JPS59118740A - Preparation of eicosapentaenoic acid or its lower alcohol ester - Google Patents

Abstract

PURPOSE:To prepare the titled compound in high purity and large amount, at a low cost, by carrying out the alcoholysis and urea addition treatment of saponified oil of aquatic animal, distilling the lower alcohol ester of the fatty acid obtained as the non-urea adduct in vacuum, and separating by using two kinds of solvents. CONSTITUTION:The saponified product of the oil of an aquatic animal such as sardine is esterified with a lower alcohol in the presence of an acid catalyst, and subjected to the urea addition treatment, or the aquatic animal oil is subjected to the alcoholysis with a lower alcohol in the presence of an alkali catalyst. The lower alcohol ester of fatty acid obtained by the urea adduct treatment is distilled in vacuum to collect the fraction containing >=50% of eicosapentaenoic acid lower alcohol ester and <=4% of docosahexanoic acid lower alcohol ester. The fraction is optionally saponified, and treated with a hydrocarbon solvent and an organic solvent immiscible with the hydrocarbon solvent. The objective compound expected to have preventive and remedying effect to thrombosis can be separated from the layer of the latter solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing highly purified eicosapentaenoic acid or its lower alcohol ester from aquatic animal oil on an industrial scale.

Diseases that have a high mortality rate in our country include stroke and heart disease.

In a broad sense, stroke and heart disease are brain and heart diseases originating from arteriosclerosis. Strokes and myocardial infarctions caused by cerebral thrombosis and cerebral infarction are directly caused by blood clots generated in the blood.

Traditionally, the formation of blood clots was thought to be closely related to blood cholesterol levels, but in recent years it has become clear that thrombotic diseases such as myocardial infarction, cerebral thrombosis, and cerebral infarction are less common in areas where people eat a lot of fish. .

One reason for this is that arachidonic acid produces thromboxane A2, which has platelet aggregation and vasoconstriction effects through cyclooxidase in the blood plate, and prostacyclin II, which has platelet aggregation and arterial contraction inhibitory effects in the arterial wall. It is said that this partner is A in balance, but thromboxane A3 from eicosapene citric acid has no platelet aggregation effect on platelets but has an arterial contraction effect, but on arterial walls, thromboxane A3 inhibits platelet aggregation. Prostacyclin ■3, which has an arterial relaxing effect, is produced, so if you eat a lot of fish oil containing a large amount of eicosapentaenoic acid, you will end up creating a state in which there is a lot of thromboxane A3 and prostacyclin ■, which inhibits platelet aggregation. Think about it.

It's a bastard.

In order to concentrate only citric acid, a fatty acid or a fatty acid ester is obtained by saponification or alcoholysis of aquatic animal oil. It is known in the prior art that this is carried out by appropriately combining the sogaium soap acetone method, the wintering method, the urea addition method, the molecular distillation method, and the silver ion chromatography method (-1
h is there. However, marine animal oils contain large amounts of long-chain polyunsaturated fatty acids of various types (e.g.
Published by Himaruzen Co., Ltd., edited by Japan Oil Chemists' Association, "Oil Chemistry Handbook", pages 1/1 to 1-1. [See page] Therefore, it is difficult to selectively purify eicosapene citric acid or its Q) ester σ) to a high degree of purity.

For example, the medium soap acetone method, urea addition method, and molecular distillation method, which can process large quantities as industrial production methods, can only concentrate the ester of eicosapene citrate to about 3S level when used alone.

Even if these methods are appropriately combined, eicosapentaenoic acid or its ester can only be concentrated to about 70% r.

On the other hand, a silver nitrate-impregnated silicate column chromatography method (JP-A-Sho Sη-ggs) has been disclosed as an effective method for obtaining high purity eicosapentaenoic acid or its ester.
The silver nitrate-impregnated silicate column used in the silicic acid column used can be regenerated (and the flow rate is QmA per minute, so it is not suitable for large-scale operations (it is difficult to reuse because the organic solvents used mix). It is.

In addition, CG-, --g of JP-A-Sho S Otsu-//37.3 Otsu No.
The reversed-phase partition column chromatography method in which the alkyl group of is chemically bonded to silica gel requires special equipment such as a high-performance liquid chromatography device, so it is not suitable for large-scale operation.

Against this background of the technical situation, the present inventor has conducted intensive research on a method for obtaining eicosapentaenoic acid or its lower alcohol ester in large quantities at low cost with high purity, and has finally completed the present invention. It was.

That is, the present invention is a non-urea adduct obtained by esterifying a saponified product of aquatic animal oil with a lower alcohol in the presence of an acid catalyst, followed by a urea addition treatment, or a lower alcohol ester of a fatty acid, or an aquatic animal oil. After urea addition treatment of the saponified product, this non-urea adduct is esterified with a lower alcohol in the presence of an acid catalyst. After alcoholysis with a lower alcohol, the lower alcohol ester of a fatty acid, which is a non-urea adduct obtained by the urea addition treatment, is vacuum rectified, and if the lower alcohol ester of eicosapencitric acid is 5 oair or more, the lower alcohol ester of docosahexaenoic acid is obtained. A fraction containing less alcohol ester (both 44 or less) is collected, and this fraction, either as it is or after saponification, is treated with both a hydrocarbon-based organic solvent and an organic solvent mixed with this to produce a hydrocarbon-based organic solvent. A method for producing eicosapentaenoic acid or its lower alcohol ester, which is characterized by collecting eicosapentaenoic acid or its lower alcohol ester from a mixed organic solvent layer, the purpose of which is to treat thrombotic diseases as a pharmaceutical. An object of the present invention is to provide a method for obtaining VrC at high purity and in large quantities from eicosapentaenoic acid or its lower alcohol ester, which is expected to have preventive and therapeutic effects.

Hereinafter, the present invention will be explained in detail in 1 (IIvC).

In the present invention, the aquatic animal oil used as a raw material can be any aquatic animal oil containing eicosapentaenoic acid. Specific examples of such marine animal oils include molluscs such as squid and octopus, sardines, cod, herring, and saury.

Examples include aquatic animal oils collected by conventional methods from fish such as mackerel, and crustaceans such as krill, shrimp, and crabs. However, in order to obtain eicosapentaenoic acid and its lower alcohol esters industrially, it is best to use oils collected from aquatic animals that have large catches (and high eicosapentaenoic acid content, such as sardines, cod, and squid). It's advantageous.

Saponification of these aquatic animal oils can be carried out by any method, but enzymatic methods and alkaline methods can be advantageously used.

The enzymatic method is carried out, for example, by adding a water bath solution in which lipase powder is dissolved in aquatic animal oil, stirring at high speed, and then allowing the mixture to stand still for at least 43 hours while maintaining the temperature at 30C. Thereafter, if the mixed liquid is heated to 70'Q or more, saponified product C fatty acid) can be obtained.

The alkaline method can be carried out using alkaline water or alkaline alcohol solution. When using alkaline water, add alkaline water (e.g., an aqueous solution of caustic soda, caustic potash, soda carbonate, etc.) with a saponification value of at least one time that of aquatic animal oil, and after stirring for several hours. , cooled and neutralized with acid to form saponified products (fatty acids)
is obtained. When using an alkaline alcohol solution, disperse or dissolve the aquatic animal oil in alcohol (e.g. methanol, ethanol, impropateur, etc.) that is three times or more stronger than the aquatic animal oil, and then add concentrated alkaline water (caustic soda, caustic potash, soda carbonate, etc.) to the aquatic animal oil. Add an aqueous solution of
Stir at room temperature for 3 hours. Next, by acidifying with sulfuric acid water and reducing the alcohol content to below SO4, a saponified fatty acid can be obtained. The amount of alkali at this time is the saponification value of SO
Excessive amount is sufficient.

As described above, after saponifying aquatic animal oil and esterifying the saponified product C fatty acid] with a lower alcohol in the presence of an acid catalyst, this lower alcohol ester is subjected to urea addition treatment to obtain a non-urea adduct of the lower alcohol of the fatty acid. To obtain an ester, or after subjecting the saponified product (fatty acid) to a urea addition treatment, this non-urea adduct is esterified with a lower alcohol in the presence of an acid catalyst to obtain a lower alcohol ester of a fatty acid, which is a non-urea adduct. Le.

In the above esterification reaction, the saponified product (fatty acid) or a non-urea adduct obtained by adding urea to the saponified product (fatty acid) is mixed with a lower alcohol in the presence of an acid catalyst such as sulfuric acid, sulfonic acid, etc. This can be done by heating at /20C for 7 to 2 hours.

Lower alcohols include alcohols with a carbon number of q or less;
For example, evaporated methanol, ethanol, infropanol, propatool, inbutanol, butanol, etc. can be used, but methanol and ethanol are preferably used. -f, the lower alcohol is the saponified product (
It is preferable that the amount of the acid catalyst is 106 L or more, which is at least 3 times the amount of fat e) or the non-urea adduct obtained by subjecting it to urea addition treatment.

Further, the urea addition treatment of the saponified product (fatty acid) or its lower alcohol ester can be carried out according to a conventional method.For example, the saponified product (fatty acid) is added to a solution of a lower alcohol (such as methanol or ethanol) to which urea has been added. ) or its lower alcohol ester and mix to form urea adduct crystals. In this case,
The usage ratio of the saponified product (fatty acid) or its lower alcohol ester, urea, and lower alcohol is in weight ratio:
2:! ;~l:y:2 is advantageous from an industrial standpoint. In order to make the urea addition treatment work effectively, it is best to add urea to lower alcohol and heat it to SO~6o'6, then drop the saponified oyster (fatty acid) or its lower alcohol ester and cool it. Although it is advantageous to lower the cooling temperature at this time, a temperature of about 1.20C is sufficient.

After the above-mentioned urea addition treatment, the crystals of the urea adduct are separated by, for example, f-filtration, and the urea is added and licked to obtain a saponified product (fatty acid) or its lower alcohol ester, which is a non-urea adduct. The saponified product (fatty acid), which is a urea adduct, is esterified into a lower alcohol ester of a fatty acid, which is a non-urea adduct, as described above.

7
．． ,”.

It can also be obtained by alcohol rinsing the raw material aquatic animal oil with a lower alcohol in the presence of an alkaline catalyst and then subjecting it to urea addition treatment.

This alcohol rinsing can also be carried out according to the usual method, for example using an alkaline solution such as caustic soda or caustic potash.
．． This can be done by adding at least 3 times as much of the lower alcohol contained on the base plate to aquatic animal oil and stirring at 20 to 20°C for 7 to 1 hour. In this case, the lower alcohol used is an alcohol having q or less carbon atoms, such as methanol 1, :11-J/-#, imbutanol, propatool, imbutanol, and butanol.

After completion of this alcoholysis, the reaction mixture is neutralized with a lower alcohol containing an acid, and the lower alcohol is recovered by distillation (for example, vacuum distillation) to obtain a lower alcohol ester of a fatty acid as a residue.

Note that the generated glycerin and neutral salts are removed by washing this residue with water.

The lower alcohol ester of fatty acid obtained by alcoholysis of aquatic animal oil in this manner is subjected to urea addition treatment to obtain a lower alcohol ester of fatty acid which is a non-urea adduct. The urea addition treatment can be carried out in the same manner as the urea addition treatment of the saponified product (fatty acid) or its lower alcohol ester described above.

Second, the lower alcohol ester of fatty acid, which is a non-urea adduct, obtained as described above was vacuum rectified to obtain 30% lower alcohol ester (hereinafter referred to as EPE) of eicosapentaenoic acid (hereinafter referred to as EPA). In the above, lower alcohol ester (hereinafter referred to as DHE) of docosahexaenoic acid C or below (hereinafter referred to as DHA) is small (4% in total).
Collect the following fractions.

Vacuum rectification has good gas-liquid contact (filling with small pressure loss,
For example, it is preferable to carry out the process under a vacuum of Q-1 to 0,00/Torr using a rectification apparatus equipped with a rectification column filled with a full-mesh McMahon, Dixon, Sigma backing, etc. or a wire Helipak, Helix, etc. . Since the low alcohol ester of fatty acid, which is a non-urea adduct obtained as described above, contains a large amount of lower alcohol ester of highly unsaturated fatty acid, it is preferable to use it under as high a vacuum as possible, but from an industrial standpoint, 0-/~0.0/Torr is sufficient. For example, if the pressure inside the rectification column is 0. In Ol Thor, go~
At 12 o C, o, i torr, an effluent temperature of /20 to igoc is a preferred temperature for fractionating EPA methyl ester, ethyl ester, etc.

When the lower alcohol ester of fatty acid, which is a non-urea adduct obtained as above, is vacuum rectified as above, E
It is possible to obtain a fraction in which the PE content can be concentrated to so-gotx and the DHE content is below the η coefficient. On the other hand, when lower alcohol esters of aquatic animal oils are directly vacuum rectified without urea addition treatment, EPE is 5 ot.
A fraction is obtained in which the DHE content does not reach s and the DHE content is in accordance with the IO equation. Furthermore, the vacuum rectification time is long (eggplant, decomposition products and polymerization products may be observed).

In fact, the EPE obtained by the vacuum rectification described above is combined with SO and a fraction in which DHE is at least as high as 100% is removed.

Highly purified EPA or EPE is obtained from the organic solvent layer that does not mix with carbonization, either as it is or by saponifying it.

The above-mentioned fraction can be saponified according to a conventional method, and EPE becomes EPA through this saponification.

The hydrocarbon organic solvent used in the above liquid-liquid extraction and Shiteha,
Examples include hydrocarbon organic solvents having a carbon number of s-g such as evapentane, hexane, cyclohexane, heptane, and octane. For liquid-liquid extraction, the above-mentioned fraction is dissolved in a hydrocarbon-based organic solvent, and the residue is mixed with the VC hydrocarbon-based organic solvent, and an organic solvent is added to EPA or EP.
E can be extracted (also, impurities mixed in the EPA or EPE fraction can be extracted by adding a hydrocarbon-based organic solvent to a solution of the above fraction in an organic solvent without mixing it with a hydrocarbon-based organic solvent). Good too.

In the case of Isuri, the organic solvent is divided into two layers: the hydrocarbon organic solvent is in the upper layer, and the organic solvent that does not mix with the hydrocarbon organic solvent is in the lower layer. EPAf or EPE is extracted and pure EPA or EPE is obtained by separating this layer and removing the organic solvent.
Get PE.

In addition, the hydrocarbon-based organic solvent and the organic solvent that does not mix with it can be used in the range of /:/-i:s and b can be used in the range of l:l to 5, but the preferred ratio of r is /, / to l: There are 2 b
is l:l-λ:/.

The above fraction and organic solvent can be operated in the range of 100 to 100, but the preferred theoretical ratio is 0.
~l:100. Furthermore, the extraction temperature may be room temperature.

(Thus, according to the present invention, it is possible to obtain high-purity EPA or EPE with a lower content of DMA or DHE than the width plate.The process according to the present invention is always carried out in an inert gas atmosphere to eliminate the oil content. It is preferable to try to prevent deterioration such as oxidation and polymerization.

Next, examples of the present invention will be shown, but the present invention is not limited thereto. In the examples, analysis was performed by gas chromatography under the following analysis conditions, and the content was expressed in area percentage.

Gas chromatography analysis conditions Liquid phase Diethylene glycol succinate (DE
GS) lo% carrier Unipot KA (
(manufactured by Gas Chrom Industry) 60~gOme 7g column 3
1φ×2m Stainless steel column Column temperature Yu15
C Detector Flame ion detector (F, ID-) Example 1 Sardine oil 3 sand (saponification value 7
90] and Metanol 9k, and while stirring, introduce nitrogen gas and add alkaline water (caustic potassium 0.2 to 1 to O2).
(dissolved in water) was added dropwise over 30 minutes. After dropping the entire amount of alkaline water, the mixture was stirred for S hours at -30'Q. Then, add 70 ml of sulfuric acid water to make the pH acidic to below 17.
In step b, water was added until saponified products (fatty acids) floated to the surface.

Separate the lower methanol layer and add methanol containing sulfuric acid of 7, 0! was added and refluxed for 15 minutes, then allowed to stand still.

Separate the methanol in the lower layer containing sulfuric acid water, and add 3.0 methanol containing 10% sulfuric acid to this! was added and refluxed for one hour, and then washed with water to remove the contained sulfuric acid and methanol, resulting in pale reddish brown methyl ester, 13.9 liters of methyl ester, and 10 liters of methyl ester of DHA.
．． 3"lr) was obtained.

SOk stainless steel crystal can with 30 methanol!
After adding r-gKy of urea, the crystal can was heated to SOC while stirring and introducing nitrogen. Next, the methyl ester prepared as above was added dropwise over 60 minutes, and the crystal can was heated to 200 After gradually cooling to
and a non-urea adduct (Liquid F).

This non-urea adduct CP liquid) was continuously charged into a rotary evaporator equipped with a 3-o, B eggplant-shaped flask to distill off methanol, and the distillation residue was acidified with dilute sulfuric acid water. The mixture was transferred to a separatory funnel at θ and washed with water. (then the non-urea adduct /, /2i (P(methyl ester of EPA: 2.5 k, methyl ester of DHA: lo +, /
eL)% obtained.

This non-urea adduct was placed in a glass distillation vessel with a diameter of 07R+, and a rectification column (diameter s 07R+, height) filled with McMahon wire mesh (' / 0 stone, Otsu 0 mesh).
+ ) and 0. Onor 0. Precision fractionation was carried out in a vacuum range of 1 Torr, and the results shown in Table 1 were obtained.

10 pieces of the No. 1 royal fraction were put into a mixture of 10,100 O each of n-hegisan and methanol, and after shaking, the lower methanol layer was separated, and when the methanol was distilled off, the methyl EPA Contains ester, N7g, q, DH
A pale yellow electric oil η, l of A with a methyl ester content of +− was obtained.

Example 2 Soo, B stainless steel reaction can was sufficiently purged with nitrogen gas (0) Cod oil 309. and caustic soda/
Add methanol 100Z in which IIy was dissolved, and boil for 30~
Stirred at 1OC for 3 hours. Next, methanol containing sulfuric acid was added dropwise to make the solution in the reaction can from neutral to slightly acidic, and then the reaction can was heated under vacuum (0 to 0 torr) VtCL to distill off the methanol.

After introducing nitrogen into the reaction can and returning the pressure inside the can to atmospheric pressure, 30. When the glycerin and neutral salts produced in step 1) are washed away with water 4 times, a light reddish brown methyl ester mixture is obtained. 5-srs
Met.

After adding methanol from vCsiop and urea from OEy to a 5ooB stainless steel cracked crystal can, the inside of the can was filled with nitrogen gas. Heat the crystal can to SOC, and when the urea is dissolved, add 2 g of the above methyl ester mixture! 9 was added dropwise to the solution, and then the crystallizer was slowly cooled and subjected to 20'QVC.

After separating the generated urea adduct (crystals) with P, the f liquid was vacuumed (J
Methanol was recovered by heating distillation under 0 to 0 torr). After introducing nitrogen into the distillation can and bringing the pressure inside the can to atmospheric pressure, the mixture of dilute sulfuric acid and methyl ester, which is a non-urea additive, was made acidic, and then washed with /S and IQ water three times. did. Smelling gave a pale reddish brown oil 12-9, which contained methyl ester of EPA, I9+5%, DHA.
It contained 7% of the methyl ester of

This light reddish brown oil, :j-3Ky is S! A rectification column (diameter 30mm, height SOOmm) filled with McMahon wire mesh (/0","' mesh) was placed in a glass container of 0.
．． 0/~0. Precision fractionation was carried out in a vacuum range of 1 Torr, and the results shown in Table 2 were obtained.

Main fraction No. obtained as above, μ / 00iV-
was dissolved in n-hebutane 70k, and acetonitrile sp was added thereto for liquid-liquid extraction, and the upper n-hebutane layer and the lower acetonitrile layer were separated from one layer of the IJ layer. The layer was freed from acetonitrile and concentrated under vacuum (/˜η0 torr). In this 7th extraction: Extract 11. -1y-(methyl ester of EPA g<
z sound) was obtained. Acetonitrile 5A is added again to the n-hebutane layer from which the acetonitrile layer has been separated, liquid-liquid extraction is carried out, and the lower acetonitrile layer is separated from the two layers, the upper n-hebutane layer and the lower acetonitrile layer, and the lower acetonitrile layer is separated from this layer by vacuum ( l
The acetonitrile was removed and the mixture was concentrated under 0 to 0 torr.

This first extraction yields an extract of 23. p(methyl ester of EpA ffu,/%). The following is the third extract obtained by liquid-liquid extraction in the same manner. y-(methyl ester of EPA go.9), in the second extraction the extract s y-(
Methyl nisdel of EPA 2g, 2%), extracted in the Sth extraction 7tt of methyl ester of EPA, 3
width] was obtained.

The extracts were combined, and after gf was dissolved in n-hebutane Vrc@, gL of acetonyl) was added thereto for liquid-liquid extraction. Then, the acetonitrile layer is separated, and the acetonitrile is removed from this layer under vacuum (l-η0 torr) to obtain the extract s/, g? (methyl ester of EPA, gg, /).
This was again diluted with sfa'rn-heptane, VC acetonitrile j-A was added thereto, shaken for liquid-liquid extraction, the acetonitrile layer was separated, and this layer was extracted under vacuum (/- 23-g of EPA methyl ester with a purity of 2%/% was obtained by removing the acetonyl (IJ) with 110 torr).
It was 2'4.

Example 3 300! Thoroughly replace the stainless steel reaction can with nitrogen gas (0) Add sardine oil (saponification value 0,!r) to this reaction can
, j) / 0 Add methanol to 30 and then add caustic powder to 3, ? Alkaline water bathed in water A was added dropwise. ,? After stirring for t hours at 0~a□C,
After making it acidic by adding 10% sulfuric acid water, 30 times 7 times! of water until the washing waste liquid became neutral.

9. Smells like pale reddish brown fatty acid mixture. -I got it.

The composition of this product is EPA//-/, DHA/,
? ,,? He was in charge.

Soo, B The mixture was stirred for S hours in Meta C of a stainless steel crystal canister vcioop. After separating the generated urea adduct (crystals) with F, the P solution was heated and distilled under vacuum (0 to 0 Torr) to remove methanol. After returning to atmospheric pressure, the fatty acid mixture was made aqueous with dilute sulfuric acid water and washed five times with water with an IQ of 71.
/, g4, DHlrg-.

I got a person in charge.

30! The above-mentioned light reddish brown oil J and Oq were put into a glass reactor, and ethanol was added to dissolve the sulfuric acid of /gO, and the reaction solution was cooled to 300 ml. Add this reaction solution 7 times to 10,1
) with water until the cleaning waste liquid becomes neutral, J, 311y
The ethyl ester of was obtained. 3.0 seconds of this ester was vacuum rectified using the same rectifier as described in Example 2VC. The results are shown in Table 3.

Main fraction No. obtained as above, <' / Og-
(EPA ethyl ester ester 1.3) was dissolved in n-hebutane/A, and acetonide 1N/A was added thereto for liquid-liquid extraction. From the upper n-hebutane layer and the lower acetonitrile layer, the lower acetonitrile layer is separated and the acetonyl layer is removed from this layer by vacuum (~30 torr) and concentrated to determine the purity. 9:1. ,? 96 EPA ethyl ester 1z,7P? 41. :.

Example 4 Among the main fractions No. and 2 obtained by vacuum rectification in Example 3, fraction U01 distilled at 7g3~/J5C was mixed with methanol OmA and caustic soda SNo.
of alkaline water and saponified in a nitrogen gas atmosphere at -θ to 30C for S hours. Next, add this to 70% sulfuric acid solution
When acidified with mt and extracted with n-hexane somb, a pale yellow fatty acid/g. llノ( EPA7 i
- Section 0, Di-IA Yu. 6) was obtained.

This fatty acid ion is n-hebutane-27VC! I understand.

Next, acetonate (IJ) was added to this and liquid-liquid extraction was performed. After separating the lower acetonitrile layer from the upper n-hebutane layer and the lower acetonitrile layer, the n-hebutane λ! was added for liquid-liquid extraction. The lower acetonitrile layer is separated from the upper n-hebutane layer and the lower acetonitrile layer, and the acetonitrile is distilled off from the lower acetonitrile layer under a vacuum of 7 to 30 torr, resulting in EPA with a purity of 9. +, got 7 no.

Example 5 Royal fraction No. 4' obtained by vacuum rectification in Example 1 ii. g
The mixture was bathed in n-heptane i'ooomb, and then furfural 1000116 was added and after shaking, the lower furfural layer was separated. Tafurfural was distilled off from this layer under reduced pressure to obtain a pale reddish-yellow oil of 2.7y-. The EPA methyl ester content of this product is 9I1. , 9th Section, DH
The methyl ester content of A was 3.0.

Claims (1)

[Claims] The saponified product of aquatic animal oil is esterified with a lower alcohol in the presence of an acid catalyst, and then subjected to urea addition treatment to obtain a lower alcohol ester of a fatty acid, which is a non-urea adduct, or the saponified product of aquatic animal oil is subjected to urea addition treatment. This non-urea adduct is then varnished with a lower alcohol in the presence of an acid catalyst. Lower alcohol esters of fatty acids, which are chilled non-urea adducts, or lower alcohols of fatty acids, which are non-urea adducts, obtained by alcoholyzing aquatic animal oil with lower alcohols in the presence of an alkali catalyst, followed by urea addition treatment. The ester is vacuum rectified to collect a fraction containing 5 Oqb or more of lower alcohol ester of eicosapentaenoic acid, at least tt of lower alcohol ester of docosahexaenoic acid, and 4 or less, and this fraction is used as it is or after saponification to produce hydrocarbons f) Eicosapentaenoic acid or its lower alcohol ester is collected by treating with both a hydrocarbon-based organic solvent and an organic solvent that is immiscible with the organic solvent. A method for producing an acid or its lower alcohol ester.