- Glycerolysis of methyl oleate on MgO: Experimental and theoretical study of the reaction selectivity
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The liquid-phase MgO-promoted glycerolysis of methyl oleate, a fatty acid methyl ester (FAME), to give acylglycerol products was studied both, experimentally and by density functional theory (DFT). Catalytic results showed that strongly basic low coordination O2- surface sites participate in kinetically relevant steps of the glycerolysis reaction. Changes in the selectivity toward the different mono- and diglyceride isomers were investigated by varying the reaction conditions. The main product was always α-glyceryl monooleate (α-MG), a monoglyceride with the ester fragment at one of the terminal positions of the glycerol molecule; the β-MG isomer, with the ester substituted at position 2 was obtained in much lower amounts. The molecular modeling of glycerol (Gly) and FAME adsorptions as well as of the glycerolysis reaction was carried out using periodic DFT calculations and a model of stepped MgO surface. Results indicated that FAME was more weakly adsorbed than Gly; the latter adsorbs on a coordinatively unsaturated surface O2- site with O-H bond breaking at position 2 of the Gly molecule, giving therefore a surface β-glyceroxide species. Calculations explained the apparent contradiction between the preferential formation of the α-MG isomer and the energetically favored dissociation of the secondary OH group of Gly that leads to the β-glyceroxide species. They predict that the β-glyceroxide species participates in the pathways conducting to both, α- and β-MG isomers. Synthesis of α-MG occurs by C-O coupling of β-glyceroxide with FAME at one of the two primary OH groups of the β-glyceroxide species. Two transition states (TS) and a tetrahedral intermediate (TI) are involved in both, α-MG and β-MG isomer formation. However, the pathway toward β-MG is limited by the large sterical effects associated to the TI formation. Contrarily, the TI leading to α-MG is relatively easy to form.
- Belelli,Ferretti,Apesteguía,Ferullo,Di Cosimo
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p. 132 - 144
(2015/09/28)
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- Purification of 2-monoacylglycerols using liquid CO2 extraction
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The fatty acid moiety of 2-monoacyl-sn-glycerol (2-MAG) undergoes spontaneous acyl migration to the sn-1(3) position, resulting in a thermodynamic equilibrium of approximately 1:9 of 2-MAG to 1(3)-monoacyl-sn-glycerol (1-MAG). Spontaneous acyl migration is an impediment to synthesizing and isolating specific 2-MAG for use as intermediates in the synthesis of structured triacylglycerols. 2-Monooleoyl-sn-glycerol was synthesized by the enzymatic ethanolysis of triolein and isolated by liquid CO2 extraction. The resultant MAG, diacylglycerol, and fatty acid ethyl esters were quantified by 1H NMR and supercritical fluid chromatography. The low polarity of the CO2 and mild extraction temperature (25 °C) resulted in very low spontaneous acyl migration rates, allowing the MAG to be isolated in 80% yield and in a very high 2-MAG:1-MAG ratios of ≥93 mol%.
- Compton, David L.,Eller, Fred J.,Laszlo, Joseph A.,Evans, Kervin O.
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p. 1529 - 1536
(2012/11/13)
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- MgO-based catalysts for monoglyceride synthesis from methyl oleate and glycerol: Effect of Li promotion
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The synthesis of monoglycerides (glyceryl monooleates) by heterogeneously catalyzed glycerolysis of an unsaturated fatty acid methyl ester (methyl oleate) was studied on MgO and Li-promoted MgO catalysts. Several MgO-based catalysts with different Li loadings were prepared by incipient wetness impregnation and characterized by XRD, N2 physisorption, and FTIR and TPD of CO 2 among other techniques. Promotion of MgO with lithium, a basic promoter, affected the textural and structural properties of the resulting oxides so that more crystalline MgO phases with decreased surface area were obtained at increasing Li contents. Furthermore, the addition of Li generated new strong base sites because of formation of dispersed surface Li2O species, and thereby increased the total base site density of parent MgO. Li-containing MgO catalysts efficiently promoted the glycerolysis reaction, achieving high monoglyceride yields (70-73%) at 493 K. The initial monoglyceride formation rate increased linearly with the Li content on the sample following the enhanced overall catalyst base strength. Although conversions at the end of the run were ≈100% for all the catalysts, the monoglyceride selectivity slightly decreased with the Li loading, probably as a consequence of the less surface affinity for glycerol adsorption that facilitates competing monoglyceride re-adsorption and transformation to diglycerides by consecutive glycerolysis or disproportionation reactions.
- Ferretti,Apesteguía,Di Cosimo
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experimental part
p. 146 - 153
(2012/02/01)
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- Synthesis and properties of ascorbyl esters catalyzed by lipozyme TL im using triglycerides as acyl donors
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Esters of l-ascorbic acid with long-chain fatty acids (E-304) are employed as antioxidants in foods rich in lipids. Although their enzymatic synthesis offers some advantages compared with the current chemical processes, most of the reported methods employ the immobilized lipase from Candida antarctica as biocatalyst and free fatty acids or activated esters as acyl donors. In order to diminish the cost of the process, we have investigated the synthesis of ascorbyl oleate and ascorbyl palmitate esters with the immobilized Thermomyces lanuginosus lipase Lipozyme TL IM-which is significantly less expensive than Novozym 435-and triglycerides as source of fatty acids. Lipozyme TL IM gave rise to a lower yield of 6-O-ascorbyl oleate than Novozym 435 when using triolein (64 vs. 84%) and olive oil (27 vs. 33%) as acyl donors. Both 6-O-ascorbyl oleate and 6-O-ascorbyl palmitate displayed excellent surfactant and antioxidant properties. The Trolox Equivalent Antioxidant Capability values for the oleate and palmitate were 71 and 84%, respectively, of those obtained with l-ascorbic acid; however, both derivatives were able to stabilize soybean oil towards peroxide formation.
- Reyes-Duarte,Lopez-Cortes,Torres,Comelles,Parra,Pena,Ugidos,Ballesteros,Plou
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scheme or table
p. 57 - 64
(2011/10/04)
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- Rapid access to structured triacylglycerols acylated with n-3 polyunsaturated fatty acids for nutritional applications
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In order to better understand the metabolic fate of n-3 polyunsaturated fatty acids (PUFAs), an efficient access to symmetrical and unsymmetrical triacylglycerols (TGs), esterified with PUFAs, with known high purity, is required. In this context, we optimized the esterification of a mixture of glycerols protected as dioxane and dioxolane with PUFAs. The kinetics of this reaction depends on various factors, such as the fatty acid chain length and the stereochemistry of the dioxane. Then, one-pot acetal hydrolysis and esterification of hydroxyl groups led to the desired structured TGs without either double bond isomerization or acyl migration (except when symmetrical TGs are acylated with long-chain saturated fatty acids in external positions). PUFAs location on the glycerol backbone was assayed by NMR, HPLC and pancreatic lipase hydrolysis.
- Vaique, Emilie,Guy, Alexandre,Couedelo, Leslie,Gosse, Isabelle,Durand, Thierry,Cansell, Maud,Pinet, Sandra
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experimental part
p. 8872 - 8879
(2011/01/04)
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- Study on acyl migration kinetics of partial glycerides: Dependence on temperature and water activity
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Acyl migration phenomenon was often observed during 1,3-positional specificity lipase-catalyzed reactions from triglycerides and partial glycerides, including acyl migration of 1,2-diglyceride (1,2-DG) to 1,3-diglyceride (1,3-DG) and 2-monoglyceride (2-MG) to 1-monoglyceride (1-MG). However, the acyl migration mechanism and kinetics were seldom studied despite of numerous researches on process optimization of 1,3-positional specificity lipase-catalyzed reaction. In this paper, the influence of related factors on acyl migration process as well as their influencing mechanism was further studied. It was found that temperature and water activity were two crucial factors that would influence acyl migration kinetics. Determination of the kinetic parameters under different temperatures revealed that the acyl migration reaction rates were greatly promoted by the increasing of temperature. The acyl migration rates of 1,2-diglyceride and 2-monoglyceride were quite different from each other, which was found to be due to the different activation energies. Further study of how would water influence the acyl migration process showed that water activity rather than water content was a key factor that influenced acyl migration and the acyl migration rate would decrease with the increase of water activity. It was further revealed that water activity influenced the charge dispersion of the transition state, which ultimately influenced the reaction activation energy and then influenced the acyl migration rate.
- Li, Wei,Du, Wei,Li, Qiang,Sun, Ting,Liu, Dehua
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scheme or table
p. 17 - 22
(2010/10/19)
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- COSMETIC EMULSION PREPARATION AND AGENT FOR EXTERNAL USE
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An emulsion which has an average particle diameter of 100 nm or smaller and comprises: (D) a polyglycerol/fatty acid ester which has an HLB of 13 or higher and in which the polyglycerol is one in which the average degree of polymerization is 8 to 12, the total content of the pentamer and hexamer is 50% by weight or higher, and the total content of the tetramer and lower polymers is less than 20% by weight, and the fatty acid residue is C14-22 hydrocarbon group; (E) a polyglycerol/fatty acid ester which has an HLB of 5 to 11 and in which the polyglycerol is one in which the average degree of polymerization is 2 to 12, the total content of the tetramer and lower polymers is 20% by weight or higher, each of (2/3)n components being contained in an amount of at least 5% by weight or more, where n (n is 2 or more) is taken to be an average degree of polymerization (when (2/3)n is not a natural number, (2/3)n is considered to be a lowest natural number greater than (2/3)n), and the fatty acid residue is a C14-22 hydrocarbon group; (F) a lecithin; and (G) an oily ingredient.
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- Modular approach to the synthesis of unsaturated 1-monoacyl glycerols
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A modular synthesis of unsaturated 1-monoacylglycerols (1) from cis-1-iodo-1-alkenes [cis-RCH=CHI] and unsaturated carboxylic acids [CH 2=CH(CH2)nCO2H] is described. The method revolves around a Suzuki coupling to establish olefin geometry.
- Coleman, Bridgett E.,Cwynar, Valerie,Hart, David J.,Havas, Fabien,Jakkam, Madan Mohan,Patterson, Suzanne,Ridenour, Sam,Schmidt, Michael,Smith, Eboney,Wells, Angela J.
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p. 1339 - 1342
(2007/10/03)
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- Substrate Specifity and Mode of Action of the Lipase Produced by Pseudomonas fragi 22.39 B
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The lipase purified from Pseudomonas fragi 22.39 B hydrolyzed not only triglycerides but also synthetic esters such as Tween, Span and methyl oleate.Of the saturated monoacid triglycerides tested, tributyrin was hydrolyzed most quickly.The lipase did not produce 1,3-diolein as a hydrolysis product from triolein.The addition of the Ca2+ ion to the reaction mixture promoted the hydrolysis rate for triglycerides and monoesters with longer-chain fatty acids (C14, C16, C18).The enzyme could hydrolyze various kinds of natural fats and oils, and the extent their hydrolysis reached above 90 percent.
- Nishio, Toshiyuki,Chikano, Takahide,Kamimura, Minoru
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p. 2525 - 2530
(2007/10/02)
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