JPH0813776B2 - Method for separating and purifying docosahexaenoic acid compound - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for separating and purifying a highly unsaturated fatty acid compound based on the difference in affinity between the unsaturated fatty acid compound and a cation-exchanged swelling clay mineral. More specifically, it relates to a method for separating and purifying a docosahexaenoic acid compound using a clay mineral in which interlayer ions of a swelling clay mineral are substantially replaced by cations other than sodium ions.

[Prior Art] Today, one of the so-called typical adult diseases such as arteriosclerotic disease, thrombotic disease, hyperlipidemia, obesity, hypertension and diabetes is caused by normal disturbance of lipid metabolism. However, some have been proposed as therapeutic or preventive agents for these. However, it is difficult to say that all of them are sufficiently satisfactory in terms of pharmacological effects and side effects, and there is an increasing demand for safer and more effective drugs.

Recently, among unsaturated fatty acids, docosahexaenoic acid (C
_{22: 6} , hereinafter abbreviated as DHA), has been found to be effective for various diseases such as its safety and arteriosclerosis obliterans, and is drawing attention.

DHA is a kind of polyunsaturated fatty acid generally contained in fish oil and the like, and is an important substance as a precursor of prostaglandins.

However, drugs, foods,
It is hard to say that feed etc. is still fully utilized. In addition, in recent years, with the progress of research, DHA is important in the infancy when DHA biosynthesis is low in addition to the above-mentioned pharmacological effects, and DHA is abundant in nerve cells and retina, and it is deep in maintaining cell functions involved in these. It has been revealed that the involvement, the ability to improve memory capacity in the brain and the possibility of preventing blurring, and the strongest anti-cancer effect among the polyunsaturated fatty acids, are being revealed one after another. The importance is being recognized. (Oil Chemistry, 37 (10), 781, 1988) On the other hand, in order to use DHA as a drug, it is necessary to separate and purify at least 90% or more of purity from a fatty acid mixture containing DHA.

Conventional methods for separating and purifying highly unsaturated fatty acid compounds from a fatty acid mixture are 1) molecular distillation, 2) urea addition, 3)
Liquid chromatography, 4) supercritical gas extraction, and 5) zeolite method are known.

[Problems to be Solved by the Invention] Problems of Prior Art However, these conventional separation and purification methods have problems to be solved in terms of purity, recovery rate, cost, etc. It is difficult to obtain a highly pure unsaturated fatty acid compound at a low cost by a simple process.

OBJECTS OF THE INVENTION Therefore, the present inventors have found that high concentrations of DHA compounds, namely DHA
As a result of intensive studies on a method for efficiently separating and / or purifying its ester, and / or its ester, a high concentration of DH was obtained by adsorbing / desorbing a fatty acid mixture using a specific clay mineral.
The present invention has been completed by finding that the compound A can be easily obtained.

An object of the present invention is to provide a more effective and highly safe method for separating and purifying a DHA compound in a large amount at low cost.

[Means for Solving the Problems] That is, the present invention provides a DHA compound from a fatty acid mixture by using a clay mineral in which interlayer ions of a swelling clay mineral are substantially replaced by cations other than sodium ions. It is a method of separation and purification.

 The configuration of the present invention will be described below.

The method of the present invention comprises the steps of 1) contacting a fatty acid mixture with a clay mineral to adsorb the DHA mixture, and 2) removing the DHA mixture from the clay mineral.

The fatty acid mixture used in the present invention means a mixture of fatty acids, a mixture of fatty acid esters optionally esterified with a fatty acid, or a mixture of fatty acids and fatty acid esters. Separation is generally easier and more efficient with a mixture of fatty acid esters than with a mixture of fatty acids alone.

Examples of the alcohol used for esterifying the fatty acid mixture include lower alcohols such as methanol, ethanol, propanol and butanol, and polyhydric alcohols such as glycol and glycerin. The fatty acid mixture and alcohol are esterified by a conventional method in the presence of a catalyst.

The swollen clay mineral used in the present invention is a layered silicate mineral belonging to the smectite genus, montmorillonite,
They are beidellite, nontronite, saponite, hectorite, and the like, which may be natural or synthetic.
Specifically, Kunipia, Smecton (Kunimine Industry),
Veegum (Vanderbilt), Laponite (Laporte), tetrafluorosilicon mica (Topy Industries) and the like can be used. In carrying out the present invention, one or two or more of these swelling clay minerals are arbitrarily selected.

As the adsorbent, the larger the specific surface area, the larger the adsorption capacity, and the stronger the ability to hold the solute molecule, the more suitable it is. From such a meaning, a swelling clay mineral which is a synthetic product is suitable, and for example, smecton which is a synthetic saponite and laponite which is a synthetic hectorite are particularly preferable.

The swelling clay mineral has a property of having a special interaction with various polar molecules on the surface of the powder or its layers, and therefore, the selectivity for solute molecules is different from that of the conventional adsorbent.

The adsorption step in the present invention may be any step as long as the fatty acid mixture and the clay mineral are brought into contact with each other, but 1) the method of bringing the fatty acid mixture into contact with the clay mineral dispersed in an organic solvent, and 2) the clay mineral packed in a column. A method of contacting a fatty acid mixture with the above can be used. A method using a column is particularly preferable in order to obtain a highly pure DHA compound.

The shape of the clay mineral used in the present invention may be either spherical or crushed, but when packed and used in the column of 2) above, the spherical shape is preferable from the viewpoint of efficiency and purity.

A convenient method for obtaining a spherical clay mineral is to use a spray drying method.

That is, it is a method of dispersing a swelling clay mineral in an aqueous solvent to form a gel, and then spray-drying the dispersion.

For spray drying, a general spray drying method such as a disc type, a pressure nozzle type, or a two-fluid nozzle type can be applied.

In either case, the inlet air temperature during spraying is
Since it is sufficiently thermally stable up to about 300 ° C,
A wide temperature range of about 300 ° C can be set. The exhaust gas temperature is regulated by the flow rate of spray from the nozzle, etc., but may be around 100 ° C. The particle size of the clay mineral thus obtained is 2 to 20 μm. These are used after being classified by a normal dry classification method as needed.

Cations such as sodium ions and lithium ions are usually present between the layers of these swelling clay minerals and electrically neutralize the entire swelling clay mineral, but these cations are exchangeable and easily Can replace other cations. This cation exchange capacity varies depending on the type of swelling clay mineral, but is approximately 60 per 100 g of clay mineral.
~ 150 meq. Furthermore, clay minerals in which sodium ions between layers are replaced with other metal cations or organic cations have no water swelling property, and even if they come into contact with water, they do not form a gel and exist as a powder. The swelling clay mineral itself swells when contacted with water and is not suitable as an adsorbent,
Also, the ability to discriminate unsaturated fatty acids is not high. The clay mineral used in the present invention is used as an adsorbent by changing the interlayer ion of the clay mineral to another metal cation so as to eliminate the water swelling property.

Metal cations other than sodium include silver, platinum,
Palladium, aluminum, iron, ruthenium, nickel, cobalt and the like are used, preferably silver, platinum,
It is palladium.

As a method for exchanging interlayer cations, metal ions are dissolved in water or an organic solvent, and the clay mineral is dispersed therein and stirred. Thereafter, the clay mineral may be separated, washed and then dried.

The salt of the metal ion used here may be any soluble salt such as chloride, nitrate or sulfate. As the organic solvent, a common one such as ethanol, methanol or acetone is used.

The concentration of the swelling clay mineral at the time of producing the adsorbent is not particularly limited, but if it is 20% by weight or more, stirring becomes difficult and ion exchange becomes difficult. The amount of metal ions in the dispersion is preferably equal to or more than the cation exchange capacity of the swelling clay mineral. The temperature of the dispersion during the ion exchange reaction may be any number of times, and room temperature is usually sufficient. The drying temperature may be any number as long as it is not higher than the decomposition temperature of the clay mineral.

Further, these clay minerals may be fired and used.
The firing temperature and firing time are selected according to the clay mineral used and the solute molecules to be separated, but it is necessary that the temperature is below the temperature at which the spherical powders sinter each other. When the interlayer ions are metal ions, the solvent resistance is increased by firing.

It can be confirmed as follows that the interlayer ions of the clay mineral thus obtained are substantially substituted with cations other than sodium. That is, the amount of metal cations exchanged can be easily confirmed by elemental analysis using atomic absorption or the like.

As the organic solvent used in the adsorption / desorption process, n-
Linear or cyclic non-polar solvents such as heptane, n-hexane, cyclohexane, n-pentane, cyclopentane, benzene and toluene, ketones such as acetone, methyl ketone and diethyl ketone, lower alcohols such as methanol, ethanol and butanol, A wide range of polar solvents such as halogenated hydrocarbons such as chloroform and ethyl bromide, ethers such as diethyl ether and isopropyl ether, and acetic acid esters such as methyl acetate and ethyl acetate can be used. In the DHA compound adsorption / desorption step, one or more of the above solvents are used.

As the method used in the adsorption / desorption step, 1) in the case of contacting a fatty acid mixture with a clay mineral dispersed in an organic solvent, after contacting the fatty acid mixture with the clay mineral,
The organic solvent is separated by filtration, and the organic solvent is dispersed several times.
Stir to remove impurities. The amount of the organic solvent with respect to the clay mineral is not particularly limited and may be appropriately changed depending on the type and composition of the organic solvent. 2) When the fatty acid mixture is brought into contact with the clay mineral packed in the column, the fatty acid mixture and the clay mineral are brought into contact with each other, and then an organic solvent is passed through the column to desorb impurities. The amount of the organic solvent passed through the clay mineral is not particularly limited and may be appropriately changed depending on the type and composition of the organic solvent.

The amount of the clay mineral used may be 5 to 50 times the weight of the fatty acid mixture to be refined, and from the viewpoint of purity and yield, it is preferably 10 times.
~ 12 times.

The contact temperature of the clay mineral and the fatty acid mixture is not particularly limited and may be about 0 ° C to 90 ° C.

Next, the DHA compound is desorbed by contacting the clay mineral with an organic solvent having a higher polarity than the aforementioned organic solvent. In the case of 1) above, after the organic solvent is separated by filtration,
A more polar organic solvent is added to the clay mineral, stirred, filtered and separated, and this is repeated several times to desorb the DHA compound. The amount of organic solvent for the clay mineral is not particularly limited,
It may be appropriately changed depending on the type and composition of the organic solvent.
In the case of 2) above, the DHA compound is desorbed by passing a more polar organic solvent through the column. The amount of the organic solvent passed through the clay mineral is not particularly limited and may be appropriately changed depending on the type and composition of the organic solvent.

Finally, by distilling off the solvent of the fractionated solution,
A highly pure DHA compound can be obtained.

The clay mineral used for purification was washed with the organic solvent used for desorbing impurities to continuously remove the next DHA.
The compound can be used for purification.

[Examples] Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto. In the examples,% is based on weight unless otherwise specified.

Example 1 300 g of Laponite XLG (manufactured by Laporte) was deionized water 1
Disperse to 0 with stirring. The obtained gel was spray-dried at a disk rotation speed of 20,000 rpm, an inlet air temperature of about 200 ° C., and an exhaust temperature of about 110 ° C. As a result, 270 g of spherical powder of 2 to 20 μm was obtained.

This spherical clay mineral is a dry classifier TARBO CLASSIFINER TC
Classify using -15N (manufactured by Nisshin Engineering),
60 g of powder with a particle size of 5-10 μm was obtained.

10.2 g of silver nitrate is dissolved in ethanol 6, 60 g of the above spherical clay mineral is dispersed, and the mixture is stirred for 4 hours. After that, it is filtered, washed with ethanol, dried at 80 ° C, and then 60 g of the powder.
Was packed in a stainless steel column having an inner diameter of 20 mm and a length of 250 mm by the equilibrium slurry method using a packer and a pump to prepare a packed column.

On the other hand, fish fat having the fatty acid composition shown in Table 1 was hydrolyzed by a conventional method to obtain a fatty acid mixture.

A liquid chromatography pump was connected to this column, and acetone / n-hexane = 1.5 / 98.5 as a mobile phase was introduced at a rate of 20 ml / min, and the above fatty acid mixture was ethyl-esterified to produce a fish fat-derived fatty acid ethyl ester mixture. To
After injecting 2 g, acetone / n-hexane = 1.5 / 98.5 solution
1000 ml of the solution was passed through to desorb impurities such as saturated fatty acid ester.

Next, acetone / n-hexane = 10/90 is added to 500 ml per minute 20
The solution was passed through the column in ml to obtain 0.30 g of DHA ethyl ester and a purity of 57.0%.

Next, 500 ml of acetone / n-hexane = 40/60 is added at 20 min / min.
The resulting solution was passed through the column in ml to obtain 0.36 g of DHA ethyl ester and a purity of 90.3%. Table 2 shows the composition of the purified DHA ethyl ester.

[Effect of the Invention] According to the method of the present invention, a highly pure DHA compound can be obtained in a simple process and with a small amount of an adsorbent for a fatty acid mixture.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyoshi Yazawa 571 Unomori, Sagamihara City, Kanagawa Prefecture Green Heights D1-501 (72) Inventor St. Kondo, 5-16-4 Churinbayashi, Yamato City, Kanagawa Prefecture Zenichi Wakimura

Claims (2)

[Claims] 1. Docosahexaenoic acid and / or docosahexaenoic acid and / or decosahexaenoic acid by adsorbing and desorbing a fatty acid mixture using a clay mineral in which interlayer ions of a swelling clay mineral are substantially replaced by cations other than sodium ions. A method for separating and purifying the lower alkyl ester. 2. A cation other than sodium ion,
The method for separating and purifying docosahexaenoic acid and / or its lower alkyl ester according to claim 1, which is a divalent or trivalent metal cation.