Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Reexamination Certificate
2001-02-26
2002-03-12
Dodson, Shelley A. (Department: 1616)
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
C424S060000, C424S400000, C424S401000
Reexamination Certificate
active
06355230
ABSTRACT:
The present invention relates to cosmetic and dermatological light protection preparations, in particular skin-care cosmetic and dermatological light protection preparations.
The harmful effect of the ultraviolet part of solar radiation on the skin is generally known. The rays have various effects on the skin as an organ depending on their particular wavelength; so-called UV-C radiation with a wavelength below 290 nm is absorbed by the ozone layer in the earth's atmosphere and therefore has no physiological significance. By contrast, rays in the range between 290 nm and 320 nm, the so-called UV-B range, cause erythema, simple sunburn or even more or less severe bums. The narrower range around 308 nm is stated to be a maximum for the erythema activity of sunlight.
Numerous compounds are known for protecting against UV-B radiation, examples thereof being derivatives of 3-benzylidenecamphor, of 4-aminobenzoic acid, of cinnamic acid, of salicylic acid, of benzophenone, of 2-phenylbenzimidazole and of s-triazine.
It has long been incorrectly assumed that the long-wavelength UV-A radiation with a wavelength between 320 nm and 400 nm has only a negligible biological effect. However, it has now
1
been proved by many studies that UV-A radiation is far more hazardous than UV-B radiation in relation to the initiation of photodynamic, specifically phototoxic, reactions and chronic changes in the skin. It is also possible for the harmful effect of UV-B radiation to be enhanced by UV-A radiation.
Thus, it has been proved, inter alia, that even UV-A radiation under entirely normal everyday conditions is sufficient to damage within a short time the collagen and elastin fibers which are of essential importance for the structure and firmness of the skin. This results in chronic light-induced skin changes—the skin “ages” prematurely. The clinical appearance of skin aged by light includes, for example, creases and wrinkles and an irregular, furrowed relief. In addition, the areas affected by light-induced skin aging may have irregular pigmentation. The formation of brown spots, keratoses and even carcinomas or malignant melanomas is also possible. Skin aged prematurely by everyday exposure to UV is additionally distinguished by a lower activity of the Langerhans cells and a slight chronic inflammation.
About 90% of the ultraviolet radiation which reaches the earth consists of UV-A rays. Whereas UV-B radiation varies greatly depending on a large number of factors (for example season and time of day or latitude), UV-A radiation remains relatively constant from day to day irrespective of seasonal and diurnal or geographic factors. At the same time, most of the UV-A radiation penetrates into living epidermis, while about 70% of UV-B rays are retained by the stratum corneum.
It is therefore of fundamental importance that cosmetic and dermatological light protection preparations provide adequate protection both against UV-B and against UV-A radiation.
In general, the light absorption characteristics of light protection filter substances are very well known and documented, especially since most industrialized countries have positive lists for the use of such substances, which impose very strict standards on the documentation.
The use concentration of known light protection filter substances is, however, frequently limited in particular in combination with other substances present as solids. There are thus certain technical difficulties in formulating to achieve higher sun protection factors and effective UV-A protection.
Advantageous light protection filters are those distinguished by the benzotriazole structural motif
An advantageous benzotriazole derivative is 2,2′-methylenebis(6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol), which has the chemical structural formula
(INCl: bisoctyltriazole). It is obtainable under the proprietary name Tinosorb® from CIBA-Chemikalien GmbH and is distinguished by good UV absorption properties. The disadvantage of this substance is the characteristic of forming imperceptibly thin films on the skin which have unpleasant tactile properties.
Another disadvantage is that such benzotriazole derivatives show only inadequate solubility, if any, in conventional oil components. Well-known solvents can dissolve only up to a maximum of 15% by weight of these compounds, which usually corresponds to a concentration of about 1 to 1.5% by weight of dissolved (=active) filter substance in the complete cosmetic or dermatological preparation.
One disadvantage of the prior art is accordingly that generally only comparatively low sun protection factors have been achievable with these filter substances because their solubility or dispersibility in the formulations is too low, i.e. they can be satisfactorily incorporated into such formulations only with difficulty or not at all.
Even if it is also possible in principle to achieve a certain UV protection when the solublity is limited, another problem frequently occurs, that is recrystallization.
Substances of low solubility in particular recrystallize comparatively rapidly, which may be induced by fluctuations in temperature or other influences. Uncontrolled recrystallization of an essential ingredient of a preparation such as a UV filter has, however, extremely disadvantageous effects on the properties of the given preparation and, not least, on the desired light protection.
It was an object of the present invention to obtain in a simple manner preparations which are distinguished by an increased content of unsymmetrically substituted triazine derivatives and a correspondingly high sun protection factor.
It was, however, surprising and not predictable for the skilled worker that the disadvantages of the prior art are remedied by active ingredient combinations effective for light protection and composed of
(a) one or more UV filter substances selected from the group of benzotriazole derivatives and
(b) one or more dialkyl naphthalates having the structural formula
in which R
1
and R
2
are, independently of one another, selected from the group of branched and unbranched alkyl groups having 6 to 24 carbon atoms.
Also according to the invention is, in particular, the use of one or more dialkyl naphthalates having the structural formula
in which R
1
and R
2
are, independently of one another, selected from the group of branched and unbranched alkyl groups having 6 to 24 carbon atoms, as solvent, solution aid, solubilizer or stabilizer for benzotriazole derivates.
In a particularly advantageous embodiment, the present invention relates to the use of one or more dialkyl naphthalates having the structural formula
in which R
1
and R
2
are, independently of one another, selected from the group of branched and unbranched alkyl groups having 6 to 24 carbon atoms, for achieving or increasing the solubility of benzotriazole derivatives in
(a) either an isolated oil component or
(b) at least one oil phase of a disperse two-phase or multiphase system which may additionally comprise one or more aqueous phases.
In another particularly advantageous embodiment, the present invention relates to the use of one or more dialkyl naphthalates having the structural formula
in which R
1
and R
2
are, independently of one another, selected from the group of branched and unbranched alkyl groups having 6 to 24 carbon atoms, for improving the incorporability of benzotriazole derivatives in
(a) either an isolated oil component or
(b) at least one oil phase of a disperse two-phase or multiphase system which may additionally comprise one or more aqueous phases,
It is assumed, especially in the case of benzotriazole derivatives of particularly low solubility, that the dialkyl naphthalate(s) display the property of forming fine dispersions of such benzotriazole derivatives
(a) either in an isolated oil component or
(b) in at least one oil phase of a disperse two-phase or multiphase system which may additionally comprise one or more aqueous phases, better than the components of the prior art were able to do or suggested this.
It is pr
Gers-Barlag Heinrich
Grundt Wiebke
Wendel Volker
Beiersdorf AG
Dodson Shelley A.
Norris & McLaughlin & Marcus
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