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Sample records for 1,2,3-trihydroxybenzene

  1. Structure-reactivity relationships of flavan-3-ols on product generation in aqueous glucose/glycine model systems.

    PubMed

    Noda, Yuko; Peterson, Devin G

    2007-05-02

    Ring structure-reactivity relationships of three flavan-3-ols [epicatechin (EC), epicatechin gallate (ECG), and epigallocatechin gallate (EGCG)] and three simple phenolic compounds (1,3,5-trihydroxybenzene, 1,2,3-trihydroxybenzene, and methylgallate as the analogous individual A, B, and C benzene rings of EGCG) on product generation in an aqueous glucose-glycine reaction model system (125 degrees C and 30 min) were investigated. The addition of EC, ECG, or EGCG to a glucose-glycine model was reported to similarly significantly reduce the formation of pyrazine, methyl-substituted pyrazines, and cyclotene. All three flavan-3-ols were also reported to generate phenolic-C2, C3, C4, and C6 sugar fragment adducts and to statistically reduce the concentration of glyoxal, glycolaldehyde, methylglyoxal, hydroxyacetone, diacetyl, acetoin, and 3-deoxyglucosone during the reaction time course, except for the EGCG reaction where 3-deoxyglucosone was not statistically different from the control after 20 min. For the simple phenolic compounds, methylgallate followed by 1,2,3-trihydroxybenzene was the least reactive, while 1,3,5-trihydroxybenzene was reported as the most reactive phenolic structure for quenching or reducing the concentration of the alpha-hydroxy- and alpha-dicarbonyl sugar fragments during the reaction time course. These results imply that the main mechanism flavan-3-ols reduced product generation was phenolic-sugar fragment carbonyl trapping reactions primarily on the A ring (the meta-polyhydroxylated benzene ring) or not due to the alteration of the reaction reduction potential.

  2. Evolution of novel O-methyltransferases from the Vanilla planifolia caffeic acid O-methyltransferase.

    PubMed

    Li, Huaijun Michael; Rotter, David; Hartman, Thomas G; Pak, Fulya E; Havkin-Frenkel, Daphna; Belanger, Faith C

    2006-06-01

    The biosynthesis of many plant secondary compounds involves the methylation of one or more hydroxyl groups, catalyzed by O-methyltransferases (OMTs). Here, we report the characterization of two OMTs, Van OMT-2 and Van OMT-3, from the orchid Vanilla planifolia Andrews. These enzymes catalyze the methylation of a single outer hydroxyl group in substrates possessing a 1,2,3-trihydroxybenzene moiety, such as methyl gallate and myricetin. This is a substrate requirement not previously reported for any OMTs. Based on sequence analysis these enzymes are most similar to caffeic acid O-methyltransferases (COMTs), but they have negligible activity with typical COMT substrates. Seven of 12 conserved substrate-binding residues in COMTs are altered in Van OMT-2 and Van OMT-3. Phylogenetic analysis of the sequences suggests that Van OMT-2 and Van OMT-3 evolved from the V. planifolia COMT. These V. planifolia OMTs are new instances of COMT-like enzymes with novel substrate preferences.

  3. The surface characterization of a series of hydroxybenzenes on Ag(111): An EELS and TDS study

    SciTech Connect

    Nielsen, B.S.

    1993-01-27

    Interaction of a series of hydroxybenzenes with Ag(111) is investigated by thermal desorption spectroscopy (TDS) and high resolution electron energy loss spectroscopy (EELS). Studied were the mono-hydroxybenzene, phenol, the o-, m- and p-dihydroxybenzenes, catechol, resorcinol, hydroquinone, respectively, and the 1,2.3-trihydroxybenzene, pyrogallol. Dehydrogenation of the hydroxyl groups upon adsorption is not directly observed in the TDS studies: however, the EELS results suggest possible dehydrogenation. The apparent O-H bond scission is attributed to hydrogen bonding between the surface molecules or to the orientation of the O-H bond aids with respect to the metal surface. Orientations of the mono- and dihydroxybenzene molecules are temperature dependent, whereas that of the trihydroxybenzene may be attributed to the number and position of the hydroxyl substitutents. Phenol and catechol both undergo an inclined-to-perpendicular orientational change. Resorcinol and hydroquinone undergo a perpendicular-to-inclined transformation. Finally, pyrogallol remains inclined at all temperatures until decomposition.

  4. Detection, identification and formation of new iodinated disinfection byproducts in chlorinated saline wastewater effluents.

    PubMed

    Gong, Tingting; Zhang, Xiangru

    2015-01-01

    The use of seawater for toilet flushing introduces high levels of inorganic ions, including iodide ions, into a city's wastewater treatment systems, resulting in saline wastewater effluents. Chlorination is widely used in disinfecting wastewater effluents owing to its low cost and high efficiency. During chlorination of saline wastewater effluents, iodide may be oxidized to hypoiodous acid, which may further react with effluent organic matter to form iodinated disinfection byproducts (DBPs). Iodinated DBPs show significantly higher toxicity than their brominated and chlorinated analogues and thus have been drawing increasing concerns. In this study, polar iodinated DBPs were detected in chlorinated saline wastewater effluents using a novel precursor ion scan method. The major polar iodinated DBPs were identified and quantified, and their organic precursors and formation pathways were investigated. The formation of iodinated DBPs under different chlorine doses and contact times was also studied. The results indicated that a few polar iodinated DBPs were generated in the chlorinated saline primary effluent, but few were generated in the chlorinated saline secondary effluent. Several major polar iodinated DBPs in the chlorinated saline primary effluent were proposed with structures, among which a new group of polar iodinated DBPs, iodo-trihydroxybenzenesulfonic acids, were identified and quantified. The organic precursors of this new group of DBPs were found to be 4-hydroxybenzenesulfonic acid and 1,2,3-trihydroxybenzene, and the formation pathways of these new DBPs were tentatively proposed. Both chlorine dose and contact time affected the formation of iodinated DBPs in the chlorinated saline wastewater effluents.

  5. Identification of Pyrogallol in the Ethyl Acetate-Soluble Part of Coffee as the Main Contributor to Its Xanthine Oxidase Inhibitory Activity.

    PubMed

    Honda, Sari; Masuda, Toshiya

    2016-10-10

    In this study, ethyl acetate-soluble parts of hot-water extracts from roasted coffee beans were found to demonstrate potent xanthine oxidase (XO) inhibition. The XO inhibitory activities and chlorogenic lactone contents (chlorogenic lactones have previously been identified as XO inhibitors in roast coffee) were measured for ethyl acetate-soluble parts prepared from coffee beans roasted to three different degrees. Although chlorogenic lactone contents decreased with higher degrees of roasting, the XO inhibitory activity did not decrease. These data led us to investigate new potent inhibitors present in these ethyl acetate-soluble extracts. Repeated assay-guided purifications afforded a highly potent XO inhibitor, which was eluted before chlorogenic lactones via medium-pressure chromatography using an octadecylsilica gel column. The obtained inhibitor was identified as pyrogallol (1,2,3-trihydroxybenzene), which had an IC50 of 0.73 μmol L(-1), much stronger than that of other related polyphenolic compounds. Quantitative analysis of pyrogallol and chlorogenic lactones revealed that pyrogallol (at concentrations of 33.9 ± 4.2 nmol mL(-1) in light roast coffee and 39.4 ± 3.9 nmol mL(-1) in dark roast coffee) was the main XO inhibitor in hot-water extracts of roasted coffee beans (i.e., drinking coffee).

  6. Electrochemical treatment of aqueous wastes containing pyrogallol by BDD-anodic oxidation.

    PubMed

    Nasr, Bensalah; Hsen, Trabelsi; Abdellatif, Gadri

    2009-01-01

    In this work, the electrochemical oxidation of pyrogallol (1,2,3-trihydroxybenzene) on boron-doped diamond anodes has been studied. The voltammetric results showed that pyrogallol oxidation takes place in the same potential region as that of phenol where the supporting electrolyte is stable. Synthetic wastewaters containing pyrogallol have been treated in a bench-scale electrolysis plant. This plant operates in a discontinuous mode by recirculating the waste continuously through a single-chamber electrochemical flow cell. The complete mineralization of pyrogallol and the electro-generated pollutants is obtained in the electrolytic device. HPLC analyses show the formation of carboxylic acids as the main intermediates. The efficiency of the electrochemical process was found to depend mainly on the pollutant concentration present in the waste and on the applied current density. The high efficiency of this technology can be explained in terms of the direct electro-oxidation at the BDD surface and the oxidation carried out by hydroxyl radicals and other electro-generated oxidants.

  7. Superoxide generated by pyrogallol reduces highly water-soluble tetrazolium salt to produce a soluble formazan: a simple assay for measuring superoxide anion radical scavenging activities of biological and abiological samples.

    PubMed

    Xu, Chen; Liu, Shu; Liu, Zhiqiang; Song, Fengrui; Liu, Shuying

    2013-09-02

    Superoxide anion radical (O2(˙-)) plays an important role in several human diseases. The xanthine/xanthine oxidase system is frequently utilized to produce O2(˙-). However, false positive results are easily got by using this system. The common spectrophotometric probes for O2(˙-) are nitroblue tetrazolium (NBT) and cytochrome c. Nevertheless, the application of NBT method is limited because of the water-insolubility of NBT formazan and the assay using cytochrome c lacks sensitivity and is not suitable for microplate measurement. We overcome these problems by using 1,2,3-trihydroxybenzene (pyrogallol) as O2(˙-)-generating system and a highly water-soluble tetrazolium salt, 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium sodium salt (WST-1) which can be reduced by superoxide anion radical to a stable water-soluble formazan with a high absorbance at 450 nm. The method is simple, rapid and sensitive. Moreover, it can be adapted to microplate format. In this study, the O2(˙-) scavenging activities of superoxide dismutase (SOD), L-ascorbic acid, N-acetyl-L-cysteine (NAC), albumin from human serum, flavonoids and herbal extracts were assessed by using this method. Meanwhile, the activities of tissue homogenates and serum were determined by using this validated method. This method, applicable to tissue homogenates, serum and herbal extracts, proved to be efficient for measuring O2(˙-) scavenging activities of biological and abiological samples.

  8. The Extent of Fermentative Transformation of Phenolic Compounds in the Bioanode Controls Exoelectrogenic Activity in a Microbial Electrolysis Cell

    DOE PAGES

    Zeng, Xiaofei; Collins, Maya; Borole, Abhijeet P.; ...

    2016-11-27

    Phenolic compounds in hydrolysate/pyrolysate and wastewater streams produced during the pretreatment of lignocellulosic biomass for biofuel production present a significant challenge in downstream processes. Bioelectrochemical systems are increasingly recognized as an alternative technology to handle biomass-derived streams and to promote water reuse in biofuel production. Thus, a thorough understanding of the fate of phenolic compounds in bioanodes is urgently needed. The present study investigated the biotransformation of three structurally similar phenolic compounds (syringic acid, SA; vanillic acid, VA; 4-hydroxybenzoic acid, HBA), and their individual contribution to exoelectrogenesis in a microbial electrolysis cell (MEC) bioanode. Fermentation of SA resulted in themore » highest exoelectrogenic activity among the three compounds tested, with 50% of the electron equivalents converted to current, compared to 12 and 9% for VA and HBA, respectively. The biotransformation of SA, VA and HBA was initiated by demethylation and decarboxylation reactions common to all three compounds, resulting in their corresponding hydroxylated analogs. SA was transformed to pyrogallol (1,2,3-trihydroxybenzene), whose aromatic ring was then cleaved via a phloroglucinol pathway, resulting in acetate production, which was then used in exoelectrogenesis. In contrast, more than 80% of VA and HBA was converted to catechol (1,2-dihydroxybenzene) and phenol (hydroxybenzene) as their respective dead-end products. The persistence of catechol and phenol is explained by the fact that the phloroglucinol pathway does not apply to di- or mono-hydroxylated benzenes. Previously reported, alternative ring-cleaving pathways were either absent in the bioanode microbial community or unfavorable due to high energy-demand reactions. With the exception of acetate oxidation, all biotransformation steps in the bioanode occurred via fermentation, independently of exoelectrogenesis. Therefore, the observed

  9. The Extent of Fermentative Transformation of Phenolic Compounds in the Bioanode Controls Exoelectrogenic Activity in a Microbial Electrolysis Cell

    SciTech Connect

    Zeng, Xiaofei; Collins, Maya; Borole, Abhijeet P.; Pavlostathis, Spyros

    2016-11-27

    Phenolic compounds in hydrolysate/pyrolysate and wastewater streams produced during the pretreatment of lignocellulosic biomass for biofuel production present a significant challenge in downstream processes. Bioelectrochemical systems are increasingly recognized as an alternative technology to handle biomass-derived streams and to promote water reuse in biofuel production. Thus, a thorough understanding of the fate of phenolic compounds in bioanodes is urgently needed. The present study investigated the biotransformation of three structurally similar phenolic compounds (syringic acid, SA; vanillic acid, VA; 4-hydroxybenzoic acid, HBA), and their individual contribution to exoelectrogenesis in a microbial electrolysis cell (MEC) bioanode. Fermentation of SA resulted in the highest exoelectrogenic activity among the three compounds tested, with 50% of the electron equivalents converted to current, compared to 12 and 9% for VA and HBA, respectively. The biotransformation of SA, VA and HBA was initiated by demethylation and decarboxylation reactions common to all three compounds, resulting in their corresponding hydroxylated analogs. SA was transformed to pyrogallol (1,2,3-trihydroxybenzene), whose aromatic ring was then cleaved via a phloroglucinol pathway, resulting in acetate production, which was then used in exoelectrogenesis. In contrast, more than 80% of VA and HBA was converted to catechol (1,2-dihydroxybenzene) and phenol (hydroxybenzene) as their respective dead-end products. The persistence of catechol and phenol is explained by the fact that the phloroglucinol pathway does not apply to di- or mono-hydroxylated benzenes. Previously reported, alternative ring-cleaving pathways were either absent in the bioanode microbial community or unfavorable due to high energy-demand reactions. With the exception of acetate oxidation, all biotransformation steps in the bioanode occurred via fermentation, independently of exoelectrogenesis. Therefore, the observed

  10. The extent of fermentative transformation of phenolic compounds in the bioanode controls exoelectrogenic activity in a microbial electrolysis cell.

    PubMed

    Zeng, Xiaofei; Collins, Maya A; Borole, Abhijeet P; Pavlostathis, Spyros G

    2017-02-01

    Phenolic compounds in hydrolysate/pyrolysate and wastewater streams produced during the pretreatment of lignocellulosic biomass for biofuel production present a significant challenge in downstream processes. Bioelectrochemical systems are increasingly recognized as an alternative technology to handle biomass-derived streams and to promote water reuse in biofuel production. Thus, a thorough understanding of the fate of phenolic compounds in bioanodes is urgently needed. The present study investigated the biotransformation of three structurally similar phenolic compounds (syringic acid, SA; vanillic acid, VA; 4-hydroxybenzoic acid, HBA), and their individual contribution to exoelectrogenesis in a microbial electrolysis cell (MEC) bioanode. Fermentation of SA resulted in the highest exoelectrogenic activity among the three compounds tested, with 50% of the electron equivalents converted to current, compared to 12 and 9% for VA and HBA, respectively. The biotransformation of SA, VA and HBA was initiated by demethylation and decarboxylation reactions common to all three compounds, resulting in their corresponding hydroxylated analogs. SA was transformed to pyrogallol (1,2,3-trihydroxybenzene), whose aromatic ring was then cleaved via a phloroglucinol pathway, resulting in acetate production, which was then used in exoelectrogenesis. In contrast, more than 80% of VA and HBA was converted to catechol (1,2-dihydroxybenzene) and phenol (hydroxybenzene) as their respective dead-end products. The persistence of catechol and phenol is explained by the fact that the phloroglucinol pathway does not apply to di- or mono-hydroxylated benzenes. Previously reported, alternative ring-cleaving pathways were either absent in the bioanode microbial community or unfavorable due to high energy-demand reactions. With the exception of acetate oxidation, all biotransformation steps in the bioanode occurred via fermentation, independently of exoelectrogenesis. Therefore, the observed

  11. Adsorption and detection of some phenolic compounds by rice husk ash of Kenyan origin.

    PubMed

    Mbui, Damaris N; Shiundu, Paul M; Ndonye, Rachel M; Kamau, Geoffrey N

    2002-12-01

    Rice husk ash (RHA) obtained from a rice mill in Kenya has been used as an inexpensive and effective adsorbent (and reagent) for the removal (and detection) of some phenolic compounds in water. The abundantly available rice mill waste was used in dual laboratory-scale batch experiments to evaluate its potential in: (i) the removal of phenol, 1,3-dihydroxybenzene (resorcinol) and 2-chlorophenol from water; and (ii) the detection of 1,2-dihydroxybenzene (pyrocatechol) and 1,2,3-trihydroxybenzene (pyrogallol) present in an aqueous medium. The studies were conducted using synthetic water with different initial concentrations of the phenolic compounds. The effects of different operating conditions (such as contact time, concentration of the phenolic compounds, adsorbent quantity, temperature, and pH) were assessed by evaluating the phenolic compound removal efficiency as well as the extent of their color formation reactions (where applicable). RHA exhibits reasonable adsorption capacity for the phenolic compounds and follows both Langmuir and Freundlich isotherm models. Adsorption capacities of 1.53 x 10(-4), 8.07 x 10(-5), and 1.63 x 10(-6) mol g(-1) were determined for phenol, resorcinol and 2-chlorophenol, respectively. Nearly 100% adsorption of the phenolic compounds was possible and this depended on the weight of RHA employed. For the detection experiments, pyrocatechol and pyrogallol present in water formed coloured complexes with RHA, with the rate of colour formation increasing with temperature, weight of RHA, concentration of the phenolic compounds and sonication. This study has proven that RHA is a useful agricultural waste product for the removal and detection of some phenolic compounds.

  12. Altering toluene 4-monooxygenase by active-site engineering for the synthesis of 3-methoxycatechol, methoxyhydroquinone, and methylhydroquinone.

    PubMed

    Tao, Ying; Fishman, Ayelet; Bentley, William E; Wood, Thomas K

    2004-07-01

    Wild-type toluene 4-monooxygenase (T4MO) of Pseudomonas mendocina KR1 oxidizes toluene to p-cresol (96%) and oxidizes benzene sequentially to phenol, to catechol, and to 1,2,3-trihydroxybenzene. In this study T4MO was found to oxidize o-cresol to 3-methylcatechol (91%) and methylhydroquinone (9%), to oxidize m-cresol and p-cresol to 4-methylcatechol (100%), and to oxidize o-methoxyphenol to 4-methoxyresorcinol (87%), 3-methoxycatechol (11%), and methoxyhydroquinone (2%). Apparent Vmax values of 6.6 +/- 0.9 to 10.7 +/- 0.1 nmol/min/ mg of protein were obtained for o-, m-, and p-cresol oxidation by wild-type T4MO, which are comparable to the toluene oxidation rate (15.1 +/- 0.8 nmol/min/mg of protein). After these new reactions were discovered, saturation mutagenesis was performed near the diiron catalytic center at positions I100, G103, and A107 of the alpha subunit of the hydroxylase (TmoA) based on directed evolution of the related toluene o-monooxygenase of Burkholderia cepacia G4 (K. A. Canada, S. Iwashita, H. Shim, and T. K. Wood, J. Bacteriol. 184:344-349, 2002) and a previously reported T4MO G103L regiospecific mutant (K. H. Mitchell, J. M. Studts, and B. G. Fox, Biochemistry 41:3176-3188, 2002). By using o-cresol and o-methoxyphenol as model substrates, regiospecific mutants of T4MO were created; for example, TmoA variant G103A/A107S produced 3-methylcatechol (98%) from o-cresol twofold faster and produced 3-methoxycatechol (82%) from 1 mM o-methoxyphenol seven times faster than the wild-type T4MO (1.5 +/- 0.2 versus 0.21 +/- 0.01 nmol/min/mg of protein). Variant I100L produced 3-methoxycatechol from o-methoxyphenol four times faster than wild-type T4MO, and G103S/A107T produced methylhydroquinone (92%) from o-cresol fourfold faster than wild-type T4MO and there was 10 times more in terms of the percentage of the product. Variant G103S produced 40-fold more methoxyhydroquinone from o-methoxyphenol than the wild-type enzyme produced (80 versus 2%) and