Use of a composition containing at least one oxidation-sensitive hydrophilic active principle and at least one N-vinylmidazole polymer or copolymer

Abstract

The invention relates to the use of a composition containing, in a physiologically acceptable medium having an aqueous phase, at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and at least one non-crosslinked N-vinylimidazole polymer or copolymer, the active principle and the polymer or copolymer both being in the aqueous phase, for preventing or combatting the harmful effects of UV radiation and/or of pollution on the skin, in particular loss of firmness and/or of elasticity of the skin.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the use of a composition comprising at least one oxidation-sensitive hydrophilic active principle and at least one N-vinylimidazole polymer or copolymer in a physiologically acceptable medium comprising an aqueous phase. Preferably the use is cosmetic or dermatological, and preferably relates to treating the skin and/or mucous membranes against UV, pollution, free radicals, and sunburn.

BACKGROUND OF THE INVENTION

[0002] It is known to introduce, into cosmetic compositions, various active principles intended to contribute specific treatments to the skin and/or hair. However, some of these active principles exhibit the disadvantage of being unstable in an aqueous medium and of easily decomposing on contact with water, in particular because of oxidation phenomena. They thus rapidly lose their activity over time and this instability conflicts with the desired effectiveness.

[0003] Attempts have thus been made for a long time to formulate ascorbic acid or vitamin C because of its numerous beneficial properties. In particular, ascorbic acid stimulates the synthesis of the connective tissue and in particular of collagen, strengthens the defences of the cutaneous tissue against external attacks, such as ultraviolet radiation and pollution, compensates for vitamin E deficiency of the skin, depigments the skin and has a role in combatting free radicals. These last two properties make it an excellent candidate as cosmetic or dermatological active principle for combatting ageing of the skin or for preventing ageing of the skin. Unfortunately, because of its chemical structure (of .alpha.-ketolactone), ascorbic acid is highly sensitive to certain environmental parameters and in particular to oxidation phenomena. There thus ensues rapid decomposition of formulated ascorbic acid in the presence of these parameters and in particular in the presence of oxygen, light or metal ions, as a function of the temperature or under certain pH conditions (Pharm. Acta. Helv., 1969, 44, 611-667; STP Pharma, 1985, 4, 281-286).

[0004] Several solutions have thus been envisaged in the prior art for reducing and/or slowing down the decomposition of ascorbic acid.

[0005] Provision has thus been made to use ascorbic acid in the form of a chemical derivative (magnesium ascorbyl phosphate or esters of fatty acids and ascorbic acid), but the bioavailability of these derivatives is very low (J. Am. Acad. Dermatol., 1996, 34, 29-33).

[0006] The instability of ascorbic acid with respect to oxygen can be improved by using specific packagings, such as twin compartments under an inert atmosphere, as disclosed in U.S. Pat. No. 5,935,584, or alternatively by the use of two-phase emulsions, one phase of which is composed of a dry powder comprising ascorbic acid and the second phase of which is a liquid phase. The mixing of the two phases has to be carried out at the time of use (WO 98/43598). These solutions have disadvantages with regard to the cost and the complexity of the manufacturing operations and significant restrictions with regard to use.

[0007] Another solution provided in the prior art consists in using a high concentration of glycols or polyols in order to reduce the solubility of oxygen in the formulation, thus protecting the ascorbic acid (WO 96/24325, EP 0 755 674, U.S. Pat. No. 5,981,578). The polyols can optionally be incorporated in liposomes, as disclosed in U.S. Pat. No. 6,020,367. However, these solutions exhibit the disadvantage of resulting in sticky formulations, the cosmetic quality of which is difficult to improve. Furthermore, the presence of a high concentration of these compounds can lead to phenomena of irritation.

[0008] Ascorbic acid can also be formulated in anhydrous media, such as silicones (U.S. Pat. No. 6,194,452), which are capable of creating an anhydrous barrier around ascorbic acid. A major disadvantage of such solutions results from the lack of freshness on application.

[0009] The need thus remains for a composition employable in particular in the cosmetics field, in which a hydrophilic active principle which is unstable in an oxidizing medium is stabilized, which is comfortable on application, which does not lead to any skin irritation after application and which is compatible with the constraints of an industrial implementation of its manufacturing process.

[0010] Cutaneous ageing of physiological nature can be accelerated by environmental factors, such as repeated exposure of the skin to sunlight, in particular to ultraviolet A radiation, or to pollution, in particular to diesel particles or to cigarette smoke. The action of the environment on the constituents of the skin (fibres, cells, enzymes) and on the sebum secreted by the skin results in particular in the formation of oxygen free radicals. In point of fact, these radicals result in significant oxidative damage, in particular in cell membranes (permeability of the membranes), cell nuclei (destruction of DNA), and tissues, in particular connective tissue (decomposition of elastin and collagen fibres). This damage results in particular in the loss of firmness and elasticity of the skin.

[0011] Ascorbic acid, by trapping free radicals, protects biological molecules. Thus, applied topically, it can accumulate in the skin and can restore the disrupted concentration of ascorbic acid, for example in the case of exposure to UV radiation. It can, moreover, protect the skin from damage induced by UV radiation (British Journal of Dermatology, 127, 1992, p. 247-253) or by environmental stress.

[0012] In parallel with this activity, ascorbic acid has an inhibitory effect on the secretion of the pro-inflammatory cytokines IL1 and IL6 induced by UV radiation (Journal of Investigative Dermatology, 108(3), 1997, p. 302-308). It is therefore of particular advantage as soothing agent for sunburn.

OBJECTS OF THE INVENTION

[0013] One object of the present invention is to provide a composition comprising an oxidation-sensitive active principle selected from the group consisting of ascorbic acid and its derivatives, which exhibits good cosmetic properties, both with regard to touch and with regard to tolerance, the preservation of which over time does not require specific precautions, and which retains the activity in combatting free radicals of the said active principle, for preventing or combatting the harmful effects of UV radiation and/or of pollution on the skin, in particular the loss of firmness and/or of elasticity of the skin.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The inventors have discovered that the use of non-crosslinked N-vinylimidazole polymers or copolymers in compositions in which the aqueous phase includes an oxidation-sensitive active principle, such as ascorbic acid or one of its derivatives, makes it possible to achieve the abovementioned object.

[0015] In the prior art, some compounds having an imidazole structure have been disclosed for their stabilizing properties. Thus, in Patent Application EP 0 586 106, several imidazole-based molecules are used to stabilize certain retinoids against chemical decomposition. Furthermore, polymeric emulsifiers composed of N-vinylimidazole, of alkyl acrylates and of vinyl acetates are disclosed in U.S. Pat. No. 4,057,622. They are used for the purpose of replacing known emulsifiers in order to overcome their disadvantages, in particular with regard to smell, and to stabilize water-in-oil emulsions. Finally, N-vinylimidazole/N-vinylcaprolactam/N-vi- nylpyrrolidone copolymers are disclosed in U.S. Pat. No. 6,191,188. They are used in the manufacture of hair-strengthening compositions.

[0016] To the knowledge of the inventors, polymers or copolymers comprising N-vinylimidazole units have never been used in combination with hydrophilic active principles sensitive to decomposition by oxidation for the purpose of improving their stability in an aqueous medium. This is true in particular in the case of ascorbic acid.

[0017] One embodiment of the present invention is therefore the cosmetic and/or dermatological use, for preventing or combatting the harmful effects of UV radiation and/or of pollution on the skin, of a composition comprising, in a physiologically acceptable medium comprising an aqueous phase, at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and at least one non-crosslinked N-vinylimidazole polymer or copolymer, the said active principle and the said polymer or copolymer both being in the aqueous phase. The copolymer is present in an amount sufficient to stabilize the said oxidation-sensitive hydrophilic active principle.

[0018] Another embodiment of matter of the present invention is the preferably cosmetic and/or dermatological use, for preventing or combatting loss of firmness and/or of elasticity of the skin, of a composition comprising, in a physiologically acceptable medium comprising an aqueous phase, at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and at least one non-crosslinked N-vinylimidazole polymer or copolymer, the active principle and the polymer or copolymer both being in the aqueous phase.

[0019] Another embodiment of the present invention is the use of a combination composed of at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and of at least one non-crosslinked N-vinylimidazole polymer or copolymer in the aqueous phase of a composition as agent for combatting free radicals.

[0020] Another embodiment of the present invention is the use of a combination composed of at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and of at least one non-crosslinked N-vinylimidazole polymer or copolymer in the aqueous phase of a composition as soothing agent for sunburn.

[0021] The term "pollution" as used herein is understood to mean both "external" pollution, for example due to diesel particles, to ozone or to heavy metals, an "internal" pollution, which can in particular be due to emissions of solvents from paints, from fitted carpet adhesives, from insulation or from wallpaper (such as toluene, styrene, xylene or benzaldehyde), or to cigarette smoke. This is because all these pollutants are capable, directly or indirectly, of generating free radicals.

[0022] According to the invention, the term "hydrophilic active principle" is understood to mean a compound having a solubility in water of at least 0.25% at ambient temperature (25.degree. C.).

[0023] According to the invention, the term "oxidation-sensitive hydrophilic active principle" is understood to mean any active principle of natural or synthetic origin capable of undergoing decomposition by an oxidation mechanism. This oxidation phenomenon can have several causes, in particular the presence of oxygen, of light or of metal ions, a high temperature or certain pH conditions. Preferably the active principle combats free radicals, and/or UV radiation or the effects thereof, and/or pollution, and/or sunburn, and/or loss of firmness and/or elasticity.

[0024] Mention may be made, by way of example and without implied limitation, of: ascorbic acid and its derivatives, such as salts or esters thereof, particularly the 5,6-di-O-dimethylsilylascorbate (sold by Exsymol under the reference PRO-AA), the potassium salt of dl-.alpha.-tocopheryl dl-ascorbyl phosphate (sold by Senju Pharmaceutical under the reference SEPIVITAL EPC), magnesium ascorbyl phosphate or sodium ascorbyl phosphate (sold by Roche under the reference Stay-C 50). Such principles may be present in any amount, preferably an amount sufficient to effect its purpose, such as for example 0.5, 1, 5, 25, etc. grams per 100 grams of composition.

[0025] In a particularly advantageous aspect, the oxidation-sensitive hydrophilic active principle is ascorbic acid.

[0026] According to the invention, the term "non-crosslinked N-vinylimidazole polymer or copolymer" is understood to mean any polymer comprising N-vinylimidazole units and not comprising a crosslinking agent. Copolymers suitable for the implementation of the invention are copolymers combining N-vinylimidazole with N-vinylpyrrolidone and/or N-vinylcaprolactam subunits.

[0027] In an advantageous aspect of the invention, the copolymer has a molar fraction of N-vinylimidazole units of between 0.1 and 1, more preferably between 0.4 and 0.9, inclusive.

[0028] According to an advantageous aspect of the invention, the molar ratio of the N-vinylimidazole unit equivalent to the oxidation-sensitive hydrophilic active principle varies between 0.004 and 16 and preferably between 0.01 and 1, inclusive.

[0029] Use will preferably be made of an N-vinylimidazole/N-vinylpyrrolido- ne copolymer.

[0030] The weight-average molar mass of the N-vinylimidazole polymers will advantageously be between 1 000 and 1.times.10.sup.7 and preferably between 5 000 and 5.times.10.sup.6.

[0031] Use may be made, to this end, of the vinylpyrrolidone/vinylimidazol- e (50/50) copolymer having a weight-average molar mass of 1 200 000 sold under the reference LUVITEC VPI 55K72W by BASF or the vinylpyrrolidone/vinylimidazole (50/50) copolymer having a weight-average molar mass of 10 000 sold under the reference LUVITEC VPI 55K18P by BASF.

[0032] The at least one polymer or copolymer is preferably present in the composition according to the invention in an amount sufficient to produce the desired effect, that is to say in an amount sufficient to stabilize the oxidation-sensitive hydrophilic active principle. Preferably, the copolymer is present at a concentration of between 0.1 and 5% by weight with respect to the total weight of the aqueous phase and more particularly at a concentration of between 0.1 and 2% by weight with respect to the total weight of the aqueous phase, inclusive. A preferred amount is a stabilizing amount, that is, an amount that slows or prevents the oxidation of the active principle, for example at 45.degree. C. for two months.

[0033] The compositions used according to the invention are intended in one embodiment for topical application to the skin and/or its superficial body growths and therefore preferably comprise a physiologically acceptable medium, that is to say a medium compatible with cutaneous tissues, such as the skin, scalp, eyelashes, eyebrows, hair, nails and mucous membranes. This physiologically acceptable medium comprises an aqueous phase and optionally a physiologically acceptable organic solvent chosen, for example, from lower alcohols comprising from 1 to 8 carbon atoms and in particular from 1 to 6 carbon atoms, such as ethanol, isopropanol, propanol or butanol; polyethylene glycols having from 6 to 80 ethylene oxide units; or polyols, such as propylene glycol, isoprene glycol, butylene glycol, glycerol or sorbitol.

[0034] When the physiologically acceptable medium is an aqueous medium, it may have a pH which is compatible with the skin, preferably ranging from 3 to 9 and better still from 3.5 to 7.5.

[0035] The compositions according to the invention can be provided in any form, including any pharmaceutical dosage form used conventionally for topical application and in particular in the form of aqueous or aqueous/alcoholic solutions, of oil-in-water (O/W) or water-in-oil (W/O) or multiple (triple: W/O/W or O/W/O) emulsions, of aqueous gels or of dispersions of a fatty phase in an aqueous phase using spherules, it being possible for these spherules to be polymeric nanoparticles, such as nanospheres and nanocapsules, or lipid vesicles of ionic and/or nonionic type (liposomes, niosomes or oleosomes). These compositions are prepared according to the usual methods.

[0036] In addition, the compositions used according to the invention can be more or less fluid and can have the appearance of a white or coloured cream, of an ointment, of a milk, of a lotion, of a serum, of a paste or of a foam. They can optionally be applied to the skin in the form of an aerosol. They can also be provided in a solid form, for example in the form of a stick.

[0037] When the compositions according to the invention comprise an oily phase, the latter preferably comprises at least one oil. It can additionally comprise other fatty substances.

[0038] Mention may be made, as oils which can be used in the composition of the invention, of, for example:

[0039] hydrocarbonaceous oils of animal origin, such as perhydrosqualene;

[0040] hydrocarbonaceous oils of vegetable origin, such as liquid triglycerides of fatty acids comprising from 4 to 10 carbon atoms, such as triglycerides of heptanoic acid or octanoic acid, or alternatively, for example, sunflower, maize, soybean, gourd, grape seed, sesame, hazelnut, apricot, macadamia, arara, castor or avocado oils, triglycerides of caprylic/capric acids, such as those sold by Starineries Dubois or those sold under the names Miglyol 810, 812 and 818 by Dynamit Nobel, jojoba oil, or karite butter oil;

[0041] synthetic esters and ethers, in particular of fatty acids, such as the oils of formulae R.sup.1COOR.sup.2 and R.sup.1OR.sup.2 in which R.sup.1 represents the residue of a fatty acid comprising from 8 to 29 carbon atoms and R.sup.2 represents a branched or unbranched hydrocarbonaceous chain comprising from 3 to 30 carbon atoms, such as, for example, purcellin oil, isononyl isononanoate, isopropyl myristate, 2-ethylhexyl palmitate, 2-octyldodecyl stearate, 2-octyldodecyl erucate or isostearyl isostearate; hydroxylated esters, such as isostearyl lactate, octyl hydroxystearate, octyldodecyl hydroxystearate, diisostearyl malate, triisocetyl citrate or heptanoates, octanoates or decanoates of fatty alcohols; polyol esters, such as propylene glycol dioctanoate, neopentyl glycol diheptanoate and diethylene glycol diisononanoate; and pentaerythritol esters, such as pentaerythrityl tetraisostearate;

[0042] linear or branched hydrocarbons of mineral or synthetic origin, such as volatile or nonvolatile liquid paraffins and their derivatives, liquid petrolatum, polydecenes or hydrogenated polyisobutene, such as parleam oil;

[0043] fatty alcohols having from 8 to 26 carbon atoms, such as cetyl alcohol, stearyl alcohol and their mixture (cetearyl alcohol), octyldodecanol, 2-butyloctanol, 2-hexyldecanol, 2-undecylpentadecanol, oleyl alcohol or linoleyl alcohol;

[0044] partially hydrocarbon-comprising and/or silicone-comprising fluorinated oils, such as those disclosed in the document JP-A-2-295912;

[0045] silicone oils, such as volatile or nonvolatile polymethylsiloxanes (PDMS) comprising a linear or cyclic silicone chain which are liquid or pasty at ambient temperature, in particular cyclopolydimethylsiloxanes (cyclomethicones), such as cyclohexasiloxane; polydimethylsiloxanes comprising pendent alkyl, alkoxy or phenyl groups or alkyl, alkoxy or phenyl groups at the end of the silicone chain, which groups have from 2 to 24 carbon atoms; or phenylated silicones, such as phenyl trimethicones, phenyl dimethicones, phenyltrimethyl-siloxydiphenylsiloxan- es, diphenyl dimethicones, diphenylmethyldiphenyltrisiloxanes, (2-phenylethyl)trimethylsiloxysilicates and polymethylphenylsiloxanes;

[0046] their mixtures.

[0047] The term "hydrocarbonaceous oil" is understood to mean, in the list of the oils mentioned above, any oil predominantly comprising carbon and hydrogen atoms and optionally ester, ether, fluorinated, carboxylic acid and/or alcohol groups.

[0048] The other fatty substances which can be present in the oily phase are, for example, fatty acids comprising from 8 to 30 carbon atoms, such as stearic acid, lauric acid, palmitic acid and oleic acid; waxes, such as lanolin, beeswax, carnauba or candelilla wax, paraffin or lignite waxes or microcrystalline waxes, ceresin or ozokerite, or synthetic waxes, such as polyethylene waxes or Fischer-Tropsch waxes; silicone resins, such as trifluoromethyl C.sub.1-4 alkyl dimethicone and trifluoropropyl dimethicone; and silicone elastomers, such as the products sold under the names "KSG" by Shin-Etsu, under the names "Trefil", "BY29" or "EPSX" by Dow Coming or under the names "Gransil" by Grant Industries.

[0049] These fatty substances can be chosen in a way varied by a person skilled in the art in order to prepare a composition having the desired properties, for example of consistency or of texture.

[0050] According to a specific embodiment of the invention, the composition according to the invention is a water-in-oil (W/O) or oil-in-water (O/W) emulsion. The proportion of the oily phase in the emulsion can range from 5 to 80% by weight and preferably from 5 to 50% by weight with respect to the total weight of the composition.

[0051] The emulsions generally comprise at least one emulsifier selected from the group consisting of amphoteric, anionic, cationic or nonionic emulsifiers, used alone or as a mixture, and optionally a coemulsifier. The emulsifiers are appropriately chosen according to the emulsion to be obtained (W/O or O/W). The emulsifier and the coemulsifier are generally present in the composition in a proportion ranging from 0.3 to 30% by weight and preferably from 0.5 to 20% by weight with respect to the total weight of the composition.

[0052] Mention may be made, for the W/O emulsions, for example, as emulsifiers, of dimethicone copolyols, such as the mixture of cyclomethicone and of dimethicone copolyol sold under the name "DC 5225 C" by Dow Corning, and alkyl dimethicone copolyols, such as the laurylmethicone copolyol sold under the name "Dow Corning 5200 Formulation Aid" by Dow Corning and the cetyl dimethicone copolyol sold under the name Abil EM 90.sup.R by Goldschmidt. Use may also be made, as surfactant of W/O emulsions, of a crosslinked solid organopolysiloxane elastomer comprising at least one oxyalkylenated group, such as those obtained according to the procedure of Examples 3, 4 and 8 of the document U.S. Pat. No. 5,412,004 and the examples of the document U.S. Pat. No. 5,811,487, in particular the product of Example 3 (synthetic example) of U.S. Pat. No. 5,412,004, and such as that sold under the reference KSG 21 by Shin Etsu. Use may also be made, as emulsifier, of a polyolefin-derived oligomer or polymer comprising a succinic ending; the latter is preferably a polyolefin comprising an esterified or amidated succinic ending or a salt of such a polyolefin and in particular polyisobutylene comprising an esterified or amidated succinic ending such as the products sold under the names L5603 and L2721 and OS131769 by Lubrizol.

[0053] Mention may be made, for the O/W emulsions, for example, as emulsifiers, of nonionic emulsifiers, such as esters of fatty acids and of glycerol which are oxyalkylenated (more particularly polyoxyethylenated); esters of fatty acids and of sorbitan which are oxyalkylenated; esters of fatty acids which are oxyalkylenated (oxyethylenated and/or oxypropylenated); ethers of fatty alcohols which are oxyethylenated (oxyethylenated and/or oxypropylenated); sugar esters, such as sucrose stearate; and their mixtures, such as the mixture of glyceryl stearate and of PEG-40 stearate.

[0054] The compositions of the invention can also comprise adjuvants conventional in the cosmetics or dermatological field, such as hydrophilic or lipophilic gelling agents, preservatives, solvents, fragrances, fillers, UV screening agents, bactericides, odour absorbers, colouring materials, plant extracts or salts. The amounts of these various adjuvants are those generally used in the field under consideration, for example from 0.01 to 20% of the total weight of the composition. These adjuvants, depending on their nature, can be introduced into the fatty phase, into the aqueous phase and/or into the lipid spherules.

[0055] Mention may be made, as fillers which can be used in the composition of the invention, for example, of pigments, silica powder; talc; particles of polyamide and in particular those sold under the name Orgasol by Atochem; polyethylene powders; microspheres based on acrylic copolymers, such as those made of ethylene glycol dimethacrylate/lauryl methacrylate copolymer which are sold by Dow Coming under the name Polytrap; expanded powders, such as hollow microspheres and in particular the microspheres sold under the name Expancel by Kemanord Plast or under the name Micropearl F 80 ED by Matsumoto; silicone resin microbeads, such as those sold under the name Tospearl by Toshiba Silicone; and their mixtures. These fillers can be present in amounts ranging from 0 to 20% by weight and preferably from 1 to 10% by weight with respect to the total weight of the composition.

[0056] According to a preferred embodiment, the compositions in accordance with the invention can additionally comprise at least one organic photoprotective agent and/or at least one inorganic photoprotective agent distinct from the above active principle which is active in the UV-A and/or UV-B regions (absorbers), and which are soluble in water or in fats or else are insoluble in the cosmetic solvents commonly used.

[0057] The organic photoprotective agents are not limited and may be chosen in particular from anthranilates; cinnamic derivatives; dibenzoylmethane derivatives; salicylic derivatives; camphor derivatives; triazine derivatives, such as those disclosed in Patent Applications U.S. Pat. No. 4,367,390, EP 863 145, EP 517 104, EP 570 838, EP 796 851, EP 775 698, EP 878 469, EP 933 376, EP 507 691, EP 507 692, EP 790 243 and EP 944 624; benzophenone derivatives; -diphenylacrylate derivatives; benzotriazole derivatives; benzalmalonate derivatives; benzimidazole derivatives; imidazolines; bisbenzoazolyl derivatives as disclosed in Patents EP 669 323 and U.S. Pat. No. 2,463,264; p-aminobenzoic acid (PABA) derivatives; methylenebis(hydroxyphenylbenzotriazole) derivatives as disclosed in Applications U.S. Pat. No. 5,237,071, U.S. Pat. No. 5,166,355, GB 2 303 549, DE 197 26 184 and EP 893 119; screening polymers and screening silicones, such as those disclosed in particular in Application WO 93/04665; dimers derived from -alkylstyrene, such as those disclosed in Patent Application DE 198 55 649; 4,4-diarylbutadienes as disclosed in Applications EP 0 967 200, DE 197 46 654, DE 197 55 649, EP-A-1 008 586, EP 1 133 980 and EP 133 981; and their mixtures.

[0058] By way of illustration, mention may be made, as photoprotective agents which are active in the UV-A and/or UV-B regions, denoted below under their INCI names, of:

[0059] p-aminobenzoic acid (PABA) derivatives, in particular PABA, ethyl PABA, ethyl dihydroxypropyl PABA, ethylhexyl dimethyl PABA (sold in particular under the name "Escalol 507" by ISP), glyceryl PABA or PEG-25 PABA (sold under the name "Uvinul P25" by BASF),

[0060] salicylic derivatives, in particular homosalate (sold under the name "Eusolex HMS" by Rona/EM Industries), ethylhexyl salicylate (sold under the name "Neo Heliopan OS" by Haarmann and Reimeri), dipropylene glycol salicylate (sold under the name "Dipsal" by Scher), or TEA salicylate (sold under the name "Neo Heliopan TS" by Haarmann and Reimer),

[0061] dibenzoylmethane derivatives, in particular butyl methoxydibenzoylmethane (sold in particular under the trade name "Parsol 1789" by Hoffmann-LaRoche), or isopropyl dibenzoylmethane,

[0062] cinnamic derivatives, in particular ethylhexyl methoxycinnamate (sold in particular under the trade name "Parsol MCX" by Hoffmann-LaRoche), isopropyl methoxycinnamate, isoamyl methoxycinnamate (sold under the trade name "Neo Heliopan E 1000" by Haarmann and Reimer), cinoxate, DEA methoxycinnamate, diisopropyl methyl cinnamate, or glyceryl ethylhexanoate dimethoxycinnamate,

[0063] , -diphenylacrylate derivatives, in particular octocrylene (sold in particular under the trade name "Uvinul N539" by BASF) or etocrylene (sold in particular under the trade name "Uvinul N35" by BASF),

[0064] benzophenone, in particular benzophenone-1 (sold under the trade name "Uvinul 400" by BASF), benzophenone-2 (sold under the trade name "Uvinul D50" by BASF), benzophenone-3 or oxybenzone (sold under the trade name "Uvinul M40" by BASF), benzophenone-4 (sold under the trade name "Uvinul MS40" by BASF), benzophenone-5, benzophenone-6 (sold under the trade name "Helisorb 11" by Norquay), benzophenone-8 (sold under the trade name "Spectra-Sorb UV-24" by American Cyanamid), benzophenone-9 (sold under the trade name "Uvinul DS-49" by BASF), benzophenone-12, or n-hexyl 2-(4-diethylamino-2-hydroxybenzoyl)benzoate,

[0065] benzylidene camphor derivatives, in particular 3-benzylidene camphor (manufactured under the name "Mexoryl SD" by Chimex), 4-methylbenzylidene camphor (sold under the name "Eusolex 6300" by Merck), benzylidene camphor sulphonic acid (manufactured under the name "Mexoryl SL" by Chimex), camphor benzalkonium methosulphate (manufactured under the name "Mexoryl SO" by Chimex), terephthalylidene dicamphor sulphonic acid (manufactured under the name "Mexoryl SX" by Chimex), or polyacrylamidomethyl benzylidene camphor (manufactured under the name "Mesoryl SW" by Chimex),

[0066] benzimidazole derivatives, in particular phenylbenzimidazole sulphonic acid (sold in particular under the trade name "Eusolex 232" by Merck), or disodium phenyl dibenzimidazole tetrasulphonate (sold under the trade name "Neo Heliopan AP" by Haarmann and Reimer),

[0067] triazine derivatives, in particular anisotriazine (sold under the trade name "Tinosorb S" by Ciba Specialty Chemicals), ethylhexyl triazone (sold in particular under the trade name "Uvinul T150" by BASF), diethylhexyl butamido triazone (sold under the trade name "Uvasorb HEB" by Sigma 3V) or 2,4,6-tris(diisobutyl 4'-amino-benzalmalonate)-s-triazine- ,

[0068] benzotriazole derivatives, in particular drometrizole trisiloxane (sold under the name "Silatrizole" by Rhodia Chimie) or methylene bisbenzotriazolyl tetramethylbutylphenol (sold in the solid form under the trade name "Mixxim BB/100" by Fairmount Chemical or in the micronized form in aqueous dispersion under the trade name "Tinosorb M" by Ciba Specialty Chemicals),

[0069] anthranilic derivatives, in particular menthyl anthranilate (sold under the trade name "Neo Heliopan MA" by Haarmann and Reimer),

[0070] imidazoline derivatives, in particular ethylhexyl dimethoxybenzylidene dioxoimidazoline propionate,

[0071] benzalmalonate derivatives, in particular polyorganosiloxane comprising benzalmalonate functional groups (sold under the trade name "Parsol SLX" by Hoffmann-LaRoche),

[0072] 4,4-diarylbutadiene derivatives, in particular 1,1'-dicarboxy (2,2'-dimethylpropyl)-4,4-diphenylbutadiene,

[0073] and their mixtures.

[0074] The organic photoprotective agents which are more particularly preferred are selected from the group consisting of ethylhexyl salicylate, ethylhexyl methoxycinnamate, octocrylene, phenylbenzimidazole sulphonic acid, benzophenone-3, benzophenone-4, benzophenone-5, 4-methylbenzylidene camphor, terephthalylidene dicamphor sulphonic acid, disodium phenyl dibenzimidazole tetrasulphonate, 2,4,6-tris(diisobutyl 4'-aminobenzalmalonate)-s-triazine, anisotriazine, ethylhexyl triazone, diethylhexyl butamido triazone, methylene bisbenzotriazolyl tetramethylbutylphenol, drometrizole trisiloxane, 1,1'-dicarboxy (2,2'-dimethylpropyl)-4,4-diphenylbutadiene, and their mixtures.

[0075] The inorganic photoprotective agents may be selected from the group consisting of pigments or alternatively nanopigments (mean size of the primary particles: generally between 5 nm and 100 nm, preferably between 10 nm and 50 nm) formed from coated or uncoated metal oxides, such as, for example, titanium oxide (amorphous or crystalline in the rutile and/or anatase form), iron oxide, zinc oxide, zirconium oxide or cerium oxide nanopigments, which are all UV photoprotective agents well known per se. Conventional coating agents are, furthermore, alumina and/or aluminium stearate. Such nanopigments formed from coated or uncoated metal oxides are disclosed in particular in Patent Applications EP 518 772 and EP 518 773.

[0076] The photoprotective agents may generally be present in the compositions according to the invention in proportions ranging from 0.1 to 20% by weight with respect to the total weight of the composition and preferably ranging from 0.2 to 15% by weight with respect to the total weight of the composition.

[0077] In another advantageous aspect of the invention, the composition can additionally comprise at least one other agent selected from the group consisting of scavengers for ozone, scavengers for heavy metals and agents for combatting free radicals.

[0078] Mention may in particular be made, as scavengers for ozone which can be used in the composition according to the invention, of phenols and polyphenols, in particular tannins, ellagic acid and tannic acid; epigallocatechin and the natural extracts comprising it; olive tree leaf extracts; tea extracts, in particular green tea extracts; anthocyanins; rosemary extracts; phenolic acids, in particular chorogenic acid; stilbenes, in particular resveratrol; sulphur-comprising amino acid derivatives, in particular S-carboxymethylcysteine; ergothioneine; N-acetylcysteine; chelating agents, such as N,N'-bis(3,4,5-trimethoxybenz- yl)ethylenediamine or one of its salts, metal complexes or esters; carotenoids, such as crocetin; and various starting materials, such as the mixture of arginine, histidine ribonucleate, mannitol, adenosine triphosphate, pyridoxine, phenylalanine, tyrosine and hydrolysed RNA sold by Laboratoires Srobiologiques under the trade name CPP LS 2633-12F.RTM., the water-soluble maize fraction sold by Solabia under the trade name Phytovityl.RTM., the mixture of fumitory extracts and of lemon extracts sold under the name Unicotrozon C-49.RTM. by Induchem and the mixture of extracts of ginseng, of apple, of peach, of wheat and of barley sold by Provital under the trade name Pronalen Bioprotect.RTM..

[0079] Finally, mention may in particular be made, as scavengers for heavy metals which can be used in the composition according to the invention, of chelating agents, such as EDTA, the pentasodium salt of ethylenediaminetetramethylenephosphonic acid, and N,N'-bis(3,4,5-trimetho- xybenzyl)ethylenediamine or one of its salts, metal complexes or esters; phytic acid; chitosan derivatives; tea extracts, in particular green tea extracts, tannins, such as ellagic acid; sulphur-comprising amino acids, such as cysteine; water hyacinth (Eichomia crassipes) extracts; and the water-soluble maize fraction sold by Solabia under the trade name Phytovityl.RTM..

[0080] The agents for combatting free radicals which can be used in the composition according to the invention comprise, in addition to certain agents for combatting pollution mentioned above, vitamin E and its derivatives, such as tocopheryl acetate; bioflavonoids; coenzyme Q10 or ubiquinone; certain enzymes, such as catalase, superoxide dismutase, lactoperoxidase, glutathione peroxidase and quinone reductases; glutathione; benzylidene camphor; benzylcyclanones; substituted naphthalenones; pidolates; phytantriol; .gamma.-oryzanol; lignans; and melatonin.

[0081] The composition according to the invention can be applied for example to the skin or lips. It can thus be used in a cosmetic treatment process for the purpose of preventing or combatting the harmful effects of UV radiation and/or of pollution on the skin or mucous membranes, comprising the application of the composition according to the invention to the skin or mucous membranes.

[0082] The invention also relates to a cosmetic treatment process for the purpose of preventing or combatting loss of firmness and/or of elasticity of the skin or mucous membranes, comprising the application of the composition according to the invention to the skin or mucous membranes.

[0083] The composition according to the invention can also be used for the manufacture of a dermatological preparation comprising an aqueous phase which is intended to prevent or combat harmful effects of UV radiation and/or of pollution on the skin.

[0084] In another embodiment, the composition according to the invention can be used for the manufacture of a dermatological preparation comprising an aqueous phase which is intended to prevent or combat loss of firmness and/or elasticity of the skin.

[0085] The examples which follow serve to illustrate the invention without, however, exhibiting a limiting nature. The compounds are, depending on the situation, cited according to chemical names or according to CTFA (International Cosmetic Ingredient Dictionary and Handbook) names.

EXAMPLES

Example 1

Accelerated Storage Test

[0086] The aim of this test is to study the decomposition of an oxidation-sensitive hydrophilic active principle after storing for two months at 45.degree. C. Various solutions were prepared and their compositions are collated in the following table:

1TABLE I Compositions (in Solution A water) (Control) Solution B Solution C Solution D Ascorbic acid 15% 15% 15% 15% Polymer 1 -- 1% -- -- Polymer 2 -- -- 1% -- Polymer 3 -- -- -- 1%

[0087] All the solutions are brought to pH 6 with 8.9 mol/l KOH.

[0088] The percentages of the polymers are given as active material.

[0089] Polymer 1: Vinylpyrrolidone/vinylimidazole (50/50) copolymer sold under the reference Luvitec VPI 55K72W of BASF (Weight-average molecular mass 1.2.times.10.sup.6).

[0090] Polymer 2: Vinylpyrrolidone/vinylimidazole (50/50) copolymer sold under the reference Luvitec VPI 55K18P of BASF (Weight-average molecular mass 10 000).

[0091] Polymer 3: Polyvinylpyrrolidone sold under the reference Kollidon 12PF of BASF (Weight-average molecular mass 3 000).

[0092] The degree of decomposition measured is given by the ratio:

(C.sub.0-C.sub.2 months)/CO

[0093] with C.sub.0 concentration of ascorbic acid at t=0 and C.sub.2 months the concentration of ascorbic acid at t=2 months, under the conditions indicated in the above table.

[0094] The concentration of ascorbic acid is determined by the HPLC technique (LaChrom Merck system). The analytical conditions are as follows:

[0095] Column: Lichrosphere100 RP18 (250 mm)

[0096] Eluent: 0.1M phosphate buffer, pH 2.1

[0097] Flow rate: 1 ml/min

[0098] Detection at 257 nm

[0099] Dilution of the sample such that the concentration of ascorbic acid is between 0.05 and 1 mg/ml.

[0100] The results obtained are collated in the following Table II:

2 TABLE II Degree of decomposition after 2 months at 45.degree. C. (in %) under air, amber glass bottle under nitrogen, aluminium flask Solution A 43 19.4 Solution B 10.8 1 Solution C 23.4 4.5 Solution D 35.8 15.7

[0101] It is found, from Table II, that the stability of ascorbic acid is improved in the presence of Polymer 1 and Polymer 2 of the invention, even in the presence of atmospheric oxygen, in comparison with the control. It is also found that the N-vinylpyrrolidone homopolymer alone is not sufficient to effectively stabilize the ascorbic acid solution.

[0102] As the polymers mentioned are hydrophilic, it would be sufficient to add them to an aqueous ascorbic acid solution to stabilize the ascorbic acid.

Example 2

Demonstration of the Activity in Combatting Free Radicals

[0103] I. Principle

[0104] This test makes it possible to evaluate the effect of a molecule in combatting OH.sup.o.

[0105] It is based on the measurement by gas chromatography of the ethylene formed from the oxidation of methionine by the hydroxyl radical. The latter is generated by a ferro-catalysed Fenton reaction maintained by the continuous generation of superoxide anions. The anions O2.sup.o--are produced by photochemical reduction at 365 nm of riboflavin (RBF) by a hydrogen donor, according to the following scheme: 1

RBFH.sub.2+O.sub.2.fwdarw.RBF+2 O.sub.2.sup.o-+2H.sup.+

2 O.sub.2.sup.o-+2H.sup.+.fwdarw.H.sub.2O.sub.2+O.sub.2

O.sub.2.sup.o-+L--Fe.sup.3+.fwdarw.O.sub.2+L--Fe.sup.2+

H.sub.2O.sub.2+L--Fe.sup.2+.fwdarw.L--Fe.sup.3++OH.sup.-+OH.sup.o

CH.sub.3--S--CH.sub.2--CH(COOH)--NH.sub.2+OH.sup.o.fwdarw.CH.sub.2=CH.sub.- 2+products

[0106] The neutralization of the OH.sup.o radicals is reflected by inhibition of the production of ethylene.

[0107] II. Procedure

[0108] Irradiation equipment: 3 low-pressure mercury vapour tubes.

[0109] The tested products are dissolved in a phosphate buffer. They are tested at final concentrations in the reaction mixture generally ranging from 0.1 to 3%, according to their solubility. The final volume is 2 ml.

[0110] The separation distance for exposure under the UV bank is adjusted in order to have an exposure time of approximately 8 minutes for a UV-A dose of 1 joule/cm.sup.2 and in order not to adjust this setting throughout the duration of the test.

[0111] The following are introduced in this order into a head space flask:

[0112] 1.4 ml of phosphate buffer

[0113] 100 .mu.l of 200 mM methionine solution

[0114] 100 .mu.l of 4 mM ferric chloride solution

[0115] 100 .mu.l of phosphate buffer, pH 7.4, (control) or of solution comprising the active principle to be tested

[0116] 100 .mu.l of 4 mM EDTA solution

[0117] 100 .mu.l of 400 mM NADH solution

[0118] The samples and the blanks are all prepared in succession and are kept sheltered from the light.

[0119] The UV-A bank is switched on, displaying a number of joules at least equal to the number of samples. The samples are irradiated one by one at intervals of 0.5 joules.

[0120] Every 0.5 joules:

[0121] 100 .mu.l of riboflavin are added

[0122] mixing is carried out

[0123] the sample is irradiated with 1 joule

[0124] the reaction is halted with 0.5 ml of IN NaOH

[0125] the sample is sheltered from the light

[0126] The flasks are inserted into the sample changer of the chromatograph. The ethylene peak exits at a retention time of approximately 2.00 minutes. A minimum of 3 measurements are carried out per sample.

[0127] III. Results:

[0128] The results are expressed as percentage of inhibition of production of ethylene with respect to the control solution.

[0129] It is apparent that, for the tested samples comprising the ascorbic acid and N-vinylimidazole/N-vinylpyrrolidone copolymer combination, inhibition of the production of ethylene is increased with respect to the control, thus demonstrating the activity in combatting free radicals of this combination.

Example 3

O/W cream

[0130] The following composition is prepared in a way conventional to a person skilled in the art.

3 Glyceryl stearate and PEG-100 stearate 2.5 g PEG-50 stearate 2.5 g Cetyl alcohol 1 g Stearyl alcohol 1 g Hydrogenated polyisobutene 5 g Water 12.23 g Glycerol 5 g Cyclopentasiloxane 15 g Carbomer 0.6 g Phenoxyethanol 1 g Water 45.17 g Ascorbic acid 5 g Potassium hydroxide (50% solution) 3 g Vinylpyrrolidone/vinyli- midazole copolymer 1 g

[0131] This soft cream, on application, makes it possible to smooth out the lines of the face and exhibits good stability for ascorbic acid.

Example 4

W/O emulsion

[0132] The following composition is prepared in a way conventional to a person skilled in the art.

4 Water 45.17 g Ascorbic acid 5 g Potassium hydroxide (50% solution) 3 g Vinylpyrrolidone/vinylimid- azole copolymer 1 g Glycerol 5 g Phenoxyethanol 1 g Cyclopentasiloxane and dimethicone copolyol 20 g Phenyl trimethicone 4 g Prunus armeniaca (apricot) kernel oil 3.5 g Dimethicone and 5 g Dimethicone/vinyl dimethicone crosspolymer Nylon-12 5 g

[0133] A white water-in-oil emulsion is obtained, which emulsion is capable of smoothing out the lines of the face and in which emulsion ascorbic acid has good stability.

[0134] The above description, as illustrated by non-limiting examples, allows one of ordinary skill in the art to make and use a composition for preventing or combatting the harmful effects of UV radiation and/or of pollution on the skin comprising, preferably in a physiologically acceptable medium comprising an aqueous phase, at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and at least one non-crosslinked N-vinylimidazole polymer or copolymer, the active principle and the polymer or copolymer both being present in the aqueous phase. Also provided is a method for preventing or combatting loss of firmness and/or of elasticity of the skin, for soothing sunburn, and to prevent or combat the harmful effects of UV radiation and/or of pollution on the skin using this composition, and the use of a combination composed of at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and of at least one non-crosslinked N-vinylimidazole polymer or copolymer in the aqueous phase of a cosmetic composition as agent for combatting free radicals. Further provided is a cosmetic treatment process to prevent or combat the harmful effects of UV radiation and/or of pollution on the skin or mucous membranes, comprising the application, to the skin or mucous membranes, of a composition comprising, preferably in a physiologically acceptable medium comprising an aqueous phase, at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and at least one non-crosslinked N-vinylimidazole polymer or copolymer, the active principle and said polymer or copolymer both being present in the aqueous phase, and a cosmetic process to combat loss of firmness and/or of elasticity of the skin or mucous membranes, comprising the application, to the skin or mucous membranes, of a composition comprising, preferably in a physiologically acceptable medium comprising an aqueous phase, at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and at least one non-crosslinked N-vinylimidazole polymer or copolymer, the active principle and the polymer or copolymer both being present in the aqueous phase.

[0135] French patent application 0115375 is incorporated herein by reference, as are all references, texts, documents, articles, standards, patents, applications, etc., mentioned above. All numerical ranges include all values therebetween as if specifically written out.

[0136] Also incorporated herein by reference are the following U.S. applications, all filed Nov. 27, 2002, where the present application is listed for information only:

5 U.S. Ser. No. . . . (Atty. Docket 230634US0) U.S. Ser. No. . . . (Atty. Docket 230608US0) U.S. Ser. No. . . . (Atty. Docket 230616US0) U.S. Ser. No. . . . (Atty. Docket 230614US0) U.S. Ser. No. . . . (Atty. Docket 230615US0)

Claims

1. A method for treating skin and/or mucous membrane, comprising applying to skin or mucous membrane a composition comprising, in a physiologically acceptable medium comprising an aqueous phase, at least one oxidation-sensitive hydrophilic active principle selected from the group consisting of ascorbic acid and its derivatives and at least one non-crosslinked N-vinylimidazole polymer or copolymer, the at least one active principle and the at least one polymer or copolymer both being present in the aqueous phase.

2. The method of claim 1, wherein said treating is selected from the group consisting of preventing or combatting harmful effects of UV radiation and/or of pollution, preventing or combatting loss of firmness and/or of elasticity, combatting free radicals, and soothing sunburn, said method comprising applying an amount of said composition to skin and/or mucous membrane to so treat.

3. The method of claim 2, wherein said treating is preventing or combatting harmful effects of UV radiation and/or of pollution.

4. The method of claim 2, wherein said treating is preventing or combatting loss of firmness and/or of elasticity.

5. The method of claim 2, wherein said treating is combatting free radicals.

6. The method of claim 2, wherein said treating is soothing sunburn.

7. The method according to claim 1, wherein the ascorbic acid derivatives are selected from the group consisting of ascorbic acid esters and ascorbic acid salts.

8. The method according to claim 1, wherein the hydrophilic active principle is selected from the group consisting of 5,6-di-O-dimethylsilylascorbate, dl-.alpha.-tocopheryl dl-ascorbyl phosphate potassium salt, magnesium ascorbyl phosphate and sodium ascorbyl phosphate.

9. The method according to claim 1, wherein the oxidation-sensitive hydrophilic active principle is ascorbic acid.

10. The method according to claim 1, wherein the composition comprises a non-crosslinked copolymer that is a combination of the N-vinylimidazole with N-vinylpyrrolidone and/or N-vinylcaprolactam subunits.

11. The method according to claim 1, wherein the composition comprises a non-crosslinked copolymer that is an N-vinylimidazole/N-vinylpyrrolidone copolymer.

12. The method according to claim 1, wherein the composition comprises a non-crosslinked copolymer that is selected from the group consisting of a vinylpyrrolidone/vinylimidazole (50/50) copolymer having a weight-average molar mass of 1 200 000 and a vinylpyrrolidone/vinylimidazole (50/50) copolymer having a weight-average molar mass of 10 000.

13. The method according to claim 1, wherein a molar ratio of N-vinylimidazole unit equivalent to the oxidation-sensitive hydrophilic active principle is from 0.004 to 16.

14. The method according to claim 13, wherein the molar ratio of the N-vinylimidazole unit equivalent to the oxidation-sensitive hydrophilic active principle varies between 0.01 and 1.

15. The method according to claim 1, wherein the polymer or copolymer is present at a concentration of 0.1 to 5% by weight of the aqueous phase.

16. The method according to claim 13, wherein the polymer or copolymer is present at a concentration of 0.1 to 2% by weight of the aqueous phase.

17. The method according to claim 1, wherein the polymer or copolymer has a molar fraction of N-vinylimidazole units of 0.1 to 1.

18. The method according to claim 15, wherein the polymer or copolymer has a molar fraction of N-vinylimidazole units of 0.4 to 0.9.

19. The method according to claim 1, wherein the composition further comprises an agent in addition to the hydrophilic active principle selected from the group consisting of scavengers for ozone, scavengers for heavy metals and agents for combatting free radicals.