Estolides from meadowfoam oil fatty acids and other monounsaturated fatty acids

The formation of estolides was detected during the studies on dimerization of meadowfoam oil fatty acids. By adjusting the reaction conditions, it was possible to produce monoestolides with little dimer or trimer formations. Estolides have potential use in lubricant, cosmetic and ink formulations and in plasticizers. This paper reports the conditions for production of estolides from mixed meadow-foam fatty acids, commercial oleic acid, high-oleic sun-flower oil fatty acids,cis-5,cis-13-docosadienoic acid, petroselinic acid and linoleic acid.     

Synthesis of Chloroalkoxy eicosanoic and docosanoic acids from meadowfoam fatty acids by oxidation with aqueous sodium hypochlorite

Chloroalkoxy substituted C₂₀ and C₂₂ fatty acids can be synthesized from the unsaturated fatty acids in meadow-foam oil by reaction of the fatty acids with primary or secondary alcohols and an aqueous sodium hypochlorite solution (commercial bleach). The reactions are conducted at room temperature for 3 h. Chlorohydroxy fatty acid derivatives are formed as by-products owing to the presence of water in the reaction mixture. Chlorinated δ-lactones are also produced by direct reaction of sodium hypochlorite with the Δ5 unsaturated fatty acids present in meadowfoam or by ring closure of the 6-chloro-5-hydroxy fatty acids. The product yield of chloroalkoxy fatty acids is dependent on the nature and volume of the alcohol used in the reaction, as well as the concentration and pH of the sodium hypochlorite solution. Primary alcohols such as methanol and butanol produce maximal yields (50–60%) of chloroalkoxy fatty acids whereas the secondary alcohol 2-propanol gives a 30% yield. Chloroalkoxy fatty acid yields can be increased to 75–80% by elimination of water from the reaction mixture through a procedure that partitions sodium hypochlorite from water into hexane/ethyl acetate mixtures. All of the reaction products were fully characterized using nuclear magnetic resonance and gas chromatography-mass spectrometry.     

Polyhydroxy fatty acids and their derivatives from plant oils

A novel process for the industrial production of hydroxylated fatty acids involves epoxidation of plant oils and their derivatives, followed by catalytic epoxy ring opening in the presence of water or other hydrogen donors, such as alcohols, diols, and amines. Depending on the starting material, epoxidation followed by opening of the oxirane ring leads to fatty acids that contain vicinal diol groups or to other substituted hydroxylated fatty acid derivatives. As an example for the preparation of a substituted hydroxylated fatty acid derivative, the reaction of epoxidized rapeseed oil with monobutylamine as hydrogen donor is described. Apart from the intended formation of hydroxyl groups with vicinal aminoalkyl groups, partial aminolysis of the ester compound was also observed. Another example describes the reaction of epoxidized rapeseed oil with different molar proportions of 1,4-butanediol as hydrogen donor. Depending on the molar proportion of the hydrogen donor, interesterification, or intermolecular ether formation were observed as side reactions. The properties of various technical hydroxylated fatty acids and their derivatives, prepared according to this novel process, are given, and potential applications of these products are suggested.     

The isolation and recovery of fatty acids with Δ5 unsaturation from meadowfoam oil by lipase-catalyzed hydrolysis and esterification

This report examines the use of lipases for isolating fatty acids with Δ5 unsaturation from the seed oil ofLimnanthes alba, or meadowfoam. Seven lipase types and three enzyme configurations (immobilized, “free” and reversemicellar encapsulated) were examined. All lipases discriminated against Δ5 acids to varying degrees, but the degree of discrimination was independent of enzyme configuration. Lipase-catalyzed esterification of meadowfoam oil’s free fatty acids was much more successful for isolating Δ5 acyl groups than was lipolysis. For example, esterification directed byChromobacterium viscosum lipase yielded a free fatty acid product containing >95% of the Δ5 acyl groups at >99% purity.     

Mineral acid-catalyzed condensation of meadowfoam fatty acids into estolides

Meadowfoam fatty acids (83% monoenoic fatty acid), reacted with 0.01–0.1 mole equivalents of perchloric acid, gave 33–71% yield of estolide, an oligomeric 2° ester, resulting from self condensation. Equimolar amounts of perchloric acid to fatty acid failed to produce estolide but converted the fatty acids to a mixture of lactones, mainly γ-eicosanolactone. Temperature plays a critical role; higher temperatures (75–100°C), at the same acid concentration, provide lactones while lower temperatures (20–65°C) yield estolides. Lower acid levels (<0.1 mole equivalents) gave the best yields (≈70%) at 65°C. The estolide and monomer were characterized by nuclear magnetic resonance, infrared high-pressure liquid chromatography, gas chromatography, gas chromatography/mass spectrometry. The estolide is a mixture of oligomers with an average distribution near 1.65 ester units. The ester linkages are located mainly at the original double bond positions but have some positional isomerization to adjacent sites in accord with carbocation migration along the alkyl chain. The residual double bond of the estolide was extensively isomerized fromcis totrans and positionally along the chain. The distilled monomer is similar in structure to the unsaturated portion of the estolide with geometrical and positional double bond isomerization. In addition, a significant amount of cyclization of the fatty acids to lactone (≈30%) had occurred.     

A highly regioselective synthesis of δ-lactones from meadowfoam fatty acids

Meadowfoam fatty acids, when treated with mineral acid catalysts in the presence of polar nonparticipating solvents, undergo a facile ring closure to form δ-lactones. Perchloric and sulfuric acids catalyze the cyclization at concentrations of 0.6–13 mole equivalents, both neat and in the presence of solvent. Under constant acid concentrations, methylene chloride was found to increase the rate of reaction, the regioselectivity for the formation of δ-lactone, and the overall yield. In the absence of solvent, increased acid concentration improved the yield of lactone but reduced regioselectivity for the δ-isomer. Solvent polarity plays a significant role in the regioselectivity of the cyclization for δ-lactone, with solvents of higher dielectric strength providing larger δ/γ ratios (38:1) and higher yields up to 92%.     

Enzymatic preparation of polyethylene glycol esters of castor oil fatty acids and their surface-active properties

This study concerns the preparation and evaluation of nonionic surfactants prepared from polyethylene glycol (PEG) esters of castor oil fatty acid, a source of hydroxy fatty acid. A lipase-catalyzed esterification reaction has been employed to prepare PEG esters of hydroxy acid to overcome problems associated with chemical processes. Castor oil fatty acid (85% ricinoleic acid) was mixed with PEG of different molecular weight. Rhizomucor miehei lipase was added as catalyst (10% level) and the reaction was continued at 60°C under 2 mm Hg pressure for 360 min. Conversion of PEG to esters was in the range of 86–94%, depending on the molecular size of PEG. The products were isolated and examined for surface activity by surface tension measurement. Surface tension values measured at 25°C were about 36–37 dynes/cm.     

Metathesis of unsaturated fatty acids: Synthesis of long-chain unsaturated-α,ω-dicarboxylic acids

The self-metathesis of readily available monounsaturated FA has the potential of being an important pathway for the synthesis of symmetrical long-chain unsaturated-α,ω-dicarboxylic acids (C₁₈−C₂₆). Previous studies on the self-metathesis of monounsaturated FA esters using ruthenium catalysts in solution, however, suffered from low conversions as a result of the thermodynamic control of the reaction. We have found that the second-generation Grubbs catalyst can effectively catalyze the solvent-free self-metathesis of monounsaturated FA of varying purity (from 90 to 99%) to afford two important products—monounsaturated dicarboxylic acids and hydrocarbons—in very high molar conversions (>80%). This solvent-free self-metathesis reaction also works for monounsaturated FA containing additional functional groups. Reactions were conducted at catalyst loadings as low as 0.005 mol%, and turnover numbers as high as 10,800 could be obtained. This discovery represents an attractive approach to the large-scale production of useful monounsaturated-α,ω-dicarboxylic acids and long-chain unsaturated hydrocarbons by means of this solvent-free ruthenium-catalyzed self-metathesis of readily available monounsaturated FA.     

Analysis of estolides in technical hydroxylated fatty acids from plant oils

Gel permeation chromatography of hydroxylated fatty acids (HOFA), prepared from various plant oils by a novel technical process, showed the presence of considerable amounts of estolides formed by intermolecular esterification of the HOFA. Thin-layer chromatographic fractionation followed by gas chromatography of the fractions revealed that the nonpolar estolides contain predominantly saturated fatty acids esterified tothero-9, 10-dihydroxy octadecanoic acid or dihydroxy tetrahydrofuran octadecanoic acids, e.g., 9,12-dihydroxy-10, 13-epoxy octadecanoic acid and 10,13-dihydroxy-9, 12-epoxy octadecanoic acid. The fractions of polar estolides consist mainly of intermolecular esters of the above dihydroxy fatty acids.     

Cyclopropenoid fatty acids of six seed oils from malvaceae

The seeds ofAlyogine hakeifolia, Alyogine huegelii,Gossypium australe, Hibiscus coatesii, Lawrencia viridigrisea andRadyera farragei (Malvaceae) contained 13.5-18.6% oil. Linoleic acid predominated (60.0-68.2%) in the component fatty acids of all the oils, followed by palmitic (9.9-18.1%) and oleic acids (7.8-15.8%). Cyclopropene fatty acids, malvalic and sterculic, were present in small concentrations (1.0-4.4%, 0.1-1.5% respectively). Dihydrosterculic acid was present in small quantities (trace-2.1%). *To whom correspondence should be addressed at Department of Chemistry, P.O. Box 320, University of Papua New Guinea, Papua, New Guinea.     

Sulfonated polystyrene: A catalyst with acid and superabsorbent properties for the esterification of fatty acids

In this work, catalysts with acid and superabsorbent properties were obtained by sulfonation of expanded polystyrene and used to promote the esterification of oleic acid with ethanol. The prepared superabsorbent polymers (SAP) showed high concentration of active sulfonic acid sites (0.7-5.9 mmol acid sites g⁻¹) and high water absorption capacity (445-900 g_water g⁻¹). It was observed that the catalytic activity increased with the number of acid site and water absorption capacity. Turnover frequencies suggested that the catalytic activity depends on the accessibility/diffusion processes determined by the crosslinks in the polymer. Commercial sulfonic acid resins and polyacrylate based superabsorbent polymers showed very low activities compared with the SAP produced. The SAP also showed higher activity compared to the homogeneous catalyst p-toluenesulfonic acid. The higher activity of the prepared SAP is discussed in terms of the acidity of sulfonic groups combined with the water absorption which shifts the esterification equilibrium.     

Densities of vegetable oils and fatty acids

Complete data for density as a function of temperature have been measured for a number of vegetable oils (crambe, rapeseed, corn, soybean, milkweed, coconut, lesquerella), as well as eight fatty acids in the range C₉ to C₂₂ at temperatures from above their melting points to 110°C (230°F). The specific gravity and density measurements were performed according to American Society for Testing and Materials (ASTM) standard test methods D 368, D 891 and D 1298 for hydrometers and a modified ASTM D 369 and D 891 for pycnometers. Correlation constants, based on the experimental data, are presented for calculating the density of fatty acids and vegetable oils in the range of temperature from 24°C (75°F) or the melting point of the substance, to 110°C (230°F). The constants are valuable for designing or evaluating such chemical process equipment as heat exchangers, reactors, process piping and storage tanks. Estimated density of fatty acids by a modified Rackett equation is also presented.     

Synthesis of secondary ethers derived from meadowfoam oil

Secondary ethers can be obtained from meadow-foam-derived delta lactones or 5-hydroxy fatty acids by using Lewis or Brønsted acid catalysts in good yield (70–90%). The conversion of δ-lactone or 5-hydroxy fatty acid to 5-ethers is performed under atmospheric pressure between 67 and 125°C with 0.5–6.4 mole equivalents of acid catalyst in the presence of 2–40 equivalents of alcohol and a reaction time of 1–140 h. Acid catalysts include mineral acids, such as perchloric and sulfuric; Lewis acids, such as boron trifluoride; and heterogeneous catalysts, such as clays and ion-exchange resins. Primary alcohols, such as methanol, butanol, decanol, and oleyl alcohol, or branched-chain alcohols, such as 2-ethylhexanol, can be used to make secondary ether fatty esters. The 5-ether fatty esters and the process for their formation have not been previously known and appear to be limited to structures where stabilized cations can be formed. The novel ethers were fully characterized by nuclear magnetic resonance and gas chromatography-mass spectrometry.     

Fatty acid selectivity of lipases: Erucic acid from rapeseed oil

The fatty acid selectivity of several commercial lipases was evaluated in the hydrolysis of high-erucic acid rapeseed oil (HEARO). The lipase ofPseudomonas cepacia catalyzed virtually complete hydrolysis of the oil (94–97%), while that ofGeotrichum candidum discriminated strongly against erucic acid, especially in esterification. A two-step process is suggested for obtaining a highly enriched erucic acid in which theG. candidum lipase is employed to selectively esterify the fatty acid residues of unsaturated C-18, and shorter chain acids, from a mixture of HEARO fatty acids obtained from total hydrolysis of the oil withP. cepacia lipase.     

Enzymatic enrichment of C20 cis-5 polyunsaturated fatty acids fromBiota orientalis seed oil

Enrichment ofcis-5 polyunsaturated fatty acids [20:3(5c,11c,14c), 4.3% and 20:4(5c,11c,14c,17c), 11.3%] fromBiota orientalis seed oil was carried out by lipase-catalyzed selective esterification and hydrolysis reactions. Lipases fromRhizomucor miehei (Lipozyme),Candida cylindracea and porcine pancreas were used. Lipozyme-catalyzed esterification ofBiota fatty acids withn-butanol inn-hexane allowed 20:3 and 20:4 (as fatty acids) to be enriched to a maximum level of 52.9%, and in the presence ofC. cylindracea lipase 61.5% enrichment was achieved. Esterification with pancreatic lipase was poor with low levels of enrichment of 20:3 and 20:4 (22%). A multigram scale esterification of the free fatty acids fromBiota seed oil by repeated treatment of the isolated fatty acid fraction withn-butanol inn-hexane in the presence ofC. cylindracea lipase furnished an enrichment yield of 72.5% of a mixture of 20:3 and 20:4 fatty acids. Urea fractionation of the free fatty acids ofBiota oil gave an initial enriched fraction of 20:3 (9.5%) and 20:4 (25.2%) which, upon treatment withC. cylindracea lipase inn-butanol andn-hexane, gave an enriched fraction of 85.3% of 20:3 and 20:4 fatty acids. Partial hydrolysis of the triglycerides ofBiota oil byC. cylindracea lipase in potassium phosphate buffer at 25°C resulted in a 2.8-fold enrichment ofcis-5 polyunsaturated fatty acids (40.8% of 20:3 and 20:4) as contained in the unhydrolyzed acylglycerol fractions.     

Analysis of hydroxylated fatty acids from plant oils

A novel process has been described recently for the preparation of hydroxylated fatty acids (HOFA) and HOFA methyl esters from plant oils. HOFA methyl esters prepared from conventional and alternative plant oils were characterized by various chromatographic methods (thin-layer chromatography, high-performance liquid chromatography, and gas chromatography) and gas chromatography-mass spectrometry as well as¹H and¹³C nuclear magnetic resonance spectroscopy. HOFA methyl esters obtained fromEuphorbia lathyris seed oil, low-erucic acid rapeseed oil, and sunflower oil contain as major constituents methylthreo-9,10-dihydroxy octadecanoate (derived from oleic acid) and methyl dihydroxy tetrahydrofuran octadecanoates, e.g., methyl 9,12-dihydroxy-10,13-epoxy octadecanoates and methyl 10,13-dihydroxy-9,12-epoxy octadecanoates (derived from linoleic acid). Other constituents detected in the products include methyl esters of saturated fatty acids (not epoxidized/derivatized) and traces of methyl esters of epoxy fatty acids (not hydrolyzed). The products that contain high levels of monomeric HOFA may find wide application in a variety of technical products.     

Biodegradation of estolides from monounsaturated fatty acids

Mono- and polyestolides, made from oleic acid, meadowfoam oil fatty acids and erucic acid, were subjected to biodegradation with mixed cultures of Penicillium verucosum, Mucor racemosus, and Enterobacter aerogenes. Fermentations were continued for 3, 5, 10, 15, 20, or 30 d. Meadowfoam oil and its fatty acids, oleic acid and soybean oil were also biodegraded under the same conditions. After 10 d, oleic acid and soybean oil were degraded 99.8 and 99.2%, respectively; meadowfoam oil and its fatty acids were degraded 89.0 and 97.7%, respectively. After 30 d, oleic acid-derived poly- and monoestolides were degraded 98.6 and 90.0%, respectively, meadowfoam estolides were degraded 75.7%, and erucic acid estolides were degraded 84.0%.     

Recovery of hydroxy fatty acids from lesquerella oil with lipases

Two hydroxy acids, lesquerolic (53 wt%) and auricolic (4%), are present at significant quantities inLesquerella fendleri seed oil. Results reported here indicate the selective release of hydroxy fatty acids during hydrolysis of this oil catalyzed byRhizopus arrhizus lipase. For example, hydroxy acids composed 85–90 wt% of the free fatty acids released during lipolysis, as compared to 54% present overall in the oil. In addition, over 80% of the lesquerolic acid is released from the triglycerides. The reason for this lipase’s success was determined to be its 1,3-positional specificity. The vast majority of lesquerella oil’s hydroxy acids is at the 1- and 3-positions of its triglycerides, as confirmed by the compositional analysis of partial glycerides formed during lipolysis.     

Enzymatic fractionation of fatty acids: Enrichment of γ-linolenic acid and docosahexaenoic acid by selective esterification catalyzed by lipases

Immobilized lipase preparations from seedlings of rape (Brassica napus L.) andMucor miehei (lipozyme) used as biocatalysts in esterification and hydrolysis reactions discriminate strongly against γ-linolenic and docosahexaenoic acids/acyl moieties. Utilizing this property, γ-linolenic acid contained in fatty acids of evening primrose oil has been enriched seven to nine-fold, from 9.5 to almost 85% by selective esterification of the other fatty acids with butanol. Similarly, docosahexaenoic acid of cod liver oil has been enriched four to five-fold, from 9.4 to 45% by selective esterification of fatty acids (other than docosahexaenoic acid) with butanol. As long as the reaction is stopped before reaching equilibrium, very little of either γ-linolenic acid or docosahexaenoic acid are converted to butyl esters, which results in high yields of these acids in the unesterified fatty acid fraction.