Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Patent
1993-04-07
1996-07-23
Dodson, Shelley A.
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
558401, A61K 742, C07C25502
Patent
active
055387160
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a photostable cosmetic composition intended for protecting the skin against UV radiation, containing a UV-A screening agent and a (4-methoxybenzylidene)cyanoacetate, to its use for protection of the skin against UV rays and to a process for stabilizing the UV-A screening agent with a (4-methoxybenzylidene)cyanoacetate.
UV-A rays of wavelengths between 320 and 400 nm, causing tanning of the skin, are known to be capable of inducing unwelcome changes in the latter, in particular in the case of sensitive skin or skin continually exposed to solar radiation. UV-A rays cause, in particular, a loss of elasticity of the skin and the appearance of wrinkles leading to a premature ageing. They promote a triggering of the erythematous reaction or enhance this reaction in certain subjects, and can even be the source of phototoxic or photoallergic reactions. It is hence desirable to screen out the UV-A radiation.
French Patent No. 2,440,933 describes 4-(1,1-dimethylethyl)-4'-methoxydibenzoylmethane as a UV-A screening agent. The proposal is made to combine this particular UV-A screening agent, sold by the company GIVAUDAN under the name "PARSOL 1789", with various UV-B screening agents with the object of absorbing all the UV radiation of wavelengths between 280 and 380 nm.
Unfortunately, when this UV-A screening agent is used alone or in combination with UV-B screening agents, it does not possess satisfactory photochemical stability for assuring constant protection of the skin during prolonged exposure to the sun, thereby necessitating repeated applications at regular and frequent intervals if it is desired to obtain effective protection of the skin against all UV rays.
The Applicant discovered that, by combining 4-(1,1-dimethylethyl)-4'-methoxydibenzoylmethane with a UV-A screening agent of the (4-methoxybenzylidene)cyanoacetate type of formula: ##STR2## in proportions and in a mole ratio that are well defined, photochemical stability of 4-(1,1-dimethylethyl)-4'-methoxydibenzoylmethane was surprisingly obtained. A stabilized combination protecting the human epidermis against UV rays of wavelengths between 320 and 380 nm is thereby obtained. This combination is especially advantageous in skin care products for daily use with the object of retarding skin ageing.
Photostable antisun compositions that screen out all UV rays of wavelengths between 280 and 380 nm can be obtained by adding UV-B screening agents to the abovementioned combination of UV-A screening agents.
In the general formula (I), the substituent R represents a linear or branched alkyl radical containing 6 to 12 carbon atoms.
n-Hexyl, n-octyl, n-decyl, n-dodecyl, isooctyl, isononyl and isodecyl radicals may be mentioned, for example.
Among the compounds of formula (I), the following are more especially preferred:
The compounds of formula (I) together with a process for preparing them are described in Application EP 0,005,182.
As a result of their lipophilic nature, the screening agents used distribute uniformly in the traditional cosmetic carriers containing at least one fatty phase or which take the form of aqueous dispersions of lipid vesicles, and can thus be applied to the skin to form an effective protective film.
The subject of the present invention is a photostable cosmetic composition that protects the skin against UV radiation of wavelengths between 320 and 380 nm, comprising, in a cosmetically acceptable carrier, from 0.5 to 5% by weight of 4-(1,1-dimethylethyl)-4'-methoxydibenzoylmethane and at least 0.5% by weight of compound of formula (I), the mole ratio of the compound of formula (I) to 4-(1,1-dimethylethyl)-4'-methoxydibenzoylmethane being greater than or equal to 0.8, and preferably greater than or equal to 1.2.
The upper limit of this mole ratio is determined by the solubility of these screening agents in the fatty phase used in the composition, or in the lipid phase present in the vesicular dispersion.
The subject of the present invention is also a process for protecting the human epidermis against the effec
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Deflandre Andre
Forestier Serge
"L'Oreal"
Dodson Shelley A.
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