JP2895258B2 - Method for selectively obtaining polyunsaturated fatty acids - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a highly pure carbon-carbon
Highly unsaturated, having 18 to 22 carbon atoms having 3 to 6 double bonds
Japanese fatty acid or its ester-type derivative or fatty acid
The present invention relates to a method for obtaining alcohol (hereinafter referred to as “polyunsaturated fatty acids”) .

[0002] The present invention, mackerel, eicosapentaenoic acid contained in fish oil sardine and the like, and highly unsaturated fatty acids or their ester derivatives such as docosahexaenoic acid, such as arachidonic acid contained in animal oils pig Polyunsaturated fatty acids and ester-type derivatives thereof, α-linolenic acid contained in vegetable oils, highly unsaturated fatty acids such as γ-linolenic acid or ester-type derivatives thereof, and polyunsaturated fatty acids or esters thereof derived from algae and microorganisms extraction and separation of such type derivatives, during purification, modified, without causing deterioration, inexpensively and efficiently selectively high in industrial practice scale
It can be used for a method of extracting, separating and purifying highly unsaturated fatty acids .

[0003]

2. Description of the Related Art Known methods for extracting, separating and purifying highly unsaturated fatty acids include urea addition, molecular distillation, solvent fractionation, and chromatography.

However, according to these methods, polyunsaturated fatty acids and esters thereof have high purity and are not denatured.
It is very disadvantageous to separate and purify a large amount at low cost.

[0005] That is, the urea addition method has a drawback that the resulting polyunsaturated fatty acids and esters thereof are low in purity, and the molecular distillation method is liable to be modified due to polymerization or isomerization.

[0006] Solvent fractionation and chromatography are not suitable for large-scale separation and purification on an industrial scale.

It is generally known that silver ions form complexes with unsaturated bonds of organic compounds.

As one method utilizing this property, Japanese Patent Application Laid-Open No. 63-208549 discloses a method in which silver ions are immobilized on an adsorbent and the difference in affinity between silver and unsaturated fatty acids is used to obtain eicosapentaenoic acid or the like. A method for purifying a derivative such as a highly unsaturated fatty acid or an ester thereof is disclosed.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned prior art by providing linolenic acid, arachidonic acid,
Carbon such as eicosapentaenoic acid and docosahexaenoic acid
A high carbon number of 18 to 22 having 3 to 6 carbon double bonds;
Highly unsaturated fatty acids or their ester-type derivatives or fats
To provide a method that can selectively extract, separate, and purify fatty alcohols (highly unsaturated fatty acids) from their contents without deteriorating the target product under extremely mild conditions, at low cost. It is.

[0010]

The present inventors Means for solving the problem] is the basis of the prior art, altitude and inclusions containing unsaturated fatty acids, unsaturated bonds and a certain concentration or more of silver salts complexes capable of forming aqueous medium soluble
By stirring the solution , highly unsaturated fatty acids can be selectively
S only aqueous medium soluble silver salt - are extracted to form a highly unsaturated fatty acids complexes in aqueous medium phase, after separated and the aqueous medium phase, subjected to dissociation means complex aqueous medium phase As a result, they have found that only highly unsaturated fatty acids can be selectively extracted, separated and purified on an industrial scale, and have completed the present invention.

The polyunsaturated fatty acids in the present invention are defined in the acronym, and include ester derivatives such as methyl ester, ethyl ester, triglyceride, diglyceride and monoglyceride , and aliphatic alcohols .

[0012]

[0013] The present invention will be specifically described by stirring 5 minutes to 4 hours by adding an aqueous medium solution of the silver salt capable of forming an unsaturated bond and complex content of highly unsaturated fatty acids, water A medium- soluble silver salt-polyunsaturated fatty acid complex is formed, and only the polyunsaturated fatty acid is selectively dissolved in the aqueous medium phase.

The lower limit of the reaction temperature is only required to be liquid, and the upper limit is up to 100 ° C. The reaction temperature depends on the stability of polyunsaturated fatty acids, the solubility of silver salt in water, the rate of complex formation, and the like. From the viewpoint of consideration, preferably around room temperature, the reaction time is 10
Minutes to two hours are desirable.

Also, the oxidation stability of polyunsaturated fatty acids,
In consideration of the stability of the silver salt, the present invention is desirably performed in an inert gas such as a nitrogen atmosphere while shielding light.

The silver salt capable of forming a complex with an unsaturated bond is not particularly limited, and is generally a silver compound soluble in an aqueous medium such as silver nitrate, silver perchlorate, silver acetate, silver tetrafluoroborate and the like. Is used.

When the molar ratio of the polyunsaturated fatty acids to the silver salt is in the range of 1: 100 to 100: 1, the concentration of the aqueous solution of the silver salt in the aqueous medium is from 0.1 mol / l to the saturated state. The invention can be implemented.

At a concentration lower than this, the complex is not sufficiently formed and the polyunsaturated fatty acids do not become soluble in the aqueous medium .

Taking into account the recovery of polyunsaturated fatty acids,
Desirably, the molar ratio is 1: 5 to 1: 1, and the concentration is 1 to 20 mol / l.

[0020] or complex formed by the above means so present in the aqueous medium phase, mechanically separating the aqueous medium phase and an oil phase,
By extracting the oil phase using an organic solvent and removing other fatty acids that do not form a complex, only the complex-containing portion can be separated from the reaction system. As the organic solvent in this case, it is preferable to use an organic solvent such as hexane and ether that can be separated from water.

The aqueous medium phase separated by this operation contains a silver salt-polyunsaturated fatty acid complex.

By subjecting the complex in the aqueous medium phase to dissociation means, polyunsaturated fatty acids can be released and the solubility in the aqueous medium can be reduced to recover it.

As a means for dissociating the complex, a method for dissociating the complex by adding a complex dissociating agent, in particular, a method for dissociating the complex by diluting it with water, or a method for dissociating the complex by reducing silver ions to silver, etc. is there.

[0024] These means will be described in detail below.

In the dissociation of the complex by the complex dissociating agent, the polyunsaturated fatty acids forming a complex with silver are replaced by the complex dissociating agent, and the complex dissociating agent forms a bond with silver ion to form a silver compound with silver. Is achieved by forming

As the complex dissociating agent, any compound having a strong action of dissociating the complex may be used. However, when listed separately by group, alcohols such as ethylene glycol, glycerin and diethylene glycol, 1,4-dioxane, tetrahydrofuran, Ethers such as crown ethers,
An oxygen-based compound having an oxygen atom containing a carbonyl compound such as acetone in a molecule and forming a bond with a silver ion.

Amine such as ammonia, isobutylamine, ethylenediamine, diethylamine, triethylamine, pyridine and piperidine; amides such as dimethylformamide and N-methylpyrrolidone; nitriles such as acetonitrile; nitrogen containing ammonium salts and amine salts. A nitrogen-based compound having an atom in a molecule, which forms a bond with a silver ion.

Sulfur compounds having a sulfur atom in the molecule including thiols such as 1,2-ethanedithiol, sulfides such as diphenyl sulfide and tetrahydrothiophene, sulfoxides such as dimethyl sulfoxide, and sulfones such as sulfolane. A compound which forms a bond with a silver ion.

Also, trivalent phosphorus compounds such as triphenylphosphine, pentavalent phosphorus compounds such as phosphoric acids such as trimethyl phosphate and hexamethylphosphoric triamide, arsenic compounds such as triphenylarsine, and phosphorus containing antimony compounds and the like. A phosphorus-based compound having a genus atom in the molecule and capable of bonding with silver ions.

Or ethylene, cyclohexene, 2-methyl-2-butene having an unsaturated bond capable of forming a complex,
Alkenes such as isoprene, alkynes, aromatic compounds, compounds serving as π-bonding ligands such as carbon monoxide, isocyanides, and nitric oxide.

Further, a compound or an ion which forms a silver ion and a silver compound which is hardly soluble in an aqueous medium or a compound which has an action of inhibiting the formation of a complex between a silver ion and a polyunsaturated fatty acid and sodium chloride which is an ion thereof , Halides such as sodium bromide, sulfates such as sodium sulfate, sulfites,
Nitrate, thiosulfate, carbonate such as sodium carbonate, carboxylate such as sodium acetate, sodium tartrate, thiocyanate such as ammonium thiocyanate, cyanide, azide such as sodium azide, permanganate And compounds of these acid types, hydroxide compounds such as sodium hydroxide, etc., which form bonds with silver ions.

A mixture of these compounds can be used, and the complex dissociating agent may have a plurality of sites for dissociating the above-mentioned complex in one molecule.

Dissociation of the complex by dilution of water occurs by adding water to the aqueous medium phase and diluting it, thereby releasing polyunsaturated fatty acids.

Although the amount of water to be diluted is not particularly limited as long as the dissociation of the complex occurs, it is usually necessary to use an equal amount or more, but preferably 10 to 40 times.

Alternatively, a method of reducing silver ions to silver, sodium borohydride, formaldehyde, Fe (II)-
The complex can also be dissociated using reduction with a reducing agent such as EDTA, hypophosphorous acid, Cu, ascorbic acid, reduction by electrolysis, reduction by light, or the like.

Considering the recycling of silver salt, the method based on dilution with water is advantageous.

The released polyunsaturated fatty acids are extracted with an organic solvent which can be separated from an aqueous medium such as hexane and ether,
The organic solvent phase which can be recovered and distributed can be washed with water and saturated saline to remove silver ions.

In the aqueous medium phase containing silver ions, the silver salt can be recovered and reused by distilling off the aqueous medium.

In the present invention, the purity of the polyunsaturated fatty acids can be further increased by repeating the above separation and purification operations.

The present invention first utilizes the complex forming ability of an aqueous medium- soluble silver salt capable of forming a complex with an unsaturated bond with a highly unsaturated fatty acid as described above, Water medium
By utilizing body solubility, it is possible to selectively separate a portion containing only polyunsaturated fatty acids, and thirdly, a fatty acid achieved by dissociating a complex and releasing polyunsaturated fatty acids. This is a method by which highly unsaturated fatty acids can be selectively extracted, separated and purified on an industrial scale from the contents of the compounds.

[0041]

According to the method of the present invention, unlike the conventional method, the operation and equipment are simple on a large scale at almost normal temperature, the operation is simple, and only the highly unsaturated fatty acids are selectively obtained from the fatty acid mixture at low cost. Can be extracted, separated and purified.

The method of the present invention can be applied to unrefined fish oil fatty acids and esters thereof, unrefined animal oil fatty acids and esters thereof, and can be applied to fish oil fatty acids and esters thereof, animal oil fatty acids and esters thereof purified by conventional methods. If applied, highly unsaturated polyunsaturated fatty acids and esters thereof with higher purity can be obtained.

[0043]

The present invention will be described in more detail with reference to examples.

In the examples, fatty acids and triglycerides
The fatty acid composition of the fatty acid ester was measured by gas chromatography after converting it to methyl ester.
And the composition of the aliphatic alcohol was also measured by gas chromatography.

[0045]

Example 1 139.6 g of silver nitrate was added to 100 g of a fatty acid mixture containing 60% of eicosapentaenoic acid, and 80 m of distilled water was used.
An aqueous solution dissolved in 1 was added under a nitrogen atmosphere while shielding light.
After stirring for 2 hours, the reaction solution was washed twice with 1 L of hexane.
2 L of distilled water was added to the obtained aqueous layer, and the mixture was stirred for 1 hour to release the fatty acid which formed the complex.

The released fatty acid was extracted twice with 1 L of hexane, and the obtained hexane layer was washed with distilled water and saturated saline,
Dried over magnesium sulfate.

After concentration under reduced pressure, 39.78 g of fatty acid was obtained.

As a result of examining the fatty acid composition, the purity of eicosapentaenoic acid was 96.0%.

Further , the obtained eicosapentaenoic acid having a purity of 96.0% was purified by the same operation as described above. As a result, eicosapentaenoic acid having a purity of 98.5% was obtained.

[0050]

Example 2 An aqueous solution obtained by dissolving 130.9 g of silver nitrate in 80 ml of distilled water was added to 101.1 g of a fatty acid mixture containing 54.0% of docosahexaenoic acid in a nitrogen atmosphere under light shielding and stirred for 2 hours. Treatment was conducted in the same manner as in Example 1 to obtain 43.52 g of a fatty acid.

As a result of examining the fatty acid composition, the purity of docosahexaenoic acid was 92.3%.

Further , the obtained docosahexaenoic acid having a purity of 92.3% was purified by the same operation as described above, and as a result, docosahexaneenoic acid having a purity of 96.4% was obtained.

[0053]

Example 3 Fatty Acid Mixture 1 Containing 53% Arachidonic Acid
An aqueous solution prepared by dissolving 142.1 g of silver nitrate in 80 ml of distilled water was added to 01 g of the mixture under a nitrogen atmosphere, and the mixture was stirred for 2 hours. The same treatment as in Example 1 was performed to obtain 30.05 g of a fatty acid.

As a result of examining the fatty acid composition, the purity of arachidonic acid was 95.2%.

Further , the obtained arachidonic acid having a purity of 95.2% was purified by the same operation as described above.
0% of arachidonic acid was obtained.

[0056]

Example 4 Eicosapentaenoic acid ethyl ester was converted to 6
1.012 g of a fatty acid ethyl ester mixture containing 2.1%
Then, an aqueous solution in which 1.688 g of silver nitrate was dissolved in 0.5 ml of distilled water was added under a nitrogen atmosphere under light shielding, followed by stirring for 2 hours.

The reaction solution was washed twice with 20 ml of hexane.

20 ml of distilled water was added to the obtained aqueous layer, and the mixture was stirred for 1 hour to release the fatty acid ethyl ester which formed the complex.

The liberated fatty acid ethyl ester was extracted twice with 20 ml of hexane, and the obtained hexane layer was distilled water,
The extract was washed with saturated saline and dried over magnesium sulfate.

After concentration under reduced pressure, 209.7 mg of fatty acid ethyl ester was obtained.

As a result of examining the composition of the fatty acid ethyl ester, the purity of the eicosapentaenoic acid ethyl ester was 9%.
8.0%.

[0062]

EXAMPLE 5 Docosahexaenoic acid ethyl ester was converted to 5
713.5 m of a fatty acid ethyl ester mixture containing 9.0%
An aqueous solution obtained by dissolving 1.6873 g of silver nitrate in 0.5 ml of distilled water was added to the resulting solution under a nitrogen atmosphere, and the mixture was stirred for 2 hours.

Processing is performed in the same manner as in the fourth embodiment.
1.4 mg of fatty acid ethyl ester were obtained.

As a result of examining the composition of the obtained fatty acid ethyl ester, the purity of docosahexaenoic acid ethyl ester was 97.0%.

[0065]

Example 6 52.5% of arachidonic acid ethyl ester
An aqueous solution in which 1.6781 g of silver nitrate was dissolved in 0.5 ml of distilled water was added to 630.2 mg of the fatty acid ethyl ester mixture containing the mixture under light shielding from light under a nitrogen atmosphere, and the mixture was stirred for 2 hours.

Processing is performed in the same manner as in the fourth embodiment.
0.3 mg of a purified fatty acid ethyl ester mixture was obtained.

As a result of examining the composition of the mixed fatty acid ethyl ester, the purity of arachidonic acid ethyl ester was 96.
It was raised to 3%.

[0068]

Example 7 An aqueous solution in which 1.0703 g of silver perchlorate was dissolved in 0.5 ml of distilled water was added to 670 mg of a fatty acid mixture containing 54.0% of docosahexaenoic acid in a nitrogen atmosphere under light shielding.

After stirring for 2 hours, the reaction solution was diluted with 20 ml of hexane.
And washed twice.

[0070] Distilled water (20 ml) was added to the obtained aqueous layer, and the mixture was stirred for 1 hour to release the complexed fatty acid.

The released fatty acid was extracted twice with 20 ml of hexane, and the obtained hexane layer was washed with distilled water and saturated saline and dried over magnesium sulfate.

The mixture was concentrated under reduced pressure to obtain 211.9 mg of a fatty acid.

As a result of examining the fatty acid composition, the purity of docosahexaenoic acid was 93.1%.

[0074]

Example 8 Pork liver oil obtained from pig liver by a conventional method was saponified to obtain pig liver oil free fatty acids.

The content of arachidonic acid was 14.3%.

1.058 g of this fatty acid was added to 0.5 parts of hexane.
An aqueous solution in which 1.128 g of silver perchlorate was dissolved in 0.5 ml of distilled water was added to the solution dissolved in ml under a nitrogen atmosphere while shielding light.

After stirring for 1 hour, the reaction solution was diluted with 20 ml of hexane.
And washed twice.

20 ml of distilled water was added to the obtained aqueous phase, and the mixture was stirred for 1 hour to release the complexed fatty acid.

The released fatty acid was extracted twice with 20 ml of hexane, and the obtained hexane layer was washed with distilled water and saturated saline and dried over magnesium sulfate.

The mixture was concentrated under reduced pressure to obtain 70.8 mg of a fatty acid. As a result of examining the fatty acid composition, the purity of arachidonic acid was 76.4%.

[0081]

Example 9 Linseed oil was saponified by a conventional method to obtain linseed oil free fatty acid.

It contained 55.8% of α-linolenic acid.

1.013 g of this fatty acid was added to 0.5 parts of hexane.
An aqueous solution in which 920 mg of silver perchlorate was dissolved in 0.5 ml of distilled water was added to the solution dissolved in 0.5 ml under a nitrogen atmosphere while shielding light.

After stirring for 1 hour, the reaction solution was diluted with 20 ml of hexane.
And washed twice.

20 ml of distilled water was added to the obtained aqueous phase, and the mixture was stirred for 1 hour to release the complexed fatty acid.

The released fatty acid was extracted twice with 20 ml of hexane, and the obtained hexane layer was washed with distilled water and saturated saline and dried over magnesium sulfate.

The mixture was concentrated under reduced pressure to obtain 150 mg of a fatty acid.

As a result of examining the fatty acid composition, the purity of α-linolenic acid was 98.2%.

[0089]

Example 10 A borage oil was saponified by a conventional method to obtain a borage oil free fatty acid.

[0090] 23.1% of γ-linolenic acid was contained.

1.037 g of this fatty acid was added to 0.5 parts of hexane.
An aqueous solution in which 809 mg of silver perchlorate was dissolved in 0.5 ml of distilled water was added to the solution dissolved in 0.5 ml under a nitrogen atmosphere while shielding light.

After stirring for 1 hour, the reaction solution was diluted with 20 ml of hexane.
And washed twice.

20 ml of distilled water was added to the obtained aqueous phase, and the mixture was stirred for 1 hour to release the complexed fatty acid.

[0094] The free fatty acids were extracted twice with hexane 20 ml, distillation and the resulting hexane layer water, washed with saturated brine and dried over sulfate Ma grayed Neshiumu.

Concentration under reduced pressure gave 59.7 mg of fatty acid.

As a result of examining the fatty acid composition, the purity of γ-linolenic acid was 93.4%.

[0097]

Example 11 Purified fish oil (triglyceride type, eicosapentaenoic acid 16.7%, docosahexaenoic acid 11.9)
An aqueous solution in which 853 mg of silver nitrate was dissolved in 0.5 ml of distilled water was added to 5.279 g of the solution under nitrogen atmosphere while shielding light.

After stirring for 1 hour, the reaction solution was diluted with 20 ml of hexane.
And washed twice.

To the obtained aqueous phase, 20 ml of distilled water was added, and the mixture was stirred for 1 hour to release triglyceride which formed a complex.

The released triglyceride was dissolved in hexane 20m
The resulting hexane layer was washed with distilled water and saturated saline and dried over magnesium sulfate.

[0101] and concentrated under reduced pressure, Toriguri of 85.8mg
I got celid .

As a result of examining the fatty acid composition, 38.5% of eicosapentaenoic acid and 24.0% of docosahexaenoic acid were obtained.
The purity was increased.

[0103]

Example 12 A solution prepared by dissolving 1.005 g of an aliphatic alcohol mixture containing 45% of docosahexaenol in 0.5 ml of hexane was mixed with 852 mg of silver nitrate in 0.5 ml of distilled water.
Was added under a nitrogen atmosphere while shielding light.

After stirring for 1 hour, the reaction solution was diluted with 20 ml of hexane.
And washed twice.

20 ml of distilled water was added to the obtained aqueous phase, and the mixture was stirred for 1 hour to release the aliphatic alcohol which formed the complex.

The liberated aliphatic alcohol was converted to hexane 20
The mixture was extracted twice with ml, and the obtained hexane layer was washed with distilled water and saturated saline, and dried over magnesium sulfate.

The mixture was concentrated under reduced pressure to obtain 145 mg of an aliphatic alcohol.

As a result of examining the composition, docosahexaenol had a purity of 98.5%.

[0109]

Example 13 To a solution in which 1.003 g of a fatty acid mixture containing 60% eicosapentaenoic acid was dissolved in 0.5 ml of hexane, an aqueous solution in which 847.2 mg of silver nitrate was dissolved in 0.5 ml of distilled water was added under a nitrogen atmosphere while protecting from light. Was.

After stirring for 2 hours, the reaction solution was diluted with 20 ml of hexane.
And washed twice.

To the obtained aqueous phase, 20 ml of ethylene glycol was added as a complex dissociating agent, and the mixture was stirred for 1 hour to release the fatty acid which formed the complex.

The liberated fatty acid was extracted twice with 20 ml of hexane, and the obtained hexane phase was washed with distilled water and saturated saline and dried over magnesium sulfate.

The mixture was concentrated under reduced pressure to obtain 133.8 mg of fatty acid.

As a result of examining the fatty acid composition, the purity of eicosapentaenoic acid was 94.4%.

[0115]

Example 14 To a solution of 1.010 g of a fatty acid mixture containing 60% of eicosapentaenoic acid in 0.5 ml of hexane, an aqueous solution of 845.2 mg of silver nitrate dissolved in 0.5 ml of distilled water was added under a nitrogen atmosphere while protecting from light. Was.

After stirring for 2 hours, the reaction solution was diluted with 20 ml of hexane.
And washed twice.

To the obtained aqueous phase, 1.05 g of sodium chloride as a complex dissociating agent was added, and the mixture was stirred for 1 hour to release a fatty acid which formed a complex.

The liberated fatty acid was extracted twice with 20 ml of hexane, and the obtained hexane phase was washed with distilled water and saturated saline, and dried over magnesium sulfate.

The mixture was concentrated under reduced pressure to obtain 150.6 mg of a fatty acid.

As a result of examining the fatty acid composition, the purity of eicosapentaenoic acid was 93.1%.

[0121]

Examples 15 to 49 As a complex dissociating agent, various compounds forming a hardly soluble bond between silver and water were tested, and the results are shown in Table 1 in terms of the purity of the polyunsaturated fatty acids. Was.

[0122] All the raw experimental conditions, about fatty acid mixtures containing eicosapentaenoic acid in Example 1 60% 1 g
Or eicosapentaenoic acid ethyl ester of Example 4
And about 1 g of a fatty acid ethyl ester mixture containing 62.1% of eicosapentaenoic acid using the dissociating agent shown in Table 1 and Example 4 for eicosapentaenoic acid and Example 4 for the ethyl ester thereof. Almost the same operation was performed for each.

[0123]

[Table 1] Table 1

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C07C 57/12 C07C 57/12 67/60 67/60 69/587 69/587 C11C 1/08 C11C 1/08 (72) Invention Masahiro Hayashi 5-9-3 Tokodai, Tsukuba City, Ibaraki Prefecture, Tsukuba Research Laboratory (72) Inventor Daisuke Sugimori 5-9-3 Tokodai, Tsukuba City, Ibaraki Prefecture Tsukuba Research Laboratory (56) ) References JP-A-54-84519 (JP, A) Food Technology (1986) Vol. 21 p. 463-469 (58) Fields investigated (Int.Cl. ⁶ , DB name) C11B 7/00 C11C 1/08 C07C 51/487 C07C 57/03 C07C 57/12 C07C 29/88 C07C 33/02 C07C 67 / 60 C07C 69/587

Claims (9)

(57) [Claims] 1. A polyunsaturated fatty acid having 18 to 22 carbon atoms having 3 to 6 carbon-carbon double bonds, an ester derivative thereof or an aliphatic alcohol, and a silver salt concentrate.
An aqueous medium containing a silver salt having a degree of 0.1 mol / l or more is brought into contact with a carbon medium having 3 to 6 carbon-carbon double bonds and having 18 to 18 carbon atoms.
22 to form a complex of silver with a polyunsaturated fatty acid or an ester derivative thereof or an aliphatic alcohol, and then removing the oil phase from the aqueous phase, and then subjecting the aqueous phase to a means for dissociating the complex to obtain carbon-carbon A method for selectively obtaining polyunsaturated fatty acids having 18 to 22 carbon atoms having 3 to 6 double bonds, ester derivatives thereof, or aliphatic alcohols, the method comprising obtaining an aliphatic alcohol. 2. The method according to claim 1, wherein the concentration of the silver salt in the aqueous medium is 1 mol / l or more. 3. The silver salt concentration in an aqueous medium is 7.8 mol / mol.
The method of claim 1 wherein the water is 1 kg or more. 4. The method according to claim 1 , wherein the means for dissociating the complex is the addition of a complex dissociating agent. 5. The method of claim 1 , wherein the means for dissociating the complex is diluting by adding water. 6. The complex dissociating agent is an oxygen-based compound containing alcohols, ethers or carbonyls, a nitrogen-based compound containing amines, amine salts, ammonium salts, amides or nitriles, or a sulfoxide or sulfone. Compounds containing thiols, thiols or sulfides, or phosphorus compounds containing trivalent or pentavalent phosphorus compounds, arsenic compounds or antimony compounds, which form a bond with silver, or functional groups of these compounds 5. The method according to claim 4 , wherein the compound is a compound having a complex of: or a mixture thereof. 7. The method according to claim 4 , wherein the complex dissociating agent is a compound or an ion that forms a silver ion and a silver compound that is hardly soluble in an aqueous medium. 8. The method according to claim 4 , wherein the complex dissociating agent is a compound having an unsaturated bond capable of forming a complex. 9. The method of claim 1, wherein the means for dissociating the complex is a means of reducing silver ions into silver.