Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
2000-02-25
2001-12-04
Wilson, James O. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S124000, C514S055000
Reexamination Certificate
active
06326475
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to essentially dry complexes of acid and chitosan which are water-soluble. More specifically, the invention relates to water-soluble acid-chitosan complexes, methods for forming such complexes and uses of these acid-chitosan complexes for, among other things, prevention of fat digestion.
BACKGROUND OF THE INVENTION
When chitosan is prepared from the chitin fraction of the shells of crustacea, such as shrimp, crab and lobster, the final step is invariably and of necessity a treatment with extremely strong sodium hydroxide. This is the predominant industrial treatment that effectively removes acetyl groups from chitin, converting it into chitosan. Because of this treatment, chitosan is always found as an aminopolysaccharide with essentially none of the amino groups being protonated. This can be referred to as the free base form of chitosan. This natural form of chitosan is not soluble in water. In order to dissolve chitosan in water-based systems, the chitosan must be made more hydrophilic. This is done by adding acid to the water being used in dissolution. The acid reacts with the amino groups, converting them into (substituted) ammonium ions, which are much more hydrophilic than the amino groups. When chitosan is added to this acid-water mix, it becomes protonated. A fully protonated (i.e., each amino group has reacted with a proton from the acid) chitosan is the other extreme of chitosan. It should be noted, however, that essentially no protonation of chitosan will result if a dry acid and chitosan are merely physically blended. It is necessary to give the acid molecule mobility, which is done by the addition of water.
Chitosan is presently used as a dietary supplement to prevent some of the ingested fat in a person's diet from being absorbed and metabolized. It is thus an agent to help control obesity. When a person takes a dosage of chitosan, the chitosan exerts a demand on the stomach to produce hydrochloric acid in order to dissolve it. It is understood in the art that the chitosan must dissolve to be able to occlude the fat, which can thereafter be passed through the digestive tract and subsequently expelled from the body. Since the body's capacity for producing hydrochloric acid is limited, an agent that supplies part of the necessary acidity would be beneficial to chitosan's performance.
Merely treating chitosan with hydrochloric acid in a manufacturing process to form a water-soluble chitosan, however has an unintended and devastating side effect. It has been observed that these hydrochloric acid salts of chitosan undergo depolymerization upon storage, producing a product with too low a molecular weight to perform in the desired manner.
Presently, in the art, water-soluble chitosans are prepared by making a slurry of the chitosan in water and then adding acid to the slurry. Alternatively, one may make a solution of the acid and water and then add the chitosan under effective agitation conditions. It would be convenient, however, and represent an advance in the art, were all or part of the acid to be compounded with the chitosan thus providing a uniform dry complex which can be a shelf-stable product that will result in a reduced demand on the stomach for acid. To date, the only way to prepare such a complex has been achieved, with great difficulty, has been for the manufacturer to 1) dissolve the chitosan in aqueous acid, 2) filter the very viscous solution to remove insolubles, if necessary, and 3) spray dry the resulting solution to form a chitosan salt that is water soluble. Such a process is cumbersome, expensive and ineffective for an economically viable commercial process. Therefore, there is a need in the art for a more efficient and effective method of preparing chitosan salts.
SUMMARY OF THE INVENTION
It is a primary object of this invention to provide a water-soluble, acid-chitosan complex.
It is also an object of the invention to provide a water-soluble acid-chitosan complex produced by a process comprising:
(1) forming a homogenous mix of chitosan and a sufficient amount of an acid; and
(2) adding an effective amount of water to the homogenous mix to form a uniform complex.
It is a further object of the invention to provide a water-soluble acid-chitosan complex produced by a process comprising:
(1) dissolving an acid in water; and
(2) applying the acid-water mix to chitosan to form a complex wherein the chitosan is not dissolved; and
(3) drying the complex.
It is an additional object of the invention to provide a method for reducing the release of triglycerides into the blood stream of an animal by administering to the animal an effective amount of a water-soluble acid-chitosan complex.
DETAILED DESCRIPTION OF THE INVENTION
The applicants have found that the physical blending of dry acid and chitosan, with the addition of controlled amounts of water, gives the acid molecules the needed mobility to accomplish protonation and thus move from a physical mixture to a complex (further defined below). The result of such a treatment is a state, or complex, somewhere between full-protonation and no protonation. The exact composition of the complex is dependent on the amount of water and acid used and the water solubility of the acid being used in the treatment. A more soluble acid, a higher amount of acid and/or the use of higher levels of water will result in a complex that is nearer to the fully-protonated extreme, whereas the use of a less soluble acid, lesser amounts of acid and/or lesser amounts of water will result in a complex that is much less protonated.
Definitions:
The following definitions apply throughout:
The term “acid-chitosan mixture” means the physical blend of dry acid and chitosan wherein no protonation of any significance of the chitosan occurs.
The term “acid-chitosan complex” means the mixture of acid and chitosan with the addition of controlled amounts of water to form a uniform, free-flowing mix such that the acid molecules attain the necessary mobility to accomplish at least partial protonation of the chitosan, to allow the acid-chitosan combination to become water-soluble.
The term “finished moisture level” means the weight percent of water in an acid-chitosan complex, based on the total weight of the complex, following the agitation step and before any optional or necessary drying of the complex is performed.
The Invention:
It is the applicants' discovery that a water-soluble acid-chitosan complex may be easily and effectively produced by adding varying amounts of one or more acids and a modest amount of water to a sufficiently-agitated chitosan powder or flake, mixing to achieve uniformity and, if necessary, drying the resulted hydrated crumb. By this technique, one can vary the amount of acid used from a very small amount up to essentially a stoichiometric quantity, and water-soluble acid-chitosan complexes may be prepared that range from completely water-soluble to hydratable and soluble by the addition of lesser quantities of acid than with native chitosan.
The technique and amount of water and acid addition are important to the successful practice of the present technology. Water is added as a carrier for the acid, allowing it to dissolve, ionize and penetrate the chitosan particle, and carry out at least partial protonation, thereby producing a complex of at least partial salt formation between the acid and the chitosan. If too little water is added, the acid molecules will not be sufficiently mobile to penetrate the particle and give a uniform product. If too much water is added, the hydrated chitosan will begin to approach a solution; this is not desired because large, hydrated gel masses may form and the product becomes very difficult to process through the necessary (in that case) drying and grinding operations required to produce a finished, marketable product. In this respect, it is preferred that the amount of water used be in the range of approximately 5% to 130% of the total weight of the chitosan and the acid, and more preferable that the amount of
Angerer J. David
Cyron Donald M.
Iyer Subramanian
Jerrell Thomas A.
Arkion Life Sciences
Krikelis Basil S.
Maier Leigh C.
Wilson James O.
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