US2350713A - Separation and purification of the - Google Patents

Description

Patented June 6, 1944 SEPARATION AND PURIFICATION OF THE TOCOPHEROLS James G. Baxter and Julius D. Taylor, Rochester, N. Y., assignors to Distillation Products, Inc., Rochester, N. Y., a corporation of Delaware No Drawing. Application April 20, 1942, Serial No. 439,776

7 Claims.

This invention relates to improved procedure for separating tocopherols from a mixture thereof: in particular it relates to a method for resolving a mixture of alpha and at least one other tocopherol into its components.

The tocopherols are known to have vitamin E activity and also antioxidant activity. However, the vitamin E activity varies inversely with the antioxidant activity; 1. e., the alpha tocopherol is highest in vitamin E and lowest in antioxidant activity while the gamma form is highest in antioxidant activity and lowest in vitamin E activity. For this and other reasons it is frequently desirable to separate the mixtures of tocopherol as vthey naturally occur into individual tocopherol constituents. Separation has heretofore been accomplished by fractional crystallization of mixed tocopherol allophanates; also by adsorbing the tocopherol mixture on an adsorbent column, breaking up the column and eluting appropriate sections of the column with eluting solvents. See, for instance, Emerson, Journal of Biological Chemistry," 1937, 90, and Drummond, Biochemical Journal," 1938, 1953. These procedures are rather costly and are not particularly suited for commercial operations due to the rather expensive and complicated steps.

This invention has for its object to provide procedure whereby the foregoing dimculties can be ture containing alpha and at least one other to- I copherol to an esteriflcation treatment adapted to form a carboxylic acid ester, terminating the esteriilcation reaction when the amount of tocopherol esterifled corresponds to about the amount of tocopherol other than alpha present in the mixture and then treating the, reaction product to separate esterifled tocopherol from unesterined alpha tocopherol. alpha tocopherol reacts much more slowly with It has beeen found that esteriiication reagents than the beta or gamma tocopherols. Therefore, if a mixture is treated in the foregoing manner a preferential esteriflcation of the forms other than alpha present takes place. It is then a simple matter to treat the esterlncation mixture to separate the esters from the non-esterifled portion.

In the following description we have given several of the preferred embodiments of our invention, but it is to be understood that these are set forth for the purpose of illustration and not in limitation thereof.

Tocopherols naturally occur as mixtures in or animal oils. Such scum is obtained by condensing the steam or like carrier gas utilized during the vacuum deodorization of vegetable and animal oils. The steam used in the deodorization treatment carries over relatively volatile matter which contains a quite high content of tocopherols. This treatment can be directly, treated in accordance with our invention, but it is preferred that it be subjected to a concentration procedure designed to increase the tocopherol content. Thus, the scum may be subjected to high vacuum unobstructed path distillation and a tocopherol fraction of high concentration separated. On'the other hand, the scum may be saponifled and the non-saponiilable treated in accordance with our invention. Alternatively,

the starting material may be obtained by saponiflcation of the natural oil itself, according to known manner. Regardless of the source of the mixed tocopherol starting material we prefer to operate'on a tocopherol concentrate starting material which contains at least 15 per cent of mixed tocopherols. The mixture may be alpha and gamma; or alpha and beta; oralpha, beta and gamma. Reference is made to Hickman application 321,913, filed March 2, 1940, for a more detailed description of the various methods of preparing tocopherol preparations from deodorizer scum.

The starting material, is treated with an esterifying agent in known manner in order to form an ester of a carboxylic acid. The esteriilcation is preferably conducted in the presence of an accelerator such as pyridine, and it is desirable to take precautions to avoid undue contact of the esteriflcation mixture with atmospheric oxygen. We prefer to utilize an anhydride as an esterifying agent and also prefer to use anhydrides of polybasic acids and especially of dibasic acids.

aration.

The degree of separation will be determined by the point at which the esterification is terminated. If a very sharp separation is necessary, it is best to determine the amount of tocopherol other than alpha present in the mixture and then carry out the esteriflcation under controlled conditions with analysis of the esterification mixture at appropriate intervals, so that the esteriilcation reaction can be closely followed and terminated at the proper point. It is best to terminate the reaction when the proportion of tocopherol which has been esterified corresponds to the proportion of gamma and/or beta tocopherol present in the mixture. It has been found by experiment that very little, if any, of the alpha tocopherol will become esterifled until substantially all of the beta and gamma tocopherols are esterii'ied. If the reaction can be followed closely and terminated at the point indicated, a very sharp separation of the tocopherols will be obtained. The rate of esterification can be controlled by varying the temperature and amount of esteriiying agent, but the ratioof esterifled alpha to esterifled beta or gamma will remain about the same. With two mols of esterifying agent such as succinic anhydride per mol of total tocopherol present'the reaction will as a general rule be completed in about 30 minutes if heated to about 60-'I0'C. The "Emmerie and Engel" test for unesterified tocopherol can be used to follow the course of the reaction.

After the reaction has been carried to the desired point the'esterification is terminated and the reaction mixture is treated to separate the esterifled and unesterifled tocopherols present therein. This separation can beaccomplished by numerous methods such as solvent extraction, reaction of tocopherol esters to form derivatives, such as salts, which can then be separated quite easily due to their radically diflerent properties from the free alpha tocopherol, high vacuum distillation to separate the lower boiling tree tocopherol from the higher boiling tocopherol ester and adsorption to preferentially remove the more strongly adsorbed free tocopherol. Partitioning oil-the two tocopherol forms between immiscible solvents, one of which contains an alkali, is also a valuable method 01 sep- Example A 38-gram'sample 01' commercial tocohperol concentrate containing 39 per cent mixed alpha and gamma tocophesols, in a ratio of 60 to 40 was heated at 70' C. for thirty minutes with 55 cc. of pyridine and 7 grams of succinic anhydride. A few minutes swirling served to dissolve the'anhydride giving a clear solution. At the end of the heating period the reaction mixture was washed in an ether solution with per cent aqueous hydrochloric acid to remove pyridine, The ether solution was then washed with water, dried, and the ether removed by distillation to leave an oil slightly darker than-the commercial starting material. This oil contained 22 per cent free tocopherol. Theoretically i! all of the gamma tocopherol had been esterifled, the residue oil should contain 23.5 per cent free tocopherol. The residue oil was'dissolved in 200 cc. oi! 83 per cent ethyl alcohol and treated with IR KOH in 83 P r cent ethyl alcohol until the solution was slightly I! e ter-med corresponds to about the amount of toi alkaline to phenolphthalein. It was then extracted three times with petroleum ether. The alcohol fraction contained gamma tocopherol acid succinate which was separated by diluting the alcohol layer with water and extracting with ether in the usual way. It weighed 12.6 grams and upon saponiflcation gave a gamma tocopherol concentrate containing 8'7 per cent tocopherol. An analysis of this material showed that the gamma to alpha ratio was 93 to 7, indicating that it was nearly free of the alpha form. The three petroleum ether extracts were combined I and the ether removed by distillation. An alpha tocopherol fraction weighing 25.3 grams was thus obtained, containing 31 per cent of alpha tocopherol. It will thus be seen that approximately 90 per cent of the gamma tocopherol present in the original tocopherol starting material was removed. Closer control of the esterification conditions would enable quantitative separation oi the two tocopherols. In this example substantially the same results would be obtained if 90 per cent aqueous methyl alcohol were used instead oi. 83 per cent ethyl alcohol.

It will be noted that the procedure results in a very satisfactory separation of the tocopherols contained in a mixture and that the procedure is relatively inexpensive as compared with prior l. The process 01 resolving a mixture of alpha and at least one other tocopherol into its components which comprises subjecting a mixture containing alpha and at least one other tocophaction product to separate esterifled tochoperol from unesterifled alpha tocopherol,

2.Theprocessotresolvingamixtureo!alpm and gamma tocopherol into its components which comprises sublecting a concentrate containing a mixture of alpha and gamma tocopherol to an esteriflcation treatment in which the esterii'ying agent is one which is adapted to form an ester of a polybasic carboxylicacid. terminating the esteriflcation reaction when the amount of tocopherol esteriiied corresponds to about the amount 01' gamma tocopherol present in the mixture whereby the 'y tocopherol present in the 'startingmixtureislargelyesterinedandtheu tocopherol remains substantially unesteriiied and then treating the reaction product to separate gamma tocopherol ester trom'unesterifled alpha tocopherol.

3.Theprocess otreslovingamix'tureotalpha and at least one other tocopherol into its components which comprises subjecting a mixture containing alpha and at least one other tocopherol to an esterincation treatment with a dibasic earboxylic acid anhydride, terminating the uteri!!- cation reaction when the amount'ot tocopherol copherol other than alpha present in the mixture whereby the tocopherol other than a tocopherol present in the starting mixture is largely esterifled and thee tocopherol remains sub stantially unesterifled and then treating the reaction product to separate esterfled tocopherol other than a from unesterifled alpha tocopherol.

4. The process of resolving a mixture of alpha and at least one other tocopherol into its components which comprises subjecting a mixture oi tocopherols containing at least 15 per cent alpha and other tocopherol isomer to an esteriflcation treatment in which the esteriiying agent is one which is adapted to form an ester of a carboxylic polybasic acid, terminating the esteriiicatiou reaction when the amount oi tocopherol esterifled corresponds to about the amount of tocopherol other than alpha present in the mixture and then treating the reaction mixture whereby the tocopherol other than a tocopherol present in the starting mixture is largely esterifled and the a. tocopherol remains substantially unesteriiled to separate esteriiled tocopherol other than a from unesterified alpha tocopherol.

5. The process of resolving a mixture of alpha and gamma tocopherol which comprises subject ing a mixture which contains at least 15 per cent tocopherol in the form of alpha and gamma to an esteriflcation treatment in which the esteriiying agent is a dibasic carboxylic acid anhydride, terminating the esterification reaction when the amount of tocopherol esterifled corresponds to about the amount of gamma tocopherol present in the mixture whereby the y tocopherol present in the starting mixture is largely esteriiled and the a tocopherol remains substantially unesterined and then treating the reaction mixture to separate esteriiled 7 tocopherol from unesterifled alpha tocopherol.

6. The process oi separating a mixture oi alpha and gamma tocopherol which comprises subjecting a mixture having a tocopherol concentration of at least 15 per cent and containing alpha and a gamma tocopherol to an esteriflcation treatment in which the esteritying agent is one which is adapted to form an ester of a polybasic carboxylic acid, terminating the esterification reaction when the amoimt oi tocopherol esterifled correlO sponds to about the amount of gamma tocopherol present in the mixture whereby the 'y tocopherol present in the starting mixture is largely esterifled and the a tocopherol remains substantialLv unesterifled, neutralizing the gamma tolo copheral acid ester thus formed, and extracting the mixture with a preferential solvent for one of the forms of tocopherol present therein.

'7. The process of resolving a mixture of alpha and gamma tocopherol into its components which 20 comprises subjecting a concentrate containing at least 15 per cent alpha and gamma tocopherols to an esterification treatment with a dibasic carbozwlic acid anhydride, terminating the esteriflcation reaction when the amount 01! tocohperol 26 esterifled corresponds to the amount of gamma tocopherol present in the mixture whereby the 'y tocopherol present in the starting mixture is largely esterifled and the a tocopherol remains substantially unesterifled, dissolving the mixture 30 of free alpha and esterifled gamma tocopherol in a lower aliphatic alcohol containing a small amount of water, neutralizing the gamma tocopherol acid ester, extracting the alcohol solution with petroleum ether and recovering the to- 88 copherol from the petroleum ether extract and from the alcoholic solution.

JAMES G. BAX'I'ER JULIUS D. TAYLOR.

CERTIFICATE OF CORRECTION Patent No. 2, 0,715. June 6, 19th,.

" JAMES G. BAX'IRR, ET AL.

It is hereby certified that error appears in the printed specification of the above m mbered patent requiring correction as follows! Pige 5, first column, lines 18 and 19, claim 11., strike out the words "and then treating the reaction mixture" and insert the same before "to" in line '23,- same claim; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 29m day of August, A. D. 191m.

Leslie Frazer (S0841) I Acting Commissioner of Patents.