FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
PROVISIONAL SPECIFICATION
(See Section 10 and Rule 13)
A SUNSCREEN COMPOSITION
HINDUSTAN LEVER LIMITED, a company incorporated under the Indian Companies Act, 1913 and having its registered office at Hindustan Lever House, 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India
The following specification describes the invention

Technical Field
The invention relates to sunscreen compositions. The invention more particularly relates to sunscreen compositions containing organic sunscreens that are so modified as to display enhanced stability.
Background and Prior Art
Sunscreens have been used in cosmetic compositions for topical application for a long time. Sunscreens are added to skin cosmetic compositions to block the ultraviolet (UV) radiation of the sun from affecting the skin exposed to sunlight. Inorganic sunscreens act by physically blocking some or all of the UV rays by causing the rays to be reflected or scattered away from the skin surface. Organic sunscreens act by absorbing some or all of the UV radiation thereby ensuring that the UV rays do not reach the skin surface. UV rays are generally classified as UV-A, UV-B or UV-C rays. UV-A generally covers the UV wavelength range from 320 to 400 nm while UV-B covers the 290 to 320 nm range, while UV-C covers the 200 to 290 nm range. While damage to the skin due to exposure to UV-A rays have been reported to cause irritation, redness and sunburns, exposure to UV-B rays causes more severe irritation, redness and sunburns in addition to erythema. UV-C rays constitute a small percentage of sunlight as most of it is absorbed by the ozone layer. Hence sunscreen formulations have generally been formulated with a combination of UV-A and UV-B sunscreens.
It has been reported that many organic sunscreens lose their efficacy on exposure to UV rays. Further some of the organic sunscreens are known to interact with each other when applied on the skin with or without exposure to UV-radiation. Thus, such compositions are not stable. They are not very effective in blocking the UV-rays a few minutes or hours after the product has been applied to the skin. Further, when such compositions are used and then exposed to sunlight or UV-rays, the period over which the skin is actually protected is very short, while the consumer is under the mistaken impression that the composition is protecting his/her skin. This false

impression can lead to the consumer exposing himself/herself more to sunlight thereby getting more damage to the skin.
There has been some efforts in improving the stability of sunscreens. It has been found that some class of sunscreens when formulated with another class improves the stability. EP0780119 (Givaudan, 1997) describes a photostable cosmetic light-screening composition comprising essentially a dibenzoyl methane type UV-A screening agent and a a-cyano-p,p-diphenyl acylate stabiliser in specified amounts and ratios.
US6436375 (Sol-Gel Tech, 2002) describes a method of preparing a sunscreen composition with improved photostability that contains atleast two sunscreen active ingredients, which are photo-unstable when formulated together, which method comprises the steps of separating the two ingredients from each other by microencapulating at least one of said ingredients in sol-gel microcapsules.
While some methods of enhancing the stability of organic sunscreens have been reported, there exists a need to develop compositions that provide enhanced stability so that the skin is protected against the harmful effects of UV radiation for longer and longer periods of time. The present inventors have during the course of intensive research into many different methods of preparing sunscreen composition where the organic sunscreens are kept stable, developed a complex of a selected class of metal ions with an organic sunscreen that solves most of the problems of the prior art sunscreen compositions.
US6419907 (L'Oreal, 2002) describes a cosmetic composition for protecting the skin against ultraviolet radiation comprising in a cosmetic vehicle containing at least one fatty phase, an effective amount of copper (II) bis(3,5-diisopropylsalicylate) and optionally one or more of a UV-B or a UV-A sunscreen.
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WO93/11095 (Richardson Vicks) describes a sunscreen complex having a UVA-absorbing chromophore, a UVB absorbing chromophore and a metal cation. The metal ion could be selected from a long exhaustive list of metal cations.
Although the above two prior art deal with some metal compounds in combination with sunscreens or metal complexes with sunscreens, it does not teach that a selective list of metals ions when complexed with organic sunscreens provides for vastly improved stability in cosmetic compositions.
It is thus an object of the invention to provide a stable sunscreen composition.
It is another object of the invention to provide a stable sunscreen composition that contains both UV-A and UV-B sunscreens, which conventionally are known to interact with each other and have low stability in the composition.
It is another object of the invention to provide for a stable sunscreen composition that can be prepared by a simple and cost-effective process.
Summary of the invention
According to the first aspect of the invention there is provided a stable sunscreen composition comprising a complex of an organic sunscreen with a paramagnetic metal ion.
Particularly preferred paramagnetic metal ions are Cu2+, Fe3+, Co2+, Mn2+ or Ti3+.
Particularly preferred organic sunscreens are 4-butyl, 4'-methoxy dibenzoylmethane or 4-methoxy cinnamate.
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According to a second aspect of the invention there is provided a process for preparation of the stable sunscreen composition of the first aspect wherein complex of the organic sunscreen with a paramagnetic metal ion is prepared using a process comprising the steps of (i) dissolving/dispersing an organic sunscreen in a solvent to prepare a
solution/dispersion (ii) treating said solution/dispersion with an alkaline material; and (iii) treating the product of step (ii) with a salt of said paramagnetic metal ion.
Detailed description of the invention
The invention provides for a stable sunscreen composition containing an organic sunscreen. The stable sunscreen composition of the invention comprises a complex of an organic sunscreen with a paramagnetic metal ion. By the use of the word "complex" is meant a co-ordination complex where the metal ion is linked to the donor atom, such as Oxygen and Nitrogen present in the organic sunscreen, by a co-ordinate covalent bond. The paramagnetic metal ions useful in the present invention are Cu2+, Fe3+, Co2+, Mn 2+, Ti 3+, V2+, V4+, Cr2+, Cr3+, Cr4+, Mn3+, Mn4+, Ni2+, Ni3+, Mo3+, Tc6+, Ru3+, Rh4+, Ce3+, Pr3+, Nd3+, Pm3+, Sm3+, Eu3+, Gd3+, Tb3+, Tb4+, Dy3+, Ho3+, Er3*, Tm3+, Yb3+, Re2+, Re4+, Re6+, Os3+, Os4+, Os6+, lr3+, lr4+, lr6+, Au3+ and Hg+. Preferred paramagnetic metal ions are those from the transition metal or inner transition metal groups i.e 'd' block or 'f block metals. More preferred paramagnetic metal ions are selected from Cu2+, Fe3+, Co2+, Mn 2+ or Ti 3+, further more preferably Cu2+, Fe3+, or Mn 2+.
A complex of any organic sunscreen complex with a paramagnetic metal ion is suitable for use in the compositions of the present invention. Preferred sunscreens are compounds containing cycloalkyl, aryl, hydroxyl, carbonyl, carboxylic or sulphonic acid functional groups. Suitable organic sunscreens include, 2-hydroxy-4-methoxybenzophenone, octyldimethyl- p-aminobenzoic acid, digalloyltrioleate, 2,2-
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dihydroxy-4- methoxybenzophenone, ethyl-4-(bis(hydroxypropyl)) aminobenzoate, 2-
ethylhexyl-2-cyano-3,3-diphenylacrylate, 2-ethylhexylsalicylate, glyceryl- p-
aminobenzoate, 3,3,5-trimethylcyclohexylsalicylate, methylanthranilate, p-dimethyl-
aminobenzoic acid or aminobenzoate, 2-ethylhexyl-p-dimethyl- amino-benzoate, 2-
phenylbenzimidazole-5-sulfonic acid, 2-(p- dimethylaminophenyl)-5-
sulfonicbenzoxazoic acid, 2-ethylhexyl-p-methoxycinnamate,
butylmethoxydibenzoylmethane, 2-hydroxy-4-methoxybenzophenone, octyldimethyl-p-aminobenzoic acid and mixtures thereof. Further preferred are sunscreens which are derivatives of p-diketone or carboxylic acid functional groups having an absorbance maximum in the range of 250-450 nm. Further more preferred sunscreens are dibenzoyi methane or cinnamic acid or derivatives thereof.
The UV-A sunscreen is preferably a dibenzoyi methane derivative. The most preferred dibenzoyi methane derivative is 4-tert-butyl 4'-methoxy dibenzoyi methane which is available under the brand name Parsol 1789 from Givaudan. Other dibenzoyi methane derivatives which may be included in the composition of the invention include 2,4-dimethyl- 4'-methoxy dibenzoylmethane, 2-methyl-5-tert-butyl-4'-methoxy dibenzoylmethane, 4,4'-diisopropyl-dibenzoylmethane and 2,4-dimethyl dibenzoylmethane. Preferred UVB sunscreen which is complexed with a paramagnetic metal ion is 4-methoxycinnamte.
Most suitable organic sunscreens are 4-methoxycinnamate and 4-tert.butyl, 4-methoxy dibenzoylmethane.
According to a preferred aspect of the present invention the sunscreen composition comprises a complex of paramagnetic metal ion with a dibenzoyi methane derivative and a complex of paramagnetic metal ion with a methoxy cinnamate derivative.
The said complex is preferably present in an amount in the range of 0.1 % to 15% by weight of the composition. The preferred amounts of the complex of
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paramagnetic metal ion with dibenzoyl methane derivative in the sunscreen composition of the present invention is in the range of 0.1 to 6% by weight of the composition. The preferred amounts of the complex of paramagnetic metal ion with methoxy cinnamate derivative in the sunscreen composition of the present invention is in the range of 0.1 to 13% by weight of the composition.
Useful inorganic sun-blocks are also preferably used in the present invention. These include, for example, zinc oxide, iron oxide, silica, such as fumed silica, and titanium dioxide.
Ultrafine titanium dioxide in either of its two forms, namely water-dispersible titanium dioxide and oil- dispersible titanium dioxide is especially suitable for the invention. Water-dispersible titanium dioxide is ultra-fine titanium dioxide, the particles of which are non-coated or which are coated with a material to impart a hydrophilic surface property to the particles. Examples of such materials include aluminium oxide and aluminium silicate.
Oil-dispersible titanium dioxide is ultrafine titanium dioxide, the particles of which exhibit a hydrophobic surface property, and which, for this purpose, can be coated with metal soaps such as aluminium stearate, aluminium laurate or zinc stearate, or with organosilicone compounds.
By "ultrafine titanium dioxide" is meant particles of titanium dioxide having an average particle size of less than 100 nm, preferably 70 nm or less, more preferably from 10 to 40 nm and most preferably from 15 to 25 nm.
By topical application to the skin of a mixture of both water- dispersible ultrafine titanium dioxide and oil-dispersible ultrafine titanium dioxide, synergistically enhanced protection of the skin against the harmful effects of both UV-A and UV-B rays is achievable.
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Ultrafine titanium dioxide is the preferred inorganic sun-block agent as per this invention. The total amount of sun block that is preferably incorporated in the composition according to the invention is from 0.1 to 5% by weight of the composition.
The sun screen composition preferably comprises a skin-lightening agent. The skin lightening agent is preferably chosen from one or more of a vitamin B3 compound or its derivative e.g. niacin, nicotinic acid, niacinamide or other well known skin lightening agents e.g. adapalene, aloe extract, ammonium lactate, anethole derivatives, apple extract, arbutin, azelaic acid, kojic acid, bamboo extract, bearberry extract, bletilla tuber, bupleurum falcatum extract, burnet extract, butyl hydroxy anisole, butyl hydroxy toluene, citrate esters, Chuanxiong, Dang-Gui, deoxyarbutin, 1,3 diphenyl propane derivatives, 2, 5 dihydroxybenzoic acid and its derivatives, 2-(4-acetoxyphenyl)-1,3 dithane, 2-(4-hydroxyphenyl)-1,3 dithane, ellagic acid, escinol, estragole derivatives, FADEOUT (available from Pentapharm), Fangfeng, fennel extract, ganoderma extract, gaoben, GATULINE WHITENING (available from Gattlefosse), genistic acid and its derivatives, glabridin and its derivatives, gluco pyranosyl-1-ascorbate, gluconic acid, glycolic acid, green tea extract, 4-Hydroxy-5-methyl-3[2H]-furanone, hydroquinone, 4 hydroxyanisole and its derivatives, 4-hydroxy benzoic acid derivatives, hydroxycaprylic acid, inositol ascorbate, kojic acid, lactic acid, lemon extract, linoleic acid, magnesium ascorbyl phosphate, MELAWHITE (available from Pentapharm), moms alba extract, mulberry root extract, 5-octanoyl salicylic acid, parsley extract, phellinus linteus extract, pyrogallol derivatives, 2,4 resorcinol derivatives, 3,5 resorcinol derivatives, rose fruit extract, salicylic acid, Song-Yi extract, 3,4,5 trihydroxybenzyl derivatives, tranexamic acid, vitamins like vitamin B6, vitamin B12, vitamin C, vitamin A, a dicarboxylic acid, resorcinol derivatives, extracts from plants viz. rubia and symplocos, hydroxycarboxylic acid like lactic acid and their salts e.g. sodium lactate, and mixtures thereof. Vitamin B3 compound or its derivative e.g. niacin, nicotinic acid, niacinamide are the more preferred skin lightening agent as per the invention, most
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preferred being niacinamide. Niacinamide, when used, is preferably present in an amount in the range of 0.1 to 10%, more preferably 0.2 to 5% by weight of the composition.
Cosmetic compositions to deliver different benefit agents are prepared using different cosmetically acceptable emulsifying systems and vehicles. For the present invention, a cosmetically acceptable base comprises 5 to 25% fatty acid or 0.1 to 80% soap. Mixtures of fatty acid and soap are also suitable e.g. vanishing cream base which gives a highly appreciated matty feel to the skin. C-i2 to C2o fatty acids are especially preferred for the present invention, futher more preferred being C-w to Cis fatty acids. The most preferred fatty acid is stearic acid. The fatty acid in the composition is more preferably present in an amount in the range of 5 to 20% by weight of the composition. Soaps in the vanishing cream base include alkali metal salt of fatty acids, like sodium or potassium salts, most preferred being potassium stearate. The soap in the vanishing cream base is generally present in an amount in the range of 0.1 to 10%, more preferably 0.1 to 3% by weight of the composition. Generally the vanishing cream base in cosmetic compositions is prepared by taking a desired amount of total fatty matter and mixing with potassium hydroxide in desired amounts. The soap is usually formed insitu during the mixing. The sunscreen composition usually comprises greater than 50% water.
Alternately the skin lightening composition is a wash off product e.g. soap having 5 to 80% salt of fatty acids.
Optional ingredients
The composition according to the invention may also comprise other diluents. The diluents act as a dispersant or carrier for other materials present in the composition, so as to facilitate their distribution when the composition is applied to the skin.
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Diluents other than water can include liquid or solid emollients, solvents, humectants, thickeners and powders. Examples of each of these types of vehicle, which can be used singly or as mixtures of one or more vehicles, are as follows:
Emollients, such as stearyl alcohol, glyceryl monoricinoleate, mink oil, cetyl alcohol, isopropyl isostearate, stearic acid, isobutyl palmitate, isocetyl stearate, oleyl alcohol, isopropyl laurate, hexyl laurate, decyl oleate, octadecan-2-ol, isocetyl alcohol, eicosanyl alcohol, behenyl alcohol, cetyl palmitate, silicone oils such as dimethylpolysiloxane, di-n-butyl sebacate, isopropyl myristate, isopropyl palmitate, isopropyl stearate, butyl stearate, polyethylene glycol, triethylene glycol, lanolin, cocoa butter, corn oil, cotton seed oil, olive oil, palm kernel oil, rape seed oil, safflower seed oil, evening primrose oil, soybean oil, sunflower seed oil, avocado oil, sesame seed oil, coconut oil, arachis oil, castor oil, acetylated lanolin alcohols, petroleum jelly, mineral oil, butyl myristate, isostearic acid, palmitic acid, isopropyl linoleate, lauryl lactate, myristyl lactate, decyl oleate, myristyl myristate;;
Propellants, such as propane, butane, isobutane, dimethyl ether, carbon dioxide, nitrous oxide;
Solvents, such as ethyl alcohol, isopropanol, acetone, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether;
Powders, such as chalk, talc, fullers earth, kaolin, starch, gums, colloidal silica sodium polyacrylate, tetra alkyl and/or trialkyi aryl ammonium smectites, chemically modified magnesium aluminium silicate, organically modified montmorillonite clay, hydrated aluminium silicate, fumed silica, carboxyvinyl polymer, sodium carboxymethyl cellulose, ethylene glycol monostearate.
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These additional materials are preferably present from 10 to 99.9%, preferably from 50 to 99% by weight of the cosmetic composition, and can, in the absence of other cosmetic adjuncts, form the balance of the composition.
Optional skin benefit agents:
The compositions of the present invention can comprise a wide range of other optional components. The CTFA Cosmetic Ingredient Handbook, Second Edition, 1992, which is incorporated by reference herein in its entirety, describes a wide variety of non-limiting cosmetic and pharmaceutical ingredients commonly used in the skin care industry, which are suitable for use in the compositions of the present invention. Examples include: antioxidants, binders, biological additives, buffering agents, colorants, thickeners, polymers, astringents, fragrance, humectants, opacifying agents, conditioners, exfoliating agents, pH adjusters, preservatives, natural extracts, essential oils, skin sensates, skin soothing agents, and skin healing agents.
According to a second aspect of the invention, there is provided a sunscreen composition of the first aspect wherein the complex of organic sunscreen with paramagnetic metal ion is prepared using a process comprising the steps of (i) dissolving/dispersing said organic sunscreen in a solvent to prepare a
solution/dispersion (ii) treating said solution/dispersion with an alkaline material; and (iii) treating the product of step (ii) with a salt of said paramagnetic metal ion.
The solvent may be selected from any organic solvent e.g. ethanol, methanol, propanol, iso-propyl alcohol, butyl alcohol, tetrahydrofuran, acetone, dichloromethane, chloroform, toluene, dimethyl sulfoxide, dimethylformamide, benzene, preferred solvents being ethanol or methanol. The alkaline material may be sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, sodium acetate, potassium t-butoxide, sodium ethoxide, sodamide, aniline, diphenyl
n

amine, N-methylaniline, pyridine, ethylenediamine, preferred alkaline material being sodium hydroxide, sodium acetate or ammonium hydroxide. Usually the complex of the organic sunscreen with the paramagnetic metal ion precipitates after step (iii) of the process. The precipitate is then usually washed and dried to prepare a powder of the complex. The powder may then be used in the sunscreen composition of the invention.
The invention will now be illustrated with reference to the following non-limiting examples.
Examples
Comparative Examples A-D
Comparative Example-A was a control sample of Parsol 1789. Comparative examples B to D were complexes of Parsol-1789 with a diamagnetic metal ion e.g. Co3+ (Comparative Example-B), Zn2+ (Comparative Example - C) and Al3+ (Comparative Example - D).
Examples 1-3
Examples 1-3 were complexes of Parsol-1789 with paramagnetic metal ion. In Example-1 the paramagnetic metal ion was Cu2+, in Example-2 it was Co2+, while in Example - 3 it was Fe3+.
The complex of Parsol-1789 with metal ions were prepared by the method given below:
Method of preparation of the metal complexes:
Parsol 1789 was taken in methanol in a 250 ml round bottom flask. An equimolar quantity of sodium acetate was added to Parsol 1789 under continuous stirring. A methanolic solution of the required salt (typically metal chloride) in the required molar ratio (metal:parsol = 1:2 for Cu(ll), Zn(ll) and Co(ll); 1:3 for Fe(lll), Co(lll) and
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Al(lll)) was added to the mixture. This reaction mixture was stirred for about an hour when the complex precipitated out. The precipitate was filtered by suction, washed thoroughly with methanol and dried in air.
The Parsol/ Parsol-complexes were tested using the Test Procedure -1 given below:
Test Procedure 1
Parsol and its metal complexes were dissolved in dichloromethane and diluted to absorbance of 1. Petridishes on which sunscreen are deposited were prepared by evaporating 25 ml of the above solution on a petridish in dark at room temperature. Several such petridishes were prepared. The dried petridishes were exposed to mid-noon sunlight and one petridish was removed after every 20 minutes of exposure. A blank was also carried out wherein the petridish was not exposed to sunlight. After sun exposure, the contents in the petridish were redissolved in dichloromethane and made up to 25 ml. Absorbance of these solutions were measured. The percentage of the sunscreen in the blank was taken to be 100% and percentage of sunscreen in exposed samples were determined relative to the blank using the formula (1) given below.

where Qt is the percentage of sunscreen present after t minutes of sun exposure, A0 and At are the absorbance of sunscreen solutions after sun exposure for 0 minutes and t minutes.
The results of the stability of Parsol and the various complexes are given in Table-1.
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Table-1

Sample 0 mins 20 mins 40 mins 60 mins
Comp. Exp - A 100 71.6 61.1 41.9
Comp. Exp - B 100 76.9 66.6 59.1
Comp. Exp - C 100 22.4 17.3 13.2
Comp. Exp - D 100 67.2 47.4 27.0
Example -1 100 97.1 98.3 96.7
Example - 2 100 94.4 93.1 92.1
Example - 3 100 98.2 96.7 94.6
The above table indicates that complex of an organic sunscreen with a paramagnetic metal ion (Examples 1-3) is far more stable as compared to the sunscreen alone or complex with diamagnetic metal ions.
Sunscreen Compositions: Comparative Example - E and Example-4 Sunscreen compositions as given in Table -2 below were prepared. Comparative Example - E is a conventional sunscreen cream having Parsol 1789 and Parsol MCX. Example 4 is a sunscreen cream of the invention comprising complex of Parsol-1789 with a paramagnetic metal ion Cu2+.
Table-2

Components Comp. Ex-E Example-4
Stearic Acid 18 18
Niacinamide 1 1
Potassium hydroxide(85%) 0.6 0.6
Cetyl alcohol 0.5 0.5
Silicone oil DC 200 0.5 0.5
Iso propyl myristate 0.75 0.75
Methyl/ Propyl paraben 0.3 0.3
Titanium dioxide 0.20 0.20
Parsol 1789 0.4 -
Cu (Parsol 1789)2 - 0.4
Parsol MCX 0.75 0.75
Water To 100 To 100

The samples were tested for stability using the following test procedure-2 and the results are summarized in Table-3 and Table-4.
Test procedure 2
10 mg of the cream was spread on two sq cm area on a glass plate. Several such glass slides were prepared. The slides were exposed to midnoon sunlight. After every 20 minutes of sun exposure, a slide was removed from sunlight. A blank experiment was also carried out in which the slide was not exposed to sunlight. The creams in the exposed and blank slides were extracted individually in dichloromethane, made up to 25 ml in a volumetric flask and their absorbance measured using a Perkin-Elmer spectrophotometer. From the absorbance, the amount of sunscreen remaining was calculated. The sunscreen in blank slide was taken to be 100% and all others were quantified with respect to it using equation (1) given above.
Table-3
The table shows the percentage of Parsol 1789 / Parsol 1789 - metal complex remaining after exposure of the sample to sunlight after a specified amount of time following test procedure 2.

Sample 0 mins 20 mins 40 mins 60 mins
Comparative Example - E 100 44 34 17
Example-4 100 100 90 83

Table 4
The table shows the percentage Parsol MCX remaining after exposure of the sample
to sunlight after a specified amount of time following test procedure 2.

Sample 0 mins 20 mins 40 mins 60 mins
Comparative Example - E 100 56 42 31
Example-4 100 91 70 63
The invention thus provides for a sunscreen composition having enhanced stability as compared to that reported in prior art.
Dated this 23rd day of August 2006 HINDUSTAN LEVER LIMITED
S. Venkatramani (Senior Patents Manager)