- Lignin modification supported by DFT-based theoretical study as a way to produce competitive natural antioxidants
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The valorization of lignins as renewable aromatic feedstock is of utmost importance in terms of the use of sustainable resources. This study provides a deductive approach towards market-oriented lignin-derived antioxidants by ascertaining the direct effect of different structural features of lignin on the reactivity of its phenolic OH groups in the radical scavenging reactions. The antioxidant activity of a series of compounds, modeling lignin structural units, was experimentally characterized and rationalized, using thermodynamic descriptors. The calculated O-H bond dissociation enthalpies (BDE) of characteristic lignin subunits were used to predict the modification pathways of technical lignins. The last ones were isolated by soda delignification from different biomass sources and their oligomeric fractions were studied as a raw material for modification and production of optimized antioxidants. These were characterized in terms of chemical structure, molecular weight distribution, content of the functional groups, and the antioxidant activity. The developed approach for the targeted modification of lignins allowed the products competitive with two commercial synthetic phenolic antioxidants in both free radical scavenging and stabilization of thermooxidative destruction of polyurethane films.
- Lauberte, Liga,Fabre, Gabin,Ponomarenko, Jevgenija,Dizhbite, Tatiana,Evtuguin, Dmitry V.,Telysheva, Galina,Trouillas, Patrick
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- An efficient environmentally friendly CuFe2O4/SiO2catalyst for vanillyl mandelic acid oxidation in water under atmospheric pressure and a mechanism study
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With the aim of the green production of vanillin, a highly efficient environmentally friendly oxidation system was introduced to oxidize vanillyl mandelic acid (VMA) with a porous CuFe2O4/SiO2 component nano-catalyst in aqueous solution under atmospheric pressure. The N2 adsorption-desorption pattern indicated that CuFe2O4/SiO2 possessed a much higher specific surface area (49.98 m2 g-1) than that of CuFe2O4 (5.02 m2 g-1), which further indicated that the SiO2 substrate restrained the aggregation of CuFe2O4 nanoparticles. The conversion for VMA and selectivity for vanillin reached 98% and 96%, respectively, under atmospheric pressure. The excellent catalytic performance was attributed to the synergistic effect of the catalytic capacity of CuFe2O4 and the adsorption capacity for the reactant of SiO2. Simultaneously, the effect of different reaction conditions for catalyst activity and selectivity were investigated. Furthermore, the probable mechanism of VMA oxidation was investigated by in situ ATR-FTIR, H2-TPR, XPS and 1H NMR. More importantly, the decarboxylation was verified to proceed in basic conditions rather than in conventional acidic conditions. This journal is
- Mao, Haifang,Wang, Hongzhao,Meng, Tao,Wang, Chaoyang,Hu, Xiaojun,Xiao, Zuobing,Liu, Jibo
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p. 982 - 992
(2021/01/25)
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- Structure-activity relationships of the ultrapotent vanilloid resiniferatoxin (RTX): The side chain benzylic methylene
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The side chain benzylic methylene is a critical element for the vanilloid activity of resiniferatoxin (2a, RTX), and introduction of branching, oxygen functions, or isosteric substitution at this center proved detrimental, with a decrease of potency of 2-3 orders of magnitude compared to the natural product. Conversely, only a modest erosion of activity was observed upon α-methylation and α-methylenation of the side chain. Surprisingly, introduction of an iodine atom in the guaiacyl moiety of the oxygen isoster 2h led to an unexpected and remarkable (>1000-fold) increase of potency, affording 2i, a compound that outperforms RTX in terms of vanilloid agonism and represents the first one-digit picomolar ligand of a TRP channel discovered to date.
- Appendino, Giovanni,Ech-Chahad, Abdellah,Minassi, Alberto,De Petrocellis, Luciano,Marzo, Vincenzo Di
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p. 97 - 99
(2010/04/06)
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