SK279878B6 - A method of preparing physiologically tolerated water-soluble starch esters, and use thereof - Google Patents

Abstract

In order to prepare physiologically tolerated water-soluble starch esters, the invention proposes that starch is converted by acid hydrolysis or enzymatic hydrolysis to a partially hydrolysed form with a mean molecular weight in the range from 10,000 to 500,000 Daltons. This partial hydrolysate is then acylated, in aqueous solution, with the anhydride or halide of an aliphatic monocarboxylic acid with 2 to 4 carbon atoms or an aliphatic dicarboxylic acid with 3 to 6 carbon atoms, or mixtures thereof, and an alkalinization agent, to give a product with a substitution ratio in the range from 0.1 to 1.0 mole/mole. Salts are removed from the resulting reaction mixture. The starch esters thus obtained are highly suited for clinical use, in particular parenteral administration and administration in the diet.

Description

Technical field

The invention relates to a process for the production of water-soluble, physiologically acceptable starch esters for clinical, especially parenteral use.

BACKGROUND OF THE INVENTION

Water-soluble, biocompatible polymers are required for other solutions, plasma substitutes, blood diluents or peritoneal dialysis and nutritional solutions. Up to now, gelatin, gelatin derivatives, dextran and hydroxyethylated starches have been used in particular for this purpose, as described, for example, in U.S. Pat. No. 3,937,821, DE 3,313,600 and Rompp's Chemie Lexicon, 9th edition, p. 919 and 1509.

For clinical use, in particular as a plasma substitute, predominantly solutions of dextran polysaccharide and hydroxyethylated starch are used. A significant disadvantage of dextran is that anaphylactic reactions may occur in the presence of pre-formed antibodies, so that the use of this substance is dangerous or it is necessary to pre-administer neutralizing low-molecular weight hapten. Side effects are rarely observed with short-term administration of hydroxyethylated starch, but with long-term administration, deposition of this substance occurs, especially in reticuloendothelial tissue, so long-term use of this derivative is severely limited. Hydroxyethylated starches can be degraded only slowly or incompletely by the enzymes of the body tissues, since ether erosion impairs the effect of glycosidases of the body tissues. Until now, it has not been established with certainty whether the deposition of these agents may affect the functional properties of the reticuloendothelial system, but itchy pruritus rash occurs and therefore administration should be discontinued. Recently, it has also been proposed to use esters of lower aliphatic monocarboxylic or dicarboxylic acids, in particular acetyl derivatives of starches, the advantage being that they do not elicit antibody formation and are completely eliminated or metabolized.

In addition to good water solubility, a polymer intended for clinical, especially parenteral administration, must meet the following requirements:

- The polymer solution must have a viscosity not higher than that of blood plasma at the concentration used for medical purposes.

- The substance must persist in the body for a period appropriate to its intended use and must be degraded after some time after parenteral administration. This requirement can be adjusted in the case of acylated starch derivatives by the degree of esterification, with increasing molar substitution slowing the degradation of alpha-amylases from the body.

- The substance must be non-toxic, pyrogen-free and must not induce antibody formation.

The starch esters known to date cannot meet these requirements or at least do not meet all these requirements.

For use in the food industry, higher viscosity acetyl derivatives of starches with an acetyl content of not more than 2.5% are required, corresponding to a molar substitution (MS) of not more than 0.064 mol / mol. These products are unsuitable for clinical use because of their tacky nature in aqueous dispersions and because of their rapid degradation due to their low molar substitution. Low viscosity and low molecular weight acetyl starch derivatives are used for starching textile materials and for sizing paper. These products are also unsuitable for clinical use due to their low molar substitution, undefined molecular weight distribution and low purity, as described, for example, in OB Wuizburg, Modified Staeches, Properties and Usec, CRC Press Inc., Boca Raton, Florida, 1986, p. 55 to 74.

U.S. Pat. No. 2,362,282 discloses the production of acetyl starch derivatives in which starch hydrolysates having a low dextrose equivalent (D.E.) value are to be obtained, which are proposed for use as adhesives. At the same time, depolymerization and acetylation are carried out by heating in a high percentage acetic acid solution. This acid hydrolysis is difficult to control and the resulting product is not physiologically acceptable, inter alia because of its too low molecular weight.

In British Pat. No. 1,476,057 describes the use of a composition containing starch derivatives for the manufacture of pastilles against pharyngitis. As the starch derivative, arnylopectin, esterified by the action of vinyl acetate, is used without mentioning how it is produced and its degree of substitution and molecular weight. Such a product is unsuitable for parenteral administration.

U.S. Pat. No. 3,639,389 describes starch syrups with a low degree of substitution, dissolved in a clear solution and obtained using starch hydrolyzates having a D.E. Because of their low molecular weight, these products are unusable for parenteral administration.

SUMMARY OF THE INVENTION It is an object of the present invention to provide water-soluble, physiologically acceptable starch esters suitable for clinical and in particular parenteral use, by means of which the disadvantages of the hitherto used products can be overcome. Said esters should meet all the requirements for polymers for clinical, especially parenteral use.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention provides a process for the preparation of water-soluble, physiologically acceptable starch esters, the process comprising the step of converting starches by hydrolysis by acid or enzyme to a partial hydrolyzate having an average molecular weight Mw of 10,000 to 500,000. in aqueous solution by treatment with an anhydride or a halide of an aliphatic monocarboxylic acid having 2 to 4 carbon atoms or an aliphatic dicarboxylic acid having 3 to 6 carbon atoms or mixtures of these substances and an alkalizing agent up to a molar substitution in the range of 0.1 to 1.0; the salts were removed.

The starches used in the process according to the invention are those which consist of amylopectin practically free of amylose and containing not more than 1% by weight of amylase. Preferred examples of such starches are corn, rice or sorghum starches in wax maturity.

The molecular structure of amylopectin corresponds to the structure of glycogen, which is common in the animal body, so that no toxicity or antigenic action is to be expected. After cleavage of acyl groups readily hydrolyzable by enzymes from the organism, the practically residual molecule cannot be distinguished from glycogen, metabolism also proceeds in the same manner as in the example of glycogen.

By partially degrading the starches by the process of the invention, the viscosity of the solutions to be used for medical use can be adjusted to the desired range. Preferably, the starches are hydrolyzed to an average molecular weight in the range of 40,000 to 250,000.

The hydrolysis can be carried out in a manner known per se by treatment with an acid or an enzyme. If an acid is used, a strong mineral acid, for example hydrochloric or sulfuric acid, is preferably used. Of the enzymes, alpha-amylase is preferred for carrying out the hydrolysis. It is also possible to combine hydrolysis using both acid and enzyme in any order.

The degree of hydrolysis can be easily monitored by measuring the viscosity of the sample diluted with water to adjust the course and completion of the hydrolysis to achieve the desired degree of degradation.

After hydrolytic degradation has been carried out, the partially hydrolyzed starch is acylated in aqueous solution by treatment with an anhydride or halide of an aliphatic monocarboxylic acid having 2 to 4 carbon atoms or an aliphatic dicarboxylic acid having 3 to 6 carbon atoms until molar substitution in the range 0.1 to 1.0 mol / mol., a preferred range is 0.3 to 0.7 mol / mol. The anhydride or halide used is derived from an aliphatic monocarboxylic acid having 2 to 4 carbon atoms or an aliphatic dicarboxylic acid having 3 to 6 carbon atoms. Of the aliphatic monocarboxylic acids, for example, butyric, isobutyric, propionic and especially acetic acid are suitable. Of the C 3 -C 6 aliphatic dicarboxylic acids, saturated or unsaturated acids may be used, preferably the derivative is derived from an alpha, -dicarboxylic acid, for example glutaric, adipic and especially succinic or maleic acids. Of the halides, chlorides are preferred, but bromides and iodides can also be used. The process according to the invention proceeds particularly well with acetyl chloride and in particular with acetic anhydride.

It is also possible to use a mixture of two or more of said monocarboxylic or dicarboxylic acids.

The acylation is carried out in the presence of an alkalizing agent so that the acids formed are simultaneously neutralized. Preference is given to using alkali metal or alkaline earth metal hydroxides, carbonates or oxides, in particular sodium hydroxide, calcium hydroxide and / or magnesium oxide, as alkalizing agents.

The reaction conditions for the acylation with anhydride or acid halide correspond to the usual conditions for this reaction, the reaction preferably being carried out with vigorous stirring at room temperature.

The removal of salts from the mixtures obtained after the acylation can preferably be carried out by dialysis, ultrafiltration (diafiltration) or ion exchange. It is also possible to use two identical or different stages or a plurality of stages in which salts are removed in succession.

Depending on the envisaged use of the starch ester, it may be expedient to remove other low molecular weight components, such as low molecular weight starch degradation products, preferably as completely as possible, in addition to salts. This removal can be carried out before and / or after the acylation step, for example by dialysis and in particular by ultrafiltration (diafiltration), whereby the membrane can be chosen depending on the intended use, with removal of the corresponding components. Suitably, the low molecular weight components are removed together with the salts after the acylation has been carried out. Depending on the desired degree of purity, two or more purification steps may be performed.

The reaction mixture obtained after hydrolysis (partial hydrolyzate) and / or in particular the reaction mixture obtained after removal of salts and optionally other low molecular weight components is preferably sterilized by filtration before further processing or before use.

The starch ester solution obtained after removal of salts and possibly other low molecular weight components can be used per se, but for better shelf life, the solution is usually converted to a dried product. For this purpose, the solution can be gently concentrated in vacuo, followed by drying the product under vacuum, but it is also possible to freeze-dry the ester solution to form a well-stored product.

Due to their properties, particularly good water solubility and physiological acceptability, the starch esters of the invention are very suitable for clinical, especially parenteral administration.

The starch esters prepared by the above process can be used for the preparation of pharmaceutical compositions for peritoneal dialysis as well as for the preparation of blood plasma substitutes, for example according to German patent application no. P 41 22 999.1 Metabolisierbarer Plasmaersatz and P 41 23 001.9 Pharmazeutischc Zusammensetzung fur die Peritonealdialyse (Laevosan-Gesellschaft mbH with the same filing date as the present application).

The following examples illustrate the invention. Unless otherwise indicated, all percentages and percentages by weight and temperature are in ° C.

BRIEF DESCRIPTION OF THE DRAWINGS

In FIG. 1 shows the serum concentration measured after a three-hour infusion immediately after the end of the infusion (A to E) and 3 hours after the end of the infusion (F, G, H). In FIG. 2 shows the renal hydrocolloid content in mg / g immediately after the end of the infusion (B, C, D, E and NaCl), 3 hours after the end of the infusion (F, G) and 18-24 hours after the end of the infusion (I, J, K, L). In FIG. 3 shows data corresponding to FIG. 2, but for the lungs.

The data A to L in FIG. 1 to 3 refer to the following plasma replacement solutions: A - 3% acetylated starch, B - 6% acetylated starch, C - 10% acetylated starch, D - 6% HES 200 / 0.5, E - 10% HES 200 / 0,5, F - 6% acetylated starch, G - 10% acetylated starch, H - 3% acetylated starch, I - 6% acetylated starch, J - 10% acetylated starch, K - 6% HES 200 / 0,5 , L - 10% HES 200/0, 5, NaCl = sodium chloride.

SK 279878 Β6

DETAILED DESCRIPTION OF THE INVENTION

Example 1

Preparation of waxy corn starch partial hydrolyzate (Mw approximately 200 000)

4000 g of waxy maize starch with a water content of 10.0%, equivalent to 3600 g of anhydrous starch, are suspended in 12.5 kg of dehydrated water, 3.85 g of calcium chloride dihydrate and 1 g of alpha-amylase are added (Termamyl 60 L, NOVO, Copenhagen) and the mixture was rapidly heated to 95 ° C with stirring. The starches enter the solution without forming a highly viscous phase. The mixture is maintained at 95 ° C until the viscosity of the sample, diluted with water to 20% 1.5, is based on the viscosity of water at 20 ° C. Degradation is stopped by acidifying the mixture with hydrochloric acid to pH 3.0, then the reaction mixture is stirred for 10 minutes at 95 ° C and then cooled to room temperature, adjusted to pH 5.5 by addition of sodium hydroxide solution and filtered. through sterile layers. A light yellow colored 15.6 kg degraded starch solution with a dry matter content of 22.4% is diafiltrated through an ultrafiltration membrane separating substances from a molecular weight of 30,000 to remove the low molecular weight components, thereby obtaining 10.2 kg of a 19.6% solution, containing 2,0 kg of amylopectin degradation products. Portions of this solution are then used as starting material in the following Examples 2 and 3.

Example 2

Preparation of acetylated starch (Mw 200 000, MS 0,35)

To 826.5 g of the degraded starch solution obtained by the method of Example 1, containing 162 g of dry matter (1 mol of CH6H10O5), was added, uniformly in portions, in one portion, 40.8 g (0.40 mole) of anhydrous acid. acetic acid is added while monitoring the pH of the 2 N sodium hydroxide solution so as to maintain the pH in the range of 8.0 to 8.5.

225 ml, 0.45 mole of solution are used.

The solution obtained is subjected to diafiltration through an ultrafiltration membrane separating substances from a molecular weight of 30,000 until a conductivity of less than 1 pS / cm is achieved. After adding 1.6 g of activated carbon, the solution is filtered through sterile layers, concentrated in vacuo to a thick syrup, and then dried to a brittle white mass in a vacuum oven. This mass was ground to yield 165.0 g of product. The molar substitution is 0.355 mol / mol. The material was tested on rabbits according to the European Pharmacopoeia and was shown to be pyrogen-free, the animals were tolerated without any reaction.

Example 3

Preparation of acetylated starch (Mw 200 000, MS 0,50)

To 826.5 g of a degraded starch solution containing 162 g of dry matter (1 mole of CH6H10O5) was added portionwise 64.85 g (0.635 mole) of acetic anhydride while stirring vigorously with a magnetic stirrer over 2 hours while monitoring the pH. 2 N sodium hydroxide solution such that the pH is in the range of 8.0 to 8.5. 500 ml of the solution (1.0 mol) is used.

The solution thus obtained is subjected to diafiltration through an ultrafiltration membrane separating substances from a molecular weight of 30,000 up to a conductivity of less than 1 pS / cm. After the addition of 1.6 g of activated carbon, the solution is filtered through sterile layers, evaporated in vacuo to a thick syrup and then dried to a brittle white mass in a vacuum oven. After milling, the yield is 166.4 g. The molar substitution is 0.502 mol / mol. The material was tested on rabbits according to the European Pharmacopoeia, pyrogen-free and the animals were tolerated without reaction.

Example of use

Preparation of a blood plasma replacement solution

The starch esters used were acetylated starches according to the invention having an average molecular weight of 200,000 and a degree of substitution of 0.3 or 0.5. The following blood plasma replacement solutions were prepared:

A solution of 3, 6 and 10% acetylated starch in 0.9% saline.

2. Acetylated starch solution at 6% w / w in a 2,5% w / w glycerol solution (electrolyte-free solution).

Monitoring of biodegradability

Prepared solutions of 3, 6 and 10% acetylated starches (degree of substitution 0.3 or 0.5) in saline were administered intravenously to rats at 18 ml in 3 hours.

Infusions were well tolerated and no side effects were immediately observed. Blood plasma concentrations of acetylated starch derivatives were measured immediately after the end of the infusion, and values of 6 to 25 mg / ml were found depending on the concentration of the solution. These values are comparable to those obtained with hydroxyethylated starches in solution (HES 200 / 0.5, Mw 200 000, molar substitution 0.5 mol). After 3 hours after the end of the infusion, 1.0-10 mg / ml of acetylated starches could be measured in animal blood. This amount also corresponds to the amount measured after administration of a hydroxyethylated starch solution (HES 200 / 0.5) under comparable conditions. 24 hours after the end of the infusion, no acetylated starch derivative could be detected in the blood.

Claims (11)

PATENT CLAIMS A process for the production of water-soluble, physiologically acceptable starch esters, characterized in that starches are converted by hydrolysis by acid or enzyme treatment to a partial hydrolyzate having an average molecular weight Mw in the range of 10,000 to 500,000, which partial hydrolyzate is acylated in an aqueous solution by treating with an anhydride or halide of an aliphatic monocarboxylic acid having 2 to 4 carbon atoms or an aliphatic dicarboxylic acid having 3 to 6 carbon atoms or mixtures of these substances and an alkalizing agent up to a molar substitution between 0.1 and 1.0 mol / mol; the salts obtained and, before and / or after the acylation, the low molecular weight constituents of the mixture are removed. Process according to claim 1, characterized in that amylopectin, practically free of amylose, is used as the starch for carrying out the process. Method according to claim 1 or 2, characterized in that the starch is corn, rice or sorghum starch in wax maturity. Process according to any one of claims 1 to 3, characterized in that the starch is hydrolyzed until the average molecular weight Mw is in the range of 40,000 to 250,000. Process according to any one of claims 1 to 4, characterized in that the enzymatic hydrolysis is carried out using alpha-amylase. Process according to any one of claims 1 to 5, characterized in that the acylation is carried out until a molar substitution of 0.3 to 0.7 mol / mol is achieved. Process according to any one of claims 1 to 6, characterized in that it is carried out using acetic anhydride or halide as a monocarboxylic acid derivative. Process according to any one of claims 1 to 6, characterized in that the dicarboxylic acid anhydride or halide is a succinic or maleic acid derivative. Process according to any one of claims 1 to 8, characterized in that sodium hydroxide, sodium carbonate, calcium hydroxide or magnesium hydroxide is used as the alkalizing agent. Method according to any one of claims 1 to 9, characterized in that the removal of salts and / or low molecular weight components is carried out by dialysis, ultrafiltration and / or ion exchange. Use of the starch esters according to claim 11 for the preparation of pharmaceutical compositions for clinical, especially parenteral use or for the preparation of dietetic compositions.