GB2058792A - Process for the Preparation of L- alpha -Glycerylphosphoryl Choline - Google Patents

Abstract

L- alpha -glycerylphosphoryl choline is obtained from lecithin in a pure state by subjecting purified lecithin to alcoholysis in the presence of a catalytic amount of an alkali metal alkoxide. The process can be carried out economically on a commercial scale because of the ease of recovery of the desired reaction product. A methanol/sodium methoxide system is preferably used in the alcoholysis.

Description

SPECIFICATION Process for the Preparation of L--glyceryl- phosphoryl Choline This invention relates to a process for the preparation of L-a-glycerylphosphoryi choline (I) in a state of high purity.

When L-r;glycerylphosphoryl choline of formula:

is administered intramuscularly or orally, it has been observed that it protects liver tissue from fatty penetration induced by a hyperlipoproteinaceous diet or caused by poisoning by carbon tetrachloride. Administration of L-a-glycerylphosphoryl choline has also been found to provide protection against cholestastis.

An important fact which has been observed is that the glycerylphosphoryl choline enters into the structure of the lipoproteins. Researches into pharmacokinetics demonstrate that the glycerylphosphoryl choline is rapidly absorbed by the intestine or at the location of intramuscular innoculation. It is circulated in the blood stream and is distributed to the organs, especially to the liver, to the kidneys and to the brain. At the liver in particular, it is put back into circulation, incorporated in the lipoproteins. It is because of this behaviour that glycerylphosphoryl choline may be considered to possess antidislipemic action.

L-a-glycerylphosphoryl choline (I) may be obtained by hydrolysis of lecithine, in particular lecithine from egg. The major problem encountered in the production of L glycerylphosphoryl choline is its purification; the secondary products which accompany the L-a- glycerylphosphoryl choline (I) obtained by hydrolysis both reduce the therapeutic value thereof and frequently lead to undesirable side effects. However some relatively successful attempts have been made to obtain (I) in particularly pure form.

Thus in United States Patent No. 2,864,848 there is disclosed a procedure in which the hydrolysis of lecithine is effected in the presence of mercuric chloride which is employed to precipitate the secondary products in the form of mercuric salts; this then makes it necessary to remove from the glycerylphosphoryl choline surplus mercuric ions, which, obviously, are toxic, and this is carried out by means of a complicated treatment with H2S and BaCO3. The same patent; nevertheless points out that such treatment does not sufficiently remove all the mercuric ions and subsequently additional purification operations are needed. In particular the final product must be purified by the formation of a complex with cadium chloride. The overall operation is thus very complicated, and the final product is not free from heavy metals.

An analogous technique to the preceding one is described in Biochemical Preparation (Vol. 6, pages 16 to 19); the final removal of the cadmium is in this case effected by passage of the reaction product over a mixture of exchange resins. This also renders the process complex and, moreover, results in a reduction in product yield.

As an alternative to hydrolysis, Brockerhoff (Journal Lipid Research 4, 96 (1963)) describes the methanolysis of a very diiute solution of lecithine (about 21 g/litre) with sodium methoxide employed in an amount of 3 mols of methoxide per mol of phosphatide. Methanolysis carried out under these conditions, has been found to lead to a partial scission of the bond P--O, with formation of harmful by-products, as well as the desired scission of the acyl-oxygen bond.

Okui and collaborators (Yakugaku Zasshi 84 (12), 1206-9 (1964)) describe the preparation of (I) from lecithine from egg by means of hydrolysis carried out using alkaline earth metal hydroxides. The product obtained is, however, rendered very impure by secondary components.

Brockerhoff and Yurkowski describe in a short note in Canadian Journal of Biochemistry, 43, 1777 (1965) that the preparation of (ì) can be carried out by hydrolysis of lecithine with a quaternary ammonium base (tetrabutyl ammonium hydroxide): the hydrolysis proceeds satisfactorily as Chadha (Chem. Phys, Lipids, 4, 104-108 (1 970)) has shown. However the overall hydrolysis with this base is commercially expensive, and does not allow glycerylphosphoryl choline to be obtained free from tetrabutyl ammonium hydroxide, which has to be separated from (I) in a crystallisation operation. Moreover this unsatisfactory process does not lend itself well to operation on large scale, being incapable of reproduction.

Finally Cubero Robies and Roels (Chem. Phys.

Lipids 6,31-38(1971)) describe a process wherein L-cr-glycerylphosphoryl choline is obtained by methanolysis of a fatty extract obtained by comminuting egg yolk. The method described by these authors includes the extraction of the powder with chloroform/methanol, the evaporation of this mixture of solvents, the dissolution of the residue in ether and the treatment of the ethereal solution with lithium methoxide.

This last reagent is employed in an amount of 1 mol per mol of phosphatide. The treatment with this reagent yields a mixture of glycerylphosphoryl choline (GPC) and glycerylphosphoryl ethanolamine (GPE). After neutralization of this mixture with HCI, the GPC and GPE are separated by means of chromatography on silica. In practice it has been observed that this chromatography yields GPC contaminated by colloidal silicic acid (as was predictable, given that the eluant is water). The silicic acid contaminant is removable only by means of repeated crystallisations of the final product. These crystallisations are very difficult to carry out.

Summing up, the processes described above for obtaining GPC of satisfactory purity are generally inconvenient and uneconomic to carry out on a commercial scale.

It has now unexpectedly been found that GPC can be obtained pure and in high yield and by a relatively simple procedure which can be carried out without difficulty on a commercial scale, if methanolysis of purified lecithine is effected in the presence of a catalytic quantity of sodium methoxide related to the amount of lecithine being employed.

Thus, according to the present invention, there is provided a process for the preparation of L-aglycerylphosphoryl choline (I)

in a pure state which comprises subjecting purified lecithine to alcoholysis catalysed by an alkali metal alkoxide of the alcohol used in the alcoholysis.

The product which is obtained is sufficiently pure for it not to need to be subjected either to recrystallisation, which, as stated above, is particularly difficult, or to complexing with CdCl2, both of which purification operations are not suitable for carrying out on an industrial scale.

The alcoholysis in the process of this invention is preferably carried out by using methanol.

Moreover, the alkoxide catalyst used is preferably a sodium alkoxide. Hence, the use of a methanol/sodium methoxide system is preferred.

In preferred practice, the process of this invention is carried out by allowing a methanolic solution of purified lecithine preferably containing about 39% by weight of lecithine and containing catalytic quantities of alkoxide to stand for about 60 minutes at ambient temperature. The alkoxide is preferably used in an amount of from 0.01 to 0.1, and more preferably 0.05 mol/mol of lecithine. At the end of the reaction the esters of the fatty acids which have separated out during the reaction are removed and the residual alcoholic solution is treated with about 8 equivalents of weak cationic resin IR--C 50 (H+) per equivalent of alkoxide in order to eliminate the alkali metal ions.

The eluate and washings from the resin are concentrated to small volume by evaporation under reduced pressure (e.g. 12 mm Hg) and, after dilution with water, are extracted with chloroform to remove the last traces of the esters of the fatty acids, the final traces of undeacylated or partially deacylated lecithine and the traces of sphingomyelin which are generally to be found in lecithine obtained from eggs. The aqueous phase is evaporated to dryness under reduced pressure, and then, if desired, the product is decolounsed with carbon SL50.

The product obtained is free from hydrolysis impurities, from inorganic salts and from esters of fatty acids and does not show significant differences in properties from samples of GPC obtained by formation of the complex with CdCI2, successive crystallisations, decomposition of the same by passage over exchange resins and final crystallisation of the L-cr-glycerylphosphoryl chloline thus obtained.

The L-cr-glycerylphosphoryl choline obtained by the method of the invention generally has a moisture content of about 1 5% by weight.

The moisture can be removed, if desired, by drying over P205 under a high vacuum followed by repeated crystallisations from ethanol/diethyl ether or from ethanol/ethyl acetate; a colourless hydroscopic solid is thus obtained melting at from 130 to 131 OC and of empirical formula C8H2oNOsP- Such operation is obviously not necessary if it is desired to utilise the L-cz-glycerylphosphoryl choline in aqueous solution or else in association with other principle active ingredients in injectible lyophilised proprietary medicines, as is usually the case. It is now possible to utilise the amorphous product as such without recourse to successive purifications since the purity of the deacylated phosphatide is more than satisfactory from all points of view.

The following examples illustrate the invention: Example 1 a) Purification of Lecithine Lecithine from raw egg (alkali labile P: 2.7 to 2.85%; P of glycerylphosphoryl choline: 2.24 to 2.52%) was used as starting material. A solution of 0.5 kg raw lecithine in 1 litre methylene chloride was poured into 6 litres of acetone which was undergoing stirring at 50C. After 60 minutes, the liquids were decanted, and purification was carried out involving dissolving the residue in methylene chloride (1 litre) and pouring the solution into acetone (6 litres) as before. The precipitate which formed was filtered and dried under vacuum (12 mm Hg) at ambient temperature (320 g).

A solution of the lecithine (320 g) in chloroform-methanol 1:1 by volume (650 ml) was chromatographed on Al203.(1.4 kg), eluting with chloroform-methanol 1:1 by volume (3.5 litres) being carried out. The eluate was concentrated to dryness under a vacuum (12 mm Hg) at a temperature of 400C and was then dissolved again in methylene chloride (350 ml), centrifuged and poured into acetone (2.4 litres) at 5 or, undergoing stirring.

After remaining for 60 minutes at 50C, the precipitate which formed was filtered and dried under a vacuum (12 mm Hg) at ambient temperature, to yield 210 g of pure lecithine (alkali-labile P: 3.703.80%: P of glycerylphosphoryl choline 3.703.80%).

b) Preparation of the L-cz-glycerylphosphoryl Choline A solution of lecithine purified as set out in a) (about 500 g; 0.7 mol) in anhydrous methanol (1 litre) containing 0.039 mol of sodium methylate was allowed to stand, at ambient temperature, for 60 minutes. The oily layer thus formed was separated off and then the solution was filtered through a bed consisting of 80 g of the resin IR C 50 H+, the bed having a height of 50 cm, the adsorbed matter being subsequently eluted with methanol, 1 litre quantities being used each time.

The eluate was concentrated under vacuum (12 mm Hg) at 400C to a volume of about 1 litre, then was diluted with water (550 ml) and was extracted with chloroform (4x400 ml).

The aqueous phase was concentrated to dryness under vacuum (12 ml Hg) at 400C, the residue was dissolved in water (410 ml), 12 g of decolourising carbon were added and the aqueous phase was stirred at ambient temperature for 1 5 minutes. It was filtered on millipore and the solvent was removed under reduced pressure (12 ml Hg) at400C, 165 g of La-glycerylphosphoryl choline in pure amorphous form being obtained.

H20=1 5.5% Total P=84.1% Phosphorus after chromatographic separation 83.94% Vicinal glycol: 84.59% Choline: 85% Products of scission of the P--O bond were not observed, as was verified by effecting analysis of the sample according to Brockerhoff (J. Lipids Research 4, 96 (1963)) or according to Dawson (J. Biochem. 75, 45 (1960)). A sample dried over P205 at 0.05 mm Hg was crystallised from ethanol 99%--ethyl ether, a white, hygroscopic crystalline solid being obtained which melted at 130 to 131 C; CED=2.84 (10% in H20).

C=37.50; H=7.70; N=5.38; P=12.06; Choline ester=46.92; Vicinal glycol=99.8%.

Calculated: C=37.35; H=7.84; N=5.45; P=12.04 Choline ester =47.12.

Example 2 Soya lecithine (alkali labile phosphorus: 2%; minimal P of GPC: 0.5%) was used as starting material. A suspension of this lecithine (600 g) in methanol (600 ml) was stirred at ambient temperature for 60 minutes. It was allowed to remain at SOC for 60 minutes and then the solvent was decanted, the residue being washed with methanol (300 ml). The methanolic extract was allowed to remain at 50C for 18 hours, then was filtered and concentrated to dryness under reduced pressure (12 mm Hg) at 400C (70 g) (alkali labile P: 3.03.1%; P of the glycerylphosphoryl choline 2.0-2.1%). The repeated purification of the residue furnished 20 g of pure lecithine.

The lecithine was treated in the same way as the egg lecithine used in Example 1. GPC of equal purity and in substantial identical yield was obtained.

Claims (12)

Claims

1. A process for the preparation of a L-a- glycerylphosphoryl choline (I)

in a pure state which comprises subjecting purified lecithine to alcoholysis catalysed by an alkali metal alkoxide of the alcohol used in the alcoholysis.

2. A process as claimed in claim 1, wherein 0.01 to 0.1 mol of alkoxide is employed per mol of lecithine.

3. A process as claimed in claim 2, wherein 0.05 mol of alkoxide is employed per mol of lecithine.

4. A process as claimed in any one of the preceding claims, wherein said alcohol is methanol.

5. A process as claimed in any one of the preceding claims, which is catalysed by a sodium alkoxide.

6. A process as claimed in claim 2 or 3, wherein methanolysis catalysed by sodium methoxide is carried out.

7. A process as claimed in any one of the preceding claims, which is carried out at ambient temperature.

8. A process as claimed in claim 7, which is carried out over a period of about 60 minutes.

9. A process as claimed in any one of the preceding claims, which is carried out using purified egg lecithine.

10. A process as claimed in any one of claims 1 to 5, which is carried out using purified soya lecithine.

11. A process for the preparation of L glycerylphosphoryl choline substantially as described in either of the foregoing examples.

12. L-a-glycerylphosphoryl choline, whenever produced by the process claimed in any one of the preceding claims.