GB2135672A

GB2135672A - Method for the preparation of vitamin E concentrate

Info

Publication number: GB2135672A
Application number: GB08323370A
Authority: GB
Inventors: Azuma Shibue; Hikaru Tamura
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-03-01
Filing date: 1983-08-31
Publication date: 1984-09-05
Also published as: MY8700479A; GB8323370D0; JPS6124393B2; JPS59161372A; GB2135672B

Abstract

The invention provides a very efficient method for the preparation of a vitamin E concentrate from fresh plant tissues containing the compounds. The method includes extraction of the vitamin E compounds contained in finely ground plant tissues freed from juice with a non-polar organic solvent not miscible with water and capable of forming an azeotropic mixture with water with simultaneous removal of free water by azeotropic distillation and ion-exchange purification of the thus extracted vitamin E compounds with an anion exchanger. A concentrate containing more than 70% of the vitamin E compounds can readily be obtained which is, when leaves or stalks of the plants belonging to the families of Gramineae or Palmeae are used as the starting material, particularly rich in the content of alpha -tocopherol.

Description

SPECIFICATION Method for the preparation of vitamin E concentrate The present invention relates to a method for the preparation of a vitamin E concentrate, i.e. a highly concentrated mixture of vitamin E compounds, or, more particularly, to an efficient method for the preparation of a vitamin E concentrate particularly rich in cg-tocopherol from the tissues of certain plants containing vitamin E compounds such as leaves and stalks of the plants belonging to the families of, for example, Gramineae and Palmae.

It has been believed for some time that vitamin E compounds have a physiological activity such that a deficiency thereof in mammals causes detrimental effects on the genital glands. When raised with feeds deficient in vitamin Es, for example, infertility or embryo assimilating abortion is caused in female mice while male mice may suffer atrophy of the spermatogenic tissues or permanent infertility. On the other hand, it has more recently been disclosed that vitamin E compounds play an important role in the effective enhancement of the function and metabolism of living cells and the prevention of cell damage due to peroxidation since, as a group of anti-oxidatant compounds, these compounds can exhibit strong anti-oxidatant effects even in animal bodies.

In recent years, accordingly, vitamin E compounds have been greatly highlighted in the fields of medicines, health foods, provender additives and the like and they are also very promising as a non-toxic antioxidant in edible oils and plastic films for food wrapping.

Vitamin E as a natural product is a generic name for seven tocopherol compounds including the first-discovered a- and p-tocopherols as the later-discovered y-, 6-, E-, T- and rl-tocopherols and four tocotrienols each as a dehydrogenated derivative of a-, p-, y- or 8-tocopherol, respectively, with six hydrogen atoms per molecule removed therefrom to introduce double bonds. Of these vitamin E compounds, the strongest in physiological activity is a-tocopherol and great efforts have been directed to developing a method for the effective extraction of this tocopherol from natural products or a method for the chemical synthesis of this compound.With regard to optical isomerism, naturally occurring atocopherol is the d-isomer while synthetic methods always give a racemic mixture of the dand I-isomers.

As is well known, the most useful natural products containing these vitamin E compounds are the leaves and stalks of certain plants belonging to the families of Gramineae and Palmae in addition to wheat germ oil, cottonseed oil, safflower oil and the like vegetable oils.

Due to the extremely small contents of the vitamin E compounds in the plant tissues of the leaves and stalks above mentioned, considerable difficulties are encountered in selectively concentrating the vitamin E compounds from the plant tissues. A conventional method for the preparation of a vitamin E concentrate usually begins with the acceierated drying by heating or sun-drying of the leaves and stalks to remove water therefrom followed by the extraction of the dried plant tissues with an organic solvent and concentration of the organic extract. Alternatively, dehydration of the plant tissues is effected by using a water-miscible organic solvent such as a lower alcohol or a ketone with simultaneous extraction of the vitamin E compounds into the solvent followed by concentration of the organic solution.

These prior art methods suffer from several disadvantages and drawbacks. For example, the former method beginning with drying of plant tissues is necessarily accompanied by the loss of some of the desired compounds during the drying step and the latter method of using a watermiscible organic solvent is economically defective due to the large cost of recycling the organic solvent because the solvent is greatly diluted with the water originating in the plant tissues.

We have now developed an efficient and economic method for the preparation of a vitamin E concentrate by separation from fresh plant leaves and stalks without the loss of the desired compounds which combines the steps of extraction of the plant tissues with a specific organic solvent on the one hand and an ion exchange treatment of the extract by the use of an anion exchange on the other.

Accordingly, the method of the present invention for the preparation of a vitamin E concentrate comprises the steps of: (a) grinding plant tissues containing vitamin E compounds to destroy the cells; (b) removing free juice from the thus ground plant tissues, preferably, by the technique of solid-liquid separation to give a pulp; (c) preparing a dispersion of the pulp in a nonpolar organic solvent not freely miscible with water at room temperature and capable of forming an azeotropic mixture therewith; (d) heating the dispersion at the boiling point of the azeotropic mixture to azeotropically distil off the water contained in the pulp with the simultaneous extraction of the vitamin E compounds into the organic solvent; (e) removing the organic solvent from the organic extract solution by distillation to give a concentrated solution containing the vitamin E compounds; and (f) subjecting the concentrated solution containing the vitamin E compounds to adsorption on and elution from an ion exchanger to give a vitamin E concentrate.

The starting materials used in the method of the invention are fresh plant tissues containing a relatively high content of vitamin E compounds.

For example, suitable starting material include leaves and stalks of plants belonging to the Gramineae family such as rice, barley, wheat, Indian corn and the like corn plants as well as higeshiba (Sporobolus piliferus Kunth) and the like wild plants and plants belonging to the Palmeae family such as oil palm and the like. Although the overall content of vitamin E compounds in the leaves and stalks of these plants are lower than in the corns and fruits of the same plants, it is known that the content of a-tocopherol relative to the other vitamin E compounds is very high in the leaves and stalks thereof.

The fresh tissues of the leaves and stalks of the above-mentioned plants are first ground as finely as possible by a suitable mechanical means to destroy the cells into a slurried form and the slurry of the plant tissue is then dehydrated by the technique of mechanical solid-liquid separation to remove the free juice as completely as possible.

The method of solid-liquid separation is not particularly limited and may be performed, for example, by filtration under compression or centrifugal separation.

The pulp left after removal of the juice from the slurry of the ground plant tissues is then dispersed in and subjected to extraction with a non-polar organic solvent. The non-polar organic solvent should be insoluble in water or not freely miscible with water at room temperature and capable of forming an azeotropic mixture therewith. Suitable non-polar organic solvents are hydrocarbon solvents such as n-hexane, n-heptane, benzene and toluene and halogenated hydrocarbon solvents such as carbon tetrachloride and trichloroethylene. The solvent is preferably used in: a volume of 400 to 1000 ml per kg of the starting plant tissues.

The dispersion of the pulp obtained from the fresh plant tissues in the above mentioned nonpolar organic solvent is then heated at the azeotropic boiling point of the water-solvent mixture to distil off the water contained in the pulp by azeotropic distillation, while the vitamin E compounds in the ground plant tissues are extracted by the organic solvent to form a solution from which the insoluble solid matter mainly composed of cellulosic materials is removed by filtration or other suitable method. The time taken for this extraction depends on the particular solvent and other factors but a time of 2 hours may be sufficient with benzene as the solvent. The solution containing the vitamin E compounds is concentrated by distilling off the organic solvent to give a concentrated solution.

The thus obtained concentration solution of the vitamin E compounds still contains considerable amounts of ingredients other than the desired vitamin E compounds. These foreign ingredients may be precipitated in a resinous form when the concentrated solution is diluted by adding a lower alcohol such as methyl or ethyl alcohol followed by heating to leave the vitamin E compounds in the alcoholic solution.

When this alcoholic solution containing the vitamin E compounds is contacted with an anionic ion exchanger, the vitamin E compounds are adsorbed on the ion exchanger. The ion exchanger used in the method of the invention is usually a basic anion exchanger which may be in the form of membranes, fibers or particles. Particularly suitable for the purpose are anion exchange resins manufactured and sold by Rohm 8 Haas Co. with tradenames of Amberlite IRA 401 in the Cl form and Amberlyst A-26, the latter being suitable for use in a non-aqueous system.

The vitamin E compounds thus adsorbed on the ion exchanger can be eluted with a known eluant which may be ethyl alcohol containing acetic acid (see, for example, Japanese Patent Publication 38-23638) to give a solution of the vitamin E compounds in ethyl alcohol acidified with acetic acid. This solution is then diluted with a waterimmiscible organic solvent such as n-hexane and then thoroughly washed with a saturated aqueous solution of sodium chloride so that the ethyl alcohol and acetic acid are transferred into the aqueous layer to leave the vitamin E compounds in the water-immiscible solvent from which, after drying with a suitable dehydrating agent such as anhydrous sodium sulfate, the solvent is removed by distillation to leave a desired concentrate of the vitamin E compounds.

The concentrate obtained in this manner usually contains about 70% or more of the vitamin E compounds of which the main component is atocopherol. Therefore, the above described method provides a very efficient and reliable means for the separation and concentration of the vitamin E compounds or, in particular, a- tocopherol from fresh plant tissues containing the compounds.

The thus obtained concentrate containing 70% or more of the vitamin E compounds mainly composed of a-tocopherol is useful as such as an additive in medicines, health foods and provendors or as a non-toxic anti-oxidant in edible oils and plastic films for food wrapping.

Following are the examples to illustrate the inventive method in further detail but not to limit the scope of the invention in any way.

Example i.

One kilogram of fresh leaves of higeshiba, a plant belonging to the family of Gramineae, growing in wilderness was finely ground into a slurry and the freed juice of the plant was removed by filtration under compression. The cellulosic pulpous material was disintegrated and added to 700 ml of benzene in a two-necked flask of 3liters capacity equipped with a reflux condenser provided at the lower end with a separatory funnel to discharge water. The dispersion of the pulpous material in benzene was heated for 2 hours at about 700 C, i.e. the azeotropic boiling point of the benzene-water mixture, and the water and benzene condensed in the condenser were introduced into the separatory funnel from which the water was discharged while the benzene was returned to the flask. During this azeotropic distillation, the benzene-soluble matter in the pulpous material was extracted into benzene.

After completion of the extraction in the above described manner, the dispersion in benzene was cooled to room temperature and filtered with suction to remove the cellulosic fibrous material from the benzene solution which was then concentrated by distillation into a volume of 300 ml. When this concentrated benzene solution was cooled to room temperature, a gel-like material was precipitated which was removed by centrifugal separation at a velocity of 7000 r.p.m.

Removal of benzene from the solution by distillation left 80 g of a greenish brown material as the benzene extract. This extract was admixed with 100 ml of ethyl alcohol and heated under agitation followed by chilling down to about 0 C so that a resinous material was precipitated which was removed by filtration with suction. The ethyl alcohol solution was warmed again to about 250 C and passed through a glass column filled with 300 ml of a basic anion exchange resin Amberlite IRA 401 in the Cl form so that the vitamin E compounds were adsorbed on the resin.

After washing of the ion exchange resin with 300 ml of ethyl alcohol, the vitamin E compounds were eluted out from the ion exchange resin with 300 ml of a 9:1 mixture of ethyl alcohol and acetic acid. The eluate solution was admixed with 300 ml of n-hexane and the solution was thoroughly washed with a saturated aqueous solution of sodium chloride to remove ethyl alcohol and acetic acid therefrom. Removal of n-hexane by distillation from the n-hexane solution after dehydration with anhydrous sodium sulfate gave 2.5 g of a viscous liquid product.

Analysis of this liquid product by highperformance liquid chromatography indicated that the product contained about 70% of vitamin E compounds of which the main component was atocopherol.

Example 2.

One kilogram of fresh leaves of oil palm, a plant belonging to the family of Palmeae, growing in the tropical district was thoroughly ground into slurry from which free juice of the plant was removed by filtration under compression. The pulpous material freed from the juicy liquid was disintegrated and added to 700 ml of n-heptane in the same flask as used in Example 1 and the dispersion was heated for 2 hours at about 80" C to remove the water in the pulpous material by azeotropic distillation with n-heptane out of the flask. During this azeotropic distillation, the vitamin E compounds contained in the oil palm leaves were extracted into the nheptane.

The dispersion after completion of the extraction was cooled to room temperature and filtered to remove the cellulosic fibrous material from the n-heptane solution. This n-heptane solution was concentrated by evaporating the solvent to give 95 g of a dark green, viscous concentrated solution. This concentrated solution was admixed with 400 ml of ethyl alcohol under agitation and heating followed by chilling down to about 0 C so that a solid material was precipitated which was removed by centrifugal separation.The thus obtained ethyl alcohol solution was passed through a glass column filled with the same ion exchanger as used in Example 1 to have the vitamin E compounds adsorbed on the ion exchange resin followed, after washing of the resin with 500 ml of ethyl alcohol, by elution of the adsorbed vitamin E compounds with 300 ml of a 9:1 mixture of ethyl alcohol and acetic acid. The eluate solution obtained in this manner was admixed with 300 ml of n-hexane and the solution was thoroughly washed with a saturated aqueous solution of sodium chloride to remove the ethyl alcohol and acetic acid from the n-hexane solution which was, after dehydration with anhydrous sodium sulfate, decolorized by adding 3 g of activated clay to have the coloring matter adsorbed thereon followed by filtration to give a clear filtrate solution. The activated clay after filtration was further washed with 100 ml of nhexane and the washings were combined with the solution obtained in the first filtration. Removal of n-hexane by distillation from the combined nhexane solution gave 2.5 g of a pale green, viscous liquid product.

Analysis of this viscous liquid product by highperformance liquid chromatography indicated that the product contained about 70% of the vitamin E compounds of which the main component was atocopherol.

Claims

1. A method for the preparation of a vitamin E concentrate from fresh plant tissues containing vitamin E compounds which comprises the steps of: (a) grinding plant tissues containing the vitamin E compounds to destroy the cells; (b) removing free juice from the thus ground plant tissues to give a pulp; (c) preparing a dispersion of the pulp in a nonpolar organic solvent not freely miscible with water at room temperature and capable of forming an azeotropic mixture therewith; (d) heating the dispersion at the boiling point of the azeotropic mixture to azeotropically distil off the water contained in the pulp with simultaneous extraction of the vitamin E compounds contained in the pulp into the organic solvent: (e) removing the organic solvent from the organic extract solution by distillation to give a concentrated solution containing the vitamin E compounds; and (f) subjecting the vitamin E compounds contained in the concentrated solution to adsorption on and elution from an ion exchanger to give a vitamin E concentrate.

2. A method for the preparation of a vitamin E concentrate as claimed in claim 1 wherein the removal of free juice in the step (b) is performed by filtration under compression or by centrifugal separation.

3. A method for the preparation of a vitamin E concentrate as claimed in Claim 1 or Claim 2 wherein the non-polar organic solvent is a hydrocarbon solvent or a halogenated hydrocarbon solvent.

4. A method for the preparation of a vitamin E concentrate as claimed in Claim 3 wherein the hydrocarbon solvent is hexane, n-heptane, benzene or toluene.

5. A method for the preparation of a vitamin E concentrate as claimed in Claim 3 wherein the halogenated hydrocarbon solvent is carbon tetrachloride or trichloroethylene.

6. A method for the preparation of a vitamin E concentrate as claimed in any one of the preceding claims wherein the ion exchanger is a basic anion exchanger.

7. A method for the preparation of a vitamin E concentrate as claimed in any one of the preceding claims wherein the adsorption of the vitamin E compounds on an ion exchanger in step (F) is performed by diluting the concentrated solution containing the vitamin E compounds with a lower alcohol and contacting this alcoholic solution with the ion exchanger.

8. A method for the preparation of a vitamin E concentrate as claimed in any one of the preceding claims wherein the elution of the vitamin E compounds adsorbed on the ion exchanger in step (F) is performed with an eluant which is a mixture of ethyl alcohol and acetic acid.

9. A method as claimed in claim 1 substantially as hereinbefore described with reference to Example 1 or Example 2.

1 0. A vitamin E concentrate whenever prepared by a method as claimed in any one of the preceding claims.