The present invention relates to a blue dye composition comprising an anthocyan and to the use thereof for dyeing human keratin materials.

For the purposes of the invention, the term "keratin materials" is intended to denote, for example, the skin, the lips, the scalp, the eyelashes, the eyebrows and the hair.

In recent years, there has been increasing interest in natural compounds that can be used as dyestuffs, especially in the cosmetics sector.

The available colour range among natural dyes is not as wide as that of synthetic dyes, and many natural dyes show poor stability when exposed to light. In particular, there are very few natural blue dyes, and these dyes are not sufficiently photostable: their hue fades and does not produce a very attractive colour effect.

The aim of the present invention is thus to provide a blue dye composition which shows good photostability without any fading of the colour hue.

The inventors have discovered that such a dye composition is obtained by using anthocyans in the presence of certain metal ions and cinnamic acid, in aqueous medium.

More specifically, the present invention relates to a dye composition having a blue colour, comprising, in an aqueous medium, at least one anthocyan, metal ions chosen from the group of ions derived from Al(lll), Ca(ll), Cu(ll), Fe(ll), Fe(lll), Mg(ll), Mn(ll) and Zn(ll), and mixtures thereof, and a cinnamic acid compound chosen from cinnamic acid and phenolic derivatives thereof.

The invention also relates to a cosmetic composition comprising, in a physiologically acceptable medium, a dye composition as defined previously.

The invention also relates to a process for dyeing keratin materials, comprising the application to the keratin materials of a dye composition as defined previously. The dye composition according to the invention comprises at least one anthocyan.

Anthocyans are, as is known, anthocyanidol glycosides (Jin-Ming Kong et al., Phytochemistry, 64, 923-933 (2003)).

More than 500 different anthocyans exist in nature. Their main differences relate to the number of hydroxyl groups and of methoxy groups, the nature and number of sugar units present, the aliphatic or aromatic carboxylate groups attached to the sugars in the molecule and the position of these bonds (A Castafieda-Ovando et al., Food Chemistry, 1 13, 859-871 (2009)). Anthocyanidols are compounds of formula (I) below:

(I) in which the radicals Ri to R ₇ independently denote H, OH or OMe.

The six most common anthocyanidols are indicated in Table 1 below with their name, abbreviation and substituents on formula (I) described previously. Table 1 : common anthocyanidols

On account of their abundance, the sugars bonded to the anthocyanidols are especially glucose, rhamnose, galactose, xylose, arabinose and glucuronic acid.

The main glycoside derivatives in nature are 3-monosides, 3-biosides, 3,5-diglucosides and 3,7-diglucosides. The anthocyans may also be acetylated, and the sugars may be acylated with methyl or malonic, p-coumaric acid, ferulic acid, sinapylic acid or caffeic acid substituents (F.J. Francis, Colorants, p. 56, Eagan Press (1999)). The most common anthocyan is cyanidin-3-O-glucoside. Advantageously, the anthocyans used according to the present invention may be chosen from those of formula (I) in which R-i, R ₂ and R ₄ independently denote H, OH, OMe, a sugar unit or an acylated sugar unit (acyl group derived from malonic acid, p- coumaric acid, ferulic acid or caffeic acid) and R ₃ , R5, R6 and R ₇ independently denote H, OH or OMe.

The anthocyans may be of natural or synthetic origin. A certain number of plants are naturally rich in anthocyans. Examples that may be mentioned include black carrot, elderberry, hibiscus, blackcurrant, purple corn and black potato. The four main anthocyans present in blackcurrant are cyanidin-3-O- rutinoside, cyanidin-3-O-rutinoside, delphinidin-3-O-glucoside and delphinidin-3-O- rutinoside. Black grape and red cabbage are the two most important sources of anthocyans in nature. The anthocyanidin units of the anthocyans present in black grape are cyanidin, peonidin, malvidin, petunidin and delphinidin; and the organic acids present are acetic acid, coumaric acid and caffeic acid. The only sugar present is glucose (F.J. Francis, Colorants, p. 56, Eagan Press (1999)). A grape anthocyan, malvidin-3,5,-diglucoside, corresponds to formula (II) below, in which Glu is glucose and Me is the methyl radical.

(II)

The anthocyans used according to the present invention may be cyanidin-3-O- rutinoside, delphinidin-3-O-rutinoside, cyanidin-3-O-glucoside or malvidin-3,5,-0- diglucoside.

Seven of the anthocyans present in red cabbage are described in formula (III). These anthocyans comprise the basic structure cyanidin-3-diglucoside, but comprise different groups Ri and R ₂ . The groups Ri and R ₂ of these seven anthocyans are sinapyl, ferulyl or p-coumaryl, as indicated in Table 1 .

(Hi)

Ferulyl p-Coumaryl Sinapyl

The anthocyans used according to the present invention may be one or more of the cyanidin-3-diglucosides A to G described previously.

The anthocyans may be added in the form of plant matter or an extract of plant matter. It may be advantageous to avoid unnecessary purification of the plant matter. Thus, the other components of the plant matter may be advantageous for the dye composition. For example, other components of the plant matter, for instance flavonoids, are advantageous for their antioxidant properties.

The plant matter may be, for example, legumes, fruit or flowers. The plant matter may be chosen from red cabbage, red onion, purple potato, grape, cranberry, strawberry, raspberry, aronia, black soybean, blackcurrant, elderberry, hibiscus, radish, gooseberry, bilberry, cherry, aubergine, black carrot and black rice.

The anthocyan may be present in the dye composition in a content ranging from 0.05% to 50% by weight, preferably ranging from 0.3% to 25% by weight and preferentially ranging from 5% to 15% by weight, relative to the total weight of solids of the dye composition.

The dye composition according to the invention comprises metal ions chosen from ions derived from Al(lll), Ca(ll), Cu(ll), Fe(ll), Fe(lll), Mg(ll), Mn(ll) and Zn(ll), and mixtures thereof. The metal ions are preferably chosen from ions derived from Fe(ll), Fe(lll) and Mg(ll), and mixtures thereof. The ion derived from Fe(ll) is preferred.

These metal ions make it possible to stabilize the anthocyans by complex formation and by effecting a bathochromic shift towards blue shades. The salts of these metal ions are well known, with anions such as gluconate, chloride, sulfate, hydroxide and acetate. For example, calcium gluconate contains the (Ca ²⁺ ) ion derived from Ca(ll); magnesium chloride, MgCI ₂ , or magnesium gluconate contains Mg(ll) ions (Mg ²⁺ ); ferrous sulfate, FeS0 ₄ , iron gluconate (CeHnOr^Fe contains Fe(ll) ions (Fe ²⁺ ); ferric sulfate, Fe ₂ (S0 ₄ ) ₃ , contains Fe(lll) ions (Fe ³⁺ ); and aluminium sulfate, AI ₂ (S0 ₄ ) ₃ , contains Al(lll) ions (Al ³⁺ ).

The metal ions may be present in the dye composition in a metal ion/anthocyan weight ratio ranging from 0.01/1 to 10/1 and preferably ranging from 0.05/1 to 5/1 by weight.

The dye composition comprises a cinnamic acid compound chosen from cinnamic acid or a phenolic derivative thereof such as caffeic acid, p-coumaric acid, ferulic acid or sinapinic acid, and mixtures thereof, and the cis or trans isomers thereof.

The term "phenolic derivatives of cinnamic acid" means derivatives containing one or more hydroxyl and/or methoxy groups on the aromatic nucleus of cinnamic acid. Advantageously, the dye composition comprises cinnamic acid.

The cinnamic acid compound may be present in the dye composition in a cinnamic acid compound/anthocyan weight ratio ranging from 0.1/1 to 10/1 , preferably ranging from 0.5/1 to 5/1 and preferentially ranging from 1/1 to 5/1 .

In addition to the ingredients mentioned previously, the dye composition may comprise additional ingredients as described below. The dye composition may comprise an amino acid, which may be chosen from taurine, proline and arginine. This amino acid acts as a bathochromic agent.

The amino acid may be present in the dye composition in an amino acid/anthocyan weight ratio ranging from 0.1/1 to 25/1 , preferably ranging from 0.5/1 to 20/1 and preferentially ranging from 1/1 to 16.5/1 .

The composition may comprise a phospholipid, and in particular phosphatidylcholine (also known as lecithin). This phospholipid allows a good interaction between the anthocyan, the metal ions and the cinnamic acid compound.

Phospholipids are a class of lipids which are predominant components of cell membranes and which may form lipid bilayers. A phospholipid molecule is constructed with three components: fatty acids, a backbone onto which the fatty acids are attached and a phosphate ester.

The phospholipid backbone may be glycerol or sphingosine. Glycerol-based phospholipids are known as phosphoglycerides (Biochemistry 5 Edition, J. Berg et al., W.H. Freeman & Co (2002)). Examples of phospholipids that may be mentioned include phosphatidic acid, phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, phosphatidylinositol, phosphatidylinositol phosphate, phosphatidylinositol bisphosphate, phosphatidylinositol triphosphate, ceramide phosphoryl choline, ceramide phosphorylethanolamine and ceramide phosphoryl glycerol.

Phospholipids are one of the constituents of lecithin. Lecithin is present in egg yolk and may also be extracted from seed oils.

The phospholipids used in the present invention may be a sunflower or soybean lecithin.

The main phospholipids of soybean or sunflower lecithin are phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine and phosphatidic acid.

Preferably, the phospholipid may be phosphatidylcholine. Use is made, for example, of the product sold under the trade name Ultralec by the company ADM.

The phospholipid may be present in the dye composition in a phospholipid/anthocyan weight ratio ranging from 0.1/1 to 50/1 and preferably ranging from 0.5/1 to 30/1 .

The composition may comprise a monocarboxylic or dicarboxylic acid containing from 2 to 6 carbon atoms, chosen especially from acetic acid, malic acid and tartaric acid. This acid is advantageously present to adjust the pH of the dye composition preparation to between 3.5 and 8. Advantageously, the pH of the dye preparation is between 3.5 and 7, preferably between 4 and 6 and preferentially between 4 and 5.5.

The composition may comprise an organic solvent chosen from C2-C8 alcohols such as ethanol, propanol, butanol or benzyl alcohol, and mixtures thereof. Ethanol or benzyl alcohol is preferably used. Such an organic solvent is useful as a hydrotrope.

The said organic solvent may be present in the dye composition in an organic solvent/anthocyan weight ratio ranging from 0.1/1 to 10/1 and preferably ranging from 0.5/1 to 3/1 .

The dye composition comprises water, especially in a water/anthocyan weight ratio which may range from 5000/1 to 5/1 and preferentially ranging from 2000/1 to 6/1 .

The dye composition comprising water is advantageously in liquid form (for example, it flows under its own weight at room temperature in less than 10 seconds).

The dye composition may be prepared by mixing in water, at room temperature, the anthocyan (especially in plant extract form), while adjusting the pH to between 3.5 and 8.0, the metal ions in salt form, the cinnamic acid compound and the other additional ingredients.

The cosmetic composition comprising the dye composition also comprises a physiologically acceptable medium, i.e. a medium that is compatible with human keratin materials and/or fibres, for instance, in a non-limiting manner, the skin, mucous membranes, the nails, the scalp and/or the hair.

The composition according to the invention may also contain cosmetic adjuvants chosen especially from water, cosmetic organic solvents, emulsifiers, thickeners, oils, waxes, preserving agents, ceramides, antioxidants, free-radical scavengers, moisturizers, vitamins, proteins and hydrolysates thereof, fragrances, fillers, UV- screening agents, pigments, fibres, and additional dyestuffs (especially mineral pigments (titanium dioxide or iron oxides) and nacres).

The amounts of these various adjuvants are those conventionally used in the cosmetics field, and may range, for example, from 0.01 % to 30% of the total weight of the composition. In general, the amounts are adjusted as a function of the formulation prepared.

A cosmetic composition according to the invention may be in the form of a product for dyeing the hair, the eyelashes, the eyebrows, the skin, the lips or the nails.

Other characteristics and advantages of the invention will emerge more clearly from the examples that follow, which are given as non-limiting illustrations. In the text hereinbelow or hereinabove, the proportions are given as weight percentages, unless otherwise indicated.

Comparative Examples 1 to 14

The following aqueous dye compositions were prepared:

Ol: outside the invention

For black carrot and red cabbage, the amount is expressed as anthocyan active material.

The following solutions were prepared in 0.1 M pH 5 sodium acetate buffer in deionized water.

Black carrot extract ColorFruit® Magenta 109 WS from CHr-Hansen: 0.2 g of anthocyan active material in 50 ml of buffer

Red cabbage extract (Red Cabbage Anthocyanins ELCHRO701 from Diana

Naturals): 0.2 g of anthocyan active material in 50 ml of buffer

Malic acid: 0.24 g in 20 ml of buffer

Cinnamic acid: 0.27 g in 20 ml of buffer

Benzyl alcohol: 0.20 g (0.19 ml) in 20 ml of buffer

Calcium gluconate: 2.33 g in 20 ml of buffer

Iron sulfate: 0.14 g in 20 ml of buffer Phosphatidylcholine (Ultralec® U from ADM): 2.4 g in 20 ml of buffer Taurine: 1 .39 g in 20 ml of buffer

Proline: 0.27 g in 20 ml of buffer

Ethanol: 0.20 g (0.19 ml) in 20 ml of buffer

The metal salt solution and then the cinnamic acid solution were added to the anthocyan solution (at pH 5-6), followed by the other ingredients, in any order.

Each final solution was placed in a quartz cuvette and then exposed to daylight.

The colour of the solution was measured at TO by measuring the absorbance at the lambda max of the curve. The colour after storage for several days was then measured as indicated in the table below. The less the absorbance value varies relative to that measured at TO, the more photostable the dye solution.

The following results were obtained:

Solutions with black carrot extract

Solutions with red cabbage extract:

It is found that the addition of cinnamic acid makes it possible to increase the absorbance values relative to those of solutions not containing this acid: the presence of this acid thus brings about a hyperchromic effect (the colour is more intense).

Moreover, after 29 days of exposure to daylight, the absorbance variations relative to those measured at TO (values AD29), show that the solutions containing cinnamic acid have a small difference. These observations show that the black carrot and red cabbage extracts in the presence of iron sulfate or calcium gluconate are stabilized in aqueous solution by means of the presence of cinnamic acid. Aqueous dye compositions of strong blue colours which are stable over time (the colour fades little over time) are thus obtained. Examples 15 to 17

Three hair dye compositions were prepared, comprising the following ingredients:

0.05 g of dye solution S5 or S6 or S7

40 μΙ of distilled water

200 μΙ of ethanol

760 μΙ of a solution consisting of 20% ethanol, 64.67% water, 5% 1 ,3-propanediol, and 10.33% (50/50 C8/C10)alkyl polyglucoside at 60% in water (Oramix® CG 1 10 from SEPPIC).

Dyeing protocol on locks of hair:

Dyeing with 1 mL of the preceding composition on a 1 g lock of hair.

Apply 1 mL of the solution to a standardized lock of hair.

Roll up the impregnated lock in aluminium foil.

Leave for 1 hour.

Wipe the lock to remove the excess dye.

Add the bicarbonate solution. Leave to stand for 15 minutes.

Rinse the lock with clear water, wash it with mild shampoo, and disentangle with a comb.

Leave the lock to dry in the open air.

The treated lock of hair has a blue colour.