WO2010020668A1

WO2010020668A1 - A cosmetic composition

Info

Publication number: WO2010020668A1
Application number: PCT/EP2009/060754
Authority: WO
Inventors: Vijay Ramchandra Gadgil; Kumar Gaurav; Balu Kunjupillai
Original assignee: Hindustan Unilever Ltd; Unilever NV
Current assignee: Hindustan Unilever Ltd; Unilever NV
Priority date: 2008-08-22
Filing date: 2009-08-20
Publication date: 2010-02-25
Anticipated expiration: 2011-02-22

Abstract

The present application relates to a composition which includes water-soluble 1,3-diketone sunscreens, more particularly, water-soluble dibenzoylmethane sunscreens, where the sunscreens exhibit relatively low photodegradation; and a method for reducing the photodegradation of the water-soluble 1,3-diketone sunscreens. It is an object of the present application to provide a composition, which includes a water-soluble 1,3-diketone sunscreen, where the photodegradation of 1,3-diketone sunscreen is relatively low. The present inventors have found that water-soluble dibenzoylmethanes too suffer from the problem of photodegradation. It has been found that use of conventional stabilizers do not provide adequate stability. It has also been found that the stability of water-soluble 1,3-diketones is affected in the presence of conventional emulsifiers/surfactants, which are often included in cosmetic compositions.

Description

A COSMETIC COMPOSITION

FIELD OF INVENTION

The present invention relates to a composition which includes water-soluble 1,3- diketone sunscreens, more particularly, water-soluble dibenzoylmethane sunscreens, where the sunscreens exhibit relatively low photodegradation; and a method for reducing the photodegradation of the water-soluble 1,3-diketone sunscreens.

The invention has been developed primarily for use in cosmetics and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.

BACKGROUND OF THE INVENTION

Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.

It is now generally accepted that ultraviolet radiation can be a serious health hazard. Even a limited, but continued exposure to solar radiation, is known to cause chronic skin damage, including conditions such as skin aging, and keratolytic lesions upon prolonged and continued exposure. The immediate effect of exposure to sunrays is sunburn (erythrema). To counter sunburn, numerous sun-screening products are commercially available for application to the skin.

It is known that UV-A (UV means ultra violet) radiation having a wavelength between 320 nm and 400 nm causes tanning of the skin. It causes, in particular, loss of elasticity of the skin and the appearance of wrinkles, leading to premature ageing. In addition, it also promotes triggering of the erythematous reaction or accentuates this reaction in some individuals. It is also known to be the cause of phototoxic or photo-allergic reactions. It is thus desirable to screen out UV-A radiation.

Various organic and inorganic sunscreens are used for this purpose. Commercial sunscreen compositions generally include at least one sunscreen active. To specifica l ly protect aga i nst UV-A radiation, a UV-A s u n sc ree n , s u c h a s a dibenzoylmethane derivative (e.g. t-butylmethoxy dibenzoylmethane, also known as Avobenzone™ or Parsol 1789™) is used to provide protection from UV-A radiation. Dibenzoylmethanes are 1,3-diketone sunscreens.

A common problem associated with 1,3 diketones, including dibenzoylmethane and/or derivatives thereof, is that they photodegrade over time on exposure to UV radiation. This results in a reduction of the UV absorbance of the composition, particularly UV-A absorbance, and thus a diminution in sunscreen protection for the user during extended exposure to sunlight.

Various attempts have been made in the past to overcome this problem of instability.

US 5 576 354 (1996, L'Oreal) describes photostabilization of Avobenzone™ with the help of diphenylacrylate sunscreens, such as Octocyrlene™, where the molar ratio of diphenylacrylate to Avobenzone™ is at least 0.8.

US 5 827 508 (1998, Procter & Gamble) describes stabilization of Avobenzone™ by incorporation of surface-treated zinc oxide particles. A combination of Avobenzone™ and Parsol-MCX™ (2-ethylhexyl-p-methoxy cinnamate) is used very widely in topical sunscreen products and US 6 071 501 (2000, Procter & Gam ble) discloses that combinations of dibenzoylmethane derivatives and 2-ethylhexyl-p-methoxycinnamate

(Parsol MCX™) are not photostable, unless the molar ratio of the methoxycinnamate to the dibenzoylmethane is in the range of 0.15:1 to 1 : 1. US 5 993 789 (CP Hall, 1999) discloses a sunscreen composition comprising a cosmetically acceptable carrier, at least about 0.5% by weight of a dibenzoylmethane derivative, and at least 0.5% by weight of a diester or polyester of naphthalene dicarboxylic acid selected from two specific formulae.

Water-soluble 1 ,3-diketones, especially derivatives of dibenzoylmethanes have been reported in US 4 704 473 (1987, Kao Corp) and in GB 2 081 716 (1982, L'Oreal). Such water-soluble derivatives find application in several cosmetic products, and are preferred because these products can be used in place of their lipophilic counterparts, thereby reducing several complexities of formulations associated therewith.

However the present inventors have found that water-soluble dibenzoylmethanes also suffer from the problem of photodegradation. It has been found by the present inventors that use of conventional stabilizers do not provide adequate stability. The present inventors have also found that conventional 1,3-diketone sunscreens (e.g. Parsol 1789™) as exemplified in US 5 999 3789 which are not water-soluble are not as well stabilised by compounds like diesters or polyesters of naphthalene dicarboxylic acid when compared to the combination disclosed and claimed in the present invention. It has also been found by the present inventors that the stability of water- soluble 1 ,3-diketones is affected by the presence of conventional emulsifiers/ surfactants which are often included in cosmetic compositions.

OBJECT OF THE INVENTION

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art.

It is an object of the present invention to provide a composition which includes a water-soluble 1,3-diketone sunscreen where the photodegradation of the 1,3-diketone sunscreen is relatively low.

It is an object of the present invention to provide a composition which includes a water-soluble 1 ,3-diketone sunscreen and conventional emulsifiers where the photodegradation of the 1,3-diketone sunscreen is relatively low.

The present inventors have surprisingly found that the photo-degradation of water- soluble 1 ,3-diketone sunscreens, and especially water-soluble dibenzoylmethane sunscreens, in cosmetic compositions could be effectively reduced when the composition includes a water-soluble reaction product of a polymer with a triplet quencher. SUMMARY OF THE INVENTION

According to a first aspect, the present invention provides a cosmetic composition comprising a water-soluble 1 ,3-diketone sunscreen and a water-soluble reaction product of a polymer with a triplet quencher.

Preferably the water-soluble 1,3-diketone sunscreen is a sodium salt of 4-methoxy-2'- carboxy-dibenzoyl methane.

Preferably the polymer is polyethyleneglycol.

Prefera b ly the tri p let q uencher i s a 3, 3-diphenylacrylonitrile derivative or a naphthalene dicarboxy derivative.

According to a second aspect, the present invention provides a method for reducing photodegradation of water-soluble 1,3-diketone sunscreens in a cosmetic composition, the method comprising the step of combining a water-soluble 1,3-diketone sunscreen with one or more water-soluble reaction products of a polymer with a triplet quencher.

According to a third aspect, the present invention provides a method for providing protection to the skin against ultraviolet radiation, said method comprising the step of applying a safe and effective amount of the cosmetic composition of the first aspect to the skin.

According to a fourth aspect, the present invention provides use of the composition according to the first aspect for providing protection against ultraviolet radiation.

These and other aspects, features and advantages will become apparent to those of ordinary skill in the art from a reading of the following detailed description and the appended claims. For the avoidance of doubt, any feature of one aspect of the present invention may be utilised in any other aspect of the invention. The word "comprising" is intended to mean "including" but not necessarily "consisting of" or "composed of." In other words, the listed steps or options need not be exhaustive. It is noted that the examples given in the description below are intended to clarify the invention and are not intended to limit the invention to those examples per se. Similarly, all percentages are weight/weight percentages unless otherwise indicated. Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word "about". Numerical ranges expressed in the format "from x to y" are understood to include x and y. When for a specific feature multiple preferred ranges are described in the format "from x to y", it is understood that all ranges combining the different endpoints are also contemplated.

For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of preferred embodiments.

DETAILED DESCRIPTION

In the first aspect, this invention relates to a cosmetic composition comprising a cosmetic composition comprising a water-soluble 1,3-diketone sunscreen and a water- soluble reaction product of a polymer with a triplet quencher.

The water-soluble 1,3-diketone sunscreen is preferably a salt of a carboxy derivative of dibenzoylmethane, or a quaternary ammonium derivative of dibenzoylmethane. Preferred salts are sodium, potassium or lithium salts. It is most preferred that the water-soluble 1 ,3-diketone sunscreen is a sodium salt of 4-methoxy-2'-carboxy- dibenzoylmethane.

By the term "dibenzoylmethane" as used herein is meant a compound of the following basic structure and includes derivatives thereof.

The carboxy group in the carboxy derivative of dibenzoylmethane and the quaternary ammonium group in the quaternary ammonium derivative of dibenzoylmethane could be attached directly to the benzene rings of dibenzoylmethane or could be attached to an alkyl group on the ring.

By "water-soluble" is meant that the solubility of the compound in water at 20 ⁰C is at least 0.1 g/l, preferably at least 1.0 g/l.

It is preferred that the water-soluble 1,3-diketone sunscreen is in the range of 0.5 wt% to 25 wt%, preferably 0.5 wt% to 10 wt%, and more preferably 0.5 wt% to 3.5 wt% in the composition.

The photodegradation of the water-soluble 1,3-diketone sunscreen is reduced when the composition includes a water-soluble reaction product of a polymer with a triplet quencher.

The reaction product of the polymer with the triplet quencher may be described as "polymer/triplet quencher complexes" as the polymer and the triplet quencher are reacted together to form the compound. Other components may also be reacted with the polymer in addition to the essential triplet quencher.

The polymer and the triplet quencher may be attached directly to each other, i.e. reacted directly together so as to be chemically linked without an 'interrupting' group present between the polymer and triplet quencher. Alternatively the polymer and triplet quencher attachment may be interrupted or substituted by one or more interrupting groups that do not have triplet quencher properties. Suitable interrupting groups include alkyl and ethylene oxide residues.

The triplet quencher may be attached in a pendent position on the polymer and/or may be present in the polymer backbone in an arrangement as found in a random or block copolymer.

References herein to a polymer include suitable co-polymers and homopolymers. The polymer used typically has a molecular weight in the range 190-200,000 g/mol, preferably 1,000-80,000 g/mol, and more preferably 10,000-25,000 g/mol.

It is especially preferred that the polymers have low polydispersity, with preferably more than 80%, especially more than 95% of the sample eluted within 90-110% of the mean number average molecular mass.

It is preferred that the polymer is selected from the group consisting of polyalkyleneglycols, polyvinylalcohol, sodium carboxymethyl cellulose, starch, natural and synthetic gums, cellobioses, pyrrolidones, acrylates, acrylamides and polyacids. It is further preferred that the polymer is polyvinylalcohol or polyalkyleneglycols. The most preferred polymer is polyalkyleneglycol; particularly polyethyleneglycol having a molecular weight in the range of 190-100000 g/mol. It is further particularly preferred that the molecular weight of polyethyleneglycol is about 200 g/mol.

The preferred triplet quencher is selected from the group consisting of 3,3- diphenylacrylonitrile derivatives, 3-phenylacrylonitrile derivatives, naphthalene d ica rboxy derivatives, benzyl idenema lonate derivatives, 4-hydroxycinnamate derivatives, fluorene derivatives, benzylidene camphor derivatives and piperidinol derivatives. It is more preferred that the triplet quencher is a 3,3-diphenylacrylonitrile derivative or a naphthalene dicarboxy derivative. A particularly preferred 3,3- diphenylacrylonitrile derivative i s 2-cyano-3,3-diphenyl acrylic acid. A particularly preferred naphthalene dicarboxy derivative is 2,6-naphthalene-dicarboxylic acid.

The preferred water-soluble reaction product of a polymer with a triplet quencher is a reaction product of 2-cyano-3,3-diphenyl acrylic acid (a 3,3-diphenylacrylonitrile derivative) with polyethyleneglycol having molecular weight 200 g/mol; or a reaction product of 2,6-naphthalene-dicarboxylic acid (a naphthalene dicarboxy derivative) with polyethyleneglycol having a molecular weight 200 g/mol.

It is preferred that in the composition the water-soluble reaction product of a polymer with a triplet quencher is in the range of 0.05 wt% to 25 wt%, preferably 0.1 wt% to 10 wt%, and more preferably 0.5 wt% to 5.0 wt%. Without wishing to be bound by theory, it is thought that water-soluble 1,3-diketone sunscreens, after absorbing UV radiation, go to a singlet excited energy state and further to a triplet excited energy state. The lifetime of the singlet excited energy state level is of the order of 10^~12 to 10^~13 seconds and therefore the sunscreens do not have time to undergo significant photodegradation. The lifetime of the triplet excited energy state is long enough to undergo considerable photodegradation. The triplet quenchers are compounds which can accept the energy from excited 1,3-diketone sunscreens and hence facilitate the return to ground state thereby minimising photodegradation. Further it is believed by the present inventors that when the water- soluble 1,3-diketone sunscreen and the triplet quencher of the 1,3-diketone sunscreen are present in different phases, e.g. one in an oil phase and the other in an aqueous phase, the energy transfer between the donor (sunscreen) and the acceptor (triplet quencher) is not efficient to give significant photostabilization as compared to the case when both of them are present in the same phase.

The photodegradation of 1,3-diketone sunscreen is reduced by the water-soluble reaction product of a polymer with a triplet quencher. Without wishing to be bound by theory, it is believed by the present inventors that owing to the water-solubility and the polymeric nature of the reaction product, the reaction product spreads uniformly and the film-formation of the triplet quencher is thereby facilitated. This therefore leads to enhanced and uniform protection from UV radiation.

The invention also relates to a method for reducing the photodegradation of a water- soluble 1,3-diketone sunscreen in a cosmetic composition, the method comprising the step of combining a water-soluble 1,3-diketone sunscreen with one or more water- soluble reaction products of a polymer with a triplet quencher.

The invention also provides a non-therapeutic (e.g. cosmetic) method of providing protection to the skin against ultraviolet radiation, said method comprising the step of applying a safe and effective amount of the cosmetic composition. In use, a small quantity of the composition, e.g. 1 to 5 ml, is applied to exposed areas of the skin from a suitable container or applicator and, if necessary, it is then spread over and/or rubbed into the skin using the hand or fingers. The invention also provides for a non-therapeutic (e.g. cosmetic) use of the composition for providing protection against ultraviolet radiation.

Useful cosmetic compositions according to the present invention can be prepared in the form of fluid suspensions, gels, sticks and others, utilizing formulation parameters known in the art. However the compositions of the invention are more typically emulsions, such as lotions and creams. In many instances it will be preferred to prepare emulsions of the oil-in-water type since these can appear to the skin as being aqueous in character and therefore give a more pleasant sensation while they are being applied. However the water-in-oil type of emulsion is also useful since, after application, contained water evaporates. Both types of emulsions will leave a nonaqueous residue on the skin.

Emulsion compositions are generally required to contain at least one emulsifier. However the present invention provides for cosmetic compositions that need not necessarily contain known emulsifiers for the purpose of emulsification. However emulsifiers may optionally be included in the compositions.

OPTIONAL INGREDIENTS One or more other types of components will frequently also be present, such as, without limitation, emulsion builders, emollients, humectants, dry-feel modifiers, antimicrobial preservatives, antioxidants, chelating agents, fragrances and colorants.

The inventors have determined that a water-soluble 1,3-diketone sunscreen in the cosmetic composition of the invention is further stabilised by the presence of emulsifiers. Typical suitable emulsifiers include sorbitan monooleate, sorbitan sesquioleate, sorbitan isostearate, sorbitan trioleate, PEG-22/dodecyl glycol copolymer, PEG-45/dodecyl glycol copolymer, polyglyceryl-3-diisostearate, polyglycerol esters of oleic/isostearic acid, polyglyceryl-6 hexaricinolate, polyglyceryl-4 oleate, polyglyceryl-4 oleate/PEG-8 propylene glycol cocoate, oleamide DEA, sodium glyceryl oleate phosphate and hydrogenated vegetable glycerides phosphate. Other emulsifiers useful in the present invention may be non-ionic, liquid or solid at room temperature and preferably compatible, i.e. soluble and stable with emollients. Other preferred emulsifiers include sorbitan sequioleate (HLB value is 3.7), sorbitan monooleate (HLB value is 4.3) and sorbitan trioleate (HLB value is 1.8). Other preferred emulsifiers include polymeric emulsifiers such as copolymers of C10-C30 alkyl acrylates and one or more monomers of acrylic acid or methacrylic acid, also known as Pemulen™ TR1 and TR2, trademark of B. F. Goodrich Inc., Cincinnati, Ohio U.S.A. Other emulsifiers include sorbitan esters such as sorbitan isostearate available as Crill 6™, trademark of Croda Inc. of New York, N. Y. U.S.A.; polyglyceryl-3 distearate available as Cremophor™, trademark of BASF, Parsippany NJ. U.S.A.; and carbomer, which is a homopolymer of acrylic acid crosslinked with an allyl ether of sucrose, available as Carbopol 941™, trademark of B. F. Goodrich, Cleveland, Ohio U.S.A.; surfactants such as such as DEA- cetyl phosphate, also known as Amphisol™, trademark of Bernel Chem ical Co., Englewood, NJ. U.S.A.; mixtures of arachidyl alcohol, behenyl alcohol and arachidyl glucoside, such as is sold by Seppic Inc. of Fairfield, NJ. U.S.A. using the trademark Montanov™ 202; and mixtures of cetearyl glucoside and cetearyl alcohol, such as is sold by Cog nis Corporation of Ci nci n natti, Ohio U . S.A. usi ng the tradema rk Emulgade™ PL 68/50. Especially suitable emulsifiers are conventional surfactants like soap e.g. sodium or potassium salt of fatty acids or salt of linear alkyl benzene sulphonate. One or more emulsifiers can be used in the compositions of the present invention in amounts ranging from about 0.05 to about 20 weight percent of the emulsion, preferably from about 0.1 to about 15%, more preferably from about 5 to about 10%.

Water is employed in amounts effective to form the cosmetic compositions and should be sufficient to at least solubilize the major ingredients of 1,3-diketone sunscreen and the water-soluble reaction product of the polymer with the triplet quencher. Thus the amount of water in the emulsion or composition can range from about 2 to 95 weight %, preferably from 50 to 85%. It frequently is desirable to use purified water to enhance the predictability of product characteristics.

Thickening agents may be used to increase the viscosity of the sunscreen formulations. Suitable thickening agents include carbomers, acrylate/acrylonitrile copolymers, xantha n gu m and com bi nations of these. The ca rbomer thickeners include the crosslinked carbopol™ acrylic polymers from B. F. Goodrich. The amount of thickener within the sunscreen formulation, on a solids basis without water, may range from about 0.001 to about 5%, preferably from 0.01 to about 1% and optimally from about 0.1 to about 0.5% by weight.

An emollient is an oleaginous or oily substance which helps to smooth and soften the skin, and may also reduce its roughness, cracking or irritation. Typical suitable emollients include mineral oil, having a viscosity in the range of 50 to 500 cP, lanolin oil, coconut oil, cocoa butter, olive oil, almond oil, aloe extracts such as aloe vera lipoquinone, synthetic jojoba oils, natural sonora jojoba oils, safflower oil, corn oil, liquid lanolin, cottonseed oil and pea nut oil . Other suitable emoll ients include squalane, castor oil, polybutene, odorless mineral spirits, sweet almond oil, avocado oi l, calophyl l um oi l, rici n oil, vita mi n E acetate, ol ive oi l, sil icone oi ls such as dimethylopolysiloxane and cyclomethicone, linolenic alcohol, oleyl alcohol, the oil of cereal germs such as the oil of wheat germ, isopropyl palmitate, octyl palmitate which is commercially available as Lexol EHP™, tradename of Inolex Co. of Philadelphia, Pa. U.S.A., isopropyl myristate, hexadecyl stearate, butyl stearate, decyl oleate, acetyl glycerides, the octanoates and benzoates of (C12-C15) alcohols, the octanoates and deca noates of alcohols and polya lcohols such as those of glycol and glycerol, ricinoleates of alcohols and polyalcohols such as those of isopropyl adipate, hexyl laurate and octyl dodecanoate. One or more emollients can optionally be included in the cosmetic composition in an amount ranging from about 10 to about 50 weight %, preferably about 20 to about 40%.

A humectant is a moistening agent that promotes retention of water due to its hygroscopic properties. Suitable humectants include urea, glycerin, polymeric glycols such as poyethylene glycol and polypropylene glycol and sorbitols. One or more humectants can optionally be included in the cosmetic composition in amounts from about 1 to 10 weight %.

A dry-feel modifier is an agent which, when incorporated in an emulsion, imparts a "dry feel" to the skin when the cosmetic compositions in the form of emulsion dries. Dry-feel modifiers may also reduce sunscreen migration on the skin. Dry feel modifiers can include starches, talc, kaolin, chalk, zinc oxide, silicone fluids, inorganic salts such as barium sulfate and sodium chloride, C6 to C12 alcohols such as octanol; sulfonated oils; surface treated silica, precipitated silica, fumed silica such as Aerosil™ available from the Degussa Inc. of New York, N. Y. U.S.A. or mixtures thereof; and dimethicone, a mixture of mixture of methylated linear siloxane polymers, available as DC200™ fluid, tradename of Dow Corning, Midland, Mich. U.S.A. One or more dry-feel modifiers can optionally be included in the cosmetic composition in amounts ranging from 0.01 to about 20 weight %, more preferably from about 0.5 to about 6 weight %.

An antimicrobial preservative is a substance or preparation which destroys, prevents or inhibits the multiplication/growth of microorganisms in the cosmetic composition and may offer protection from oxidation. Preservatives are used to make self-sterilizing, aqueous based products such as emulsions. This is done to prevent the development of microorganisms that may be in the product during manufacturing and distribution and during use by consumers who may inadvertently contaminate the products. Typical preservatives i ncl ude the lower a l kyl esters of pa ra-hydroxybenzoates (parabens) especially, methylparaben, propylparaben, isobutylparaben and mixtures thereof, benzyl alcohol and benzoic acid. One or more antimicrobial preservatives can optionally be included in the cosmetic composition in an amount ranging from about 0.001 to about 10 weight %, more preferably about 0.05 to about 2 %.

An antioxidant is a natural or synthetic substance added to the cosmetic compositions to protect from or delay its deterioration due to the action of oxygen from the air, or to protect the skin against damage from free radicals that form due to the action of ultraviolet radiation. Typical suitable antioxidants include propyl, octyl and dodecyl esters of gallic acid, butylated hydroxyanisole (BHA) which is usually as a mixture of ortho and meta isomers, butylated hydroxytoluene (BHT), vitamin E, vitamin E acetate, vitamin C and alkylated parabens such as methylparaben and propylparaben. One or more antioxidants can optionally be included in the cosmetic compositions in an amount ranging from about 0.001 to about 5 weight percent, preferably about 0.05 to about 2 percent. Chelating agents are substances used to complex or bind metallic ions in a frequently heterocylic ring structure so that the ion is held by chemical bonds from members of the ring. Suitable chelating agents include ethylene diaminetetraacetic acid (EDTA), EDTA disodium, calcium disodium EDTA, EDTA trisodium, EDTA tetrasodium and EDTA dipotassium. One or more chelating agents can optionally be included in the cosmetic composition in amounts ranging from about 0.001 to about 0.1 weight %.

Fragrances are aromatic compounds which can impart an aesthetically pleasing aroma to the cosmetic composition. Typical fragrances include aromatic materials extracted from botanical sources (i.e. rose petals, gardenia blossoms, jasmine flowers, etc.) which can be used alone or in any combination to create essential oils. Alternatively alcoholic extracts may be prepared for compounding fragrances. One or more fragrances can optionally be included in the cosmetic composition in an amount ranging from about 0.001 to about 10 weight %, preferably about 0.05 to about 5 %.

The invention will now be described in detail with the help of the following non- limiting examples.

EXAMPLE 1 1. Preparation of water-soluble 1.3-diketone sunscreen (sodium salt of 4- methoxy-2'-carboxy-dibenzoylmethane) (Compound A)

500 ml of high purity methanol (HPLC grade) was taken in a distillation flask and further dried to remove traces of water. 150 ml of dried methanol was taken in 1000 ml round bottom flask and 5.75 g (0.25 moles) of sodium metal was added to prepare sodium methoxide in methanol, which was then transferred to a 1000 ml flask fitted with reflux condenser and magnetic stirrer containing 400 ml azeotropically dried xylene (AR). This content was then heated to 120 ⁰C to distill- off the methanol . Fifteen grams (0.1 moles) of p-methoxyacetophenone (LR grade; SD Fine Chem India) was then added to this solution and the temperature was raised to 120 ⁰C to distill-off the methanol which was being formed as the side product. Heating was continued for next 30 minutes after the complete discharge of methanol as to allow complete reaction. Heating was switched off and the system was allowed to cool to 65 ⁰C. Seventeen grams (0.12 moles) of phthalic anhydride (LR grade; Ex SD Fine Chem India) was then added to the reaction mixture. Liquid reaction mass was converted into slurry with the progress of reaction. After completion of reaction, the temperature was raised to 150 ⁰C to distill off xylene from reaction mass. This slurry was added to 500 ml of methyl ethyl ketone (AR; Ex Merck ) and acidified with 12% aqueous solution of hydrochloric acid (LR grade: Ex LOBA Chem India) while stirring until solid mass was dissolved in it. The organic layer was separated and washed three times with 150 ml water. After washing, the solvent was dried completely to get a yellow mass. This solid matter was then purified by column chromatography using silica gel as stationary phase and hexane: ethyl acetate (80:20) as mobile phase. The column extract was then concentrated and allowed to crystallise in hexane: ethyl acetate mixture. About 2Og of 4-methoxy-2'-carboxy dibenzoylmethane was obtained in the form of yellow crystals. The UV spectrum of this product showed a λ_max at 350 nm. 10 g of 4-methoxy-2'-carboxy dibenzoylmethane was dissolved in 100 ml of hot ethanol (AR grade; Ex Merck). 2.7 g of sodium bi-carbonate (95% purity; Ex SD Fine Chem, India) was dissolved in mixed solvent containing water and ethanol (100 g, & 50 g respectively) in 500 ml round bottom flask. The solution was then added to sodium bicarbonate solution. After stirring for nearly 30 minutes, the solvents were dried and resulting yellow mass was then dissolved in 125 ml of Dl (deionised) water. This aqueous solution was washed three times with 100 ml of chloroform (AR grade, Ex Merck) to remove all un-reacted 4- methoxy-2'-carboxy dibenzoylmethane. Finally water was distilled off to get about 9 g of "sodium salt of 4-methoxy-2'-carboxybenzoylmethane" This product showed UV λ_max at 347 nm.

2. Preparation of the water-soluble reaction product of a polymer with a triplet quencher

(A) Reaction product of 2-cyano-3,3-diphenylacrylic acid ( a 3 , 3- diphenylacrylonitrile derivative) with polyethyleneglycol 200 (Compound B)

2 5 g o f 2-ethylhexyl-2-cyano-3,3-diphenylacrylate, (Merck, catalog no 1477411 Lot no 5377V054 542) was dissolved in 50 ml Ethanol. 16 g of sodium hydroxide (95% purity; Ex. Merck) was dissolved in 65 ml water in 250 ml double necked round bottom flask. The solution of 2-ethylhexyl 2- cyano-3,3-diphenyacrylate was then added drop wise to sodium hydroxide solution. After stirring for nearly 24 hours at room temperature the reaction mixture was extracted twice with 50 ml ethyl acetate to remove unreacted 2-ethylhexyl 2-cyano-3,3-diphenylacrylate. The aqueous layer was acidified with 1 N HCI and resulting pale yellow solid (2-cyano-3,3-diphenylacrylic acid) was dried. The yield was ~ 13g. Five grams of the above pale yellow solid was dissolved in 100 m l of hot toluene in a 500 ml double necked round bottom flask fitted with condenser. Three grams of thionyl chloride (LR grade; Ex LOBA Chem India) was then added in this solution. After stirring for nearly 2 hours at 80 ⁰C 4 g polyethyleneglycol-200 (PEG-200, Sigma Aldrich having a molecular weight of about 200 g/mol) were added and the reaction mixture was refluxed for 3 hours. After removal of solvents by rotary evaporation, the crude product was obtained. The pure product wa s o bta i ned by co l u m n ch romatog ra p hy (si l ica gel, 80/20 ethyl acetate/hexane, Methanol) to yield pale yellow viscous oil. The yield of (compound B) was ~ 5.6 g

(B) Reaction product of 2,6-naphthalene-dicarboxylic acid (a naphthalene derivative) with polyethyleneglycol 200 (Compound C)

2,6-naphthalene-dicarboxylic acid (0.50 g, Supplied by Aldrich) was taken in 100 ml of dried toluene in a 250 ml double necked Round bottom flask fitted with condenser. Thionyl chloride (0.60 g, LR grade Ex LOBA Chem India) was then added to the above mixture. After refluxing and stirring for nearly 2 hours at 80 ⁰C 10 g polyethyleneglycol-200 (PEG-200, supplied by

Sigma Aldrich) were added and the reaction mixture was refluxed for 3 hours with stirring. After removal of solvents by rotary evaporation the crude product was obtained. This crude was subjected to column chromatography (silica gel, 80/20 ethyl acetate/hexane, methanol) to yield pale yellow viscous oil, being compound C. EXAMPLE 2

(A) Effect of compound B on the photodegradation of compound A

The effect of compound B on the photodegradation of compound A was studied and the results were compared with the effect of an admixture of 2-ethylhexyl-2-cyano-3,3- diphenylacrylate and PEG-200 on the photodegradation of compound A.

In one case, a known amount of compound A and compound B were mixed in 1 litre deionised water, while in the other case, a known amount of compound A, PEG-200 and 2-ethylhexyl-2-cyano-3,3-diphenylacrylate were mixed in 1 litre deionised water and homogenized using a Silverson™ stirrer. This control experiment was done to ascerta i n the effect of a n ad m ixtu re of PEG-200 and 2-ethylhexyl-2-cyano-3,3- diphenylacrylate on the photodegradation of compound A, i nstead of a reaction product of the two. Where present, 2-cyano-3,3-diphenylacrylate was added drop wise to the water. Table 1 below gives details of the compositions that were tested.

Table 1

Procedure for measurement of photo-degradation

The above compositions were separately taken (100ml of each) in identically sized glass beakers and were exposed to simulated sunlight from an artificial sunlamp

(Suntest™CPS , from Heraeus) for 0, 15, 30, 45 and 60 minutes respectively. After exposu re for the i nd icated time i n mi n utes, the contents of each bea ker was transferred into separate 100 ml standard flasks, where the volumes were fixed to 100 ml. UV absorption curves were plotted (using a Perkin Elmer UV/Visible Spectrometer) for each test sample using deionised water as reference. Absorption values (A) were recorded at λ_max for each of sample. The percentage of absorbance values (which is an i ndicator of the degree of photo-degradation of the water-soluble 1,3-diketone sunscreen) were calculated using following formula:

(Absorbance at λ_maxper unit weight)

%A= X lOO

(Absorbance at X_1n^_x per unit weight at time=0)

The results are presented in Table 2 below.

Table 2

It can be readily seen that even after 60 minutes the photo-degradation of compound A is significantly lower in composition A. It can also be readi ly seen that a mere ad m i xt u re of 2-ethylhexyl-2-cyano-3,3-di phenylacrylate and PEG-200 does not significantly reduce the photodegradation (control composition B) and, in fact, has little or no effect.

(B) Effect of compound B on photodegradation of compound A in the presence of conventional emulsifiers

The effect of compound B on the photodegradation of compound A in the presence of conventional emulsifiers was studied and the results were compared with the effect of a n ad m ixtu re of 2-ethylhexyl-2-cyano-3,3-diphenylacrylate a nd PEG-200 on the photodegradation of compound A. The conventional emulsifiers/surfactants chosen were potassium stearate and sodium LAS (sodium salt of dodecyl benzene sulphonic acid). The requisite amounts of compound A, PEG-200, 2-ethylhexyl-2-cyano-3,3- diphenylacrylate, compound B, sodium LAS and potassium stearate were mixed in 1 litre deionised water and homogenized using a Silverson™ stirrer. Wherever present, 2-ethylhexyl-2-cyano-3,3-diphenylacrylate was added drop wise to the water. Table 3 below gives the compositions which were tested.

Table 3

Note: Comp-means Composition

Percentage Absorbance va lues i nd icating the actua l percentage of compound A remaining in the compositions have been presented in table 4 below.

Table 4

Note: Comp means Composition

It can be readily seen that even after 120 minutes the photodegradation of compound A is significantly lower in compositions E and H having significant levels of emulsifiers. These compositions include the reaction product of 2-cyano-3,3-diphenylacrylic acid with polyethyleneglycol (compound B) . O n the other ha nd, the com pa rative compositions C, D, F and G show significantly higher photodegradation. EXAMPLE 3

Preparation of a cosmetic composition according to the invention and measuring photodegradation of a 1.3-diketone sunscreen contained therein

Four oil-in-water creams (vanishing creams) were made which contained sodium salt o f 4-methoxy-2'-carboxy dibenzoylmethane (compound A) as the 1,3-diketone sunscreen. In one case, the reaction product of 2-cyano-3,3-diphenylacrylic acid with polyethyleneglycol 200 (compound B) was i ncluded, while in the other case the reaction product of 2,6-naphthalene dicarboxylic acid with polyethyleneglycol 200 (compound C) was included. In addition, a control formulation containing compound A, 2-ethylhexyl-2-cyano-3,3-diphenylacrylate and polyethyleneglycol 200 was prepared, and another control formulation containing compound A, d imethyl ester of 2,6- naphthalene dicarboxylic acid, and polyethyleneglycol-200 was also prepared. The formulation of experimental and control creams is given in table 5 below.

Table 5

Note:

(1) Comp - means Composition

(2) Hysteric acid is a commercially available product, which is a 55:45 mixture of palmitic acid and stearic acid. The composition includes stearic acid and potassium hydroxide. A part of stearic acid reacts in-situ to form potassium stearate, which is a conventional emulsifier.

(3) The amount of compound B in the formulation was equivalent to the amount of a d m i x t u r e o f 2- ethyl hexyl-2-cyano-3, 3-d i phenyl a cry I ate and polyethyleneglycol-200 in terms of the molar strength, and in terms of UV absorption.

(4) The amount of compound C in the formulation was equivalent to the amount of admixture of dimethyl ester of 2,6-naphthalene dicarboxylic acid and polyethyleneglycol-200 in terms of the molar strength and in terms of UV absorption.

The compositions (vanishing creams) were prepared in a manner well-known in the art.

The photodegradation of the 1,3-diketone sunscreen (sodium salt of 4-methoxy-2'- carboxy dibenzoylmethane, compound A) in all the cosmetic compositions was then determined by the procedure described in example 2 above. The results are presented in table 6 below.

Table 6

Note: Comp means Composition The data indicates that the photodegradation of compound A in composition J and composition L, which are in accordance with the invention, is significantly lower than in the respective control compositions I and K.

It will be appreciated that the illustrated examples, provide a composition which includes a water-soluble 1,3-diketone sunscreen, where the photodegradation of the 1,3-diketone sunscreen is relatively low. It will be appreciated that the illustrated examples provide a composition which includes a water-soluble 1 ,3-diketone sunscreen and conventional emulsifiers where the photodegradation of the 1,3- diketone sunscreen is relatively low.

It should be understood that the specific forms of the invention herein illustrated and described are intended to be representative only as certain changes may be made therein without departing from the clear teachings of the disclosure.

Although the invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

The invention thus provides for a composition which includes a water-soluble 1,3- d i ketone su nscreen a nd optiona l ly conventional em ulsifiers, where the photodegradation of the 1,3-diketone sunscreen is relatively low.

Claims

1. A cosmetic composition comprising a water-soluble 1,3-diketone sunscreen and a water-soluble reaction product of a polymer with a triplet quencher.

2. A cosmetic composition as claimed in claim 1 wherein said water-soluble 1,3- diketone sunscreen is a salt of a carboxy derivative of dibenzoylmethane, or a quaternary ammonium derivative of dibenzoylmethane.

3. A cosmetic composition as claimed in claim 2 wherein said salt of a carboxy derivative of dibenzoylmethane is a sodium salt of 4-methoxy-2'-carboxy- dibenzoylmethane.

4. A cosmetic composition as claimed in any one of the preceding claims wherein said triplet quencher is selected from the group consisting of 3,3- diphenylacrylonitrile derivatives, 3-phenylacrylonitrile derivatives, naphthalene dicarboxy derivatives, benzylidenemalonate derivatives, 4-hydroxycinnamate derivatives, fluorene derivatives, benzylidene camphor derivatives and piperidinol derivatives.

5. A cosmetic composition as claimed in claim 4 wherein said 3,3- diphenylacrylonitrile derivative is 2-cyano- 3,3-diphenylacrylic acid.

6. A cosmetic composition as claimed in claim 4 wherein said naphthalene dicarboxy derivative is 2,6- naphthalene dicarboxylic acid.

7. A cosmetic composition as claimed in any one of the preceding claims wherein said polymer is selected from the group consisting of polyalkyleneglycols, polyvinylalcohol, sodium carboxymethyl cellulose, starch, natural and synthetic gums, cellobioses, pyrrolidones, acrylates, acrylamides and polyacids.

8. A cosmetic composition as claimed in claim 7 wherein said polyalkyleneglycol is polyethyleneglycol.

9. A cosmetic composition as claimed in claim 8 wherein the said polyethyleneglycol has a molecular weight of about 200 g/mol.

10. A cosmetic composition as claimed in claim 8 or claim 9 wherein the triplet quencher is 2-cyano-3,3-diphenylacrylic acid.

11. A cosmetic composition as claimed in claim 8 or claim 9 wherein the triplet quencher is the 2,6-naphthalene dicarboxylic acid.

12. A cosmetic composition as claimed in any one of the preceding claims comprising an emulsifier.

13. A method for reducing photodegradation of a water-soluble 1,3-diketone sunscreen in a cosmetic composition, the method comprising the step of combining a water-soluable 1,3-diketone sunscreen with one or more water- soluble reaction products of a polymer with a triplet quencher.

14. A non-therapeutic method of providing photoprotection to the skin, said method comprising the step of applying a safe and effective amount of the cosmetic composition of any one of claims 1 to 12 to the skin.

15. Use of a composition as claimed in any one of claims 1 to 12 for providing non- therapeutic photoprotection against ultra-violet radiation.