Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Carbohydrate doai
Reexamination Certificate
2000-06-30
2004-03-23
Wang, Shengjun (Department: 1617)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Carbohydrate doai
C514S844000, C514S880000, C536S055100, C424S401000, C424S423000, C424S443000, C424S489000
Reexamination Certificate
active
06710038
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to propylene glycol hyaluronate esters and agent for external use to skin, which refers to “skin preparations for external use” hereinafter, containing said propylene glycol hyaluronate esters. Skin preparations for external use according to the present invention can be widely used as cosmetic and pharmaceutical products because of their excellent viscosity stability, emulsifiability, hydration power and moisturizing effect.
RELATED ART
Dry skin is caused by excessive loss of moisture from the surface of the skin exposed to dry air or cleansing. In these days, various environmental chemical substances also inhibit skin functions such as lipid secretion to often invite dry skin. Therefore, there is a demand for a skin preparation for external use to prevent dry skin and provide an excellent moisturizing effect.
Various active compounds having a moisturizing effect have been provided, which are mainly based on water-soluble polyols. Some of them including propylene glycols have already been commercialized. However, many of commercialized moisturizing compounds are associated with uncomfortable feel during application or insufficient moisturizing effect, so that there is still a demand for the development of a new moisturizing compound.
An alternative moisturizing compound is sodium hyaluronate, which draws special interest as a valuable compound because of high hydration effect. However, aqueous solutions of sodium hyaluronate have a disadvantage in stability, which is high at neutral pH range but lowered in acidic solutions or salt solutions. This leads to the problem that the moisturizing effect cannot be effectively produced under some storage conditions or application conditions during use as cosmetics or the like, and there is a need for a solution thereto.
In view of these problems of the prior art, our studies were devoted to provide a material that stably exists even in low-pH solutions or salt solutions and has excellent emulsifiability and hydration effect. Thus, an object of the present invention is to provide a compound that can be widely used as cosmetic and pharmaceutical products because of excellent viscosity stability, emulsifiability, hydration power and moisturizing effect.
SUMMARY OF THE INVENTION
As a result of careful studies to attain the above object, we accomplished the present invention on the basis of the finding that propylene glycol hyaluronate esters satisfying specific conditions have excellent properties.
Accordingly, the present invention provides propylene glycol hyaluronate esters having an esterification degree of 10-90%, preferably 20-80%, more preferably 30-70%, even more preferably 40-60%. The present invention also provides propylene glycol hyaluronate esters having a limiting viscosity of 3-35 dL/g, preferably 11-27 dL/g, more preferably 14-20 dL/g. Especially preferred propylene glycol hyaluronate esters of the present invention are compounds having an esterification degree of 40-60% and a limiting viscosity of 14-20 dL/g.
Propylene glycol hyaluronate esters of the present invention are preferably combined with imidazoline-based amphoteric surfactants such as 2-lauryl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine and 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine.
The present invention also provides skin preparations for external use containing said propylene glycol hyaluronate esters. Skin preparations for external use according to the present invention are useful as moisturizers and emulsifiers, especially as emulsifiers for low-pH systems, emulsifiers for cation-containing systems and high-hydration emulsifiers.
Numerical ranges used herein include both limits.
DETAILED DESCRIPTION OF THE INVENTION
Propylene glycol hyaluronate esters and skin preparations for external use according to the present invention will now be explained in detail.
Propylene glycol hyaluronate esters of the present invention are compounds having an esterification degree of 10-90% or a limiting viscosity of 3-35 dL/g. The esterification degree is preferably 20-80%, more preferably 30-70%, even more preferably 40-60%. The limiting viscosity is preferably 11-27 dL/g, more preferably 13-23 dL/g, even more preferably 14-20 dL/g.
Propylene glycol hyaluronate esters of the present invention are preferably compounds having an esterification degree of 10-90% and a limiting viscosity of 3-35 dL/g, more preferably compounds having an esterification degree of 20-80% and a limiting viscosity of 11-27 dL/g, even more preferably compounds having an esterification degree of 30-70% and a limiting viscosity of 13-23 dL/g, most preferably compounds having an esterification degree of 40-60% and a limiting viscosity of 14-20 dL/g.
As used herein, the “esterification degree” means the proportion of esterified carboxylates among those forming hyaluronic acid. The limiting viscosity of propylene glycol hyaluronate esters can be determined according to the method of Laurent et al. (T. C. Laurent et al. Biochem. Biophys. Acta, 42(1960)476-485).
The type and structure of the hyaluronic acid moiety forming propylene glycol hyaluronate esters of the present invention are not specifically limited. The molecular weight of hyaluronic acid, which is a polysaccharide having repeating units of a disaccharide consisting of D-glucuronic acid and N-acetyl-D-glucosamine, is not specifically limited so far as the limiting viscosity of the resulting propylene glycol esters falls within said range. Hyaluronic acid used herein may be synthesized or purified from natural origins by known means. Substituents on D-glucuronic acid and N-acetyl-D-glucosamine forming ihyaluronic acid may be partially derivatized unless the effects of the present invention are excessively hindered. For example, hydroxyl groups may be substituted by alkoxy or other groups. These substitutions can be appropriately carried out within the scope of those skilled in the art.
In propylene glycol hyaluronate esters of the present invention, acid moieties and ester moieties may be localized in their molecules or may be widely distributed. However, those having two or more molecules of hyaluronic acid crosslinked via propylene glycol are excluded.
Processes for preparing propylene glycol hyaluronate esters of the present invention are not specifically limited. An especially preferred process involves reacting a mixture of hyaluronic acid and sodium hyaluronate with propylene oxide. More specifically, sodium hyaluronate is first partially converted into hyaluronic acid in the presence of a hydrochloric acid/ethanol solution or the like and then the reaction mixture is washed with ethanol to give a mixture of hyaluronic acid and sodium hyaluronate. Then, this mixture is esterified with a solution of propylene oxide in ethanol. Preferably, the temperature of the esterification reaction here is 50-80° C. and the reaction time is about 1-10 hours. After reaction, the reaction product may be washed with ethanol, neutralized with a solution of sodium acetate in ethanol, washed with ethanol again, and then dried. According to this process, a propylene glycol hyaluronate ester having the intended effects of the present invention can be efficiently prepared.
Propylene glycol hyaluronate esters of the present invention are quite useful as ingredients of skin preparations for external use. Propylene glycol hyaluronate esters of the present invention are compounds showing excellent viscosity stability in low-pH systems and cation-containing systems and also showing high emulsifiability, hydration power and moisturizing effect. Thus, skin preparations for external use containing a propylene glycol hyaluronate ester of the present invention are useful as moisturizers, emulsifiers for low-pH systems, emulsifiers for cation-containing systems and high-hydration emulsifiers.
Skin preparations for external use according to the present invention were found to have especially high stability and excellent moisturizing effect so that they provide appropriate moisture to the surface of
Asai Michiki
Hirai Hideki
Browdy and Neimark , P.L.L.C.
Kibun Food Chemifa Co., Ltd.
Wang Shengjun
LandOfFree
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