US2322906A - Isolation of sterols from fats and oils - Google Patents

Description

Patented June 29, .1943

' ISOLATION OF STEROLS FROM FATS AND OILS Lester Yoder, Ames, Iowa, assignor to Iowa State College Research Foundation, Ames,

corporation of Iowa Iowa, at

No Drawing Application June 15, 1940, Serial No. 340341 7 Claims. (Cl.260397.2)

This invention relates to the isolation of certain sterols from complex mixtures of fats and oils, and to their subsequent purification. More specifically it relates to the separation of sterols containing one reactive double bond from the fatty and oily mixtures in which they occur.

An example of a sterol containing one reactive double bond is cholestrol, which is obtained from animal sources such as wool grease, nerve tissue fat, etc. Isa-cholesterol, a mixture of lanosterol and agnosterol, is obtained from wool grease and resembles cholesterol in many respects. Phytosterol, another example, is found in vegetable oils such as pine oi-l, tall oil, corn oil etc.

' The processes used at present to separate these sterols from the materials with which'they are mixed in nature are expensive and diflcult. It is a purpose of this invention to provide an economical, practical, commercial method for their extraction. Fatty or oily mixtures containing the above sterols will hereinafter be termed substrates.

It is desirable, before the process of this invention is applied to a substrate, that the sterol content of the substrate be in the form of free alcohols. It is also desirable, although not essential, that a large bulk of the saponiflable fraction of the substrate be removed. In many substrates, such as nerve tissue fat and tall oil, the sterols appear naturallyin this form. In

others, such as wool fat, a substantial fraction of the sterols appear in the form of esters and a preliminary treatment is necessary to recover these .fractions.

.Where esters of the desired sterols are present, their conversion to alcohols can be brought about by the saponiflcation of the substrate with a suitable basic ion, such as sodium or potassium hydroxide. The saponified portion is preferably separated from the unsaponifled fraction at this point and the latter retained for treatment in accordance with the process of this invention, or, at the option of the operator, the basic ion may be neutralized by the addition of acid ion and the entire mixture subjected to the process herein set forth.

The starting point of my process may be a substrate containing one or more sterols which have one reactive double bond and which are in the form of free alcohols. This substrate is dissolved in some substantially anhydrous solvent. Because of the solubility in them of addition products formed in a later step, alcohol solvents are not suitable. Nor should a solvent be used which reacts readily with th acid used in a later what less than is necessary to dissolve the substrate to a large excess over that amount. However, a large excess of solvent tends to lower the yield of sterols.

To the dissolved or partially dissolved substrate I add a molar excess of a strong, monobasic, anhydrous acid which does not contain oxygen. The acid should b in a form in which it is soluble or miscible in the solvent. Because of the ease with which they may be dissolved, I prefer gaseous acids, such as the hydrogen halides, for this reaction. Hydrogen chloride is especially suitable because of its cheapness,

solubility, ease of handling and absence of sidereactions.

The optimum temperature for this reaction for a particular combination of sterol, solvent and acid may easily be determined by one skilled in the art. I prefer temperatures between about 5 C. and about 20 C.- At lower temperatures there is a gradually increasing tendency toward the precipitation of other products from the solution of substrate, while at higher temperatures the solubility of the acid in the solvent is decreased, side reactions of the acid with the solvent and other materials present are increased, and the yield of sterols is reduced.

The result of the above treatment with acid is the precipitation from the solution of sterolacid addition'products, which, at the temperatures suggested, are relatively insoluble in the solvents. This crystalliine precipitate can be easily separated from the solution by filtrationor otherwise.

Addition of a molar excess of an alkaline ion to the precipitated sterol-acid addition product. removes the acid therefrom, leaving the free sterol. While it is not necessary, I find it convenient to add the alkaline ion in aqueous solution since the insolubility of the sterols in water makes the elimination of the salt solution formed very simple.

If two sterols, each containing one reactive double bond, are present in the same substrate,

such as, for example, cholesterol and iso-cholesterol in wool grease, I use the following procedure to separate them:

I dissolve the mixed precipitate of cholesterolacid addition product and iso-cholesterol-acid addition product obtained above in one of my solvents, which may or may not contain some of the acid used to precipitate the addition products. Solution is obtained by heating the solvent to a sufficiently high temperature. large crystals of cholesterol-acid addition productcrystallize and may be collected separately before the micro-crystals of iso-cholesterol-acid addition product crystallize. Then I neutralize each fraction with alkaline ion as shown above.

The following examples are illustrative of my invention:

Example 1 One hundred parts of a non-saponiflable fraction 'ofcommercial wool grease, containing 25 parts of free cholesterol, were dissolved in 500 parts of ethylene chloride and the solution cooled to 10 C. A molar excess of gaseous hydrogen chloride was passed into the solution, which thickened to a paste. After one-halt hour at the low temperature, the crystalline precipitate was filtered out and redissolved, at a temperature of 70 0., in ethylene chloride containing dissolved hydrogen chloride gas. deposited large crystals of cholesterol-hydrochloride which were filtered out. After a period of further cooling and standing, small crystals" of iso-cholesterol-hydrochlorlde were removed from the filtrate. Each portion was treated with a 4 per cent solution of sodium hydroxide and washed, producing 22 parts of cholesterol and 13 parts of iso-cholesterol in the form of alcohols.

Example I! tralizing solution, 0.9 part of cholesterol remained.

- Example 111 I Forty parts of nonsaponiflable oil containing 1 parts of phytosterol was dissolved in 130 parts of acetone, cooled to 15 C. and hydrogen bromide gas added in excess. The phytosterol hydrobromide separated rapidly and, after a period, of

I time, was filtered off and treatedwith excess 5 per cent solution of soda ash and washed, producing 8 parts of phytosterol. I

1. In a process for the 'separation,'from oily or fatty substrates, of sterols having one reactive double bond in the hydrophenanthrene nucleus, the steps of subjecting wool grease to saponifleation, separating the saponiflable and unsaponifiable portions thereof, dissolving the unsaponiflable portion in 'a tat-dissolving non-alcoholic n cooling, the- On cooling, the solution (In cooling the solution deposited 1 part of large crystals of cholesterol.-hydrochloride. After removal 01' the aqueous alkaline neu asaaooa solvent, treating the solution with a strong, monobasic, anhydrous acid which contains no oxygen. to form a precipitate of acid addition products of the-sterols, separating the precipitate from the solution, and treating the precipitate with an alkaline ion.

2. A process for the separation of sterols having one reactive double bond in thehydrophenanthrene nucleus from wool grease comprising, subjecting the wool grease to saponiflcation, separating the saponiflable from the unsaponifiable portions thereof, dissolving the unsaponiflable portion in a fat dissolving non-alcoholic solvent, treating the solution with a hydrogen halideat a temperature between C. and 20 C. to form a precipitate of hydrohalic acid addition products of the sterols, separating the precipitate, and treating the precipitate with an alkaline ion.

3. In a process for the separation, from nonsaponifiable fraction of oils or fatty substrates, of sterols having one reactive double bond in the hydrophenanthrene nucleus, the steps of .dissolving such substrate in a fat-dissolving nonalcoholic solvent and dissolving a hydrogen halide in such solution to precipitate the sterol acid addition product therefrom.

4. In a, process for the separation from the nonsaponifiable fraction of oily or fatty substrates; of sterols having one reactive double bond in the ing such substrate ina fat-dissolving non-alcoholic solvent, and treating such solution with a strong monobasic anhydrous acid which contains no oxygen to precipitate the sterol acid addition product therefrom.--

5. In a process for the separation from the nonsaponifiable fraction of oily or fatty substrates, of sterols having one reactive double bond in the hydrophenanthrene I nucleus, the steps of dissolving such substrate in a fat-dissolving nonalcoholic solvent, and treating such solutions with a hydrogen halide at a temperature between about 5 C. and about 20 C. to precipitate from the solution the sterol acid addition product.

saponifiable fraction of oily or fatty substrates, of

sterols having one reactive double bond inthe hydrophenanthrene nucleus, the steps of dissolving such substrate in a fat-dissolving nonalcoholic solvent, and dissolving hydrogen chloride in such solution at a temperature between about 5 C. and about 20 C. to precipitate the I sterol acid addition product therefrom. I

7. A process for the separation of cholesterol in a fat-dissolving non-alcoholic solvent, and

treating such solution with a hydrogen halide to I hydrophenanthrene nucleus, the steps of dissolv- 6. In a process for the separation from the nonfrom the non-saponifiable fraction of oily or fatty substrates, comprising dissolving such substrate CERTIFICATE or CORRECTION. Patent No. 2,322,9 6. June '29, 1915.

LESTER YYODER. r.

It is hereby certified that error appears in the printed specification or the above numbered patent requiring correction as follows: Page 1, first column, line 8, for "cholestrol" read --cho1esterol--; page 2, second column, 1ine 20, claim '5, for the Word "oils" read-wily"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case inthe Patent Office.

Signed and sealed this 10th day of August, A. D. 1914.}.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.