Synthesis of propylene glycol monoesters of docosahexaenoic acid and eicosapentaenoic acid by lipase-catalyzed esterification in organic solvents

Propylene glycol monoesters (PGM) of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are potentially health-beneficial water-in-oil emulsifiers useful in the food industry. These esters were synthesized enzymatically to overcome the problems associated with chemical processes. The products were analyzed by gas chromatography. The immobilizedMucor miehei lipase was found to be the best enzyme for the synthesis of both propylene glycol monoesters of EPA and DHA among nine lipases tested. The anhydrous enzyme and hydrophobic organic solvents were favored for the production of both monoesters. The yields of monoesters were also affected by temperature, pH memory, fatty acid/propylene glycol ratio, and reaction time. The yields of PGMDHA and PGMEPA with 50 mM fatty acid and 225 mM propylene glycol as substrates in 1 mL solvent mixture (hexane/t-butyl alcohol=9:1), catalyzed by Lipozyme IM-20 (50 mg) at 40°C for 24 h, were 47 and 49 mM, respectively. The enzyme still retained over 60% of its original activity after 10 d of batch-type operation (1 d per cycle) at 40°C for the synthesis of both PGMDHA and PGMEPA.     

High performance liquid chromatographic separation of sucrose fatty acid esters

The synthesis of sucrose fatty acid esters always results in complex mixtures. Two procedures for quantitative analysis of sucrose monoesters, respectively sucrose diesters, by means of high performance liquid chromatography on reversed-phase columns, are described. A mixture of methanol and water (85:15, v/v) was used for the separation of the monoesters, while methanol, ethyl acetate and water (65:25:10, v/v/v) was used for the separation of diesters. These methods gave information about the amount of monoesters and diesters in the product; the ratio between sucrose monopalmitate and sucrose monostearate, and the number of the most important structure isomers. A complete separation of all the possible diester products seemed to be impossible, due to the presence of more complex structure isomers. The described procedures can give important support during preparative work on sucrose fatty acid esters and also in the evaluation of these products for application purposes.     

Urea adducts of mono- and diesters of fatty acids

Summary The experimental work has shown how molecular configurations of fatty acid glycerides affect urea complex formation. Extraction data indicate that urea will form a complex with glycerol monopalmitate, monostearate, and mono-oleate but not under these conditions with glycerol monolinoleate or monolinolenate from mixtures containing these monoesters. Data also indicate that it is easier for urea to form a complex with monoglycerides than with diglycerides. In a mixture containing mono- and diglycerides of saturated and unsaturated fatty acids, urea will separate first on the basis of saturation, then secondly on the basis of the degree of esterification of the glycerol. An erratum to this article is available at .     

Preparation and phase behavior of positionally isomeric propylene glycol monoesters

Primary even-chain-length monoesters of propylene glycol (1,2-propanediol), myristate through behenate, have been prepared, and also the secondary monostearate. Phase behavior of the pure compounds and of the binary system of isomeric stearates has been studied. This behavior is one of considerable complexity. The highest-melting stable form of the primary stearate is a single-chain-length (SCL) perpendicular form (Form II) of very weak long-spacing intensities. A metastable perpendicular double-chain-length (DCL)a form occurs at the (metastable) melting point after chilling the primary esters; it transforms to a perpendicular DCL Form III on cooling. Low temp crystallization from dilute hexane gives a titled DCL Form I, the typical room temp form in crude preparations of primary ester. The secondary stearate exhibits a single similar DCL Form I at 25C and a perpendicular SCL a form just under the melting point of the chilled melt. Polymorphism is modified by mol wt and purity. Primary arachidate and behenate do not show Form II, hence show stable a at their (stable) melting points. Repeated crystallization of the 80% primary ester obtained on direct esterification with stearic acid yields pure primary ester. Special synthesis via 1-tetrahydropyranyl propylene glycol is necessary to prepare pure secondary ester. The pure primary monobehenate could be obtained only by acylation of 2-tetrahydropyranyl propylene glycol obtained by reduction of tetrahydropyranyl ethyl lactate. Removal of the tetrahydropyranyl blocking groups was accomplished without acyl migration by using boric acid as a cleaving agent.     

Enzymatic esterification of glycerol II. Lipase-catalyzed synthesis of regioisomerically pure 1(3)-rac-monoacylglycerols

Regioisomerically pure 1(3)-rac-monoacylglycerols are conveniently prepared in high yields (>75%) and in multigram quantities by enzymatic esterification of glycerol in the presence of various lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) with a variety of different acyl donors, such as free fatty acids, fatty acid alkyl esters, vinyl esters and triacylglycerols, as well as natural fats and oils. All reactions are carried out in aprotic organic solvents with low water content, namelyn-hexane, diethyl ether, tBuOMe or mixtures of these solvents. Essential for the success of these transformations were the following two factors. First, the creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol and the hydrophobic reaction medium by its adsorption onto a solid support. Second, a facile system for the separation of the desired monoacylglycerol from the reaction mixture, coupled with the continuous recycling of acyl donor and undesirable by-products.     

Enzymatic esterification of glycerol I. Lipase-catalyzed synthesis of regioisomerically pure 1,3-sn-diacylglycerols

Regioisomerically pure 1,3-sn-diacylglycerols are conveniently prepared in high yields (>80%) and in large quantities by enzymatic esterification of glycerol in the presence of various 1,3-selective lipases(Chromobacterium viscosum, Rhizopus delemar, Rhizomucor miehei) and a variety of different acyl donors like free fatty acids, fatty acid alkyl esters and vinyl esters. All reactions are carried out in aprotic organic solvents of low water content, namelyn-hexane, diethyl ether or tBuOMe. The creation of an artificial interphase between the solvent-immiscible hydrophilic glycerol and the hydrophobic reaction media by the adsorption of glycerol onto a solid support prior to use was essential for the success of these transformations. The effects of reaction conditions and the regioselectivities of the lipases on the product yields are described in detail.     

Associative structures of polyglycerol esters in food emulsions

Liquid crystalline types and the crystalline gel state of the commercially available tri- and octaglycerol esters are identified. The behavior of crystalline and liquid crystalline forms of these polyglycerol esters were studied in water dispersions, soybean oil and water emulsions, and in food emulsions. Triglycerol monoesters, primarily a mixed ester composition of palmitate and oleate, show hexagonal liquid crystalline activity as well as limited regions of stable α crystalline gels. Octaglycerol monostearate and monooleate primarily exhibit hexagonal liquid crystalline behavior which (below their Krafft point) form stable α-gels. A relationship between the associative structures and functional performance of these polyglycerol esters in food emulsions is presented. Presented at the ISF-AOCS World Congress, April 1980, New York.     

Impact of Fatty Acid Structure on CALB‐Catalyzed Esterification of Glucose

Enzymatic synthesis of fatty acid glucose esters from different fatty acyl donors are performed via enzymatic catalysis in the presence of Candida antarctica lipase B (CALB), using acetonitrile as the solvent. The acyl donor nature (fatty acid or fatty acid vinyl ester) and structure are varied. Lower reaction rates and lower conversions are obtained with fatty acids in comparison to their corresponding vinyl esters. Moreover, the acyl donor with the longest chain length gives the highest conversions. The presence of unsaturation on the acyl donor chain is also shown to be detrimental to the conversion. Practical Applications: The practical applications of the present work are related to the production of gluco‐esters that could be used as nonionic surfactants as detergents, cosmetics and food emulsifiers, emollients or conservatives, respectively. In this study, it is shown that in order to get high production yields, each reaction parameter has to be tuned properly.     

Application of lipases to the regioselective synthesis of sucrose fatty acid monoesters

A regioselective synthesis of 6′-O-acyl sucrose monoesters has been developed through the lipase-catalyzed esterification of sucrose acetals with fatty acids in both organic solvents and under solvent-free conditions. The products were obtained in overall yields of 20–27% after hydrolysis of the isopropylidene groups with aqueous acids. The strict selectivity of the enzymes used also enabled the preparation of a monoester fraction that was highly enriched in 6-O-acyl sucrose. This was accomplished by lipase-catalyzed transesterification of sucrose monoesters, prepared by conventional chemical methods, in propan-2-ol. After removal of the transesterification products (sucrose and fatty acid isopropyl esters) and column chromatography on silica gel, the obtained monoester product contained 80% of the single regioisomer, 6-O-acyl sucrose.     

Enzymic enhancement of n−3 fatty acid content in fish oils

Commercially available fish oils with n−3 fatty acid contents ranging from 29 to 34% were converted enzymically, with Amano P lipase, to mixtures of glycerides with n−3 fatty acid contents ofca. 50%, in weight recovery yields of 23–50%, depending upon extraction procedures. Glyceride mixtures with n−3 fatty acid contents above 70% were obtained in yields of 14–21%. The processes are based on the relative stability of the ester linkages that involve n−3-fatty acyl groups and the regioselectivity of the enzyme toward acyl groups at the 1,3-positions of glycerol. This paper was presented at the 82nd AOCS Annual Meeting, May 12–15, 1991.     

Surface lipids ofLigia oceanica; Part II: The ester fractions

The surface lipids ofLigia oceanica have been isolated and fractionated into long chain wax esters, secondary alkylacetates, sterol esters, triglycerides, and alkenyl acyl diol esters. The fatty acid composition of these classes have been determined by gas liquid chromatography on Apiezon L, diethyleneglycol succinate and show that there are different biosynthetic pools of fatty acid for wax esters and triglycerides. The surface lipids have unusual constituents which may be important in water proofing the crustacean.     

Fatty acid monoesters of 1-ascorbic acid and d-isoascorbic acid

Summary Fat-soluble fatty acid monoesters of 1-ascorbic acid (vitamin C) and d-isoascorbic acid have been prepared from lauric, myristic, palmitic, and stearic acids in 40–50 per cent yields. Evidence has been presented to show that only the primary hydroxyl group of each of the ascorbic acids has been esterified. Antioxidant properties of these esters are being studied. Preliminary tests on the esters have indicated that they may have useful properties as interfacial modifiers.     

Isocyanate-modified dehydrated castor oil

Esters of dehydrated castor oil fatty acids with polyhydric alcohols like ethylene glycol, propylene glycol, glycerol, pentaerythritol and sorbitol have been prepared. The esters, having hydroxyl value ranging from 78.5 to 167, were reacted with toluene diisocyanate. The scratch hardness and other film properties of the resulting urethanes have been studied. Urethanes obtained from various mixtures of the above esters also have been studied. The best results have been obtained when a mixture of ethylene glycol ester and plenaerythritol ester of dehydrated castor oil fatty acids in the ratio of 4:1 are reacted with one equivalent of toluene diisocyanate. One equivalent of glycerol ester (hydroxyl value 78.5), ethylene glycol ester (hydroxyl value 167), or propylene glycol ester (hydroxyl value 159.4) of DCO fatty acids when reacted with 1.25 equivalent of toluene diisocyanate also gave satisfactory products.     

O-etherification between glycerol and glycerol monooleate—demonstration of formation of diglycerol monooleate and triglycerol monooleate by fast atom bombardment-mass spectroscopy and 13C nuclear magnetic resonance

To prepare glycerol monooleate, we reacted glycerol with oleic acid in the presence of a K1411 sulfonic acid resin in the H⁺ form. We utilized glycerol monooleate as an emulsifying agent, as it is a nonionic surfactant that is compatible with the initially biphasic reaction medium. If the expected product does not form, small amounts of a highly polar compound are produced. Both diglycerol monooleate and triglycerol monooleate were isolated by preparative chromatography on a silica column (hexane/chloroform/acetone, 25∶50∶50), and were formally identified by fast atom bombardment (FAB)-mass spectroscopy in positive mode. The products were polyglycerol monoesters. The nature of the products was confirmed by the use of different FAB matrices with or without cationization by alkali metals. The structure of the product was then confirmed by ¹³C nuclear magnetic resonance. we can now propose a new method of polyglycerol ester preparation that yields interesting nonionic emulsifying agents.     

Regioselective Synthesis of Palm-Based Sorbitol Esters as Biobased Surfactant by Lipase from Thermomyces lanuginosus in Nonaqueous Media

This paper describes the regioselective production of palm-based sorbitol monoesters via esterification catalyzed by Lipozyme^® TL IM (Thermomyces lanuginosus lipase adsorbed onto silica gel, Novozymes, Inc., Franklington, NC, USA). Effects of various reaction parameters including types of solvent, substrate molar ratio, molecular sieve and lipase concentration, temperature, reaction time, and fatty acid chain length were investigated. Approximately 76% conversion of sorbitol to sorbitol esters was achieved within 24 h under optimal conditions: sorbitol (0.4 M), fatty acid (0.8 M), 20 wt% Lipozyme^® TL IM in 100 mL tert-butanol at 55 °C for 24 h in the presence of 25 wt% 3 Å molecular sieve as water absorbent. The reactions were conducted in an orbital incubator shaker at a shaking rate of 200 rpm. Lipozyme^® TL IM was highly regioselective, esterifying exclusively at sorbitol's primary hydroxyl groups, producing 1-O- and 6-O-sorbitol monoesters. The biocatalyst also exhibited substrate selectivity toward shorter chain acyl donors, with caprylic acid exhibiting the highest conversion of sorbitol. In addition, Lipozyme^® TL IM was reused up to four successive reaction cycles without significant loss of activity. The biocatalytic process reported in this paper is a one-step process to produce biobased surfactants that does not involve the use of toxic or expensive solvents that are commonly employed for derivatization of sugars, or pre-derivatization of the substrates molecules.     

Micro-emulsion process for the preparation of sucrose esters

A new process, based on micro-emulsion technology, has been developed for the production of sucrose esters of fatty acids. Sucrose dissolved in propylene glycol, methyl stearate, sodium stearate, and catalyst (K₂CO₃) are combined to form a transparent emulsion and interacted. The system remains transparent throughout the distillation of the propylene glycol, indicating the formation of a micro dispersion of sucrose. Upon completion of the distillation all of the methyl stearate is converted to sucrose stearate. Starting with a 1.5:1.0:0.9 molar ratio of sucrose, methyl stearate, and sodium stearate, the reaction product, after purification, is 85% sucrose monostearate, 15% sucrose distearate. Presented at the AOCS Meeting in Philadelphia, October 1966.     

The synthesis,properties, and applications of ascorbyl esters

Ascorbic acid is a naturally occurring antioxidant. Nevertheless, its primary applications as an antioxidant in the life science, food and pharmaceutical industries are limited because of its hydrophilic nature. Alternatively, ascorbyl acid esters are potential surfactants and antioxidants. Chemical methods for the synthesis of ascorbyl esters lead to the formation of side products and simultaneous decomposition of ascorbic acid due to harsh reaction conditions. In contrast, lipases are used as regioselective and mild catalysts for the synthesis of ascorbyl esters. So far, various acyl donors namely, fatty acids, fatty acid alkyl esters, fatty acid vinyl esters and triacylglycerols have been explored for the synthesis of ascorbyl fatty esters. Other compounds such as L‐methyl lactate, bixin, phenyl butyric acid are also used as acyl donors. This article is focused on the recent developments of lipase‐catalyzed synthesis of ascorbyl esters, their antioxidant properties and applications.     

Preparation of Some New Ethylene Glycol Monoesters and Mixed Diesters of Fatty Acids

Tri-(2-hydroxyethyl)-orthoborate, obtained by reaction of ethylene glycol with boric acid, was esterified with palmitic, stearic, arachidic, oleic, hydnocarpic, elaidic and stearolic acids. Pure monoesters were obtained on hydrolysis with water in high yields. Monoelaidate and monostearolate are reported for the first time. The monoesters were reacted with acyl chlorides to yield the mixed diesters, viz., oleostearate, oleopalmitate, oleoarachidate, oleoelaidate, oleostearolate, elaidohydnocarpate, stearocaproate and stearolaurate. Except oleostearate the other compounds are reported for the first time.     

Preparation and properties of fully esterified erythritol

Pure tetraesters of erythritol with C₁₀, C₁₂, C₁₄, C₁₆, C₁₈ saturated, and C_18:1 unsaturated (oleoyl) fatty acyl chains have been prepared for the first time and characterized using the acylating systems fatty acid/N,N′‐dicyclohexylcarbodiimide/4‐dimethylaminopyridine (DMAP), fatty acid anhydride/DMAP, fatty acyl chloride/pyridine, and fatty acyl chloride/boron trifluoride etherate. For the first three systems the yields were in the range of 80–90% while the fatty acyl chloride/pyridine system has the advantage of lower cost. The fatty acyl chloride/boron trifluoride etherate system gave lower (ca 70%) yields of the tetraesters. The tetraesters of erythritol may have applications analogues to those of triglycerides. In addition, new applications can be envisaged for these compounds, as a result of their differences in physical, chemical, and biochemical properties compared to triglycerides. Practical applications: The tetraesters of erythritol with saturated fatty acyl chains may have applications analogous to those of saturated triglycerides. However, tetraesters with unsaturated fatty acid chains may have greater prospects of having industrial uses after doing chemistry on the carbon–carbon double bonds.     

Herstellung,Analyse und DC-Trennung von Fettsäurepartialestern mehrwertiger Alkohole

Preparation, Analysis and TLC-Separation of Partial Esters of Fatty Acids with Polybasic Alcohols Direct esterification of 99% capric acid, lauric acid, myristic acid, palmitic acid and stearic acid with ethyleneglycol, diethyleneglycol, thiodiethyleneglycol, triethyleneglycol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,5-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,2,4-butanetriol, glycerol, 1,2,6-hexanetriol, trimethylolpropane and pentaerythritol in a molar ratio of 1 :1.25 yields 100 different partial esters of fatty acids. These partial esters are extensively freed from the polyhydric alcohols by washing with sodium sulfate solution and recrystallization in ethanol. Chemical constants and TLC-separation into classes and into polyhydric alcohols permit the evaluation of these compounds as emulsifiers, stabilizers and solubilization acids. All the partial esters of the fatty acids are mixtures, which can be separated by TLC according to the polyhydric alcohol moiety into monoester, diester, triester and tetraester; furthermore, the separation of positional isomers of monoesters and diesters is possible. Several observations made during the synthesis and analysis of partial esters of fatty acids are reported.