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Ludger Beerhues - One of the best experts on this subject based on the ideXlab platform.

  • formation of biphenyl and dibenzofuran phytoalexins in the transition zones of fire blight infected stems of malus domestica cv holsteiner cox and pyrus communis cv conference
    Phytochemistry, 2012
    Co-Authors: Cornelia Chizzali, Till Beuerle, Mohammed N A Khalil, Wolfgang Schuehly, Klaus Richter, Henryk Flachowsky, Andreas Peil, Magdaviola Hanke, Benye Liu, Ludger Beerhues
    Abstract:

    Abstract In the rosaceous subtribe Pyrinae (formerly subfamily Maloideae), pathogen attack leads to formation of biphenyls and Dibenzofurans. Accumulation of these phytoalexins was studied in greenhouse-grown grafted shoots of Malus domestica cv. ‘Holsteiner Cox’ and Pyrus communis cv. ‘Conference’ after inoculation with the fire blight bacterium, Erwinia amylovora . No phytoalexins were found in leaves. However, both classes of defence compounds were detected in the transition zone of stems. The flanking stem segments above and below this zone, which were necrotic and healthy, respectively, were devoid of detectable phytoalexins. The transition zone of apple stems contained the biphenyls 3-hydroxy-5-methoxyaucuparin, aucuparin, noraucuparin and 2′-hydroxyaucuparin and the Dibenzofurans eriobofuran and noreriobofuran. In pear, aucuparin, 2′-hydroxyaucuparin, noreriobofuran and in addition 3,4,5-trimethoxybiphenyl were detected. The total phytoalexin content in the transition zone of pear was 25 times lower than that in apple. Leaves and stems of mock-inoculated apple and pear shoots lacked phytoalexins. A number of biphenyls and Dibenzofurans were tested for their in vitro antibacterial activity against some Erwinia amylovora strains . The most efficient compound was 3,5-dihydroxybiphenyl (MIC = 115 μg/ml), the immediate product of biphenyl synthase which initiates phytoalexin biosynthesis.

  • Phytoalexins of the Pyrinae: Biphenyls and Dibenzofurans.
    Beilstein journal of organic chemistry, 2012
    Co-Authors: Cornelia Chizzali, Ludger Beerhues
    Abstract:

    Biphenyls and Dibenzofurans are the phytoalexins of the Pyrinae, a subtribe of the plant family Rosaceae. The Pyrinae correspond to the long-recognized Maloideae. Economically valuable species of the Pyrinae are apples and pears. Biphenyls and Dibenzofurans are formed de novo in response to infection by bacterial and fungal pathogens. The inducible defense compounds were also produced in cell suspension cultures after treatment with biotic and abiotic elicitors. The antimicrobial activity of the phytoalexins was demonstrated. To date, 10 biphenyls and 17 Dibenzofurans were isolated from 14 of the 30 Pyrinae genera. The most widely distributed compounds are the biphenyl aucuparin and the dibenzofuran γ-cotonefuran. The biosynthesis of the two classes of defense compounds is not well understood, despite the importance of the fruit crops. More recent studies have revealed simultaneous accumulation of biphenyls and Dibenzofurans, suggesting sequential, rather than the previously proposed parallel, biosynthetic pathways. Elicitor-treated cell cultures of Sorbus aucuparia served as a model system for studying phytoalexin metabolism. The key enzyme that forms the carbon skeleton is biphenyl synthase. The starter substrate for this type-III polyketide synthase is benzoyl-CoA. In apples, biphenyl synthase is encoded by a gene family, members of which are differentially regulated. Metabolism of the phytoalexins may provide new tools for designing disease control strategies for fruit trees of the Pyrinae subtribe.

  • differential effect of elicitors on biphenyl and dibenzofuran formation in sorbus aucuparia cell cultures
    Journal of Agricultural and Food Chemistry, 2010
    Co-Authors: Cornelia Huttner, Helge Scharnhop, Till Beuerle, Ludger Ernst, Ludger Beerhues
    Abstract:

    The Rosaceous subtribe Pyrinae (formerly subfamily Maloideae) is well-known for its economically important fruit trees, such as apple and pear, and also includes Sorbus aucuparia. Elicitor-treated S. aucuparia cell cultures are used to study the biosynthesis of the Pyrinae-specific phytoalexins, biphenyls and Dibenzofurans. Three biphenyls (aucuparin, noraucuparin, 2′-hydroxyaucuparin) and a dibenzofuran (eriobofuran) were isolated and structure elucidated using GC-MS and NMR. A second dibenzofuran of low abundance was tentatively assigned as noreriobofuran. Treatment of S. aucuparia cell cultures with yeast extract induced the formation of aucuparin as the major phytoalexin. In contrast, addition of preparations from the fire blight bacterium, Erwinia amylovora, and the scab-causing fungus, Venturia inaequalis, resulted in accumulation of eriobofuran as the major inducible constituent. Methyl jasmonate was a poor elicitor. The observations are suggestive of a biogenic relationship between biphenyls and d...

  • differential effect of elicitors on biphenyl and dibenzofuran formation in sorbus aucuparia cell cultures
    Journal of Agricultural and Food Chemistry, 2010
    Co-Authors: Cornelia Huttner, Helge Scharnhop, Till Beuerle, Ludger Ernst, Ludger Beerhues
    Abstract:

    The Rosaceous subtribe Pyrinae (formerly subfamily Maloideae) is well-known for its economically important fruit trees, such as apple and pear, and also includes Sorbus aucuparia. Elicitor-treated S. aucuparia cell cultures are used to study the biosynthesis of the Pyrinae-specific phytoalexins, biphenyls and Dibenzofurans. Three biphenyls (aucuparin, noraucuparin, 2'-hydroxyaucuparin) and a dibenzofuran (eriobofuran) were isolated and structure elucidated using GC-MS and NMR. A second dibenzofuran of low abundance was tentatively assigned as noreriobofuran. Treatment of S. aucuparia cell cultures with yeast extract induced the formation of aucuparin as the major phytoalexin. In contrast, addition of preparations from the fire blight bacterium, Erwinia amylovora, and the scab-causing fungus, Venturia inaequalis, resulted in accumulation of eriobofuran as the major inducible constituent. Methyl jasmonate was a poor elicitor. The observations are suggestive of a biogenic relationship between biphenyls and Dibenzofurans. Elicitor-treated S. aucuparia cell cultures provide an interesting in vitro system for studying biphenyl and dibenzofuran metabolism in the economically valuable Pyrinae.

Jiping Chen - One of the best experts on this subject based on the ideXlab platform.

  • electrophilic chlorination of dibenzo p dioxin and dibenzofuran over composite copper and iron chlorides and oxides in combustion flue gas
    Chemosphere, 2020
    Co-Authors: Meihui Ren, Dan Wang, Yun Fan, Yuan Gao, Jiping Chen
    Abstract:

    Abstract Dibenzo-p-dioxin (DD) and dibenzofuran (DF) chlorination mediated by Cu and Fe chlorides can make a direct contribution to the formation of polychlorinated dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) in combustion flue gas. In this study, a kind of composite Cu and Fe chlorides and oxides (CuFe9O9.5Cl10) was prepared by impregnating oxides with HCl solution to imitate the coexistence status of Cu and Fe species in combustion flue gas. Composite CuFe9O9.5Cl10 was active in promoting the electrophilic chlorination of DD/DF at 150–300 °C, with the highest activity at 200 °C. DD/DF chlorination could occur under inert atmosphere, and 5% O2 atmosphere was most favorable for DD/DF chlorination. Electrophilic chlorination of DD/DF primarily favored at 2,3,7,8 positions. Hybridization of Cu and Fe chlorides and oxides not only decreased the starting temperature and activation energy of DD/DF chlorination, but also induced a synergistic effect for accelerating the chlorination of DD/DF. The measured activities of composite CuFe9O9.5Cl10 for promoting the chlorination of DD/DF were near to those of composite Cu chloride and oxide (CuO0.2Cl1.6), whereas 2 orders of magnitude higher than those of composite Fe chloride and oxide (FeO0.3Cl2.4). Comparison of PCDD/F congener distribution patterns indicated that DD/DF chlorination should be a main source of Cl1−3DFs and Cl1−2DDs in combustion flue gases.

  • mechanistic aspects of polychlorinated dibenzo p dioxins and Dibenzofurans pcdd fs formation from chlorine bleaching of non wood pulp
    Journal of Hazardous Materials, 2020
    Co-Authors: Yuwen Ni, Faqiang Zhan, Boyu Song, Yichi Zhang, Jiping Chen
    Abstract:

    Abstract Chlorine bleaching of non-wood pulp can produce and release polychlorinated dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) into environment. In this study, a series of chlorination experiments were conducted to explore the source, formation pathway and formation kinetics of Cl1−8DD/Fs during the chlorine bleaching of wheat straw pulp. The 13C isotope-labeling experiment verified that PCDD/Fs could not be formed from the chlorination of phenols in pulp. Above 80% of the observed PCDFs originated from the direct chlorination of dibenzofuran (DBF) in unbleached wheat straw pulp, while approximately 60% of the observed PCDDs came from the chlorination of nonextractable precursors in the pulp. The yield of total PCDFs was 2 orders of magnitude higher than that of total PCDDs. The kinetic study indicated that DBF was more easily chlorinated than dibenzo-p-dioxin (DBD) in the pulp solution. Pseudo-first-order reaction kinetic equations fitted the formation and degradation of PCDD/Fs well. The direct chlorination of DBD/F primarily preferred a selective pattern at the 2 position, followed by the 8, 7 and 3 positions. A higher content of DBF in unbleached pulp led to a higher yield of 2,3,7,8-Cl4DF. Finally, the practical implication for dioxin formation control was discussed.

  • polychlorinated dibenzo p dioxin and dibenzofuran precursors and formation mechanisms during non woodpulp chlorine bleaching process
    Chemosphere, 2018
    Co-Authors: Xueli Wang, Jiping Chen
    Abstract:

    Abstract There is great concern about decreasing the amounts of polychlorinated dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) that are formed and emitted during the chlorine bleaching of pulp. The formation of PCDD/Fs during non-woodpulp chlorine bleaching was investigated in the study described here. Wheat straw was separated into three components, cellulose, hemicellulose, and lignin. Chlorination experiments were performed, and lignin and hemicellulose contributed more than cellulose to PCDD/F formation when the pulp was bleached using chlorine. The chemical components of lignin were identified by gas chromatography mass spectrometry, and nine possible PCDD/F precursors were quantified by gas chromatography tandem mass spectrometry. Spiked chlorination experiments were performed to investigate the effects of these compounds on PCDD/F formation. 4-Ethyl-2-methoxyphenol had the strongest effect on PCDD/F formation, followed by p-chlorophenol, and guaiacol. All the test compounds promoted polychlorinated dibenzofuran formation but had limited effects on polychlorinated dibenzo-p-dioxin formation. The results allowed mechanisms for the formation of PCDD/Fs from phenol, chlorophenol, catechol, and guaiacol to be proposed.

Peter Haglund - One of the best experts on this subject based on the ideXlab platform.

Maria Jose Gonzalez - One of the best experts on this subject based on the ideXlab platform.

Jianhua Yan - One of the best experts on this subject based on the ideXlab platform.

  • formation of df pcdd fs and epfrs from 1 2 3 trichlorobenzene over metal oxide silica surface
    Waste Management, 2020
    Co-Authors: Tong Chen, Slawo Lomnicki, Chen Sun, Tianjiao Wang, Mingxiu Zhan, Jianhua Yan
    Abstract:

    Abstract The formation of dibenzofuran (DF), polychlorinated dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) and environmentally persistent free radicals (EPFRs) from 1,2,3-trichlorobenzene (1,2,3-TrCBz) over metal oxide / silica surface were investigated using a tubular furnace. PCDD/Fs increased exponentially from 250 to 550 °C over copper oxide / silica surface and PCDD/Fs had the maximum growth from 400 to 450 °C. The ratio of PCDD / PCDF was much less than 1, especially when the temperature raised from 450 to 550 °C. Pentachlorianated dibenzo-p-furan (PeCDF) dominated among the homologues, which contributed 45–61% to the total PCDD/Fs. Two peaks of the yield of DF occurred at 400 °C and 500 °C respectively. Furthermore, the oxygen contents have different effects for PCDD and PCDF formation, and low oxygen could promote PCDD production, especially for tetrachlorinated dibenzo-p-dioxin (TCDD). More PCDF were formed on the oxygen rich condition, indicating that the oxygen promoted the chlorination of DF. Iron oxides are better than copper oxides to catalyze the formation of PCDD/Fs from 1,2,3-TrCBzs at 350 °C, especially for PCDF. The major EPFRs on the catalysts were formed with g values in the range of 2.0040 to 2.0049, which were phenoxy radicals and semiquinone occurred with higher g value of 2.0075 when the temperature increased to 550 °C, and more EPFRs were produced with the temperature increasing. The addition of iron oxides reduced the spins concentrations of oxygen-centered radicals but increase the spins concentrations of signals with lower g values. The different possible formation pathways of PCDD and PCDF from 1,2,3-TrCBz over metal oxide surface were also proposed.

  • concentrations profiles and sources of atmospheric pcdd fs near a municipal solid waste incinerator in eastern china
    Environmental Science & Technology, 2009
    Co-Authors: Jianhua Yan, Tong Chen, Huifen Dai, Fei Wang, Kefa Cen
    Abstract:

    Ambient air monitoring of polychlorinated dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) was performed to investigate their concentrations, profiles, and sources near a municipal solid waste inciner...