Method to produce water-soluble oligomer homologs of chitosans in heterogeneous system

FIELD: biotechnologies.

SUBSTANCE: method includes depolymerisation of a high-molecular chitosan with hydrogen peroxide. The process of chitosan depolymerisation is carried out in a double-phase system. The solid phase is activated chitosan with Mav = 450-650 kDa and the average particle size of 0.05-0.20 mm. The liquid phase is a water solution of H2O2 with concentration of H2O2 in a reaction system equal to 1-7%. The reaction is carried out for 120-180 minutes at 70°C. Then phase separation of produced chitosan homologs is carried out by means of filtration via paper or textile surface of the produced reaction mixture. The produced filtrate contains water-soluble chitosan oligomers.

EFFECT: invention makes it possible to quantitatively control extent of conversion of an initial high-molecular chitosam into oligomer and low-molecular structures of its homologs.

1 tbl, 1 ex

 

The invention relates to the field of chemistry of biopolymers-aminoglycan and can be used in pharmacy, medicine, veterinary medicine, cosmeceuticals.

Known for authoring, publishing, dedicated to the study of the process of peroxide hydrolysis of chitosan with the aim of obtaining its low molecular weight homologues. The regularities of the development process of the decomposition of chitosan in heterogeneous systems. The dependence of the degree of destruction aminoglycan from process parameters. Eksperimentalno determined following dependence DD=ln(M0/M)=f{[H2O2]}·τ}, where DD is the degree of decomposition, M0and M - srednevozrastnoe molecular mass (MM), respectively, the source and destruktivnogo acid-soluble chitosan, τ is the time in min, allows you to set conditions of degradation for a given MM target chitosan for any values of MM of the original polymer. It is shown that the degree of deacetylation of the original chitosan in the process of peroxide decomposition is practically unchanged (Sychuk AV Universal measure the depth of the degradation of the polymer. The logarithm of the relationship of molecular masses. RBM. Chem. Journe. 1991. T. 11. S; Gamzazade, A.I., Slimak V.M., Sklar A.M., Shtikova E.V., Pavlova S.V., Rogojin S.V. // Acta Polymerica. 1985. V.36. 8. P.420). Destruction rigid aminoglycan chitosan in a heterogeneous system leads to lower MM and the extension m is LeCoultre mass distribution (MMD) due to the increase in the content of the oligomeric fraction of homologues. Data obtained by the method of exlusionary chromatography show that when you change the relationship of M0/M ~of 6.7 (DD=1,9) to ~21,1 (DD=3,1) under conditions of heterogeneous peroxide hydrolysis-depolymerization of chitosan expansion of DFID, and the content in the products of hydrolysis of oligomeric fractions, including monomer, increases to 30%. For chitosan, destruktivnogo in heterogeneous conditions with srednevozrastnoe MM ~80-100 kDa, characterized by a broad MMP - from 150 kDa to oligomeric fractions; for option MM chitosan ≤25 kDa MMP includes fractions from ~50 kDa to monomer.

Closest to the proposed method of obtaining water-soluble oligomeric homologues chitosan is a method of peroxide hydrolysis aminoglycan with MM ~350 to 600 kDa in a heterogeneous system used to obtain homologues of chitosan with low molecular weight in the range of ~80 kDa to oligomeric structures with a degree of polymerization of 1-10. This method is included in the description of the patent for a method of obtaining water-soluble chitosan (RF patent 2215749, SW 37/08, A61K 32/722, 2003). The essence of the proposed method is to obtain samples of mixtures of homologues of chitosan with a range of molecular masses from ~100 kDa to oligomeric groups, including the monomer (glucosamine). The ultimate aim of the invention was to prepare drugs with an extended range of biological dei is of conduct for use in medicine, veterinary medicine and cosmetics.

Homologues of chitosan was used to conduct hydrolysis and salt formation with organic (amber, L-glutamine) and inorganic (hydrochloric, phosphoric) acids, and anhydrides of organic acids. In addition to these methods of processing high molecular weight chitosan were ways amorphous polymer to increase its reactivity and hydrophilicity by resultant deposition rates from solutions in acids with increasing pH. With the same purpose used method of homogenization of the suspension of chitosan in aqueous solutions of organic acids in the mode of creating cavitation mechanical fields with shear effect on the working volume.

Description of methods of depolymerization of chitosan in a heterogeneous system involving as oxidant glycosidic centers (misbelieve ties) of hydrogen peroxide is provided in two ways:

a) Hydrolysis of chitosan with MM ~600 kDa in the system containing 0.15% of H2O2at 80°C for 25 minutes the result is a mixture of homologues of chitosan is insoluble in water with Mcf~80 kDa.

b) Hydrolysis of chitosan with MM ~300 kDa in the system containing 0.2% H2O2at 80°C for 34 minutes the Resulting mixture of homologues of chitosan is characterized by Mcf~20-25 kDa (insoluble in water).

Oligom the RNA fraction of homologues of chitosan was obtained under the conditions of acid hydrolysis aminophenol in aqueous solution of orthophosphoric acid.

a) Hydrolysis of chitosan with MM ~350 kDa. Phosphoric acid was used when the ratio of the chitosan to 0.6:1. The process was carried out at 70°C for 4 hours. After neutralization of the mixture (Ca(OH)2), phase separation, freeze drying and lyophilization selected mixture of water-soluble oligomers of chitosan (degree of polymerization=1-10); the output of 13.4%.

b) Hydrolysis of chitosan with MM ~25 kDa. The value entered in the hydrolysis of phosphoric acid and chitosan (aqueous medium) is identical to the method (a). The temperature and duration of the process is identical to the method (a). After processing by the method specified in (a) selected oligomeric water-soluble fraction of homologues of chitosan (degree of polymerization=1-10) with a yield of 20%.

The disadvantages of the known methods of obtaining water-soluble oligomeric and acid-soluble low molecular weight homologues of chitosan is the complication of the process of acid hydrolysis (orthophosphoric acid); stage hydrolysis, neutralization of the acid, lyophilization of the target product, and a low yield of oligomeric fraction (degree of polymerization=1-10) up to 20%.

Variants of known methods of peroxide hydrolysis of chitosan have a limited capacity due to the formation of only hydrophobic fractions homologues of chitosan with Mcf~20-80 kDa. The possibility of obtaining fractions of water-soluble oligomers method p is Rossignol depolymerization of chitosan is not implemented.

The task of the invention is to develop a method of peroxide depolymerization of chitosan to obtain fractions of water-soluble oligomers.

The technical result consists in the possibility to quantitatively establish the degree of transformation of the original high-molecular aminoglycan in oligomeric and low molecular structures of homologues.

The technical result is achieved in that in the method of obtaining water-soluble oligomeric homologues of chitosan in a heterogeneous system by depolimerizaciei high molecular weight chitosan by hydrogen peroxide, according to the invention, the process of depolymerization of chitosan is carried out in a two-phase system, the solid phase which is activated chitosan with Mcf=450-650 kDa and an average particle size of 0.05 to 0.20 mm, the liquid phase is an aqueous solution of H2O2with a concentration ofH2O2in the reaction system 1-7%, the duration of the reaction 120-180 min and a temperature of 70°C. then a phase separation of the resulting homologues of chitosan by filtering through a paper or textile surface, the resulting filtrate contains water-soluble oligomers of chitosan.

As a result of depolymerization are formed two fractions of low molecular weight homologues of chitosan. Fraction of homologues of chitosan soluble in water (neutral among the (a), is a mixture of oligomers with degree of polymerization in the range 3-8; the fraction that is not soluble in water, but soluble in 1-2% of water

CH3COOH, is a mixture of low molecular weight homologues aminoglycan with srednevozrastnoe MM to 25-46 kDa. The regulation process of peroxide hydrolysis of chitosan by varying process parameters: the concentration of H2O2in the reaction system and the duration of the reaction. As constant values of technological parameters of the process adopted indicators: temperature, ratio of solid and liquid phases in the system for an initial period of interaction, the particle size of chitosan.

Thus, the developed method of hydrolysis is possible to quantitatively determine the extent of transformation of the original high-molecular aminoglycan in oligomeric and low molecular structures of homologues. On the developed indicators yield of the target fraction of homologues of water-soluble chitosan oligomers with degree of polymerization 3-8 reaches more than 53% (mass).

Phase separation of the resulting homologues of chitosan is filtered through a paper or textile surface and an additional extraction by processing the respective solvents. Real is the possibility of additional fraction the Finance mixtures of water-soluble oligomeric homologues of chitosan by processing the selected primary corresponding fractions of aqueous solutions of ethyl alcohol (extraction and sedimentation at low temperatures). This is achieved by the selection of mixtures, consisting of 2-3 oligomers.

The estimation of the average degree of polymerization of fractions of chitosan oligomers produced according to the chemical method of determining the content of the reducing elements in the tested sample, the polymer-homolog. Quantitative blocking aldehyde groups (polyacetylenic hydroxyl) is carried out by the action of the hydrazide of isonicotinic acid in the aquatic environment using iodometry. To characterize the hydrophobic fraction of homologues of chitosan produced by the proposed method were used viscometric method, including calculating srednevozrastnoe Mcfthe equation of the Mark-Kuhn-Houwink: [η]=KMαwhere K=3,5·10-4α=0,76.

Data on the conditions of peroxide hydrolysis of chitosan and the results of the process are shown in table (1).

Example

10 g (0.06 mol) of Chitosan (HTZ) (ASD>90%; [η]=29 DL/g, 2% SN3COOH. Mcf=600-650 kDa), particle size distribution prepared by abrasion with an average particle size of 0.05-0.20 mm and 100 ml of distilled water was placed in a three-neck flask, equipped with a mixing device and a reverse air refrigerator. Formed by stirring the suspension thermostatically at 40-50°C for 30 min 5,46 g (0.16 mol) of hydrogen peroxide in 50 ml aqueous solution was added to water susp is SIU chitosan and continued stirring at 70°C for 180 minutes The concentration ofH2O23,6% of the mass. Liquid module reaction system 15; a reagent ratio of 1:2.6 mol (excess H2O2) (table 1). At the final stage of processing visually observed increase in volume of solid polymer particles. The resulting reaction mixture was cooled to 25-30°C and held phase separation by filtration on a Buchner funnel with a paper filter surface -0,3-(-0,4) ATM). The residue on the filter with a soft, slightly yellow coloured particles polymeranalogous chitosan is not soluble in water, washed with distilled water in a volume of 150-200 ml to exhaustive extraction of the water-soluble fraction of the polymer hydrolysate. Selected solid phase in the form of swollen granules were dried in air at room temperature for 48-50 hours. The residual moisture content (5-6%) in the composition of the obtained polymeranalogous determined by additional extraction of volatile products from the polymer in the vacuum of-0.6 bar; 50°C). Selected solid powdery product, painted in a very pale yellow color, soluble in 1-2% aqueous acetic acid, but is practically insoluble in water. For subsequent analytical testing conducted additional extraction of the low molecular weight fractions of the polymer by treatment with distilled water in a flask with a magnetic stirrer pre-45°C for 30-45 min The output of hydrophobic fractions polymeranalogous chitosan - 3.4 g (34% of the mass of the initial chitosan).

The filtrate obtained during the phase separation of the reaction mass formed after peroxide hydrolysis of chitosan, was placed in a glass mold (diameter 17 cm). Removal of volatile reaction products produced in an open system at 40-45°C for 48-50 hours. Observed the formation of colorless solids "visual assessment" with an amorphous structure. The mixture of hydrophilic oligomers of chitosan was extracted with 95% ethanol (40-45°C); the residue after extraction was dried under vacuum bell (15 mm Hg) at ambient temperature. Dedicated colorless powdery product with signs of crystalloid structures (observation under the microscope when a 16-fold increase). The mixture of oligomers readily soluble in water at 20-30°C. For solutions installed characteristically expressed reducing capacity, which was confirmed by the reaction of formation of a silver mirror when added to a solution of ammonium AgNO3. The output of the oligomers is 6 g (60% by weight of the original chitosan).

The determination of the degree of polymerization and Mcfsynthesized oligochitosan by reducing links

A. 0.5 g of a mixture of oligomers of chitosan and 0.17 g (0,0012 mol) of isoniazid (pharmacopoeial) dissolve and 40 ml of dist, water, the solution was placed in a flat-bottomed flask with a return air refrigerator. The solution was heated at 60-70°C for 90 minutes the resulting solution laboelouacac color was placed in the flask vyurts attached to the system with a vacuum of-0.6-(a-0.7) ATM and was evacuated at 60-70°C until the formation of gel-like residue, which was extracted with 95% ethanol for exhaustive extraction of the excess of isoniazid. The resulting biphasic system was separated by treatment on the sintered glass filter with paper gasket (vacuum -0,3 ATM). The solid residue on the filter surface is a mixture of hydrazone polymer-based oligochitosan. The filtrate was placed in the flask vyurts (100 ml) and drove ethanol at 60-70°C (0.4 ATM). The residue after removal of ethanol (excess isoniazid) was dissolved in 100 ml of dist. water. The polymer concentration in the solution was determined by iodometric method (GF XI). 2 g NaHCO3and 50 ml of 0.1 n solution of I2was mixed with the resulting solution of isoniazid. The mixture thermostatically at 30°C in conditions of Svetozara for 30 minutes In the mixture upon cooling, it was added 20 ml of an aqueous solution of HCl of 1:2 (neutralization of sodium bicarbonate). Residual I2was titrated with 0.1 n sodium thiosulfate solution. For titration spent 34 ml of a solution of Na2S2O3(K=1, the starch indicator). Thus, 16 ml yo is and has entered into cooperation with an excess of isoniazid. Given that 0,003428 g of isoniazid, spent 1 ml of 0.1 n iodine, the amount of isoniazid, which entered into interaction with oligochitosan - 0,054 g (to 0.0039 mol). The number of mol of isoniazid corresponds to reducing the number of links in the synthesized oligochitosan. Mcf. the resulting oligochitosan is 1282. The calculated molecular mass of chitosan oligomer with a degree of polymerization (P) is equal to 7, is 1177.

B. Description viscometric method of determining the Mcf. 1.0 g of hydrophobic fraction of peroxide hydrolysis of chitosan was dissolved in 100 ml of 2% aqueous

CH3COOH. The adjusted concentration of the obtained solution was determined by the average value of dry residue (1.0 g/DL). The resulting solution was filtered.

For viscometric evaluation of chitosan solution in 2% CH3COOH used Ostwald viscometer (the diameter of the capillary 0.9 mm, capacity 10 ml), placed in a water bath with the temperature of 20°C. the expiry Time of the solvent and solutions with different concentrations (C1-C4identified the triple checked after incubation for 10 minutes was used For this concentration of solutions obtained by diluting the original solution of 2% acetic acid: C1=0,13,2=0,05,3=0,04,4=0,032 g/DL. A graphical method defined features and advantages of the static viscosity of chitosan solution ([η] of 0.54 DL/g). For the calculation of Mcfused the equation Mark-Kuhn-Houwink; Mcf=20-21 kDa.

Determination of degree of deacetylation (ASD)

Prepared 100 ml of an aqueous solution containing 0.2 g of the oligomeric fraction of chitosan. Potentiometric titration of 50 ml of the obtained solution was made 0,1N rustom NaOH using pH meter pH-150M with a universal electrode ESKL M at a fixed temperature of 20°C. the data obtained were built schedule. The analysis of the graphical dependence of pH=f (D), where D is the number of mmol of NaOH. The results of the analysis of the obtained schedule and the corresponding calculation shows that for titration of the salt form oligochitosan (0.10 g) consumed 5.6 mmol NaOH, which corresponds to the degree of deacetylation oligochitosan of 0.91 to 0.92 t(91-92%).

The method of obtaining water-soluble oligomeric homologues of chitosan in a heterogeneous system by depolymerization of high molecular weight chitosan by hydrogen peroxide, characterized in that the process of depolymerization of chitosan is carried out in a two-phase system, the solid phase which is activated chitosan with MCP=450-650 kDa and an average particle size of 0.05 to 0.20 mm, the liquid phase is an aqueous solution of H2O2with the concentration of N2About2in the reaction system 1-7%, the duration of the reaction 120-180 min and a temperature of 70°C. then a phase separation of the image is outstanding homologues of chitosan by filtering through a paper or textile surface obtained reaction mixture, the resulting filtrate contains water-soluble oligomers of chitosan.



 

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