IMPROVED SKIN LIGHTENING COSMETIC COMPOSITION

Technical Field

The invention relates to a skin lightening composition and in particular to a skin lightening composition that is effective in providing a skin colour highly preferred by dark skinned consumers.

Background and Prior art

Many people in the world who have dark skins have a desire to have a lighter skin colour. Technology has been keeping pace with this consumer felt need and many products claiming skin lightening efficacy have been marketed all over the world over the last thirty years. Conventional skin lightening compositions are based on use of skin lightening agents that are believed to control dispersion of melanosomes or inhibit tyrosinase. These skin- lightening agents include niacinamide, carboxylic acids like azelaic acid and kojic acid, plant extracts and hydroquinone etc. Niacinamide, which is a Vitamin B3 compound, is one such widely used skin lightening agent in compositions for topical application.

Skin lightening compositions generally contain sunscreens which maintain skin colour against the darkening effects of ultra-violet radiation and are based on materials which absorb these incident rays. Skin lightening agents along with sunscreen compounds, both organic and inorganic in nature, both naturally occurring and synthetically prepared, have been combined in skin-lightening compositions to provide synergistic benefits.

The present inventors during the course of their intensive research in this area and their continued interactions with a large number of consumers of such products have found that consumers with different classes of skin colour have very different expectations of the skin type they aspire to achieve. Hence, the present inventors, in working towards producing products tailor-made to various segments of skin colours, have made this invention. The present invention is specifically targeted to very dark skin coloured consumers who have a skin colour greater than 6 on a scale of 1 to 10 (1 being very fair and 10 being the darkest).

The present inventors have found during their extensive interaction with such consumers that very dark skinned consumers have an aspiration to have a lighter skin colour that have a glow and radiant appearance while attaining a yellowish hue on the skin.

US 2004/0223928 (The Procter & Gamble Company) describes a topical composition comprising gold-coloured particulates and silver coloured particulates wherein the composition when measured at 15° from specular 15 minutes after topical application of 2μl/cm ² in vivo, has a reflectance of less than 200 and and a delta E value of less than about 4.

Many consumers prefer the draggy sensorial and matty finish provided by vanishing cream bases. The present inventors have found it is difficult to formulate the composition described in the above US patent application in skin lightening products having a cosmetic base high in fatty acid and/or soap e.g. vanishing cream base. The pigments described therein interact with the fatty acid/soap thereby giving low stability. Further, formulations containing high amounts of fatty acid interact with the pigments altering the desired optical effects and therefore a carefully selective combination of colouring pigment and pearlescent pigment is required to get desired effect on skin. The present inventors have evaluated a large number of alternative possibilities before arriving at the present invention which provides consumers, especially very dark skinned consumers, with the desired level of skin lightening while giving the aspirational level of skin glow and radiance and yellowish hue to the skin. The inventors have further ensured that the ingredients added to achieve the present invention are suitably configured to minimize interaction with other possible ingredients of such formulations e.g. the organic sunscreens.

It is thus an object of the present invention to provide for a skin lightening composition which gives dark skinned consumers the desired glow and hue on their skins while having a composition that is stable over the lifetime of the product.

It is another object of the present invention to provide for a skin lightening composition that in addition to providing the desired skin lightening, glow, skin hue and stability of the product, ensures high efficacy of the sunscreen present in the composition.

Summary of the invention

The present invention provides for a skin lightening composition comprising

(i) a skin lightening agent;

(ii) 0.01 to 3 % pearlescent pigment; (iii) 0.01 to 3% a yellow pigment; and

(iv) a cosmetically acceptable base comprising 5 to 25% fatty acid and/or 0.01 to 80% soap.

Detailed description of the invention The invention relates to a skin lightening composition comprising a yellow pigment. The yellow pigment is generally present in an amount sufficient to provide a visually perceptible yellow colour to the composition.

Further, it is preferred that the yellow hue is perceptible on the skin after the composition has been applied on the skin.

This is especially preferred by very dark skinned consumers who have a skin colour grading of greater than 6 on a scale of 10 (1 being very fair and 10 being the darkest). The yellow pigment is preferably present in an amount in the range of 0.05 to 2.3 % by weight of the composition. The yellow pigment is preferably a metal oxide. Suitable metal oxides include titanium dioxide, iron oxide, or stannous oxide. Suitable non-metal oxide is silicon dioxide, alternately the yellow pigment is of organic origin. The preferred metal oxide is iron oxide. The iron oxide is preferably suitably coated or encapsulated to minimize interactions with other ingredients of the compostion. When organic sunscreens are present in the formulation e.g. butylmethoxydibenzoylmethane sold as Parsol 1789 (Givaudan), it interacts with iron oxide and produces an undesirable red colour. To minimize such interaction, the metal oxide particles are coated with materials like mica, silicones e.g. methyl hydrogen polysiloxanes, more preferably silicones. Commercially available yellow pigments which may be used in the formulation include SI2 Yellow LLXLO (from Daito Kasei Kogyo Company, Japan), Bronze 43737 (from Sudarshan Chemicals, India), Tatrazine Yellow (from Davarson, India) or turmeric extract.

The composition of the invention comprises a pearlescent pigment. The pearlescent pigments useful in the present invention include a base material having a plate like structure e.g. mica. The pearlescent pigment is preferably coated with one or more other coating materials. Suitable coating materials are metal oxides e.g. titanium dioxide, iron oxides (black, yellow or red) or chromium oxide. Mica, which is the most preferred base material is a transparent mineral which is mined from the earth in thin sheets. It can be opalescent and sparkling or completely matte, ranging in color from grey to blue to green. It is often treated with iron oxides to yield brilliant color effects. Mica has a sheer, translucent and skin-hugging effect which causes the natural skin tone to shine through

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when it is used in skin compositions e.g. creams, facial powders or eye shadows. Mica causes the light incident on it to reflect from the face, creating an illusion of a smoother, softer and more radiant skin tone. The preferred pearlescent pigment for the present invention is mica coated with titanium dioxide or iron oxide, most preferred being mica coated with both titanium dioxide and red iron oxide. Commericially available pearlescent pigment as per the invention include Colorona Bright Gold (from Merck) or Cloissone Gold (Engelhard Corporation). The pearlescent pigment is more preferably present in an amount in the range of 0.1 to 1 % by weight of the composition.

Cosmetic compostions to deliver different benefit agents are prepared using different cosmetically acceptable emulsifying systems and vehicles. For the present invention, the 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 ₁₂ to C ₂ 0 fatty acids are especially preferred for the present invention, more preferred being Ci ₄ to Ci ₈ 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 in-situ during the mixing.

Alternately the skin lightening composition is a wash off product e.g. soap having 5 to 80% salt of fatty acid.

The skin lightening composition of the invention 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 or 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

(Pentapharm), Fangfeng, fennel extract, ganoderma extract, gaoben, Gatuline Whitening (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, lemon extract, linoleic acid, magnesium ascorbyl phosphate, Melawhite (Pentapharm), morus 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, dicarboxylic acids, resorcinol derivatives, extracts from plants viz. rubia and symplocos, hydroxycarboxylic acids like lactic acid and their salts e.g. sodium lactate, and mixtures thereof. Vitamin B3 compound or its derivative e.g. niacin, nicotinic acid or niacinamide are the more preferred skin lightening agent as per the invention, most 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.

The skin lightening composition preferably additionally comprises one or more UV sunscreens. The UV sunscreens may be inorganic or organic.

A wide variety of organic sunscreen agents are suitable for use in combination with the essential ingredients of this invention. Suitable UV-A / UV-B sunscreen agents include, 2- hydroxy-4-methoxybenzophenone, octyldimethyl p-aminobenzoic acid, digalloyltrioleate, 2,2-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. The most suitable organic sunscreens are 2-ethylhexyl-p-methoxycinnamate and butylmethoxydibenzoylmethane.

A safe and effective amount of sunscreen may be used in the compositions useful in the subject invention. The composition preferably comprises from about 0.1 % to about 10%, more preferably from about 0.1 % to about 5%, of a sunscreen agent.

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 an 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 an 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.

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 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.

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 include 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 and myristyl myristate.

Solvents include ethyl alcohol, isopropanol, acetone, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether and diethylene glycol monoethyl ether.

Powders include chalk, talc, Fullers earth, kaolin, starch, gums, colloidal silica sodium polyacrylate, tetraalkyl and/or trialkyl aryl ammonium smectites, chemically modified magnesium aluminium silicate, organically modified montmorillonite clay, hydrated aluminium silicate, fumed silica, carboxyvinyl polymer, sodium carboxymethyl cellulose and ethylene glycol monostearate.

The cosmetically acceptable base is usually from 10 to 99.9%, preferably from 50 to 99% by weight of the composition, and can, in the absence of other cosmetic adjuncts, form the balance of the composition.

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.

The composition is formulated in any known format, more preferred formats being creams or lotions. The invention is now further described by way of the following non-limiting examples.

Examples

Comparative Example A

A conventional skin lightening composition prepared using a vanishing cream base with the ingredients listed in table 1 was prepared.

Comparative Example B

A conventional skin lightening composition with no fatty acid was prepared (see table 1 )

Examples 1 to 3

Skin lightening compositions as per the invention containing a pearlescent pigment and a yellow pigment were prepared in a vanishing cream base (see table 1 ).

The compositions of comparative examples A and B and examples 1 to 3 were used by about 5 to 32 very dark skinned consumers. The protocol involved applying a measured quantity of the samples on their faces two times a day for seven days. At the end of the test, the consumers were asked to rate the products on a scale of 1 to 10 (10 being most preferred), based on perception of glow and radiance on their face. The average preference scores are summarized in table 1.

Table 1 : Amount of components in a formulation given in weight percent

Minors: Includes vitamins, chelating agents, emollient, perfume, and other benefits agents

The data in table 1 indicates that consumers overwhelmingly preferred the compositions as per the invention as compared to conventional samples.

Correlation between Consumer Perception Data and Instrumental Analysis For the compositions of comparative example A and example 1 , the volunteers were additionally asked to give a score of the perception whiteness and yellow glow of the skin which was recorded as a consumer preference score and the same was also measured using a Minolta chromometer. The data is presented in table 2. According to the Commission Internationale de I'Eclairage (CIE), the colour space is represented by L ^* = black to white, a ^* = green to red and b ^* = blue to yellow. These devices are based on the measurement of chromophore content like melanin, haemoglobin and deposited pigments, etc. which contribute to skin colour. The individual typology angle (ITA ⁰ ) which is [ATan ((L ^* -50)/b ^* )]180/ was calculated based on the L ^* and b ^* values measured using the Minolta chromometer. When the ITA ⁰ value was greater (corresponding to an optimal combination of whiteness and yellowness), the skin was also perceived to have a greater desired whiteness and yellow glow by the volunteers.

Table 2

The data p resented in table 2 shows that when the composition according to the invention was used there was a significant whiteness and yellow glow perception by the volunteers and this correlated with the ITA ⁰ data obtained using the Minolta chromometer.

Examples 4 and 5

Further skin lightening compositions as per the invention containing a pearlescent pigment and a yellow pigment were prepared in a vanishing cream base (see table 2).

The values in table 3, obtained using a Minolta chromometer, indicate that the formulation containing only niacinamide (Comparative Example A) has a very high L ^* value i.e. whiteness index, but a very low and unacceptable b ^* value, i.e. yellowness index.

On the other hand, compositions within the scope of the invention, examples 1 , 4 and 5 have a desired balance of L ^* and b ^* values.