spanish companies. An initial questionnaire with 3 questions was sent to companies and answered by those responsible for prevention, and another questionnaire with 34 questions to be answered by exposed workers was also sent. Validation was performed by analysis of overall alpha of the second questionnaire to assess the internal consistency and reliability of Cronbach of the questionnaires. Results The final sample included 518 workers in 51 companies in which there was exposure to biological agents. The questionnaire obtained a Cronbach's alpha greater than 0.7. Significant differences in biological risk management work depending on the size of the company (p-value <0.05) were found. Conclusions Our results provide an adequate internal consistency of the questionnaire. Furthermore occupational exposure to biological agents is a factor to be taken into account since it is not fully developed. This is because neither businesses nor prevention professionals have tools available that allow easy implementation, and, therefore, management of overall biological hazards is inadequate.(AU)

[Differences of occupational biohazard protection risk in relation to company size]. / Diferencias de protección frente al riesgo biológico laboral en función del tamaño de la empresa.

Objective To obtain information on the level of exposure and protection of workers to biological agents working in the health sector, farms, meat industry, laboratories, sewage treatment plants, food industry and veterinary centers, valuing their differences in relation to the size of the company. Method A study in which 590 workers belonging to 59 Spanish companies. An initial questionnaire with 3 questions was sent to companies and answered by those responsible for prevention, and another questionnaire with 34 questions to be answered by exposed workers was also sent. Validation was performed by analysis of overall alpha of the second questionnaire to assess the internal consistency and reliability of Cronbach of the questionnaires. Results The final sample included 518 workers in 51 companies in which there was exposure to biological agents. The questionnaire obtained a Cronbach's alpha greater than 0.7. Significant differences in biological risk management work depending on the size of the company (p-value <0.05) were found. Conclusions Our results provide an adequate internal consistency of the questionnaire. Furthermore occupational exposure to biological agents is a factor to be taken into account since it is not fully developed. This is because neither businesses nor prevention professionals have tools available that allow easy implementation, and, therefore, management of overall biological hazards is inadequate.

Benzo[b]thiophene-6-carboxamide 1,1-dioxides: inhibitors of human cancer cell growth at nanomolar concentrations.

Benzo[b]thiophenesulfonamide 1,1-dioxide derivatives (BTS) were described as candidate antineoplastic drugs. In the hope of finding new compounds with improved antitumour activity and reduced toxicity, we have designed and synthesized a small series of benzo[b]thiophene-6-carboxamide 1,1-dioxide derivatives (BTC) structurally related with the best reported BTS. Growth inhibition of HTB-54, CCRF-CEM and HeLa tumour cells lines at nanomolar concentrations was exhibited by some of the BTC. Hydrophobic substituents on the carboxamide group increased cytotoxicity but substitution by a hydroxy group diminished it, thus pointing to the electronic density on benzo[b]thiophene nucleus as a determinant factor. The process of cell death induced by BTC derivatives was further analyzed in CCRF-CEM cells, where these compounds induced apoptosis in a time and dose-dependent manner and cell cycle arrest at S phase. BTC derivatives also induced a significant increase in intracellular ROS levels in this cell line. Previous treatment of the cells with the antioxidant N-acetyl-cysteine abrogated the induction of apoptosis by BTC indicating that ROS generation is a previous event required to trigger the BTC induced apoptotic process.

QM/MM modeling of enantioselective pybox-ruthenium- and box-copper-catalyzed cyclopropanation reactions: scope, performance, and applications to ligand design.

An extensive comparison of full-QM (B3LYP) and QM/MM (B3LYP:UFF) levels of theory has been made for two enantioselective catalytic systems, namely, Pybox-Ru and Box-Cu complexes, in the cyclopropanation of alkenes (ethylene and styrene) with methyl diazoacetate. The geometries of the key reaction intermediates and transition structures calculated at the QM/MM level are generally in satisfactory agreement with full-QM calculated geometries. More importantly, the relative energies calculated at the QM/MM level are in good agreement with those calculated at the full-QM level in all cases. Furthermore, the QM/MM energies are often in better agreement with the stereoselectivity experimentally observed, and this suggests that QM/MM calculations can be superior to full-QM calculations when subtle differences in inter- and intramolecular interactions are important in determining the selectivity, as is the case in enantioselective catalysis. The predictive value of the model presented is validated by the explanation of the unusual enantioselectivity behavior exhibited by a new bis-oxazoline ligand, the stereogenic centers of which are quaternary carbon atoms.

Carbonic anhydrase inhibitors: inhibition of cytosolic/tumor-associated carbonic anhydrase isozymes I, II, and IX with benzo[b]thiophene 1,1-dioxide sulfonamides.

A series of selected benzo[b]thiophene-5- and 6-sulfonamide derivatives previously reported to show cytotoxic activity and some others newly synthesized has been tested for the interactions with several CA isozymes, some of which are known to be involved in tumorigenesis (hCA IX), whereas others are ubiquitously found in many normal tissues (the cytosolic isoforms hCA I and II). The unsubstituted sulfonamides inhibited hCA I with inhibition constants in the range of 63-138 nM, hCA II with inhibition constants in the range of 6.3-8.8 nM, and hCA IX with inhibition constants in the range of 2.8-15 nM, being thus more active than clinically used inhibitors such as acetazolamide, methazolamide, ethoxzolamide, dichlorophenamide or indisulam (E 7070). Some of these derivatives also showed some selectivity for the inhibition of the tumor-associated (hCA IX) over the cytosolic isozyme hCA II. Although these derivatives may act on many targets other than the CAs (such as the NADH oxidase) or may induce apoptosis by accumulation of reactive oxygen species, it is quite important to try to decipher as many as possible of the potential mechanisms that lead to derivatives with potent antitumor activity in order to develop novel therapeutic strategies for the management of cancer.

A flexible and versatile strategy for the covalent immobilization of chiral catalysts based on pyridinebis(oxazoline) ligands.

[reaction: see text] Flexible and versatile methods have been developed for the immobilization of chiral pyridinebis(oxazoline) ligands by covalent bonding to a solid support, either by grafting or by polymerization. Different spacers can easily be introduced to modulate the support-ligand distance and the electronic properties of the chiral ligand. As an example, 2,6-bis[(S)-4-isopropyloxazolin-2-yl]pyridine has been immobilized on polystyrene resins, both on a Merrifield-type resin by grafting and on supports prepared by polymerization of 4-vinyl-substituted ligands. The corresponding Ru complexes have been tested as catalysts in the cyclopropanation reaction between styrene and ethyl diazoacetate. The catalytic activity, the enantioselectivity, and the recyclability are strongly dependent on the catalyst preparation method and the total exclusion of oxygen and moisture in the filtration process. Under such optimized conditions, yields over 60% with up to 90% ee can be obtained in four successive reactions-the best cyclopropanation results described to date for a chiral solid ruthenium catalyst.

Design, synthesis and biological evaluation of new potent 5-nitrofuryl derivatives as anti-Trypanosoma cruzi agents. Studies of trypanothione binding site of trypanothione reductase as target for rational design.

Design, using force-field calculations on the catalytic site of trypanothione reductase from Trypanosoma cruzi, has led to the development of new 5-nitrofuryl derivatives as potential anti-trypanosomal agents. The synthesized compounds were tested in vitro against T. cruzi and more than 75% of the prepared derivatives showed higher activity than nifurtimox. Compounds 5 and 11, hexyl 4-(5-nitrofurfurylidene)carbazate and N-hexyl 3-(5-nitrofuryl)propenamide, showed the highest in vitro trypanocidal effect reported to date for members of the nitrofuran family. Partition coefficients and energies for the single-electron reduction of compounds were theoretically determined. These properties could be not the major cause of the activities' differences. The physicochemical environment around E19, W22, C53 and Y111 residues within the trypanothione binding site of trypanothione reductase resulted a valuable target for the rational design of anti-trypanosomal drugs.

Theoretical insights into the role of a counterion in copper-catalyzed enantioselective cyclopropanation reactions.

The effect of a coordinating counteranion on the mechanism of Cu(I)-catalyzed cyclopropanation has been investigated extensively for a medium-sized reaction model by means of theoretical calculations at the B3LYP/6-31G(d) level. The main mechanistic features are similar to those found for the cationic (without a counteranion) mechanism, the rate-limiting step being nitrogen extrusion from a catalyst-diazoester complex to generate a copper-carbene intermediate. The cyclopropanation step takes place through a direct carbene insertion of the metal-carbene species to yield a catalyst-product complex, which can finally regenerate the starting complex. However, the presence of the counteranion has a noticeable influence on the calculated geometries of all the intermediates and transition structures. Furthermore, the existence of a preequilibrium with a dimeric form of the catalyst, together with a higher activation barrier in the insertion step, explains the lower yield of cyclopropane products observed experimentally in the presence of chloride counterion. The stereochemical predictions of a more realistic model (made by considering a chiral bis(oxazoline)-copper(i) catalyst) have been rationalized in terms of the lack of significant steric repulsions, and the model shows good agreement with the low enantioselectivities observed experimentally for these kinds of catalytic systems.