Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Cosmetic – antiperspirant – dentifrice
Patent
1998-04-29
1999-12-28
Page, Thurman K.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Cosmetic, antiperspirant, dentifrice
424 59, A61K 700, A61K 742
Patent
active
060078286
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to the use of substituted diphenylmalononitriles as photostable UV-A filters in cosmetic formulations to protect the human epidermis from UV radiation, specifically in the range from 320 to 400 nm.
The sunscreen agents employed in cosmetic formulations have the task of preventing harmful effects of sunlight on the human skin or at least reducing their consequences. In addition, however, these sunscreen agents also serve to protect other ingredients from decomposition or degradation by UV radiation.
The sunlight reaching the surface of the earth contains UV-B (280 to 320 nm) and UV-A (>320 nm), radiation which is immediately adjacent to the visible light region. The effect on the human skin, especially of UV-B radiation, is manifested by sunburn. Accordingly the industry supplies quite a large number of substances which absorb UV-B radiation and thus prevent sunburn.
Dermatological investigations have now shown that UV-A radiation is also perfectly able to cause skin damage by, for example, damaging the keratin or elastin. This results in a reduction in the elasticity and water-storage capacity of the skin, ie. the skin becomes less supple and is prone to wrinkles. The noticeably high incidence of skin cancer in regions exposed to strong sunlight shows that evidently damage to the genetic information in the cells is also caused by sunlight, specifically by UV-A radiation. All these findings therefore make it appear necessary to develop efficient filter substances for the UV-A region.
There is a growing need for sunscreen agents for cosmetic formulations which can be used in particular as UV-A filters and whose absorption maxima should therefore be in the region from about 320 to 380 nm. In order to achieve the desired effect with use of the minimum amount, sunscreen agents of this type should additionally have a highly specific extinction. In addition, sunscreen agents for cosmetic products must also meet a large number of other requirements, for example good solubility in cosmetic oils, high stability of the emulsions produced with them, toxicological acceptability and little intrinsic odor and color.
Another requirement which must be met by sunscreen agents is adequate photostability. However, this is only inadequately ensured, if at all, with UV-A absorbing sunscreen agents available to date.
French patent No. 2 440 933 describes 4-(1,1-dimethylethyl)-4'-methoxydibenzoylmethane as UV-A filter. The proposal is to combine this specific UV-A filter, which is sold by GIVAUDAN under the name "PARASOL 1789", with various UV-B filters in order to absorb all UV rays with a wavelength from 280 to 380 nm.
However, this UV-A filter has insufficient photochemical stability, when used alone or in combination with UV-B filters, to ensure permanent protection of the skin during lengthy exposure to the sun, which makes repeated applications at regular and short intervals necessary if effective protection of the skin from all the UV rays is desired.
This is why, according to EP 0514491, the UV-A filters with inadequate photostability are to be stabilized by adding 2-cyano-3,3-diphenylacrylic esters which themselves act as filters in the UV-B region.
It is an object of the present invention to propose sunscreen agents for cosmetic purposes which absorb in the UV-A region and are photostable.
We have found that this object is achieved by adding compounds of the formula I ##STR1## where R.sup.1 and R.sup.2 are identical or different straight-chain or branched aliphatic or cycloaliphatic radicals which are in the para and/or ortho position and have 1 to 18 carbon atoms, and where R.sup.1 can additionally be a hydrogen atom, and where furthermore n is 1 or 2, when these compounds have their essential absorption in the range from 320 to 380 nm, as UV-A filters in cosmetic formulations to protect the human skin from the sun's rays, together with compounds which absorb in the UV-B region and are known per se for cosmetic formulations.
Aliphatic and cycloaliphatic radicals mean in particular
REFERENCES:
patent: 3270045 (1966-08-01), Strobel et al.
patent: 3275520 (1966-09-01), Strobel
Aumuller Alexander
Holderbaum Martin
Sperling Karin
Westenfelder Horst
Wunsch Thomas
BASF - Aktiengesellschaft
Howard Sharon
Page Thurman K.
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