Sample records for 1,2,3-trihydroxybenzene

  1. 氧脱木素过程中超氧阴离子自由基的控制%Regulation of Superoxide Anion Radical During the Oxygen Delignification Process

    Institute of Scientific and Technical Information of China (English)

    曹石林; 詹怀宇; 付时雨; 陈礼辉


    In this study, the superoxide anion radicals were generated by the auto-oxidation of 1,2,3-trihydroxybenzene and determined by UV spectrophotometry, and the reaction was found to be facilitated by anthraquinone-2-sulfonic acid sodium salt. The bamboo kraft pulps were treated by the 1,2,3-trihydroxybenzene auto-oxidation method or the 1,2,3-trihydroxybenzene auto-oxidation combined with anthraquinone-2-suffonic acid sodium salt to show the effect of the superoxide anion radicals during the oxygen delignification of bamboo kraft pulp and the enhancing affect of anthraquinone compounds as an additive on delignification. The results indicated that the superoxide anion radicals could react with lignin and remove it from pulp with negligible damage on cellulose, and the anthraquinone-2-sulfonic acid sodium salt could facilitate the generation of superoxide anion radical to enhance delignification of pulps. The oxygen delignification selectivity could be improved using the 1,2,3-trihydroxybenzene auto-oxidation system combined with anthraquinone-2-sulfonic acid sodium salt.

  2. Evolution of novel O-methyltransferases from the Vanilla planifolia caffeic acid O-methyltransferase. (United States)

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


    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. Essential Structural Requirements and Additive Effects for Flavonoids to Scavenge Methylglyoxal. (United States)

    Shao, Xi; Chen, Huadong; Zhu, Yingdong; Sedighi, Rashin; Ho, Chi-Tang; Sang, Shengmin


    Reactive dicarbonyl species, such as methylglyoxal (MGO), are considered as the major precursors of advanced glycation end products (AGEs), which are believed to be one of the physiological causes of diabetes and its complications. Scavenging of reactive dicarbonyl species using naturally occurring flavonoids has been proposed as an effective way to prevent diabetic complications. To elucidate the structural requirements of flavonoids in scavenging MGO, seven flavonoids (quercetin, luteolin, epicatechin, genistein, daidzein, apigenin, and phloretin) and five sub-components of the flavonoids (gallic acid, phloroglucinol, pyrogallol, pyrocatechol, and resorcinol) were examined in this study. Our results showed the following: (1) 1,2,3-trihydroxybenzene (pyrogallol) has higher MGO scavenging activity than 1,3,5-trihydroxybenzene and 1,2- and 1,3-dihydroxybenzene, and substitution at position 5 of pyrogallol diminished the scavenging activity, indicating that position 5 is the active site of pyrogallol; (2) the A ring is the active site of flavonoids in contributing the MGO-trapping efficacy, and the hydroxyl group at C-5 on the A ring enhances the trapping efficacy; (3) the double bond between C-2 and C-3 on the C ring could facilitate the trapping efficacy; and (4) the number of hydroxyl groups on the B ring does not significantly influence the trapping efficacy. In addition, we found there is an additive effect in MGO trapping by two common flavonoids, quercetin and phloretin, indicating that flavonoid-enriched foods and beverages hold great promise to prevent the development of diabetic complications.

  4. 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. (United States)

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


    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.

  5. Detection, identification and formation of new iodinated disinfection byproducts in chlorinated saline wastewater effluents. (United States)

    Gong, Tingting; Zhang, Xiangru


    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.

  6. Adsorption and detection of some phenolic compounds by rice husk ash of Kenyan origin. (United States)

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


    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.

  7. The extent of fermentative transformation of phenolic compounds in the bioanode controls exoelectrogenic activity in a microbial electrolysis cell. (United States)

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


    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

  8. Study on effects of lead on the antioxidant activities of Aloe vera%铅污染对芦荟抗氧化活性影响的研究

    Institute of Scientific and Technical Information of China (English)

    蔡卓; 卢登峰; 梁信源; 莫创荣; 杜良伟; 莫利书; 黄富嵘


    The variation of the antioxidant enzyme system of Aloe vera under the stress of different Pb concentrations was studied using pot experiments. The scavenging abilities of the potted Aloe vera to ·OH and O2- o were determined by flow injection chemiluminescence method using methylene blue-Fenton system and 1,2,3 -trihydroxybenzene system. The effects of lead pollution on the enzymatic activity of Aloe vera were evaluated. The results showed that at a relatively low lead pollution level, the enzymatic activity of polluted Aloe vera was higher than that of the un-polluted, and increased with the increase of lead concentration in Aloe vera body; while at a relatively higher lead pollution level, the enzymatic activity of polluted Aloe vera was lower than that of the un-polluted, and the activity decreased with the increase of lead concentration in Aloe vera body. These indicated that at a low pollution level the physiological response of Aloe vera antioxidant enzyme system to heavy metal stress resulted in the rise of enzymatic activity of Aloe vera; while at a high pollution level, the self protection system of Aloe vera is damaged, which in turn led to the damage of antioxidant enzyme system, and then results in the decrease of the enzymatic activity.%采用盆栽试验,对芦荟在不同浓度Pb胁迫下抗氧化酶系统的变化进行了研究.用流动注射化学发光分析法,以亚甲基蓝-Fenton体系、鲁米诺-邻苯三酚体系分别测定盆栽芦荟体内抗氧化酶清除·OH和清除O2-·的能力,进而评价铅污染对芦荟生物活性的影响.结果表明,在相对低浓度铅污染水平下,芦荟提取酶的活性均比无污染时的对照值有所升高,并与芦荟体内铅含量成正相关;而在相对较高浓度铅污染下,提取酶的活性均比对照值有所下降,与芦荟体内铅含量成负相关.说明在低浓度铅毒害作用下,芦荟体内抗氧化酶系统对重金属胁迫的生理的响应使其活性有所上升