Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Carbohydrate doai
Patent
1996-08-02
1997-10-21
Kight, John
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Carbohydrate doai
514 53, 536 552, 536 553, 536115, 536116, 536119, 536124, 536127, A61K 31715, C07H 506, C07H 1304, C07H 100
Patent
active
056796579
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a low molecular weight acetylhyaluronate, a skin-softening composition, a method of manufacturing the same, and a method of purifying the same. In particular, it relates to improvement in acetylhyaluronate in which acetyl group is bonded to alcoholic hydroxyl group thereof with a high rate.
Hyaluronic acid is a high molecular weight material derived from organisms and has specific physical characteristics such as high viscous property, viscoelasticity, and thread-forming ability, while having high biocompatibility. Accordingly, it is expected to be applied to various fields.
In particular, it should be a notable physical characteristic that hyaluronic acid has a very high moisturizing effect. Accordingly, it is used as a humectant in various external preparations for skin. Further, it is expected to be used as a thickener in organic solvent systems, various emulsification stabilizers in oily bases, a coating enforcement for liposomes, an embedded base for organisms, a capsule base, or the like.
However, since hyaluronic acid has various kinds of specific physical characteristics mentioned above, due to a part of its characteristics, it may deteriorate the usability of a product when a large amount of it is added thereto.
Also, since it is highly water-soluble, hyalucronic acid cannot be used as a humectant in organic solvent systems or oily bases.
In view of the foregoing problems of the prior art, the first object of the present invention is to provide inexpensive methods for manufacturing and purifying acetylhyaluronate which has various kinds of specific physical characteristics while maintaining the functions inherent in hyaluronic acid.
The second object of the present invention is to provide low molecular weight acetylhyaluronate which can exhibit an excellent skin-softening effect while improving shortcomings in hyaluronic acid such as thread-forming ability.
As a result of diligent studies conducted by the inventors in order to attain the above-mentioned objects, it has been found that acetylhyaluronate can be inexpensively manufactured when hyaluronic acid is reacted in the presence of acetic anhydride and concentrated sulfuric acid and that a specific kind of acetylhyaluronate having specific limiting viscosity and substitutional number of acetyl group, namely, specific molecular weight and hydrophobic property, can be remarkably improved in terms of thread-forming ability and can exhibit a high level of skin-softening effect. Thus, the present invention has been accomplished.
Namely, low molecular weight acetylhyaluronate in accordance with the present invention is characterized by the following characteristics:
Here, in the present invention, the intrinsic viscosity refers to that measured in phosphate buffer solution of pH 7.4 at 25.degree. C.
The a skin-softening composition in accordance with the present invention is mainly composed of low molecular weight hyaluronic acid.
The method of manufacturing acetylhyaluronate in accordance with the present invention is characterized by comprising the steps of suspending hyaluronic acid powder in an acetic anhydride solvent and then adding concentrated sulfuric acid thereto to effect acetylation, thereby yielding acetylhyaluronate.
In the above-mentioned method, acetic acid may preferably be mixed into the acetic anhydride solvent with a mixing ratio of acetic acid:acetic anhydride at 1:4 to 1:1. In this case, highly acetylhyaluronate having a high acetylation rate can be obtained.
Also, acetic acid may preferably be mixed into the acetic anhydride solvent with a mixing ratio of acetic acid:acetic anhydride at 2:1 to 4:1. In this case, acetylation advances mildly, whereby minute control of the acetylation rate can be easily effected.
Preferably, an amount of concentrated sulfuric acid added is 2 to 7% by volume with respect to the solvent.
The method of purifying acetylhyaluroate in accordance with the present invention is characterized by comprising the steps of adding raw acetylhyaluronate to an aqueous acetone solu
Oka Takashi
Yamaguchi Michihiro
Yanaki Toshio
Kight John
Shiseido Co. Ltd.
Snider Ronald R.
White Everett
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