Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...
Reexamination Certificate
2000-06-28
2001-11-06
Carr, Deborah D. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Fatty compounds having an acid moiety which contains the...
C554S191000
Reexamination Certificate
active
06313330
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process of selectively separating and purifying eicosapentaenoic and docosahexaenoic acids or the esters thereof from a mixture comprising a highly unsaturated fatty acid or the derivative thereof.
BACKGROUND OF THE INVENTION
There are known highly unsaturated fatty acids or the derivatives thereof such as the esters thereof which originate from fish oils such as oils of sardines, mackerels, tunas or the like. Especially, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and the esters thereof have been used in the field of health foods and drugs because of their pharmacological effects.
The known processes for the purification of these unsaturated fatty acids or the derivatives thereof are a urea-addition process, a precision distillation process, a chromatographic process, a supercritical fluid extraction process and the like. However, these prior processes are individually difficult to purify a mixture comprising highly unsaturated fatty acids or their derivatives originating from fish oils, in high purity, without modification, in large quantity and at low cost. In the urea-addition process, the resultant mixture comprising highly unsaturated fatty acids or their esters is low in a degree of purity. In the precision distillation process, polymerization and isomerization occur with easy modification of the product and it is difficult to remove eicosatetraenoic acid (ETA) or its ester which is not desirable when used as drugs and foods. Further, the chromatographic and supercritical fluid extraction processes are not suitable for the separation and purification on an industrial scale.
Japanese Patent Kokai 9-151390 discloses a process for the purification of a highly unsaturated fatty acid and the derivative thereof, which comprises contacting a mixture of highly unsaturated fatty acids or their derivatives with a carrier carrying a silver salt, and subsequently separating and extracting by contacting the carrier with a solvent. It is described therein that silica gel, zeolite, kaolin, active china clay, pearlite and the combination thereof are used as a carrier. However, this publication gives no reference to the use of diatomaceous earth and the effect achieved thereby. Further, this prior process gives the limitations that the amount of the carrier for the silver salt should be 19 parts by weight in terms of silver relative to 45-55 parts by weight of the carrier, and further, that the amount of the mixture of highly unsaturated fatty acids or their derivatives to be contacted with the silver salt-carried carrier should be 15 parts by weight. The departure from such limitations results in lowering a degree of purification. Although the prior process can separate and purify a highly unsaturated fatty acid component in high purity, there are several problems that a process for preparing the silver-carried carrier is complicated, and that an extraction operation including repeated stirring and filtering is troublesome.
There has been a demand for a practical process of selectively separating and purifying desired EPA and DHA from fish oils containing various highly unsaturated fatty acids and their derivatives.
SUMMARY OF THE INVENTION
An object of the invention is to provide a process of separating and purifying EPA and DHA in high purity, which has more increased weight ratio of a silver salt to a carrier than the prior art process, thus exhibiting a high processing power, and which eliminates the incorporation of a silver compound.
The object of the invention can be attained by using a diatomaceous earth as a carrier for carrying a silver salt, filling the carrier in a column, flowing an aqueous medium containing the silver salt through the column to easily prepare a silver-carried carrier, and flowing a specified developing solvent in turn through the column.
The present invention provides a process of selectively separating and purifying eicosapentaenoic and docosahexaenoic acids or the esters thereof from a mixture comprising a highly unsaturated fatty acid or the derivative thereof, which comprises the steps of: flowing an aqueous medium comprising a silver salt through a column filled with a diatomaceous earth to carry the silver salt on the diatomaceous earth;
flowing a solvent solution of a mixture comprising the highly unsaturated fatty acid or the derivative thereof through the silver salt-carried diatomaceous earth in the column; and
flowing a developing solvent through the column.
The present invention of the above construction can effectively separate and purify EPA and DHA from the mixture comprising highly unsaturated fatty acids or the derivatives thereof originating from fish oils, and further, it can inhibit an effusion of a silver, thus preventing the reduction in separation ability and the incorporation of silver into a separated and purified product. Moreover, the present process can reduce the content of eicosatetraenoic acid (&ohgr;6 ETA) which is not desirable in health foods and drugs, as low as possible.
DETAILED DESCRIPTION OF THE INVENTION
The raw materials, a mixture comprising highly unsaturated fatty acids or their derivatives which are used for purification in the present invention can include, but are not limited to, those originating from fish oils such as oils of sardines, mackerels, tunas or the like, which contain highly unsaturated fatty acids, e.g., ETA, EPA or DHA, ester derivatives of these unsaturated fatty acids or the mixtures thereof. The composition of the raw materials may be variable when they originate from fish oils. Thus the degree of separation or purification of EPA and DHA or their esters may vary depending on the composition of the raw material. Even if several % or more of ETA is contained in the raw material, the present process can selectively separate and purify EPA and DHA, and further, reduce the content of ETA to a specified low level.
The present invention is characterized by using the diatomaceous earth as the carrier for carrying the silver salt. The diatomaceous earth is a fossil of a single cell plant which is a kind of the waterweed propagating in both areas of the fresh water and the vexation water. One of the reasons for the selective use of diatomaceous earth is that the ability to hold water in the diatomaceous earth is about two times as high as that in other materials when the silver salt is carried on the diatomaceous earth in the form of a solution dissolved in the aqueous medium. For reference, the ability to hold water is compared below, using a pore volume per weight (oil absorption, ml/g).
Silica
Active
Diatomaceous
gel
Zeolite
Kaolin
china clay
Pearlite
earth
0.75
0.45
0.5-0.55
0.55
—
1≧
The diatomaceous earth can be usually used in its uncalcined or calcined form, but the calcined earth is preferable. The calcined diatomaceous earth can be produced by crushing a raw diatomaceous earth, drying the crushed product, subjecting it to repeated grinding and classification operations to remove impurities, calcining the classified product at high temperature, and further subjecting it to repeated grinding and classification operations to adjust the particle size. It is preferable that the diatomaceous earth has a pore size of 0.1-10 &mgr;m, a specific surface area of 0.5-50 m
2
/g and a pore volume of 1-10 ml/g for increasing the ability to hold an aqueous silver salt solution and securing good contact with highly unsaturated fatty acids or their derivatives to be treated. It is more preferable that the diatomaceous earth has a bulk density of 0.1-0.3 g/ml, taking the size of column into consideration. The diatomaceous earth which can be used in the present invention is commercially available, but not limited to a specified one, a typical example of which is “Extrelut® 13076”available from Merck Co., Ltd.
As the silver salts to be carried on the diatomaceous earth, any silver salts can be used if they can form a complex on the diatomaceous earth with the mixture comprising highly unsaturated fatty acids or their derivatives. Silver nitra
Fujita Shiro
Kiyohara Satoshi
Carr Deborah D.
Nisshin Pharma Inc.
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