Catalytic conversion of glucose to 5-hydroxymethyl furfural using inexpensive co-catalysts and solvents

Efficient conversion of glucose to 5-hydroxymethyl furfural (5-HMF), a platform chemical for fuels and materials, was achieved using CrCl₂ or CrCl₃ as the catalysts with inexpensive co-catalysts and solvents including halide salts in dimethyl sulfoxide (DMSO) and several ionic liquids. 5-HMF (54.8%) yield was achieved with the CrCl₂/tetraethyl ammonium chloride system at mild reaction conditions (120 °C and 1 h). The 5-HMF formation reaction was found to be faster in ionic liquids than in the DMSO system. Effects of water in the reaction system, chromium valence and reaction temperature on the conversion of glucose into 5-HMF were discussed in this work.     

The protective role of 5-HMF against hypoxic injury

In an attempt to find new types of anti-hypoxic agents from herbs, we identified 5-hydroxymethyl-2-furfural (5-HMF) as a natural agent that fulfills the criterion. 5-HMF, the final product of carbohydrate metabolism, has favorable biological effects such as anti-oxidant activity and inhibiting sickling of red blood cells. The role of 5-HMF in hypoxia, however, is not yet. Our pilot results showed that pretreatment with 5-HMF markedly increased both the survival time and the survival rate of mice under hypoxic stress. The present study was aimed to further investigate the protective role of 5-HMF and the underlying mechanisms in hypoxic injury using ECV304 cells as an in vitro model. ECV304 cells pretreated with or without 5-HMF for 1 h were exposed to hypoxic condition (0.3% O₂) for 24 h and then cell apoptosis, necrosis, the changes of mitochondrial membrane potential (MMP) and the expressions of phosphorylation- extracellular signal-regulated kinase (p-ERK) were investigated. Pretreatment with 5-HMF markedly attenuated hypoxia-induced cell necrosis and apoptosis at late stage (p < 0.01). Furthermore, pretreatment with 5-HMF rescued both the decline of the MMP and the increase of p-ERK protein under hypoxia. In a word, these results indicated that 5-HMF had protective effects against hypoxic injury in ECV304 cells, and its effects on MMP and p-ERK may be involved in the mechanism.     

Heterogeneous Catalytic Oxidation of Phenanthrene by Hydrogen Peroxide in Soil Slurry: Kinetics,Mechanism, and Implication

The degradation of phenanthrene sorbed on soil has been carried out using a H₂O₂/goethite heterogeneous catalytic oxidation process. The effect of operating variables, such as the goethite concentration, pH, H₂O₂ concentration, soil organic matter, and bicarbonate ions has been investigated. The reaction followed pseudo-first order kinetics. The rate constants were evaluated and varied between 2.0×10^?4 and 1.1×10^?3?min^?1 depending on the H₂O₂ concentration. The highest rate of degradation of phenanthrene was observed at a H₂O₂ concentration of 5?M and 134.0?g/kg goethite. The intermediate product formed during the degradation of phenanthrene was identified to be salicylic acid that finally degraded to CO₂ and H₂O. H₂O₂ consumption continued as the OH radical attacked the salicylic acid. More than 80% consumption of the 5?M H₂O₂ took place within 30?min, and the degradation was almost complete after 3?h of reaction. Neutral pH was found to be effective in the removal of phenanthrene. Both soil organic matter (SOM) and bicarbonate ions in the soil inhibited the oxidation rate of phenanthrene.     

Catalytic dehydration of xylose to furfural: vanadyl pyrophosphate as source of active soluble species

The acid-catalysed, aqueous phase dehydration of xylose (a monosaccharide obtainable from hemicelluloses, e.g., xylan) to furfural was investigated using vanadium phosphates (VPO) as catalysts: the precursors, VOPO₄·2H₂O, VOHPO₄·0.5H₂O and VO(H₂PO₄)₂, and the materials prepared by calcination of these precursors, that is, γ-VOPO₄, (VO)₂P₂O₇ and VO(PO₃)₂, respectively. The VPO precursors were completely soluble in the reaction medium. In contrast, the orthorhombic vanadyl pyrophosphate (VO)₂P₂O₇, prepared by calcination of VOHPO₄·0.5H₂O at 550 °C/2 h, could be recycled by simply separating the solid acid from the reaction mixture by centrifugation, and no drop in catalytic activity and furfural yields was observed in consecutive 4 h-batch runs (ca. 53% furfural yield, at 170 °C). However, detailed catalytic/characterisation studies revealed that the vanadyl pyrophosphate acts as a source of active water-soluble species in this reaction. For a concentration of (VO)₂P₂O₇ as low as 5 mM, the catalytic reaction of xylose (ca. 0.67 M xylose in water, and toluene as solvent for the in situ extraction of furfural) gave ca. 56% furfural yield, at 170 °C/6 h reaction.     

Purification,characterization, and coal depolymerizing activity of lignin peroxidase from <Emphasis Type="Italic">Gloeophyllum sepiarium</Emphasis> MTCC-1170

Lignin peroxidase from the liquid culture filtrate of Gloeophyllum sepiarium MTCC-1170 has been purified to homogeneity. The molecular weight of the purified enzyme was 42 kDa as determined by SDS-PAGE. The K _m values were 54 and 76 μM for veratryl alcohol and H₂O₂, respectively. The pH and temperature optima were 2.5 and 25°C, respectively. Depolymerization of coal by the fungal strain has been demonstrated using humic acid as a model of coal. Depolymerization of humic acid by the purified lignin peroxidase has been shown by the decrease in absorbance at 450 nm and increase in absorbance at 360 nm in presence of H₂O₂. Depolymerization of humic acid by the purified enzyme has also been demonstrated by the decrease in the viscosity with time of the reaction solution containing humic acid, H₂O₂, and the purified lignin peroxidase. The influence of NaCl and NaN₃ and inhibitory effects of various metal chelating agents on the lignin peroxidase activity were studied.     

Comparison of two co-culture systems to assess the survival of in vitro produced bovine blastocysts after vitrification

The ability of bovine blastocysts to recover after cryopreservation and thawing procedures is often assessed by evaluating their re-expansion during in vitro co-culture. However, the influence of factors such as feeder cell type and gas atmosphere on blastocyst survival and evolution have never been considered. This study therefore compared two cell co-culture systems and two different gas atmospheres to assess survival of in vitro produced bovine blastocysts after vitrification. Day-7 blastocysts (n=181) were vitrified in a mixture of 25% glycerol/25% ethylene glycol. After warming and dilution, they were co-cultured either on Buffalo rat liver cells (BRL CC cell line) or on granulosa cells (GR CC primary culture) in TCM 199 supplemented with 10% FCS and under an atmosphere of 5% or 20% O₂. Surviving and hatching rates were recorded at 24 h intervals for 3 days. After 72 h of culture, surviving blastocysts were treated for differential counting of inner cell mass (ICM) and trophectoderm cells. Blastocyst survival rates were higher when BRL and granulosa co-culture were performed under 20% oxygen as compared to 5% oxygen (20% O₂: 62% vs. 5% O₂: 25%, P<0.0001). However, the quality of blastocysts surviving in the granulosa co-culture condition was lower under 20% O₂ than under 5% O₂ as indicated by lower total and trophectoderm cell numbers (respectively 79±6 and 56±6 at 20% O₂ vs. 100±10 and 74±10 at 5% O₂, P<0.05), by an altered ICM/trophectoderm ratio (20% O₂: 28% vs. 5% O₂: 23%, P<0.05), by a higher total nuclear fragmentation (20% O₂: 3.7% vs. 5% O₂: 1.5%, P<0.05) and a trend to decreased hatching (20% O₂: 32% vs. 5% O₂: 81%, P=0.07). Whereas, for BRL co-culture, 20% O₂ yielded higher quality blastocysts than 5% O₂ as evaluated by higher ICM and trophectoderm cell numbers (19±1 and 71±5 at 20% O₂ vs. 15±2 and 48±9 at 5% O₂, respectively, P<0.05), by lower nuclear fragmentation in the ICM (20% O₂: 2.2% vs. 5% O₂: 6.7%, P<0.05). In conclusion, co-culture conditions may influence blastocysts survival and quality after cryopreservation. In our conditions, co-culture with BRL cells under 20% O₂ seems to be the best combination to evaluate blastocyst survival and quality after vitrification.     

Determination of tannic acid in industrial wastewater based on chemiluminescence system of KIO4–H2O2–Tween40

The oxidation reaction of H₂O₂ with KIO₄ can produce chemiluminescence (CL) in the presence of the surfactant Tween40 and the CL intensity of the CL system KIO₄–H₂O₂–Tween40 can be strikingly enhanced after injection of tannic acid. On this basis, a flow injection method with CL detection was established for the determination of tannic acid. The method is simple, rapid and effective to determine tannic acid in the range of 7.0 × 10^?9 to 1.0 × 10^?5 mol/L with a determination limit of 2.3 × 10^?9 mol/L. The relative standard deviation is 2.6% for the determination of 5.0 × 10^?6 mol/L tannic acid (n = 11). The method has been applied to determine the content of tannic acid in industrial wastewater with satisfactory results. It is believed that the CL reaction formed singlet oxygen ¹O₂* and the emission was from an excited oxygen molecular pair O₂(¹Δ_g)O₂(¹∑^?_g) in the KIO₄–H₂O₂–Tween40 reaction. Tween40 played an important role in enhancing stabilization of the excited oxygen molecular pair O₂(¹Δ_g)O₂(¹∑^?_g) and in increasing CL intensity. Copyright © 2010 John Wiley & Sons, Ltd.     

Biotransformation of furfural and 5-hydroxymethyl furfural by enteric bacteria

Summary A survey was conducted with seventeen enteric bacterial strains (including the generaKlebsiella, Enterobacter, Escherichia, Citrobacter, Edwardsiella andProteus) to examine their ability to transform furfural and 5-hydroxymethyl furfural (5-MHF). The enteric bacteria were able to convert furfural to furfuryl alcohol under both aerobic and anaerobic conditions in a relatively short incubation time of 8 h. 5-HMF was transformed by all the enteric bacteria studied to an unidentified compound postulated to be 5-hydroxymethyl furfuryl alcohol, which had an absorbance maximum of 222 nm. These bacteria did not transform furfuryl alcohol or 2-furoic acid. The enteric bacteria did not use furfural, 5-HMF, furfuryl alcohol or 2-furoic acid as sole source of carbon and energy. Biotransformation of furfural and 5-HMF was accomplished by co-metabolism in the presence of glucose and peptone as main substrates. The rate of transformation was similar under both aerobic and anaerobic conditions. These transformations are likely to be of value in the detoxification of furfurals, and in their ultimate conversion to methane and CO₂ by anaerobic digestion.     

An EPR Investigation of Human Methaemoglobin Oxidation by Hydrogen Peroxide: Methods to Quantify all Paramagnetic Species Observed in the Reaction

The method of Electron Paramagnetic Resonance (EPR) spectroscopy was used to study the reaction of human methaemoglabin (metHb) with hydrogen peroxide. The samples for EPR measurements were rapidly frozen in liquid nitrogen at different times after H₂O₂ was added at 3- and 10-fold molar excess to 100 μM metHb in 50 mM phosphate buffer, pH 7.4, 37°C. Precautions were taken to remove all catalase from the haemoglobin preparation and no molecular oxygen evolution was detected during the reaction. On addition of H₂O₂ the EPR signals (- 196°C) of both high spin and low spin metHb rapidly decreased and free radicals were formed. The low temperature (- 196°C) EPR spectrum of the free radicals formed in the reaction has been deconvoluted into two individual EPR signals, one being an anisotropic signal (g° = 2.035 and g° = 2.0053), and the other an isotropic singlet (g = 2.0042, AH = 20 G). The former signal was assigned to peroxyl radicals. As the kinetic Pehaviour of both peroxyl (ROO^*) and nonperoxyl (P^*) free radicals were similar, we concluded that ROO^* radicals are not formed from P^* radicals by addition of O₂. The time courses for both radicals showed a steady state during the time required for H₂O₂ to decompose. Once all peroxide was consumed, the radical decayed with a first order rate constant of 1.42 ± 10^-3 s^-1 (1:3 molar ratio). The level of the steady state was higher and its duration shorter at lower initial concentration of H₂O₂. The formation of the rhombic Fe(III) non-haemcentres with g = 4.35 was found. Their yield was proportional to the H₂O₂ concentration used and the centers were ascribed to haem degradation products. The reaction was also monitored by EPR spectroscopy at room temperature. The kinetics of the free radicals measured in the reaction mixture at room temperature was similar to that observed when the fast freezing method and EPR measurement at —196°C were used.     

Detoxification of hydrolysate by reactive-extraction for generating biofuels

We introduce a reactive extraction to detoxify hydrolysate before fermentation to biofuels. In the selection of diluents, n-octanol showed the highest removal yield of 5-hydroxymethylfurfural (5-HMF) and levulinic acid. The removal yields of inhibitors were normalized to 30-min reactions. In treatments with pure extractant or diluents, only 2 ～ 4.1% of the formic acid was removed. Tri-n-octylamine (extractant) removed levulinic acid and acetic acid more efficiently, and furfural was removed more efficiently than formic acid or 5-HMF. n-Octanol (polar diluent) removed levulinic acid and acetic acid, furfural, and 5-HMF at 21.2, 33.7, and 65.7%, respectively. In contrast, kerosene (inert diluent) only removed the furfural by 27.6%. Based on these results, the optimum reactiveextraction system comprised tri-n-octylamine as the extractant, n-octanol as the polar diluent, and kerosene as the inert diluent. The optimal proportion of complex extractant was 20% trialkylamine, 70% n-octanol, and 10% kerosene. By detoxification, 63.9% of acetic acid and levulinic acid, 24.4% of 5-HMF, 63.9% of formic acid, and 64.0% of furfural could be removed.     

Oxidation of ascorbic acid with superoxide anion generated by the xanthine-xanthine oxidase system.

Ascorbic acid was found to be oxidized by O₂^$\text{?}$ which was generated by the xanthine-xanthine oxidase system. From a kinetic analysis of the inhibition of this reaction by superoxide dismutase, the second-order rate constant for the reaction between ascorbic acid and O₂^? at pH 7.4 was estimated to be 2.7 × 10⁵ M^?1 sec^?1. A function of ascorbic acid as a defense against O₂^? is presented.     

Preparation and properties of mono, homo- and heterobinuclear complexes with a new heptadentate Schiff base ligand

A new heptadentate Schiff base, containing an inner N₃O₂ and an outer O₂O₂ site, has been obtained by the reaction of 3-formylsalicylic acid and diethylenetriamine. By reaction of this ligand with copper(II), nickel(II) or uranyl(VI) salts, mononuclear and dinuclear complexes have been synthesized. The mononuclear complexes can act as ligands towards a second metal ion giving rise to homodinuclear or heterodinuclear complexes. The enlargement of the inner coordination chamber allows the synthesis of dinuclear uranyl(VI) species, impossible to obtain with the inner N₂O₂ site of the ligands previously employed. The equatorial pentacoordination of the UO₂²⁺ group in the outer O₂O₂ chamber is reached with the coordination of a solvent molecule to the central metal ion. The electrochemical behaviour of some complexes prepared is also reported.     

The oxidation of aminoethylcysteine ketimine dimer by oxygen reactive species

Summary The prominent spontaneous reaction of aminoethylcysteine ketimine in the neutral pH range is the concentration-dependent dimerization (Hermann, 1961). The carboxylated dimer first produced loses the free carboxyl yielding the more stable decarboxylated dimer (named simply the dimer in this note). In the search for a possible biochemical activity of this uncommon tricyclic compound we have assayed whether it could interact with oxygen reactive species (H₂O₂, O₂ ^–,OH) thus exhibiting a scavenging effect of possible biomedical interest. The dimer interacts with H₂O₂ producing compounds detectable by chromatographic procedures. The presence of Fe²⁺ stimulates the oxidative reaction by yielding the hydroxyl radical (the Fenton reaction). Using the system xanthine oxidase-xanthine as superoxide producer, the dimer oxidation by O₂ ^– has also been documented. Among the oxidation products the presence of taurine and cysteic acid has been established. Identification of remaining oxidation products and investigation of the possible function of the dimer as a biological scavenger of oxygen reactive species are now oncoming.Abbreviations HPLC high performance liquid chromatography - AAÅ amino acid analyzer - SOD superoxide dismutase - EDTA ethylenediaminetetraacetic acid     

New acyclic and cyclie Schiff bases derived from 2,6-diformyl-4-chlorophenol and their interaction with uranyl(Vl), copper(II) and nickel(Il) ions

A new heptadentate compartmental ligand has been synthesized by condensation of 3-formylsalicylic acid and 1,5-diamino-3-thiapentane in methanol (H₄L_a). This Schiff base contains an inner N₂SO₂ and an outer O₂O₂ site and gives, by reaction with copper(II), nickel(II) and uranyl(VI) diacetate, mononuclear, homo- and heterobinuclear complexes. In the mononuclear copper and nickel complexes, the metal ion is in the inner N₂SO₂ site, while it is in the outer O₂O₂ for uranyl; a solvent molecule fills the fifth equatorial coordination position in this last complex. The physico-chemical properties of the compounds are discusscd on the basis of infrared, electronic and magnetic data and by comparison with the analogous complexes with the ligand obtained by reaction of 3- formylsalicylic acid and diethylenetriamine (H₄L_b). The mononuclear copper and the heterodinuclear copper-uranyl complexes show anomalously low magnetic moments.     

31P nuclear magnetic resonance study on changes in phosphocreatine and the intracellular pH in rat skeletal muscle during exercise at various inspired oxygen contents

We measured ATP, phosphocreatine (PCr), inorganic phosphate (P_i), and the intracellular pH in rat hindlimb muscles during submaximal isometric exercise with various O₂ deliveries using³¹P nuclear magnetic resonance spectroscopy (³¹P NMR) to evaluate changes in energy metabolism in relation to O₂ availability. Delivery of O₂ to muscles was altered by controlling the fractional concentration of inspired oxygen (F _IO₂) at 0.50, 0.28, 0.21, 0.11 and 0.08 with monitoring partial pressure of oxygen and carbon dioxide, and bicarbonate at the femoral artery. The steady-state ratio of PCr : (PCr + P_i) during exercise decreased as a function ofF _IO₂ even at 0.21. Significant acidification of the intracellular pH during exercise occurred at 0.08F _IO₂. Change in the PCr : (PCr + P_i) ratio demonstrated that the oxidative capacity, i.e. the maximal rate of the oxidative phosphorylation reaction, in muscle was not limited by O₂ delivery at 0.50F _IO₂, but was significantly limited at 0.21F _IO₂ or below. Change in the intracellular pH at 0.08F _IO₂ could be interpreted as an increase in lactate, suggesting activation of glycolysis. Correlation between the PCr : (PCr + P_i) ratio and the intracellular pH revealed the existence of a critical PCr : (PCr + P_i) ratio and pH for glycolysis activation at around 0.4 and 6.7, respectively.     

Uranyl(VI), copper(II) and nickel(II) complexes derived from a new compartmental ligand

A new heptadentate compartmental ligand has been synthesized by condensation of 3-formylsalicylic acid and 1,5-diamino-3-thiapentane in methanol (H₄L_a). This Schiff base contains an inner N₂SO₂ and an outer O₂O₂ site and gives, by reaction with copper(II), nickel(II) and uranyl(VI) diacetate, mononuclear, homo- and heterobinuclear complexes. In the mononuclear copper and nickel complexes, the metal ion is in the inner N₂SO₂ site, while it is in the outer O₂O₂ for uranyl; a solvent molecule fills the fifth equatorial coordination position in this last complex. The physico-chemical properties of the compounds are discusscd on the basis of infrared, electronic and magnetic data and by comparison with the analogous complexes with the ligand obtained by reaction of 3- formylsalicylic acid and diethylenetriamine (H₄L_b). The mononuclear copper and the heterodinuclear copper-uranyl complexes show anomalously low magnetic moments.     

Determination of L-ascorbic acid levels in culture medium: Concentrations in commercial media and maintenance of levels under conditions of organ culture

Summary The method of Deutsch and Weeks was modified to provide a reliable and reasonably quick method for assaying the L-ascorbic acid content of culture medium. The modified method was used to determine the decay of L-ascorbic acid under various conditions of culture and the concentration of the vitamin in commercially prepared media. The half-life of L-ascorbic acid in a modified New circulator gassed with 95% O₂+5% CO₂ was 1.5 hr.; and when gassed with 20% O₂+5% CO₂+75% N₂, about 2 hr. In Petri dishes gassed with 20% O₂+5% CO₂+75% N₂, the half-life of L-ascorbic acid was 0.9 hr. About 4% of the L-ascorbic acid was lost per day when medium was stored at 0°C and about 9% per day when stored at 5°C. When medium with an initial content of 300 μg per ml was stored at room temperature, the half-life was found to be 15.5 hr. The L-ascorbic acid in five commercially available media, which contain the vitamin in their formulations, was assayed immediately after their delivery to the laboratory. The values of L-ascorbic acid measured in these media were in all cases far lower than prescribed. A continuous-flow organ culture system has been designed which allows the provision of a relatively constant level of L-ascorbic acid to an explant by taking advantage of the slow oxidation of L-ascorbic acid at 0°C.     

Can dimedone be used to study selenoproteins? An investigation into the reactivity of dimedone toward oxidized forms of selenocysteine

Dimedone is a widely used reagent to assess the redox state of cysteine‐containing proteins as it will alkylate sulfenic acid residues, but not sulfinic acid residues. While it has been reported that dimedone can label selenenic acid residues in selenoproteins, we investigated the stability, and reversibility of this label in a model peptide system. We also wondered whether dimedone could be used to detect seleninic acid residues. We used benzenesulfinic acid, benzeneseleninic acid, and model selenocysteine‐containing peptides to investigate possible reactions with dimedone. These peptides were incubated with H₂O₂ in the presence of dimedone and then the reactions were followed by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI‐MS). The native peptide, H‐PTVTGCUG‐OH (corresponding to the native amino acid sequence of the C‐terminus of mammalian thioredoxin reductase), could not be alkylated by dimedone, but could be carboxymethylated with iodoacetic acid. However the “mutant peptide,” H‐PTVTGAUG‐OH, could be labeled with dimedone at low concentrations of H₂O₂, but the reaction was reversible by addition of thiol. Due to the reversible nature of this alkylation, we conclude that dimedone is not a good reagent for detecting selenenic acids in selenoproteins. At high concentrations of H₂O₂, selenium was eliminated from the peptide and a dimeric form of dimedone could be detected using LCMS and ¹H NMR. The dimeric dimedone product forms as a result of a seleno‐Pummerer reaction with Sec‐seleninic acid. Overall our results show that the reaction of dimedone with oxidized cysteine residues is quite different from the same reaction with oxidized selenocysteine residues.     

An unexpected by-product obtained during the preparation of technetium(III) boronic acid adducts of dioximes. The single crystal structure of TcCl(DMG)2(BDI)BEt (DMG=dimethylglyoxime, BDI=butane-2, 3-dione imine-oxime)

An unusual Tc(III) boron-capped imine-oxime complex has been isolated from the reaction of ⁹⁹TcCl₃(CH₃CN)(PPh₃)₂, dimethyl glyoxime (DMG) and ethyl boronic acid (EtB(OH)₂). A single crystal X-ray structure analysis of this molecule ⁹⁹TcCl(DMG)₂(BDI)BEt (BDI=butane-2, 3-dione imine-oxime) shows it to be seven coordinate: TcClC₁₄H₂₅N₆O₅B, a=9.073(2), b=23.686(5), c=19.539(6) Å; β=93.77(2)°, P2₁/n, Z=8. Its structure is very similar to that of previously reported Tc(III) complexes ⁹⁹TcCl(dioxime)₃BR, except that one dioxime ligand on the molecule has been reduced to an imineoxime.