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Chung S. Yang - One of the best experts on this subject based on the ideXlab platform.
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Identification and characterization of methylated and ring-fission metabolites of tea catechins formed in humans, mice, and rats.
Chemical research in toxicology, 2002Co-Authors: Xiaofeng Meng, Shengmin Sang, Nanqun Zhu, Shuqun Sheng, Mao-jung Lee, Chung S. YangAbstract:(-)-Epigallocatechin gallate (EGCG), the most abundant tea catechin, has been proposed to be beneficial to human health based on its strong antioxidative and other biological activities in vitro. Inadequate knowledge regarding the bioavailability and biotransformation of EGCG in humans, however, has limited our understanding of its possible beneficial health effects. In this study, 4',4' '-di-O-methyl-EGCG (4',4' '-DiMeEGCG) was detected in human plasma and urine by LC/MS/MS following green tea ingestion. Both 4',4' '-DiMeEGCG and EGCG reached peak plasma values (20.5 +/- 7.7 and 145.4 +/- 31.6 nM, respectively, in 4 subjects) at 2 h after the dose. The half-lives of 4',4' '-DiMeEGCG and EGCG were 4.1 +/- 0.8 and 2.7 +/- 0.9 h, respectively. The cumulative urinary excretion of 4',4' '-DiMeEGCG during a 24 h period was 140.3 +/- 48.6 microg, about 5-fold higher than that of EGCG, but the excreted 4',4' '-DiMeEGCG and EGCG in urine only accounted for about 0.1% of ingested EGCG. (-)-5-(3',4',5'-Trihydroxyphenyl)-Gamma-Valerolactone (M4) and (-)-5-(3',4'-dihydroxyphenyl)-Gamma-Valerolactone (M6), along with another possible ring-fission metabolite, (-)-5-(3',5'-dihydroxyphenyl)-Gamma-Valerolactone (M6'), were detected in human urine after green tea ingestion. The cumulative excretion of M4, M6', and M6 during a 24 h period ranged from 75 microg to 1.2 mg, 0.6 to 6 mg, and 0.6 to 10 mg, respectively. The combined excretion of all three ring-fission metabolites accounted for 1.5-16% of ingested catechins. M4, M6', and M6 were all observed after the ingestion of pure EGCG or EGC by human subjects, whereas only M6 was produced after EC ingestion. These metabolites as well as monomethylated EGCG were detected in mice and rats after tea or EGCG administration, and the tissue levels reflected the rather low bioavailability of EGCG in rats. The presently characterized methylated EGCG metabolites and ring-fission products exist in substantial quantities and may contribute to the biological activities of tea.
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Analysis of urinary metabolites of tea catechins by liquid chromatography/electrospray ionization mass spectrometry.
Chemical research in toxicology, 2001Co-Authors: Xiaofeng Meng, Shuqun Sheng, Mao-jung Lee, Bozena Winnik, Brian Buckley, Chung S. YangAbstract:Tea has been proposed to have beneficial health effects which have been attributed to the polyphenolic compounds known as catechins. The bioavailability and biotransformation of these compounds, however, are not clearly understood. In this study, we used liquid chromatography/electrospray ionization-mass spectrometry (LC/ESI-MS) to determine urinary glucuronidated and sulfated tea catechins and their metabolites (including methylated and ring-fission metabolites) based on the detection of deprotonated molecular ions and aglycone fragment ions. The compound resolution was achieved both chromatographically and mass spectroscopically. After green tea administration, the major conjugates appeared in human, mouse, and rat urine samples were identified as monoglucuronides and monosulfates of (-)-epigallocatechin (EGC) and (-)-epicatechin. We also found O-methyl-EGC-O-glucuronides and -O-sulfates and O-methyl-epicatechin-O-sulfates in human urine. (-)-5-(3',4',5'-Trihydroxyphenyl)-Gamma-Valerolactone (M4) and (-)-5-(3',4'-dihydroxyphenyl)-Gamma-Valerolactone (M6), the ring-fission metabolites of EGC and (-)-epicatechin, respectively, were also predominantly in monoglucuronide and monosulfate forms in the urine. In comparison to rats, the urinary metabolite profiles of tea catechins in mice resemble more closely to those in humans. This is the first report describing direct simultaneous analysis of multiple tea catechin conjugates in urine samples. This method will allow more thorough investigations of the biotransformation of tea polyphenols.
László T. Mika - One of the best experts on this subject based on the ideXlab platform.
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Isobaric Vapor–Liquid Equilibria for Binary Mixtures of Gamma-Valerolactone + Toluene
Journal of Chemical & Engineering Data, 2020Co-Authors: Munaf Al-lami, Dávid Havasi, Katalin Koczka, László T. MikaAbstract:Because of the outstanding physical and chemical properties of biomass-originated γ-valerolactone (GVL), it has been characterized as a promising alternative platform molecule, which can be utilize...
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Stability of Gamma-Valerolactone under neutral, acidic, and basic conditions
Structural Chemistry, 2017Co-Authors: Claire Yuet Yan Wong, László T. Mika, Bálint Fridrich, Alex Wing-tat Choi, Matthew Y. Lui, Attila K. Horváth, István T. HorváthAbstract:Dry Gamma-Valerolactone (GVL) is stable for several weeks at 150 °C and its thermal decomposition only proceeds in the presence of appropriate catalysts. Since GVL does not react with water up to 60 °C for several weeks, it could be used as a green solvent at mild conditions. At higher temperatures, GVL reacts with water to form 4-hydroxyvaleric acid (4-HVA) and reaches the equilibrium in a few days at 100 °C. Aqueous solutions of acids (HCl and H_2SO_4) catalyze the ring opening of GVL even at room temperature, which leads to the establishment of an equilibrium between GVL, water, and 4-HVA. Although the 4-HVA concentration would be below 4 mol% in the presence of acids, it could be higher than the concentration of a reagent or a catalyst precursor, not to mention a catalytically active species. The latter could be especially worrisome as 4-HVA could be an excellent bi- or even a tri-dentate ligand for transition metals. Aqueous solution of bases (NaOH and NH_4OH) also catalyzes the reversible ring opening of GVL. While in the case of NaOH, the product is the sodium salt of 4-hydroxyvalerate, the reversible reaction of GVL, with NH_4OH results in the formation of 4-hydroxyvaleric amide. The reversible ring opening of ( S )-GVL in the presence of HCl or NaOH has no effect on the stability of the chiral center.
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Rhodium-catalyzed hydroformylation in γ-valerolactone as a biomass-derived solvent
Journal of Organometallic Chemistry, 2017Co-Authors: Péter Pongrácz, Brigitta Bartal, László Kollár, László T. MikaAbstract:Abstract Rhodium-catalyzed hydroformylation of styrene, α-methylstyrene, dimethyl itaconate, and ( R )-limonene was performed in Gamma-Valerolactone (GVL) as a proposed biomass-based environmentally benign solvent for hydroformylation referring to toluene as a generally used conventional solvent. Both achiral (triphenylphosphine, 1,3-bis(diphenylphoshino)propane) and enantiopure bidentate phosphine ligands (( S , S )-BDPP, ( R )-BINAP, ( R )-QUINAP, ( R , R )-DIOP, ( R c ),( S p )-JOSIPHOS, ( S )-SEGPHOS, ( S )-(DM)-SEGPHOS) were investigated in in situ generated Rh-diphosphine catalyst systems. In general, the catalysts' activity in GVL was lower than in toluene; however, remarkable chemo- (>99%) and regioselectivities (>95%) were achieved in GVL under identical conditions. The BDPP-modified Rh-catalyst was recycled for three consecutive cycles; however a decrease in its activity was detected.
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Vapor–Liquid Equilibrium Study of the Gamma-Valerolactone–Water Binary System
Journal of Chemical & Engineering Data, 2016Co-Authors: Dávid Havasi, Peter Mizsey, László T. MikaAbstract:Gamma-Valerolactone (GVL) has been proposed as a biomass-based platform molecule. However, its vapor–liquid equilibrium has not been exhaustively studied yet. Antoine constants of GVL were determined and vapor–liquid equilibrium (VLE) data for water(1)–GVL(2) binary system were measured at atmospheric and reduced (50.66 and 10.1 kPa) pressures. The thermodynamic consistency was investigated by applying Herrington’s area test. It was established that no azeotropic mixture was formed for the water–GVL system in the full concentration range. Data were regressed using ChemCAD software to generate binary interaction parameters for Wilson, NRTL, and UNIQUAC activity coefficient models. Good agreements between calculated and experimental VLE data were obtained.
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Use of Gamma-Valerolactone as an Illuminating Liquid and Lighter Fluid
ACS Sustainable Chemistry & Engineering, 2015Co-Authors: Viktória Fábos, László T. Mika, Matthew Y. Lui, Yiu Fung Mui, Yuet Yan Wong, Edit Cséfalvay, Viktória Barbara Kovács, Tibor Szűcs, István T. HorváthAbstract:The sulfuric acid-catalyzed conversion of paper wastes in Gamma-Valerolactone (GVL) or dioxane leads to the formation of levulinic acid (LA) and formic acid (FA), which can be converted to GVL by transfer-hydrogenation using the Shvo catalyst in situ or separately. The isolation of LA and FA was assisted by the neutralization of the sulfuric acid with ammonia to form a biphasic system. While the ammonium sulfate and most of FA and some of LA were in the aqueous phase, the organic solvent-rich phase contained most of the LA and some of the FA. GVL was used as an illuminating liquid in glass lamps for hours without the formation of noticeable smoke and/or odor even in a small room. While neat GVL can be used for the safe but somewhat slow lighting of charcoal, the ignition with different mixtures of GVL (95 or 90 vol %) and ethanol (5 or 10 vol %) was reduced to a convenient few seconds. Ignition tests of charcoal combined with emission analyses revealed that by increasing the ethanol content to 10 vol % th...
Jacek Grams - One of the best experts on this subject based on the ideXlab platform.
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The Influence of Carbon Nature on the Catalytic Performance of Ru/C in Levulinic Acid Hydrogenation with Internal Hydrogen Source.
Molecules (Basel Switzerland), 2020Co-Authors: Marcin Jędrzejczyk, Jacek Grams, Emilia Soszka, Joanna Goscianska, Marcin Kozanecki, Agnieszka M RuppertAbstract:The influence of the nature of carbon materials used as a support for Ru/C catalysts on levulinic acid hydrogenation with formic acid as a hydrogen source toward Gamma-Valerolactone was investigated. It has been shown that the physicochemical properties of carbon strongly affect the catalytic activity of Ru catalysts. The relationship between the hydrogen mobility, strength of hydrogen adsorption, and catalytic performance was established. The catalyst possessing the highest number of defects, stimulating metal support interaction, exhibited the highest activity. The effect of the catalyst grain size was also studied. It was shown that the decrease in the grain size resulted in the formation of smaller Ru crystallites on the catalyst surface, which facilitates the activity.
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ru catalysts for levulinic acid hydrogenation with formic acid as a hydrogen source
Green Chemistry, 2016Co-Authors: Agnieszka M Ruppert, Olga Snekaplatek, Alexandre S Dumon, Maciej Jedrzejczyk, Philippe Sautet, Nicolas Keller, C. Michel, Jacek GramsAbstract:The catalytic hydrogenation of levulinic acid (LA) with formic acid (FA) as a hydrogen source into γ-valerolactone (GVL) is considered as one of the crucial sustainable processes in today's biorefinery schemes. In the current work, we investigated the modification of Ru/C as efficient catalysts for both formic acid decomposition and levulinic acid hydrogenation in comparison with Pd and Pt catalysts. In order to better understand what features are responsible for high catalytic performance, we combined experimental tests, DFT calculations together with extensive material characterization. In LA hydrogenation with FA as a hydrogen source, the intermediate surface formate inhibits at least partially the LA hydrogenation. In addition, the FA decomposition is highly sensitive to the kind of the preparation method of the Ru/C catalyst: (i) the process looks structure sensitive favored on larger particles and (ii) residual chlorine decreases significantly the FA decomposition rate.
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Role of water in metal catalyst performance for ketone hydrogenation: a joint experimental and theoretical study on levulinic acid conversion into Gamma-Valerolactone
Chemical communications (Cambridge England), 2014Co-Authors: Carine Michel, Jacek Grams, Agnieszka M Ruppert, Jérémie Zaffran, Joanna Matras-michalska, Marcin Jędrzejczyk, Philippe SautetAbstract:While Ru is a poor hydrogenation catalyst compared to Pt or Pd in the gas phase, it is efficient under aqueous phase conditions in the hydrogenation of ketones such as the conversion of levulinic acid into Gamma-Valerolactone. Combining DFT calculations and experiments, we demonstrate that water is responsible for the enhanced reactivity of Ru under those conditions.
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Role of water on metal catalyst performance for ketone hydrogenation. A join experimental and theoretical study on levulinic acid conversion into Gamma-Valerolactone
Chemical Communications, 2014Co-Authors: Carine Michel, Jacek Grams, Agnieszka M Ruppert, Jérémie Zaffran, Joanna Matras-michalska, Marcin Jędrzejczyk, Philippe SautetAbstract:While Ru is a poor hydrogenation catalyst compared to Pt or Pd in the gas phase, it is efficient under aqueous phase conditions in the hydrogenation of ketones such as the conversion of levulinic acid into Gamma-Valerolactone. Combining DFT calculations and experi- ments, we demonstrate that water is responsible for the enhanced reactivity of Ru under those conditions.
Philippe Sautet - One of the best experts on this subject based on the ideXlab platform.
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ru catalysts for levulinic acid hydrogenation with formic acid as a hydrogen source
Green Chemistry, 2016Co-Authors: Agnieszka M Ruppert, Olga Snekaplatek, Alexandre S Dumon, Maciej Jedrzejczyk, Philippe Sautet, Nicolas Keller, C. Michel, Jacek GramsAbstract:The catalytic hydrogenation of levulinic acid (LA) with formic acid (FA) as a hydrogen source into γ-valerolactone (GVL) is considered as one of the crucial sustainable processes in today's biorefinery schemes. In the current work, we investigated the modification of Ru/C as efficient catalysts for both formic acid decomposition and levulinic acid hydrogenation in comparison with Pd and Pt catalysts. In order to better understand what features are responsible for high catalytic performance, we combined experimental tests, DFT calculations together with extensive material characterization. In LA hydrogenation with FA as a hydrogen source, the intermediate surface formate inhibits at least partially the LA hydrogenation. In addition, the FA decomposition is highly sensitive to the kind of the preparation method of the Ru/C catalyst: (i) the process looks structure sensitive favored on larger particles and (ii) residual chlorine decreases significantly the FA decomposition rate.
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Role of water in metal catalyst performance for ketone hydrogenation: a joint experimental and theoretical study on levulinic acid conversion into Gamma-Valerolactone
Chemical communications (Cambridge England), 2014Co-Authors: Carine Michel, Jacek Grams, Agnieszka M Ruppert, Jérémie Zaffran, Joanna Matras-michalska, Marcin Jędrzejczyk, Philippe SautetAbstract:While Ru is a poor hydrogenation catalyst compared to Pt or Pd in the gas phase, it is efficient under aqueous phase conditions in the hydrogenation of ketones such as the conversion of levulinic acid into Gamma-Valerolactone. Combining DFT calculations and experiments, we demonstrate that water is responsible for the enhanced reactivity of Ru under those conditions.
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Role of water on metal catalyst performance for ketone hydrogenation. A join experimental and theoretical study on levulinic acid conversion into Gamma-Valerolactone
Chemical Communications, 2014Co-Authors: Carine Michel, Jacek Grams, Agnieszka M Ruppert, Jérémie Zaffran, Joanna Matras-michalska, Marcin Jędrzejczyk, Philippe SautetAbstract:While Ru is a poor hydrogenation catalyst compared to Pt or Pd in the gas phase, it is efficient under aqueous phase conditions in the hydrogenation of ketones such as the conversion of levulinic acid into Gamma-Valerolactone. Combining DFT calculations and experi- ments, we demonstrate that water is responsible for the enhanced reactivity of Ru under those conditions.
Agnieszka M Ruppert - One of the best experts on this subject based on the ideXlab platform.
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The Influence of Carbon Nature on the Catalytic Performance of Ru/C in Levulinic Acid Hydrogenation with Internal Hydrogen Source.
Molecules (Basel Switzerland), 2020Co-Authors: Marcin Jędrzejczyk, Jacek Grams, Emilia Soszka, Joanna Goscianska, Marcin Kozanecki, Agnieszka M RuppertAbstract:The influence of the nature of carbon materials used as a support for Ru/C catalysts on levulinic acid hydrogenation with formic acid as a hydrogen source toward Gamma-Valerolactone was investigated. It has been shown that the physicochemical properties of carbon strongly affect the catalytic activity of Ru catalysts. The relationship between the hydrogen mobility, strength of hydrogen adsorption, and catalytic performance was established. The catalyst possessing the highest number of defects, stimulating metal support interaction, exhibited the highest activity. The effect of the catalyst grain size was also studied. It was shown that the decrease in the grain size resulted in the formation of smaller Ru crystallites on the catalyst surface, which facilitates the activity.
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ru catalysts for levulinic acid hydrogenation with formic acid as a hydrogen source
Green Chemistry, 2016Co-Authors: Agnieszka M Ruppert, Olga Snekaplatek, Alexandre S Dumon, Maciej Jedrzejczyk, Philippe Sautet, Nicolas Keller, C. Michel, Jacek GramsAbstract:The catalytic hydrogenation of levulinic acid (LA) with formic acid (FA) as a hydrogen source into γ-valerolactone (GVL) is considered as one of the crucial sustainable processes in today's biorefinery schemes. In the current work, we investigated the modification of Ru/C as efficient catalysts for both formic acid decomposition and levulinic acid hydrogenation in comparison with Pd and Pt catalysts. In order to better understand what features are responsible for high catalytic performance, we combined experimental tests, DFT calculations together with extensive material characterization. In LA hydrogenation with FA as a hydrogen source, the intermediate surface formate inhibits at least partially the LA hydrogenation. In addition, the FA decomposition is highly sensitive to the kind of the preparation method of the Ru/C catalyst: (i) the process looks structure sensitive favored on larger particles and (ii) residual chlorine decreases significantly the FA decomposition rate.
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Role of water in metal catalyst performance for ketone hydrogenation: a joint experimental and theoretical study on levulinic acid conversion into Gamma-Valerolactone
Chemical communications (Cambridge England), 2014Co-Authors: Carine Michel, Jacek Grams, Agnieszka M Ruppert, Jérémie Zaffran, Joanna Matras-michalska, Marcin Jędrzejczyk, Philippe SautetAbstract:While Ru is a poor hydrogenation catalyst compared to Pt or Pd in the gas phase, it is efficient under aqueous phase conditions in the hydrogenation of ketones such as the conversion of levulinic acid into Gamma-Valerolactone. Combining DFT calculations and experiments, we demonstrate that water is responsible for the enhanced reactivity of Ru under those conditions.
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Role of water on metal catalyst performance for ketone hydrogenation. A join experimental and theoretical study on levulinic acid conversion into Gamma-Valerolactone
Chemical Communications, 2014Co-Authors: Carine Michel, Jacek Grams, Agnieszka M Ruppert, Jérémie Zaffran, Joanna Matras-michalska, Marcin Jędrzejczyk, Philippe SautetAbstract:While Ru is a poor hydrogenation catalyst compared to Pt or Pd in the gas phase, it is efficient under aqueous phase conditions in the hydrogenation of ketones such as the conversion of levulinic acid into Gamma-Valerolactone. Combining DFT calculations and experi- ments, we demonstrate that water is responsible for the enhanced reactivity of Ru under those conditions.
