Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1988-02-03
1990-05-29
Griffin, Ronald W.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
21050027, 424 59, 424443, 424444, 424449, 514 55, 514947, 514953, 536 552, C08B 3708, A61K 748, A61L 1501
Patent
active
049297228
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates in general to a novel, inexpensive process for the decrystallization of aminopolysaccharides. In one aspect this invention is directed to a method for the heterogeneous, acid decrystallization of a particular aminopolysaccharide, chitosan. In a further aspect the invention is related to the preparation of various derivatives of the decrystallized product. In a still further aspect, the invention is directed to the use of such derivatives alone or in combination with other naturally occurring compounds for a wide variety of applications.
BACKGROUND OF THE INVENTION
Chitosan is a partially or fully deacetylated form of chitin, a naturally occurring polysaccharide. Structurally, chitin is a polysaccharide consisting of beta-(1.fwdarw.4) 2-acetamido-2-deoxy-D-glucose units, some of which are deacetylated: ##STR1## wherein x=0.85-0.95 and y=0.15-0.05. The degree of deacetylation usually varies between 8 and 15 percent, but depends on the species from which the chitin is obtained, and the method used for isolation and purification.
Chitin is not one polymer with a fixed stoichiometry, but a class of polymers of N-acetylglucosamine with different crystal structures and degrees of deacetylation, and with fairly large variability from species to species. The polysaccharide obtained by more extensive deacetylation of chitin is chitosan: ##STR2## wherein x=0.50-0.10, and y=0.50-0.90.
Like chitin, chitosan is a generic term for a group of polymers of acetylglucosamine, but with a degree of deacetylation of between 50 and 90 percent. Chitosan is the beta-(1-4)- polysaccharide of D-glucosamine, and is structurally similar to cellulose, except that the C-2 hydroxyl group in cellulose is substituted with a primary amine group in chitosan. The large number of free amine groups (pKa=6.3) makes chitosan a polymeric weak base. Both chitin and chitosan are insoluble in water, dilute aqueous bases, and most organic solvents. However, unlike chitin, chitosan is soluble in dilute aqueous acids, usually carboxylic acids, as the chitosonium salt. Solubility in dilute aqueous acid is therefore a simple way to distinguish chitin from chitosan.
Chitosan is unique in that it is a polysaccharide containing primary amine groups. Chitosan and its derivatives are therefore useful materials in precious metal recovery, ion-exchange resins, surgical dressings and sutures, ocular bandages and lenses, and other applications in the biomedical field. Chitosan forms water-soluble salts with many organic and inorganic acids, and these chitosonium derivatives are useful in biomedical applications for several reasons.
First, as hereinafter indicated, these salts are biologically compatible with skin, hair, and most living tissues, and second, these chitosan salts are known to accelerate the healing process in damaged tissue. The tissue compatibility and healing acceleration of chitosan salts are also shared by covalent chitosan derivatives, covalent chitin derivatives, chitosan, and chitin.
However, prior to the present invention widespread use of chitosan derivatives had been limited because of the difficulty in their preparation. Chitosan is a highly crystalline polymer, and without rendering it amorphous and swollen with diluent, it cannot be easily derivatized. The methods known today to render chitosan reactive involve unusual, expensive, and toxic solvents such as dimethyl formamide or dimethyl sulfoxide, or expensive mechanical processes such as repetitive freezing of a chitosan slurry. In addition, while chitosan salt solutions may be prepared by dissolution of chitosan in dilute aqueous acids, such solutions are cumbersome because they must be very dilute, about five percent or less, to be pourable. Isolating the solid chitosan salt from these solutions requires expensive processes such as freeze-drying or spray drying, and these isolation techniques do not remove any unreacted acid which may not be desired in the final dried chitosan salt.
A variety of other methods have been reported in the
REFERENCES:
patent: 2795579 (1957-06-01), Doczi
patent: 3879376 (1975-04-01), Vanlerberghe et al.
patent: 3953608 (1976-04-01), Vanlerberghe et al.
patent: 4031025 (1977-06-01), Vanlerberghe et al.
patent: 4424346 (1984-01-01), Hall et al.
patent: 4528283 (1985-07-01), Lang et al.
patent: 4542014 (1985-09-01), Bresak et al.
patent: 4574150 (1986-03-01), Austin
Brode, II George L.
Partain, III Emmett M.
Gibson Henry H.
Griffin Ronald W.
Union Carbide Chemicals and Plastics Company Inc.
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