Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Having -c- – wherein x is chalcogen – bonded directly to...
Reexamination Certificate
2000-05-15
2001-04-03
Henley, III, Raymond (Department: 1614)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Having -c-, wherein x is chalcogen, bonded directly to...
Reexamination Certificate
active
06211231
ABSTRACT:
BACKGROUND OF THE INVENTION
For many years, researchers have been investigating methods for stabilizing 1-ascorbic acid (vitamin C), due to its beneficial properties. Indeed, 1-ascorbic acid has many known biological functions, such as the stimulation of collagen synthesis, the strengthening of skin tissue against external attack (UV radiation, pollution), depigmentation, activity against free radicals and the compensation for vitamin E deficiency. Some of these beneficial properties have been reported by England and Seifter in the article “The biochemical functions of ascorbic acid” (Ann. Rev. Nutri. (1986) 6:365-406).
However, due to its alpha-keto lactone structure, ascorbic acid is very sensitive to the influence of environmental parameters such as light, oxygen, and water. An unavoidable degradation of ascorbic acid in solution occurs over time due to its pH and the presence of trace metals.
This problem has been addressed in a variety of ways in the art. In order to reduce or delay the degradation of ascorbic acid in solution, U.S. Pat. No. 5,140,043 recommends stabilization by introducing ascorbic acid into aqueous-alcoholic solutions, formed of at least 80% water and having a pH below 3.5. These solutions are not usable in the cosmetic and/or pharmaceutical field because of a combination of pH, drying of the skin by the alcohol, and a lack of aesthetic “feel.” Indeed, repeated application of these solutions may disrupt the equilibrium of the skin and may in particular irritate, or even burn, the skin.
Others have tried different ways to produce a stable ascorbic acid solution. B. R. Hajratwala, in “Stability of ascorbic acid”, published in the Revue Sciences Pharmaceutiques on Mar. 15, 1905, discloses that ascorbic acid may be stabilized as an acidic aqueous solution by adding an oxyethylenated sorbitan ester surface-active agent. In particular, Hajratwala states that at pH3.4 and 25° C., the addition of this agent reduced the rate of oxidation, and thus the rate of degradation, of ascorbic acid in solution. Hajratwala also discloses the use of a chelating agent such as ethylenediaminetetraacetic acid (EDTA) and packaging under nitrogen, in the absence of light, in order to enhance the stability of the aqueous ascorbic acid solution. However, such an acidic aqueous solution, applied to the skin, has the same drawbacks as those described above for acidic aqueous-alcoholic solutions. Furthermore, the stabilization obtained is still insufficient. Other ways of stabilizing ascorbic acid have been proposed, in particular by a coating technique (FR-A- 1,600,826) or by granulation of ascorbic acid (JP-A-53-127,819) for the agri-foods industry.
These techniques, while providing some stability, are, on the one hand, expensive and may, on the other hand, damage the ascorbic acid, for example during heating. Generally, these techniques lead to compositions of poor cosmetic acceptability, as in the case of granules. Consequently, none of the previous proposals have made it possible to overcome the technical problem associated with the instability of ascorbic acid in solution, in a form which is suitable for the cosmetic and/or dermatological fields and at a cost which is compatible with industrial requirements.
Accordingly, an object of the invention is to provide a method and formulation containing ascorbic acid that has improved stability.
Another object of the invention is to provide a method and formulation containing ascorbic acid that has proper aesthetic qualities for use in a dermatological or cosmetic product.
A further object of the invention is to provide a method and formulation containing ascorbic acid that is relatively inexpensive while providing the desire stability and aesthetic properties.
These and other objects and features of the invention will be apparent from the detailed description and the claims.
SUMMARY OF THE INVENTION
The invention pertains, at least in part, to a method of stabilizing free 1-ascorbic acid from oxidation by dispersing the free 1-ascorbic acid in a mixed glycol carrier. This mixed glycol carrier provides both high levels of solubility and stability at a relatively low price. The mixed glycol carrier contains a mixture of at least propylene glycol and butylene glycol, but may contain other glycols such as polyethylene glycol, and stabilizing and solubility assisting agents as well. These additional agents may include diisopropyl adipate, myristyl ether propionate, polyacrylamide (e.g., Sepigel 305), isodecyl neopentonate, diethylene glycol monoethyl ether (e.g., transcutol), lactil (a mixture of sodium lactate, sodium pyrrolidone carboxylic acid, urea, niacinamide, inositol, lactic acid, sodium benzoate, and hydrolized animal protein sold by Goldschmidt A. G.), or mixtures thereof.
The invention also features a solution containing free 1-ascorbic acid stabilized from oxidation in the mixed glycol carrier. The mixed glycol carrier contains a mixture of at least propylene glycol and butylene glycol, but may contain other glycols such as polyethylene glycol, and stabilizing and solubility assisting agents as well. These additional agents may include diisopropyl adipate, myristyl ether propionate, Sepigel 305, isodecyl neopentonate, transcutol, lactil, or mixtures thereof. The preferred range of the propylene glycol in the mixed carrier is 25-80% by weight, with the butylene glycol being 5-30% by weight. A mixed glycol solution of this type can provide a stable solution of 5% or even higher levels of ascorbic acid without oxidative degradation. The dispersion may also include a cosmetically, dermatalogically or pharmaceutically acceptable carrier.
DETAILED DESCRIPTION OF THE INVENTION
The invention features a method of stabilizing free 1-ascorbic acid from oxidation by dispersing the free 1-ascorbic acid in a mixed glycol carrier and a solution containing the ascorbic acid in the mixed glycol solution. The mixed glycol carrier contains a mixture of at least propylene glycol and butylene glycol, but may contain other glycols such as polyethylene glycol, and stabilizing and solubility assisting agents as well. These additional agents may include diisopropyl adipate, myristyl ether propionate, polyacrylamide, isodecyl neopentonate, diethylene glycol monoethyl ether, lactil, or mixtures thereof. The preferred range of the propylene glycol in the mixed carrier is 25-80% by weight, with the butylene glycol being 5-30% by weight. A mixed glycol solution of this type can provide a stable solution of 5% or even higher levels of ascorbic acid without oxidative degradation.
The following, non-limiting examples help in illustrating the invention.
EXEMPLIFICATION OF THE INVENTION
REFERENCES:
patent: 4983392 (1991-01-01), Wilmott et al.
patent: 5002761 (1991-03-01), Mueller et al.
patent: 5035895 (1991-07-01), Shibusawa et al.
patent: 5140043 (1992-08-01), Darr et al.
patent: 5552446 (1996-09-01), Candau et al.
patent: 5587149 (1996-12-01), Punto
patent: 5843411 (1998-12-01), Hernandez et al.
patent: 1600826 (1970-09-01), None
patent: 53-127819 (1978-11-01), None
patent: WO 9800102 (1998-01-01), None
patent: WO 9823152 (1998-06-01), None
England et al., “The biochemical functions of ascorbic acid,”Ann. Rev. Nutr., 6:365-406 (1986).
Henley III Raymond
IGEN, Inc.
Lahive & Cockfield LLP
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