Procedure for the purification of hyaluronic acid and fraction of pure hyaluronic acid for ophthalmic use
First Claim
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1. A hyaluronic acid fraction, or a salt thereof, having a mean molecular weight in the range of 750,000 Daltons to 1,230,000 Daltons and having the following characteristics:
- a) limiting viscosity number ranging between 14.5 and 21 dl/g, when determined at 25°
C. in 0.15M NaCl at pH 7.0 using an Ubbelhode suspended level viscosimeter;
b) protein content not exceeding 0.2% expressed as albumin;
c) a U.V. absorbance at 257 nm and at 280 nm not exceeding 1.0 A.U., when measured on a 1% weight per volume aqueous solution;
d) a dynamic viscosity of a 1% weight per volume solution in 0.15 NaCl at pH=7.0, not exceeding the following limits at the defined shear rates, using a rotational viscosimeter at a temperature of 20°
C.;
space="preserve" listing-type="tabular">______________________________________ Shear rate Dynamic viscosity (mPa ·
s at 20°
C.) ______________________________________ 1 s.sup.-1 not more than 20000 mPa ·
s 10 s.sup.-1 not more than 2000 mPa ·
s 100 s.sup.-1 not more than 1000 mPa ·
s 350 s.sup.-1 not more than 500 mPa ·
s ______________________________________ e) a sulfated mucopolysaccharide content not exceeding 0.07% as sulfur;
f) an iron content not exceeding 10 p.p.m.; and
g) stability of isotonic buffered solutions with a physiological pH of the fraction, naturally aged and heat-sterilized, determined by assessment of the limiting viscosity number and expressed with the corresponding decrease in mean molecular weight, not exceeding the following limits;
the actual value after storage at 25°
C. for 6 months must not be lower than 97% of the initial valuethe actual value after sterilization at 118°
C. for 32 minutes must not be lower than 75% of the initial valuethe actual value after sterilization at 121°
C. for 16 minutes must not be lower than 80% of the initial valuethe actual value after sterilization at 124°
C. for 8 minutes must not be lower than 90% of the initial value.
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Abstract
A highly pure fraction of hyaluronic acid is disclosed which is non-inflammatory and avoids post-operative complications in ocular surgery. Also disclosed is a process for the preparation of hyaluronic acid characterized by converting hyaluronic acid into a corresponding quaternary ammonium salt and, following purification procedures, reconverting the quaternary ammonium salt into a sodium salt of hyaluronic acid.
27 Citations
25 Claims
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1. A hyaluronic acid fraction, or a salt thereof, having a mean molecular weight in the range of 750,000 Daltons to 1,230,000 Daltons and having the following characteristics:
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a) limiting viscosity number ranging between 14.5 and 21 dl/g, when determined at 25°
C. in 0.15M NaCl at pH 7.0 using an Ubbelhode suspended level viscosimeter;b) protein content not exceeding 0.2% expressed as albumin; c) a U.V. absorbance at 257 nm and at 280 nm not exceeding 1.0 A.U., when measured on a 1% weight per volume aqueous solution; d) a dynamic viscosity of a 1% weight per volume solution in 0.15 NaCl at pH=7.0, not exceeding the following limits at the defined shear rates, using a rotational viscosimeter at a temperature of 20°
C.;
space="preserve" listing-type="tabular">______________________________________ Shear rate Dynamic viscosity (mPa ·
s at 20°
C.) ______________________________________ 1 s.sup.-1 not more than 20000 mPa ·
s 10 s.sup.-1 not more than 2000 mPa ·
s 100 s.sup.-1 not more than 1000 mPa ·
s 350 s.sup.-1 not more than 500 mPa ·
s ______________________________________e) a sulfated mucopolysaccharide content not exceeding 0.07% as sulfur; f) an iron content not exceeding 10 p.p.m.; and g) stability of isotonic buffered solutions with a physiological pH of the fraction, naturally aged and heat-sterilized, determined by assessment of the limiting viscosity number and expressed with the corresponding decrease in mean molecular weight, not exceeding the following limits; the actual value after storage at 25°
C. for 6 months must not be lower than 97% of the initial valuethe actual value after sterilization at 118°
C. for 32 minutes must not be lower than 75% of the initial valuethe actual value after sterilization at 121°
C. for 16 minutes must not be lower than 80% of the initial valuethe actual value after sterilization at 124°
C. for 8 minutes must not be lower than 90% of the initial value. - View Dependent Claims (2, 22, 25)
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3. A process for the purification of hyaluronic acid or a salt thereof, which comprises:
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a) converting hyaluronic acid or a salt thereof into a corresponding quaternary ammonium salt; b) dissolving said corresponding quaternary ammonium salt in an organic solvent capable of dissolving such ammonium salts; and c) filtering the solution and treating with a sodium halogenide to recover the hyaluronic acid in the form of a sodium salt. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 19)
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11. A process for the preparation of a fraction of hyaluronic acid which comprises
a) extracting hyaluronic acid from an animal organ with a first organic solvent in the presence of an iron-chelating agent to obtain a hyaluronic acid-containing extract which is substantially free of iron ions; -
b) treating said hyaluronic acid-containing extract with a proteolytic agent; c) contacting the thus treated hyaluronic acid-containing extract with an acid ion exchanger in the form of a quaternary ammonium salt; d) dissolving the extract from the ion exchanger in a second organic solvent which is capable of dissolving a quaternary ammonium salt of hyaluronic acid; e) treating the mixture of step (d) with a sodium halogenide to convert the quaternary ammonium salt of hyaluronic acid to the corresponding sodium salt; and f) isolating the desired sodium salt of hyaluronic acid. - View Dependent Claims (16, 17, 18, 23, 24)
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20. A process for the preparation of a fraction of sodium hyaluronate which comprises:
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a) extracting organic material from hen crests with an extraction solvent comprised of acetone or ethanol and phenanthroline or phenanthroline to produce an extract which is substantially free of iron ions; b) treating said extract with a proteolytic agent selected from the group consisting of papain, pepsin, trypsin, pronase and cysteine hydrochloride; c) contacting the thus treated extract with a column filled with a sulfonic acid resin in the form of tetrabutylammonium salt; d) eluting the column to obtain a solution containing the tetrabutylammonium salt of hyaluronic acid; e) drying the solution to obtain a residue comprised of the tetrabutylammonium salt of hyaluronic acid; f) dissolving said residue in an aprotic solvent; g) filtering the solution of step (f); h) washing the solution of step (g) with methylene chloride; i) treating the solution of step (h) with a sodium halogenide to produce sodium hyaluronate; j) precipitating said sodium hyaluronate; k) dissolving the precipitate in water and subjecting the solution to dialysis; l) precipitating sodium hyaluronate from the dialyzed solution; and m) subjecting said precipitate to molecular filtration with a membrane having a molecular exclusion limit of 30,000 Daltons, to produce a solution containing the sodium salt of hyaluronic acid having an average molecular weight of between 750,000 and 1,230,000 Daltons. - View Dependent Claims (21)
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Specification