WO2002100991A2

WO2002100991A2 - Mono-, di- and triglycerides or their mixtures containing trans-fatty acid residues and method of their formation

Info

Publication number: WO2002100991A2
Application number: PCT/EP2002/006506
Authority: WO
Inventors: Carla Ferreri; Chryssostomos Chatgilialoglu
Original assignee: Biorama 2000 S.R.L.
Priority date: 2001-06-13
Filing date: 2002-06-13
Publication date: 2002-12-19
Also published as: WO2002100991A3

Abstract

The present invention is related to the conversion of mono-, di- and triglycerides containing cis unsaturated fatty acid residues to their corresponding geometrical trans isomers by free radicals. The process can be performed with glycerides, alone or with other components in mixtures, as well with the naturally available oils, in a variety of reaction media, such as in solution of organic solvents or in aqueous suspensions. A large variety of novel oils containing trans fatty acid residues can be obtained. The invention comprises the preparation of oils with a high trans fatty acid content, which may have useful properties for application as lubricating oils, and the preparation of a mixture of isomerized oils to be used as the analytical reference for trans geometrical isomers.

Description

Mono-, di- and triglycerides or their mixtures containing trans-fatty acid residues and method of their formation

Field of the invention

The present invention is related to the preparation of mono-, di- and triglycerides or of their mixtures, or of natural oils, which contain fatty acid residues as geometrical cis/trans isomers, and to the compounds obtained by such a process and their use. State-of-art

The transformation from cis to trans alkenes is a chemical process mediated by radical species, which has been known for many years on several substrates (see for example, Walling, C. et al. J. Am. Chem. Soc. 81 , 1144-1148 (1959); Chatgilialoglu, C. et al. J. Org. Chem. 60, 3826-3831 (1995)), and also on methyl esters of mono unsaturated fatty acids (Kircher, W. J. Am. Chem. Oil Soc. 41 , 351-354 (1964); Sgoutas, D., Kummerow, F. Lipids, 4, 283-287 (1969)). The application to polyunsaturated fatty acid derivatives and the use of thiyl radicals as catalysts for the isomerization process are also reported, as well as the extension to pure phosphatidylcholine (DOPC) and to phospholipid mixtures, such as soybean lecithin (see, Ferreri, C. et al. Chem. Commun. 407-408 (1999); Sprinz, H. et al. Biochim. Biophys. Acta, 1483, 91-100 (2000); Chatgilialoglu, C. et al. . J. Am. Chem. Soc. 122, 4593-4601 (2000); Ferreri, C. et al. . J. Am. Chem. Soc. 123, 4459-4468 (2001)). However, there is no reference on the possibility of applying the isomerization procedure to glycerides, pure or in mixtures, or to naturally occurring oils. Glycerides containing trans double bonds are found among the by-products of the catalytic hydrogenation of natural oils, carried out in heterogeneous or homogenous phases, (for a review on this subject, see: Ackman, R. G. et al. Trans Fatty Acids in Human Nutrition, The Oily Press, 1998, Ch. 2, 35-58). On the other hand, the synthesis of trans glycerides can be achieved by esterification of glycerol with 1-3 equivalents of trans methyl esters or acid chlorides in dehydrating alkaline medium (Jie, M. S. Chem. Phys. Lipids, 77, 155-171 (1995)). It is worth noting that the catalytic hydrogenation of oils is used to obtain saturated and partially saturated glycerides, that often contain trans isomers. However, these trans isomers do not have the double bond in the same position as the starting material, but are the so-called positional isomers, that is, isomers where the trans double bond is distributed in various unnatural positions.

Trans glycerides could be obtained by esterification of glycerol but in this case glycerol reacts with fatty acid derivatives, such as esters or chlorides, which already have the trans double bond. This synthesis has an obvious limitation due to the availability of a few trans isomers.

Up to now, the isomerization process has not been applied to glycerides probably due to experimental difficulties, associated with the radical catalysis in a heterogeneous phase created by the glyceride and the reaction solvent, and to the analytical complexity.

It is important to remember that recognition of trans fatty acid isomers in fats and oils is a very important issue for food industries, since trans components can be introduced in food products by chemical manipulation of fats and they can have harmful effects on human health (for a comprehensive treatment of this subject, see: Trans Fatty Acids in Human Nutrition, Christie, W. W., Sebedio, J. L. Eds, The Oily Press, 1998, Ch. 2, 35-

58).

Recognition of trans fatty acid isomers is also of fundamental importance in biological samples (such as blood or tissues), and a large body of literature in medicine is related to the fatty acid composition and the trans content of cell membranes as a marker for the functional status of biological processes and for some pathological events (cancer, cardiovascular diseases, etc.) (Ip, C, Marshall, J. R. Nutr. Rev. 54, 138-145 (1996);

Siguel, E. N., Lerman, R. Am. J. Cardiol. 71 , 916-920 (1993)).

Summary of the invention

The invention refers to a process for catalytically isomerizing mono-, di- or triglycerides or their mixtures , such as naturally available oils and fats, which consists of contacting them with sulfur radicals, generated in different ways from thiols or sulfides or disulfides.

The invention refers also to the compounds obtained by such a process and to their use.

Detailed description of the invention

The present invention allows to solve the above said problem by a process consisting of the cis/trans isomerization of glycerides of general formula 1 CH^-X

CH— X

or their mixtures, wherein X is chosen in the group consisting of: OH or OC(O)R wherein R is an alkyl chain containing at least a double bond, provided that at least one of X is not OH, in the presence of a sulfur containing catalyst, a radical initiation and possibly a solvent.

According to the invention the term glycerides means for example the following compounds: triolein, diolein, trierucin, trimirystolein, trilinolein, trinervonin, tripalmitolein, tripetroselinin

1 ,3-dilinolein, 1 ,2-dilinoleoyl-3-oleoyl glycerol

1-monolinoleoyl glycerol or mixtures of glycerides, but it includes also natural occurring oils containing them such as for example: Borage, Canola, Crambe, Fish, Lineseed, Olive, Palm, Rapeseed, Rice, Soybean oils, etc.

Alkyl chain containing at least a double bond, according to the invention is preferably a

C4-C30 chain containing from 1 to 6 double bonds, more preferably they are the chain of unsaturated fatty acids having 14 - 22 carbon atoms, more preferably the fatty acids chains usually described by the notations: 14:1 , 16:1 , 18:1 , 18:2, 18:3, 18:4, 20:1 , 20:2, 20:3, 20:4, 20:5, 22:1 , 22:6. The sulfur containing catalysts according to the invention is a compound of general formulas RSH, RSR' and RS-SR', where R and R' are identical or different, and are chosen in the group consisting of: a hydrogen atom, or an aryl group, or an alkyl chain. Aryl group according to the invention means preferably phenyl, or p-X-C6H4, wherein X = Cl, Me, OMe.etc, while preferred alkyl chain are C2-C10 such chains possibly containing other groups, such as hydroxyl or amino, or aminoacid functions. All sulphur compounds capable of displaying a radical reactivity can be used. For a general application, the preferably used compound is a thiol, i.e., 2-mercaptoethanol. Sulphur compounds is preferably used in catalytic quantities, that is 1-50 moles % compared to the glyceride equivalents, preferably 10-30%;

The radical initiators, i.e., a substance that decomposes by heating, thus providing the first radical species and trigger the radical reaction between the glyceride and the sulphur compound, belong to known categories, and are commercially available. Their use is coupled with heating of the reaction mixture. As preferred radical initiators of this invention, are diazoalkanes with a general formula R-N=N-R, where R is a branched alkyl chain with different substituents, or with acid/basic groups which can be present as salts. For example, diazoalkanes such as AIBN [azobis(isobutyronitrile)], AMVN [azobis(methylvaleronitrile)], AAPH [azobis(amidinopropane)hydrochloride], can be utilized in different solvents, such as organic solvents or water, at various temperatures, from 30 °C to temperatures as high as 160 °C. Peroxides can also be used as the initiators, having a general formula RO-OR, where R is an acyl or alkyl group with various substituents. The use of the initiators involves catalytic quantities, ca. 5-20 moles % with regards to the glyceride equivalents. The initiation can be obtained under a variety of conditions, which include: gamma- irradiation, ultrasound sources, photochemical conditions.

For example, gamma irradiation with a ⁶⁰Co source of the glyceride dissolved together with the sulphur compounds in alcoholic or aqueous solutions or photochemical generation of radicals (for example, from di-tert-butyl ketone) in the presence of thiol, or UV irradiation of disulfides, can be used as efficient radical initiations and as reaction conditions. Due to the presence of radical species, the preliminary use of degassing techniques is recommendable, that is, for example, the passage of a gas stream through the reaction mixture with the aim of evacuating oxygen. The invention indicates gases such as nitrogen, argon or nitrogen dioxide, the latter is preferably required when gamma-irradiation is used. Reaction solvents are organic solvents, such as carbon tetrachloride, chloroform, hexanes, alcohols (for example, methanol, ethanol or tert-butanol), or aqueous media, such as distilled water or saline buffers with pH between 2-8 (for example, physiological saline solution, phosphate buffer, etc.). According to the invention process the glycerides, or their mixtures or natural oils containing them, are dissolved in organic solvents or aqueous suspensions/solutions; the initiator, (or sensitizer) if required, and the sulfur compound are added; preferably, the mixture is degassed prior to the reaction start; the reaction mixture is irradiated or heated, according to the chosen protocol, for a variable time between 1 and 24 hours. The protocol can include a series of gas chromatographic or infrared analyses in order to stop the reaction when the desired quantity of trans isomers is formed.

Work-up procedures are carried out according to the reaction solvent. In case of organic solvents, work-up is done as follows: a) partition of the final reaction mixture between ethyl acetate (or hexanes) and 0.1 M sodium hydroxide solution, in order to eliminate the sulfur compound; b) separation of the organic layer which contains the product, and washing with distilled water; c) evaporation under vacuum to have the crude reaction product.

When an alcohol is used as the solvent, the final reaction mixture is evaporated under vacuum, thus leaving a reaction crude which is then treated by the work-up procedure (a-c). When water is the solvent, the final reaction mixture can be directly separated if it forms a two-phases-system, or separated as described by the work-up procedure (a-c). The final products may be further purified by known chromatographic or distillation procedures.

As previously described, the invention process can be applied to glycerides for themselves, or to solutions or suspensions containing a mixture of glycerides, or natural oils, as for example vegetable or animal oils, such as Borage, Fish, Rice, Canola, Soybean, Oilve, Lineseed, Rapeseed, Crambe oils, etc. In the case of mixed glycerides the final product will contain unsaturated fatty acid residues as a mixture of cis/trans geometrical isomers in a known proportion, which depends on the reaction protocol. The products of this invention can further be purified by means of separation techniques, such as distillation, chromatographies or silver ion based chromatographic methods, in order to obtain pure trans isomers. Some of these isomers are new compounds which can be fully characterized (NMR, IR, UV, GC, Mass).

The process according to the invention is easy and quantitative and allows to prepare trans geometrical glycerides in percentages comprised between 1 - 90%, preferably between 30 - 80%. The reaction conditions are environmentally compatible and the reaction components and products are biodegradable and recyclable. The process allows the synthesis of isomerised oils, i.e. oils containing variable percentage of the glyceride fatty acid chains as the corresponding geometrical trans isomer form. The final trans content can be determined by known infrared spectroscopy procedures. The presence of trans bonds determines interesting changes in the starting oil properties for example viscosity which can be play an important role for example in the field of lubricant oils. The following examples illustrate the present invention more clearly: EXAMPLE 1

2-Mercaptoethanol (0.0063 mmol; 0.49 mg) and AIBN (0.0021 mmol; 0.34 mg) are added to a nitrogen-degassed suspension of triolein (20 mg; 0.0225 mmol, 95.6% oleate content equal to 0.021 mmol) in absolute ethanol (0.14 mL) kept in a closed screw-cap glass reaction vessel. Temperature is raised up to 85 °C and after three hours the reaction is stopped and the solvent evaporated. The crude residue is partitioned between hexane (or ethyl acetate) (4 x 3 mL) and 0.1 M NaOH solution (1 x 1 mL). The organic layers are washed with saturated saline solution (2 x 1 mL), dried with anhydrous sodium sulfate and evaporated under a nitrogen stream. 20 mg of an oil is obtained (0.071 mmol; quantitative yield) and analysed by transesterification and GC chromatography (see, Example 5). A 70% trans isomer content has been determined. The oil can be further purified by chromatography on silica gel using n-hexane as the eluent. Its characteristics are similar to the those described in literature (Jie, M. S. F., Lam, C. C. Chem. Phys. Lipids, 78; 15-28 (1995)). EXAMPLE 2 Example 1 is repeated with the same molar quantities of substrates, using water as the solvent. An aqueous buffer, for example phosphate buffer at pH = 7, can instead be used. The radical initiator is AAPH, in the same molar quantities indicated for AIBN in Example 1 , and the reaction is heated at 45 °C for 21 hours. The result is analogous to example 1. EXAMPLE 3

Example 1 is repeated with the same molar quantities of 2-mercaptoethanol and triolein but without initiator. The solvent is tert-butanol and the reaction mixture is preliminarily saturated with nitrogen dioxide. Then the reaction vessel is introduced into a γ-irradiation apparatus (dose/rate is determined by a known methodology. The example is carried out with a dose/rate of 20 Gy/min). The reaction mixture is kept for 4 hours in the source at room temperature and the resulting product, obtained as described in example 1 , has a 10% trans content. Leaving the reaction mixture for a longer time, such as 21 hours, a 45% trans content is found in the final product. EXAMPLE 4 Example 1 was repeated with borage oil (average m. w. 850; 40 mg; 0.047 mmol; ca. 95% fatty acid content equal to 0.045 mmol) as substrate in ethanol as the solvent (0.3 mL), using AMVN as radical initiator (0.0050 mmol) and 2-mercaptoethanol (0.014 mmol; 1.12 mg) at a temperature of 54 °C. After 21 hours borage oil was isolated as previously described for triolein, and a quantitative yield of oil was obtained, which has a trans content of 30% as determined by gas chromatographyc analysis under known conditions (Ferreri, C. et al. J. Am. Chem. Soc. 123, 4459-4468 (2001 )). ¹H NMR (CDCI₃) δ 1.96 (bisallylic protons in the trans isomers). ¹³C NMR (CDCI₃): (new ethylenic resonances attributable to trans isomers): δ 130.2, 130.3, 130.5, 130.6, 130.7, 130.8, 130.9, 131.1. IR (CHCI₃) (v) 968.6 cm^"1 characteristic of trans unconjugated C-H bending absorption. EXAMPLE 5

A mixture containing a 1/1 ratio of borage and fish oils (20 mg of each) is dissolved in methanol (0.4 mL) in a closed screw cap glass vessel and degassed by means of a nitrogen stream. 2-Mercaptoethanol (0.014 mmol; 1.12 mg) and AMVN (0.0050 mmol) are added and the reaction mixture is heated at 54 °C for 21 hours. After this time a mixture of oils which contain a 30% trans isomers is obtained. The reaction mixture is poured into chloroform (5 mL) and saturated saline solution (1 mL) extracted and the organic phase is essiccated and evaporated to dryness. The crude is then treated for transesterification, in order to transform the fatty acid chains of glycerides to the corresponding methyl esters. The protocol follows these steps: a) treatment with 1 mL of a 0.5 M solution of KOH in Methanol for 10 minutes at room temperature; b) the basic reaction mixture is essiccated under vacuum and the residue is extracted with n-hexane (3 x 5 ml) and saturated saline solution (2 mL); c) the organic layers are washed with distilled water (2 x 1 mL), essiccated with anhydrous sodium sulfate and evaporated under a nitrogen stream then under vacuum; d) the residue is dissolved in n-hexane (1 :50 in volume) and injected in the GC/MS apparatus under known analytical conditions (Ferreri, C. et al. J. Am. Chem. Soc. 123, 4459-4468 (2001)).

The residue contained a total of 30% trans isomers and is proposed as a reference standard for the analysis of fatty acids contained in biological samples, as detected by gas chromatographic analysis. EXAMPLE 6

2-Mercaptoethanol (0.0063 mmol; 0.49 mg) and AIBN (0.0021 mmol; 0.34 mg) are added to a solution of rice oil (20 mg; 0.0225 mmol, 95.6% oleate content equal to 0.021 mmol) in ethanol (0.14 mL) kept in a closed screw-cap glass reaction vessel. Temperature is raised up to 85 °C and after four hours the reaction is stopped and the solvent evaporated. Workup is done as described in example 1 and 20 mg of an oil is obtained (0.071 mmol; quantitative yield) and analysed by transesterification and GC chromatography (see, Example 5). A 70% trans isomer content has been determined as detected by gas chromatographic analysis under known conditions (Ferreri, C. et al. J. Am. Chem. Soc. 123, 4459-4468 (2001)). ¹H NMR (CDCI₃) δ 1.97 (bisallylic protons in the trans isomers).

¹³C NMR (CDCI₃): (new ethylenic resonances attributable to trans isomers): δ 130.05, 130.08, 130.3, 130.4, 130.66, 130.9.

IR (CHCI₃) v new absorption at 965.2 cm^"1 (trans unconjugated C-H bending absorption) EXAMPLE 7

Borage oil (average m. w. 850; 40 mg; 0.047 mmol; ca. 95% fatty acid content equal to

0.044 mmol) was dissolved in tert-butanol (0.3 mL), and di-n-butyl disulfide (0.023 mmol;

4 mg) was added. After 1.5 hours of irradiation with an UV lamp (at 254 hv), borage oil was isolated as previously described in example 1 , and a quantitative yield of oil was obtained, which had a trans content of 40% as determined by gas chromatographyic analysis under known conditions (Ferreri, C. et al. J. Am. Chem. Soc. 123, 4459-4468

(2001)). Spectroscopic characteristics are described in Example 4.

EXAMPLE 8

2-Mercaptoethanol (0.0063 mmol; 0.49 mg) and AIBN (0.0021 mmol; 0.34 mg) are added to a solution of echium oil (20 mg; 0.0225 mmol, 95.6% oleate content equal to

0.021 mmol) in ethanol (0.14 mL) kept in a closed screw-cap glass reaction vessel.

Temperature is raised up to 85 °C and after four hours the reaction is stopped and the solvent evaporated. Workup is done as described in example 1 and 20 mg of an oil is obtained (0.071 mmol; quantitative yield) and analysed by transesterification and GC chromatography (see, Example 5). A 70% trans isomer content has been determined as detected by gas chromatographic analysis under known conditions (Ferreri, C. et al. J.

Am. Chem. Soc. 123, 4459-4468 (2001 )).

¹H NMR (CDCI₃) δ 1.95 (bisallylic protons in the trans isomers).

¹³C NMR (CDCI₃) δ 130.2, 130.4, 130.6, 130.8, 131.7, 131.9, 132.2, 132.4. IR (CHCI₃) v new absorption at 968.4 cm^"1 (trans unconjugated C-H bending absorption)

According to the procedures described in the examples above the following compounds were also obtained:

Trans almond oil which contains ca. 60-80% of monounsaturated fatty acids and 8-28% of polyunsaturated fatty acids, with a 70% of trans isomers. Trans apricot kernel oil which contains ca. 50-70% of monounsaturated fatty acids and

20-30% of polyunsaturated fatty acids, with a 70-80% of trans isomers.

Trans canola oil which contains ca. 60% of monounsaturated fatty acids and 30% of polyunsaturated fatty acids, with a 50-60% of trans isomers. Trans cod liver oil which contains ca. 70% of monounsaturated fatty acids and 20% of polyunsaturated fatty acids, with a 70-80% of trans isomers.

Trans corn oil which contains ca. 30-50% of monounsaturated fatty acids and 50-35-

50% of polyunsaturated fatty acids, with a 40-60% of trans isomers.

Trans cotton seed oil which contains ca. 20-45% of monounsaturated fatty acids and 35- 50% of polyunsaturated fatty acids, with a 50-70% of trans isomers.

Trans crambe oil which contains ca. 65-70% of monounsaturated fatty acids and 20% of polyunsaturated fatty acids, with a 60-70% of trans isomers.

Trans echium oil, which contains ca. 20% of monounsaturated fatty acids and 55% of polyunsaturated fatty acids, with a 30-40% of trans isomers. Trans flaxseed oil which contains ca. 15% of monounsaturated fatty acids and 70% of polyunsaturated fatty acids, with a 50-60% of trans isomers.

Trans linola oil which contains ca. 35% of monounsaturated fatty acids and 50-70% of polyunsaturated fatty acids, with a 50-60% of trans isomers.

Trans linseed oil which contains ca. 10-20% of monounsaturated fatty acids and 50-80% of polyunsaturated fatty acids, with a 50-70% of trans isomers.

Trans marine-based oil which contains ca. 25% of monounsaturated fatty acids and 25-

40% of polyunsaturated fatty acids, with a 50-70% of trans isomers.

Trans olive oil which contains ca. 75% of monounsaturated fatty acids and 10% of polyunsaturated fatty acids, with a 70% of trans isomers. Trans palm oil which contains ca. 50% of monounsaturated fatty acids and 10% of polyunsaturated fatty acids, with a 50-60% of trans isomers.

Trans peanut oil which contains ca. 40-65% of monounsaturated fatty acids and 15-30% of polyunsaturated fatty acids, with a 40-70% of trans isomers.

Trans rape seed oil which contains ca. 60-80% of monounsaturated fatty acids and 50- 70% of polyunsaturated fatty acids, with a 10-20% of trans isomers. Trans safflower oil which contains ca. 75% of monounsaturated fatty acids and 15% of polyunsaturated fatty acids, with a 60-70% of trans isomers.

Trans soybean oil, which contains ca. 22-34% of monounsaturated fatty acids and 50- 70% of polyunsaturated fatty acids, with a 50-60% of trans isomers. Trans sunflower oil which contains ca. 20% of monounsaturated fatty acids and 60-70% of polyunsaturated fatty acids, with a 40-60% of trans isomers.

Trans high oleic sunflower oil which contains ca. 90% of monounsaturated fatty acids and 5% of polyunsaturated fatty acids, with a 70% of trans isomers. Trans walnut oil which contains ca. 15-20% of monounsaturated fatty acids and 50-65% of polyunsaturated fatty acids, with a 50-60% of trans isomers.

As it is clear from the above reported description and examples the main advantage of this invention consists of a reliable and easy methodology for the selective transformation of cis glycerides to their corresponding geometrical trans isomers, by a radical process, which can also be controlled and stopped at any stage in order to get the desired trans isomer percentage. The total trans content can be determined by FT- IR spectroscopy, as described in the protocol of the American Oil Chemist's Society (AOCS Official Methods, Champain, IL (1999) Cd.14b-93;Cd-14-96;Cd 15-95). By the present invention a variety of trans oils is produced, including those which cannot be obtained by any esterification procedure. By this process the transformation of oils to semi-solid products can be obtained, with a change of organoleptic and physical properties compared to oils obtained by catalytic hydrogenation processes. (Hoffmann, G. The Chemistry and Technology of Edible Oils and Fats and their High Fat Products, Academic Press, 1989). By this invention, for example, oils with a high erucic acid content (erucic acid is a monounsaturated fatty acid with 22 carbon atom and one cis unsaturation in position 11), such as Rapeseed oil, can be converted to trans erucic acid-containing oils.

Moreover, according to another aspect of the invention, a glyceride mixture of cis and trans isomers obtained from borage and fish oils by the invention process can also be applied as an analytical standard, for the recognition of a large variety of geometrical trans isomers of unsaturated fatty acids not yet commercially available. The analytical methodology for the identification of lipid components containing double bonds as the trans geometrical isomers, is based on the transesterification of the lipid fraction contained in the sample, and on the comparison with an isomeric mixture of mono- and polyunsaturated fatty acid methyl esters, which contains a definite trans isomer percentage; the methodology is widely described in the Italian application FI2001A000106 in the name of the same applicant to which reference is made for application.

Therefore the invention refers also to a kit containing the chemical reagents to perform the above described analytical test and, a sample containing the unsaturated fatty acid methyl esters in mixtures of cis ad trans isomers, obtained as previously described, or eventually, a GC chromatogram with full details about the analytical procedure to follow, in order to make a comparative evaluation of the isomeric content (analytical composition of the reference sample, GC conditions and apparatus, etc.). By the present invention new trans isomers can be obtained and analysed, which derive from oils containing long chain polyunsaturated fatty acid residues, such as gamma- linolenic acid, eicosapentaenoic acid, docohexaenoic acid and so on. It is worth recalling that an intermediate step is required in the process, because the fatty acid chains present in the oils have to be transformed to their corresponding methyl esters prior to the gas chromatographic analysis. This can be done by known procedures and without altering the trans isomer structures obtained during the isomerization process (Kramer, J. K. C, Fellner, V., Dugan, M. E. R., Sauer, F. D., Mossoba, M. M:, Yurawecz, M. Lipids, 32, 1219-1228 (1997)).

Claims

CLAIMS:

1. A process for catalytically isomerizing mono-, di- or triglycerides or their mixtures wherein the compounds to be isomerised are reacted with a sulfur-centered radical

2. A process according to claim 1 wherein the glycerides are of general formula (I) CH^-X

CH— X

or their mixtures, wherein X is chosen in the group consisting of: OH or OC(O)R wherein R is an alkyl chain containing at least a double bond, provided that at least one of X is not OH,

3. Process according to claim 2 wherein the alkyl chain containing at least a double bond, according to the invention is a C4-C30 chain containing from 1 to 6 double bonds.

4. Process according to claim 3 wherein the alkyl chain is the chain of an unsaturated fatty acid having 14 - 22 carbon atoms,

5. Process according to claim 4 wherein the unsaturated fatty acids chains is described by the notations: 14:1 , 16:1 , 18:1 , 18:2, 18:3, 18:4, 20:1 , 20:2, 20:3, 20:4, 20:5, 22:1 , 22:6.

6. A process according to claim 1 wherein the glyceride is a natural oil chosen in the group consisting of: Borage, Fish, Rice, Canola, Palm, Soybean, Olive, Line seed, Rape seed, Crambe oils, etc.

7. A process according to claim 1 wherein the glyceride mixture can be dissolved together with the sulfur compound in organic solvents, such as carbon tetrachloride, chloroform, hexanes, alcohols (methanol, ethanol or tert-butanol), or aqueous media, such as distilled water or saline buffer with a pH between 2-8.

8. Process according to claim 1 wherein homogeneous solutions of oils dissolved in an organic solvent or heterogeneous phases constituted by an aqueous and the oil phases, are used as reaction media.

9. A process according to claiml wherein the source of the sulfur-centered radicals are sulfur compounds having the general formulas of RSH, RSR' or RS-SR, where R is a hydrogen atom or an alkyl chain and can contain other groups, such as hydroxyl, amino or aminoacid functions.

10. A process according to claims 1 and 9 wherein the source of sulfur-centered radicals is preferably 2-mercaptoethanol in the amount of 0.05 to about 0.50 moles/mole, preferably 0.1-0.3 moles/mole.

11. A process according to claims 1 , 9 and 10 where the sulfur radicals can be obtained from thiols by a thermal initiation in the presence of diazoalkanes, with a general formula R'-N=N-R', or peroxides, with a general formula R'O-OR", in the temperature range of 30 °C - 160 °C. Radical initiators are added in the amount of 0.05-0.10 moles/mole.

12. A process according to claims 1 and 9 where the sulfur radicals can be obtained from disulfides, by using a photochemical apparatus and eventually adding a 0.01-0.10 moles/mole of a sensitizer (di-tert-butylketone) to the glyceride and disulfide reaction mixture.

13. A process according to claims 1 and 9 where the sulfur radicals can be generated from thiols or sulfides or disulfides by a gamma-irradiation apparatus (⁶⁰Co source). The mixture of the glyceride and sulfur compound in degassed alcoholic (tert-butanol) or aqueous solution is irradiated for a variable time from 1 up to 24 hours.

14. Compounds obtained by the process according to claims 1 - 13.

15. Compounds according to claim 14 chosen in the group consisting of:

Trans borage oil containing 30% trans isomer

Trans rice oil containing 70% trans isomer

Trans borage oil containing 40% trans isomer Trans echium oil containing 70% trans isomer

Trans almond oil containing a 70% of trans isomers.

Trans apricot kernel oil containing a 70-80% of trans isomers.

Trans canola oil containing a 50-60% of trans isomers.

Trans cod liver oil containing a 70-80% of trans isomers. Trans corn oil containing a 40-60% of trans isomers. Trans cotton seed oil containing a 50-70% of trans isomers. Trans crambe oil containing a 60-70% of trans isomers. Trans echium oil containing a 30-40% of trans isomers. Trans flaxseed oil containing a 50-60% of trans isomers. Trans linola oil containing a 50-60% of trans isomers. Trans linseed oil containing a 50-70% of trans isomers. Trans marine-based oil containing a 50-70% of trans isomers. Trans olive oil containing a 70% of trans isomers. Trans palm oil containing a 50-60% of trans isomers. Trans peanut oil containing a 40-70% of trans isomers. Trans rape seed oil containing a 10-20% of trans isomers. Trans safflower oil containing a 60-70% of trans isomers. Trans soybean oil containing a 50-60% of trans isomers. Trans sunflower oil containing a 40-60% of trans isomers. Trans high oleic sunflower oil containing a 70% of trans isomers. Trans walnut oil containing a 50-60% of trans isomers.

16. A kit for the analysis which contains a sample consisting of a reference mixture of unsaturated fatty acid methyl esters according to claim 1.

17. Kit according to claim 16 wherein the sample is a mixture of isomerized oils.