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Hélène Fulcrand - One of the best experts on this subject based on the ideXlab platform.

  • Furanolysis with Menthofuran: A New Depolymerization Method for Analyzing Condensed Tannins
    Journal of Agricultural and Food Chemistry, 2019
    Co-Authors: Guillaume Billerach, Laurent Rouméas, Eric Dubreucq, Hélène Fulcrand
    Abstract:

    An improved analytical depolymerization method for characterizing condensed tannins was developed with menthofuran (3,6-dimethyl-4,5,6,7-tetrahydro-1-benzofuran) as the nucleophilic trapping reagent. Herein, menthofuran was compared with routinely used nucleophiles, phloroglucinol and 2-Mercaptoethanol. At 30 °C and in the presence of 0.1 M HCl, menthofuran displayed the outstanding ability to enable the fast and full depolymerization of procyanidin B2 using only a 1:1 molar ratio of both reactants. Under the same conditions, phloroglucinol and 2-Mercaptoethanol led to a reaction equilibrium with significantly lower conversion yields. Application to commercial tannin extracts showed that a menthofuran-to-extract weight ratio of 1 gave the same yields of procyanidin constitutive units as 10-fold higher molecular equivalent phloroglucinol and 100-fold 2-Mercaptoethanol. Finally, guidelines for implementing the menthofuran depolymerization method are proposed to assess the tannin content and composition of extracts as well as of plant materials without prior extraction.

  • Furanolysis with Menthofuran: A New Depolymerization Method for Analyzing Condensed Tannins
    Journal of Agricultural and Food Chemistry, 2019
    Co-Authors: Guillaume Billerach, Laurent Rouméas, Eric Dubreucq, Hélène Fulcrand
    Abstract:

    An improved analytical depolymerization method for characterizing condensed tannins was developed with menthofuran (3,6-dimethyl-4,5,6,7-tetrahydro-1-benzofuran) as the nucleophilic trapping reagent. Herein, menthofuran was compared with routinely used nucleophiles, phloroglucinol and 2-Mercaptoethanol. At 30°C and in the presence of 0.1 M HCl, menthofuran displayed the outstanding ability to enable the fast and full depolymerization of procyanidin B2 using only a 1:1 molar ratio of both reactants. In the same conditions, phloroglucinol and 2 mercaptoethanol led to a reaction equilibrium with significantly lower conversion yields. Application to commercial tannin extracts showed that a menthofuran to extract weight ratio of 1 gave the same yields of procyanidin constitutive units as 10-fold higher mol. eq. phloroglucinol and 100 fold 2-Mercaptoethanol. Finally, guidelines for implementing the menthofuran depolymerization method are proposed to assess the tannin content and composition of extracts as well as of plant materials without prior extraction.

  • Furanolysis with Menthofuran: A New Depolymerization Method for Analyzing Condensed Tannins
    2019
    Co-Authors: Guillaume Billerach, Eric Dubreucq, Laurent Rouméas, Hélène Fulcrand
    Abstract:

    An improved analytical depolymerization method for characterizing condensed tannins was developed with menthofuran (3,6-dimethyl-4,5,6,7-tetrahydro-1-benzofuran) as the nucleophilic trapping reagent. Herein, menthofuran was compared with routinely used nucleophiles, phloroglucinol and 2-Mercaptoethanol. At 30 °C and in the presence of 0.1 M HCl, menthofuran displayed the outstanding ability to enable the fast and full depolymerization of procyanidin B2 using only a 1:1 molar ratio of both reactants. Under the same conditions, phloroglucinol and 2-Mercaptoethanol led to a reaction equilibrium with significantly lower conversion yields. Application to commercial tannin extracts showed that a menthofuran-to-extract weight ratio of 1 gave the same yields of procyanidin constitutive units as 10-fold higher molecular equivalent phloroglucinol and 100-fold 2-Mercaptoethanol. Finally, guidelines for implementing the menthofuran depolymerization method are proposed to assess the tannin content and composition of extracts as well as of plant materials without prior extraction

Guillaume Billerach - One of the best experts on this subject based on the ideXlab platform.

  • Furanolysis with Menthofuran: A New Depolymerization Method for Analyzing Condensed Tannins
    Journal of Agricultural and Food Chemistry, 2019
    Co-Authors: Guillaume Billerach, Laurent Rouméas, Eric Dubreucq, Hélène Fulcrand
    Abstract:

    An improved analytical depolymerization method for characterizing condensed tannins was developed with menthofuran (3,6-dimethyl-4,5,6,7-tetrahydro-1-benzofuran) as the nucleophilic trapping reagent. Herein, menthofuran was compared with routinely used nucleophiles, phloroglucinol and 2-Mercaptoethanol. At 30 °C and in the presence of 0.1 M HCl, menthofuran displayed the outstanding ability to enable the fast and full depolymerization of procyanidin B2 using only a 1:1 molar ratio of both reactants. Under the same conditions, phloroglucinol and 2-Mercaptoethanol led to a reaction equilibrium with significantly lower conversion yields. Application to commercial tannin extracts showed that a menthofuran-to-extract weight ratio of 1 gave the same yields of procyanidin constitutive units as 10-fold higher molecular equivalent phloroglucinol and 100-fold 2-Mercaptoethanol. Finally, guidelines for implementing the menthofuran depolymerization method are proposed to assess the tannin content and composition of extracts as well as of plant materials without prior extraction.

  • Furanolysis with Menthofuran: A New Depolymerization Method for Analyzing Condensed Tannins
    Journal of Agricultural and Food Chemistry, 2019
    Co-Authors: Guillaume Billerach, Laurent Rouméas, Eric Dubreucq, Hélène Fulcrand
    Abstract:

    An improved analytical depolymerization method for characterizing condensed tannins was developed with menthofuran (3,6-dimethyl-4,5,6,7-tetrahydro-1-benzofuran) as the nucleophilic trapping reagent. Herein, menthofuran was compared with routinely used nucleophiles, phloroglucinol and 2-Mercaptoethanol. At 30°C and in the presence of 0.1 M HCl, menthofuran displayed the outstanding ability to enable the fast and full depolymerization of procyanidin B2 using only a 1:1 molar ratio of both reactants. In the same conditions, phloroglucinol and 2 mercaptoethanol led to a reaction equilibrium with significantly lower conversion yields. Application to commercial tannin extracts showed that a menthofuran to extract weight ratio of 1 gave the same yields of procyanidin constitutive units as 10-fold higher mol. eq. phloroglucinol and 100 fold 2-Mercaptoethanol. Finally, guidelines for implementing the menthofuran depolymerization method are proposed to assess the tannin content and composition of extracts as well as of plant materials without prior extraction.

  • Furanolysis with Menthofuran: A New Depolymerization Method for Analyzing Condensed Tannins
    2019
    Co-Authors: Guillaume Billerach, Eric Dubreucq, Laurent Rouméas, Hélène Fulcrand
    Abstract:

    An improved analytical depolymerization method for characterizing condensed tannins was developed with menthofuran (3,6-dimethyl-4,5,6,7-tetrahydro-1-benzofuran) as the nucleophilic trapping reagent. Herein, menthofuran was compared with routinely used nucleophiles, phloroglucinol and 2-Mercaptoethanol. At 30 °C and in the presence of 0.1 M HCl, menthofuran displayed the outstanding ability to enable the fast and full depolymerization of procyanidin B2 using only a 1:1 molar ratio of both reactants. Under the same conditions, phloroglucinol and 2-Mercaptoethanol led to a reaction equilibrium with significantly lower conversion yields. Application to commercial tannin extracts showed that a menthofuran-to-extract weight ratio of 1 gave the same yields of procyanidin constitutive units as 10-fold higher molecular equivalent phloroglucinol and 100-fold 2-Mercaptoethanol. Finally, guidelines for implementing the menthofuran depolymerization method are proposed to assess the tannin content and composition of extracts as well as of plant materials without prior extraction

Jan Feijen - One of the best experts on this subject based on the ideXlab platform.

  • stabilization of solutions of feather keratins by sodium dodecyl sulfate
    Journal of Colloid and Interface Science, 2001
    Co-Authors: Peter M M Schrooyen, Radulf C Oberthur, Pieter J Dijkstra, Adriaan Bantjes, Jan Feijen
    Abstract:

    Feather keratins were extracted from chicken feathers with aqueous solutions of urea and 2-Mercaptoethanol. After filtration of the insoluble residue, a feather keratin solution was obtained. Removal of 2-Mercaptoethanol and urea by dialysis resulted in aggregation of the keratin polypeptide chains and oxidation of the cysteine residues to afford a gel. The addition of sodium dodecyl sulfate (SDS) to the keratin solution prior to dialysis prevented extensive aggregation of the keratin chains. The effect of the addition of various quantities of SDS on the rate of aggregation of the polypeptide chains and the rate of oxidation of cysteine residues during dialysis was studied. With size exclusion chromatography, it was found that lower initial SDS/keratin ratios (0.125–0.5 g SDS/g keratin) resulted in larger SDS–keratin complexes. This indicates that more intermolecular cross-links had formed. Higher SDS/keratin ratios (1–2 g SDS/g keratin) resulted in small SDS–keratin complexes, comparable in size to the keratin monomer. High amounts of SDS seemed to prevent the oxidation reaction between different keratin chains, resulting in more intramolecular disulfide bond formation.

  • partially carboxymethylated feather keratins 1 properties in aqueous systems
    Journal of Agricultural and Food Chemistry, 2000
    Co-Authors: Peter M M Schrooyen, P J Dijkstra, Radulf C Oberthur, A Bantjes, Jan Feijen
    Abstract:

    Feather keratins were extracted from chicken feathers with an aqueous solution of urea and 2-Mercaptoethanol. The keratin solution obtained was dialyzed to remove the reagents. Upon dialysis, extensive protein aggregation occurred. To obtain stable solutions or dispersions in water, cysteine residues were modified prior to dialysis with iodoacetamide, iodoacetic acid, or bromosuccinic acid, thereby blocking free thiol groups and introducing hydrophilic groups. For the development of biodegradable materials with good mechanical properties from these biopolymers, disulfide bonds between the keratin molecules are needed. Therefore, cysteine residues were only partially modified by using different reagent/cysteine molar ratios. The reaction rate constants of iodoacetate with glutathione and 2-Mercaptoethanol were successfully used to predict the degree of modification of keratin cysteine. It was shown that, for carboxymethylated keratin, fewer aggregates were formed for higher degrees of cysteine modification, while more protein was present as oligomers. Aggregates and oligomers were stabilized through intermolecular disulfide bonds.

Bruno Ameduri - One of the best experts on this subject based on the ideXlab platform.

  • unexpected radical telomerisation of vinylidene fluoride with 2 mercaptoethanol
    Molecules, 2021
    Co-Authors: Michel Duc, Bernard Boutevin, Bruno Ameduri
    Abstract:

    The radical telomerisation of vinylidene fluoride (VDF) with 2-Mercaptoethanol as chain transfer agent (CTA) was studied to synthesise fluorinated telomers which bear a hydroxy end-group, such as H(VDF)nS(CH2)2OH, under thermal (di-tert-butyl peroxide as the initiator) or photochemical initiations. A careful structural study of a typical H-VDF-S(CH2)2OH telomer was performed by 1H and 19F NMR spectroscopy. These analytical methods allowed us to explore the selective addition of the thiyl radical onto the hydrogenated side of VDF, and the telomer containing one VDF unit was obtained selectively. Surprisingly, for higher [VDF]o initial concentrations, a monoadduct telomer was produced as well as PVDF homopolymer. This feature was related to the fast consumption of the CTA. The kinetics of radical telomerisation led to a quite high transfer constant of the CTA (40 at 140 °C) that evidences the formation of a monoadduct as the only telomer formed.

  • synthesis and use of hydroxyl telechelic polybutadienes grafted by 2 mercaptoethanol for polyurethane resins
    Journal of Applied Polymer Science, 2000
    Co-Authors: Gilles Boutevin, Bruno Ameduri, Jeanpaul Joubert
    Abstract:

    The grafting of hydroxy telechelic polybutadienes (HTPBD) by 2-mercap- toethanol to saturate 1,2-double bonds which enabled an increase of theOOH func- tionality of HTPBD is presented. The functionalities of the virgin and grafted HTPBD were characterized both by 1 H-NMR after silylation of the hydroxy end groups and the consumption of the mercaptan was determined by iodine titration. The radical addition of 2-Mercaptoethanol to HTPBD was not complete, which is not acceptable for an industrial application. Hence, the excess of mercaptan was reacted to allyl alcohol, leading to a new short telechelic diol able to be incorporated in the polyurethane (PU) network as a chain extender. This PU was prepared by addition of hexamethylene diisocyanate to both these diols. The thermal (glass transition, Tg, and decomposition temperatures), physical (gel time and viscosity), and mechanical (Shore hardness) properties were assessed. It was noted that the higher the hydroxyl functionality, the greater the Shore hardness, the viscosity, and the modulus but the lower the gel time and the break elongation. However, no improvement of the thermal stability was observed with the use of grafted HTPBD in PU resins. Their Tg's were observed to undergo a slight increase (of 4°C) in the case of PU prepared from Poly BD R45 HTt in contrast to that noted from Poly BD 20 LMt (20°C), showing a lower phase segregation in that latter case. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1655-1666, 2000

Bernard Boutevin - One of the best experts on this subject based on the ideXlab platform.

  • unexpected radical telomerisation of vinylidene fluoride with 2 mercaptoethanol
    Molecules, 2021
    Co-Authors: Michel Duc, Bernard Boutevin, Bruno Ameduri
    Abstract:

    The radical telomerisation of vinylidene fluoride (VDF) with 2-Mercaptoethanol as chain transfer agent (CTA) was studied to synthesise fluorinated telomers which bear a hydroxy end-group, such as H(VDF)nS(CH2)2OH, under thermal (di-tert-butyl peroxide as the initiator) or photochemical initiations. A careful structural study of a typical H-VDF-S(CH2)2OH telomer was performed by 1H and 19F NMR spectroscopy. These analytical methods allowed us to explore the selective addition of the thiyl radical onto the hydrogenated side of VDF, and the telomer containing one VDF unit was obtained selectively. Surprisingly, for higher [VDF]o initial concentrations, a monoadduct telomer was produced as well as PVDF homopolymer. This feature was related to the fast consumption of the CTA. The kinetics of radical telomerisation led to a quite high transfer constant of the CTA (40 at 140 °C) that evidences the formation of a monoadduct as the only telomer formed.

  • synthesis of biobased polyols by thiol ene coupling from vegetable oils
    Macromolecules, 2011
    Co-Authors: Myriam Desroches, Sylvain Caillol, Vincent Lapinte, Remi Auvergne, Bernard Boutevin
    Abstract:

    A model study of the radical addition of 2-Mercaptoethanol onto oleic acid was performed under mild conditions (generation of radicals under UV light at room temperature without any photoinitiator). To evaluate the efficiency and the robustness of thiol−ene reaction, experimental parameters were varied, such as the irradiation intensity (ranging from 0.5 to 15.0 W/cm2), the thiol/double bond ratio (ranging from 1.2/1 to 5.0/1), the solvent/double bond ratio (ranging from 0/1 to 500/1), and the number of double bonds per chain. It was especially shown that the higher the content of polyunsaturated fatty chains, the lower the rate of 2-Mercaptoethanol grafting. Best yields were reached in 1 h reaction for a thiol/ene ratio of 3/1, without solvent, using maximum UV intensity. Side reactions, identified by NMR, FT-IR, LC-MS, and iodine titration, were upon esterification between the carboxylic acid function of oleic acid and the hydroxyl function of 2-Mercaptoethanol, disulfide formation, double-bond isomeriz...