WO2021122717A1

WO2021122717A1 - New henna-based extract for use in dyeing keratin fibers, its preparation method and compositions containing it

Info

Publication number: WO2021122717A1
Application number: PCT/EP2020/086382
Authority: WO
Inventors: Steve PANNAKAL; Sandip KEDAR; Amit Tewari
Original assignee: L'oreal
Priority date: 2019-12-17
Filing date: 2020-12-16
Publication date: 2021-06-24

Abstract

New henna-based cosmetic extract for use in dyeing keratin fibers, its preparation method and compositions containing it The invention relates to a new extract comprising: • 10-50 % by weight of 2,3,4,6-tetrahydroxy acetophenone (THA) relat ive to the total weight of the extract; and • 5-30 % by weight of of 2-hydroxy-1,4-naphthaquinone (lawsone) relat ive to the total weight of the extract; being understood that the weight ratio THA/Lawsone is higher than 1, and the method for preparing it. It also relates to compositions comprising said extract.

Description

New henna-based extract for use in dyeing keratin fibers, its preparation method and compositions containing it

The present invention relates to a new cosmetic henna extract, the method for preparing it, and to compositions comprising the new cosmetic henna extract. It also relates to a process for treating keratin fibers using the compositions as well as the use of the new henna extract for treating keratin fibers, and in particular for dyeing keratin fibers.

In the field of dyeing keratin fibers, in particular human keratin fibers such as hair, several processes may be used.

A first process for dyeing human keratin fibers implies dye compositions containing oxidation dye precursors, generally known as oxidation bases. These oxidation bases are colourless or weakly coloured compounds, which, when combined with oxidizing products, may give rise to coloured compounds via a process of oxidative condensation.

The shades obtained with these oxidation bases can be modified by combining them with couplers or coloration modifiers. The variety of molecules used as oxidation bases and couplers allows a wide range of colours to be obtained.

A second process for dyeing human keratin fibers is known as direct dyeing or semi-permanent dyeing. It comprises the application of direct dyes, which are coloured and colouring molecules that have affinity for fibers. The main advantages of this type of dyeing are that it does not require any oxidizing agent, which limits the degradation of the fibers.

The first hair dyes were semi-permanent. One of the best known natural dyes is that derived from the henna plant. Henna is still used in beauty enhancement for colouring the hair, the nails or the skin, as well as for dyeing leather, silk and wool.

This dye affords an orange-red coloration on grey hair, and a "warm" i.e. coppery to red colour on chestnut-brown hair.

However, the dyeing process using henna is difficult to perform. A kind of "paste" (often referred to as a "poultice") is first made from ground or powdered henna leaves, which is then diluted at the time of use with warm water, and the said paste is then applied to the keratin fibers.

This process using the said paste has drawbacks. A lumpy mixture is obtained and due to this poor consistency of the composition obtained from the coarsely ground powder, it is not always possible to obtain a satisfactory impregnation during the application of the composition to keratin fibers.

Furthermore, it is very difficult to reproduce the shades exactly, since the lawsone content very often varies from one batch to another and between different ground materials.

In addition, the leave-on time of the said paste is very long. It may vary from several tens of minutes to several hours (overnight) depending on the desired intensity, with no ability to control the result.

As much as the colour obtained on chestnut-brown hair has a natural look, grey hair is dyed and an anaesthetic and unnatural orange colour with henna is obtained ("Hair preparations" , Kirk-Othmer Encyclopedia of Chemical Technology , John Wiley & Sons, Inc.).

In addition, the colorations obtained are not always uniform between the root and the end or from one fiber to another {The Science of Hair Care, C. Bouillon, J. Wilkinson, 2d Ed., CRC Press, Taylor & Francis Group; Boca Raton, London, pp. 236-241 (2005)).

There is thus a real need to develop a new cosmetic henna extract for use in treating, more particularly in dyeing, keratin fibers, which is stable and provides more homogeneous and chromatic colorations from the root to the end of said fibers .

Moreover, there is a need to provide a natural dye-based dyeing composition comprising the new cosmetic henna extract, that does not have the drawbacks mentioned above, that is readily miscible (rapid breakdown) in water, and that can especially result in colorations that are fast and homogeneous, while at the same time remaining chromatic, intense and rich, as well as improved conditioning properties. The Applicant has now discovered that these aims and others could be achieved by means of a new cosmetic henna extract as defined below. This new henna extract may be used thereafter in a cosmetic composition.

Said new cosmetic henna extract is especially obtained by acidic hydrolysis of henna and extraction with a particular solvent.

This new henna extract is stable and allows obtaining stable compositions and an improved homogeneous coloration as well as improved conditioning properties such as shine, smoothness and an easy disentangling.

By “stable henna extract or composition” is meant a henna extract or composition which shows the same efficacy as at to, and no sign of phase separation and discoloration, and which is not malodorous, when stored at a given temperature ranging from 0 to 50 °C, during a period ranging from one day to two months.

In general the Henna leaf content comprises a small amount of 2-hydroxy- 1 ,4-naphthoquinone (Lawsone) (around 0.8-2. 1 % by weight relative to the weight of the leaf) and 2,3,4,6-tetrahydroxy acetophenone (THA) (around 2-3.4% by weight relative to the weight of the leaf). Therefore, another goal of the invention is to easily prepare extract enriched in hydroxy- 1 ,4-naphthoquinone (Lawsone) and in 2,3,4,6-tetrahydroxy acetophenone (THA).

Therefore, a subject-matter of the present invention is directed to a henna extract comprising:

• 10-50 %, preferably 10-49%, more preferably 10-48 %, specifically 10-45 %, more specifically 10-44 %, and better 13-43.5 % by weight of 2,3,4,6-tetrahydroxy acetophenone (THA) relative to the total weight of the extract; and

• 5-30 %, particularly 5-27%, preferably 5-25 %, more preferably 5- 24 %, specifically 5-23.5%, and better 7-23% by weight of 2- hydroxy- 1 ,4-naphthaquinone (lawsone) relative to the total weight of the extract. being understood that the weight ratio THA/Lawsone is higher than 1 , preferably higher than 1.5 and more preferably higher than 1.75.

According to one embodiment, the henna extract may comprise: • 35-49%, preferably 35-48%, more preferably 37-45%, specifically 38-44%, more specifically 39-43.5% by weight of 2, 3,4,6- tetrahydroxy acetophenone (THA) relative to the total weight of the extract; and

• 15-27%, preferably 17.5-25%, more preferably 17.5-24%, specifically 18.5-24%, more specifically 19.5-23% of 2-hydroxy- 1 ,4-naphthaquinone (lawsone) relative to the total weight of the extract, being understood that the weight ratio THA/Lawsone is higher than 1 , preferably higher than 1.5 and more preferably higher than 1.75.

The present invention also relates to a method for preparing the cosmetic henna extract of the invention by acidic hydrolysis of henna and extraction with a particular water-immiscible organic solvent or a particular mixture of water-immiscible organic solvents.

Another subject-matter of the invention is a composition, especially an aqueous composition for dyeing keratin fibers comprising the cosmetic henna extract of the invention.

The present invention is also directed to a process for treating keratin fibers, in particular human keratin fibers such as hair, which consists in mixing a composition according to the invention with water, and applying the mixture obtained to the keratin fibers, and in rinsing.

Still another subject-matter of the present invention is the use of the cosmetic henna extract for treating, and more particularly for dyeing keratin fibers, in particular human keratin fibers such as hair.

Other subjects, characteristics, aspects and advantages of the invention will emerge even more clearly on reading the description and the example that follows.

In the text herein below, unless otherwise indicated, the limits of a range of values are included in that range, for example in the expressions "between" and "ranging from ... to ..." .

Moreover, the expression "at least one" used in the present description is equivalent to the expression "one or more" .

According to the invention, the henna extract comprises: • 10-50 %, preferably 35-49%, more preferably 35-48 %, specifically 37-45 %, more specifically 38-44 %, and better 39-43.5 % by weight of 2,3,4,6-tetrahydroxy acetophenone (THA) relative to the total weight of the extract; and

• 5-30 %, particularly 15-27%, preferably 17.5-25 %, more preferably 18.5-24 %, specifically 17.5-24 %, more specifically 19- 23.5%, and better 19.5-23% by weight of 2-hydroxy- 1 ,4- naphthaquinone (lawsone) relative to the total weight of the extract, being understood that the weight ratio THA/Lawsone is higher than 1 , preferably higher than 1.5 and more preferably higher than 1.75.

In a preferred embodiment, the weight ratio THA/Lawsone ranges from 1.1 to 2.5, preferably from 1.5 to 2.2, especially from 1.6 to 2.1.

The henna extract is generally obtained from Lawsonia inermis (Henna) leave, especially in powder form.

Method for preparing henna extract

The method for preparing the cosmetic henna extract of the invention comprises the following steps:

(i) hydrolysis of aqueous dispersion of henna at a pH ranging from 1 to 3.5, preferably for 1 minute to 24 hours, more preferably for 20 minutes to 24 hours such as 1 hour, then

(ii) extraction of the aqueous phase obtained in step (i) with a water- immiscible organic solvent or a mixture of water-immiscible organic solvents (liquid-liquid partitioning), wherein the water- immiscible organic solvent or the mixture of water-immiscible organic solvents has a polarity index of 3.5 or more.

In step (i), henna is mixed with water.

According to one embodiment, the first step (i) of the method of preparation of the invention uses henna which is immerged in acidic water preferably at least during 5 minutes at a temperature of 15°C to 40°C, preferably 20°C to 30°C, more preferably 25°C to 30°C, particularly for 20 minutes to 24 hours. According to another variant, henna is mixed in hot water (35°C - 80°C) for several minutes (2 minutes - 30 minutes). According to one variant, leaf of Henna or dry henna leaf powder, is mixed in water with stirring and/or sonication and/or heating to obtain a homogeneous aqueous dispersion.

Particularly the weight amount of henna leaf, powder or not, preferably powder, is from 1 % to 50 %, preferably from 5 % to 25 %, more preferably from 7 to 15 % by weight relative to the weight of water, such as 10 % by weight relative to the weight of water.

Step (i) is carried out in presence of a (in)organic acid or a mixture of (in)organic acids.

The term (in)organic acid means an organic acid or an inorganic acid.

A mixture of (in)organic acids means a mixture of organic acids, or a mixture of inorganic acids or a mixture of organic and inorganic acids.

The term "organic acid" is understood to mean an acid, i.e. a compound that is capable of releasing a cation or proton H⁺ or H₃0⁺, in aqueous medium, which comprises at least one optionally unsaturated, linear or branched C1-C20 hydrocarbon-based chain, or a (hetero)cycloalkyl or (hetero)aryl group and at least one acid chemical function chosen in particular from carboxyl COOH, sulfuric SO3H, SO2H, and phosphoric PO3H2, PO4H2.

The term " inorganic acid " is understood to mean an acid, i.e. a compound that is capable of releasing a cation or proton H⁺ or H₃0⁺, in aqueous medium, which does not comprise carbon atom.

More particularly, the acid used in the acidic hydrolysis step i) are chosen from hydrochloric acid HC1, hydrobromic acid HBr, sulfuric acid H2SO4, alkylsulfonic acids: (Ci-C₆)Alk-S(0)₂0H such as methylsulfonic acid and ethylsulfonic acid; arylsulfonic acids: Ar- S(0)₂OH such as benzenesulfonic acid and toluenesulfonic acid; (C 1 - C₆)alkoxysulfinic acids: (Ci-C₆)Alk-0-S(0)0H such as methoxysulfinic acid and ethoxysulfinic acid; aryloxysulfinic acids such as tolueneoxysulfinic acid and phenoxysulfinic acid; phosphoric acid H3PO4; triflic acid CF3SO3H and tetrafluoroboric acid HBF4 , and carboxylic acid(s) of formula below: or a salt thereof, in which :

A represents a saturated or unsaturated, cyclic or non-cyclic and aromatic or non-aromatic hydrocarbon-based group, which is monovalent when t is 0 or polyvalent when t is greater than or equal to 1 , comprising from 1 to 20 carbon atoms, which is optionally interrupted with one or more heteroatoms and/or optionally substituted, especially with one or more hydroxyl groups; preferably, A represents a monovalent (Ci-C₆)alkyl group or a polyvalent (Ci- C₆)alkylene group optionally substituted with one or more hydroxyl groups.

According to one embodiment of the invention, step (i) is carried out in presence of an organic acid such as acetic acid or (hydroxyl)(Ci-Cio)carboxylic acid, or in the presence of an inorganic acid such as hydrochloric acid or sulfuric acid, and preferably in the presence of an organic acid such as an (hydroxyl)(Ci-Cio)carboxylic acid such as citric acid, lactic acid, glycolic acid, or tartaric acid, and more preferably citric acid.

By “(hydroxyl)(Ci-Cio)carboxylic acid” it is understood a carboxylic acid containing at least one carboxy group (C(O)OH), (preferably from 1 to 5 carboxy group, especially 3) linked to alkyl group comprising from 1 to 10 carbon atoms, preferably 1 to 6 and more preferably 1 to 4, the said alkyl group potentially being substituted by one or more hydroxyl groups (preferably from 1 to 5 hydroxyl groups, and preferably one).

The pH during the hydrolysis step (i) ranges from 1 to 3.5, preferably from 1 to 3, more preferably from 2 to 3 , even more preferably from 2.5 to 3 such as 3.

The henna used in the invention is a pure natural henna, especially in the form of leaves, preferably in the powder form.

The henna powder may be screened to obtain particles with upper limit sizes corresponding to the orifices or mesh sizes of the screen particularly between 35 and 80 mesh (US). According to one particular mode of the invention, the size of the henna powder particles is fine. According to the invention, a particle size of less than or equal to 500 pm is more particularly intended. Preferentially, the powder consists of fine particles with sizes inclusively between 50 and 300 pm and more particularly between 10 and 200 pm.

It is understood that the said henna particles preferentially have a moisture content of between 0 and 10 % by weight relative to the total weight of the powders.

More particularly, the henna is red henna ( Lawsonia inermis, alba).

Red henna consists of leaves of shrubs of the genus Lawsonia from the family of Lythraceae, which is based on the principle of dyeing with the active agent lawsone: 2-hydroxy- 1 ,4-naphthoquinone. Lawsone [83-72-7] (Cl Natural Orange 6 ; Cl 75420), also known as isojuglone, may be found in henna shrubs (Lawsonia alba, Lawsonia inermis) ("Dyes, Natural" , Kirk-Othmer Encyclopedia of Chemical Technology, "Henna" Encyclopedia Britannica).

In a particular embodiment, decontaminated henna is used in step (i). In such a case, the method of the invention comprises a further step (io) consisting in decontaminating henna, which is performed before step (i).

In step (io), henna is cleaned to remove contaminants such as micro-organisms.

The number of micro-organisms is on average between 10⁵ and 10⁷ microorganisms per gram of powder or of leaves before decontamination.

Any process known to those skilled in the art may be used with the condition that the number of micro-organisms has been reduced, i.e. by a factor of 10² to 10⁶, that is to say preferably between 99.9 and 99.99999% .

The term "micro-organisms" includes in particular fungi, moulds, spores and bacteria. Examples of decontamination method are hot air drying, microwave, dry heat, steam sterilization, ethanol flotation and irradiation.

According to one embodiment of the invention after step (i) of the method for preparing henna extract, the aqueous extract is filtered preferably through a Buchner screening with a mesh size from 5 to 100 mhi (US), especially IOmhi (US). According to a particular embodiment of the invention, the filtration step occurs after step (i) of the method for preparing henna extract, and before step (ii).

In step (ii), the water extract of henna is partitioned through liquid-liquid partition using a water-immiscible organic solvent or a mixture of water-immiscible organic solvents. In other words, the aqueous phase obtained in step (i) is mixed with one or more water- immiscible organic solvent(s), wherein the water-immiscible organic solvent or the mixture of water-immiscible organic solvents has a polarity index of 3.5 or more, preferably in a weight ratio solvent or mixture of solvents/aqueous phase ranging from 10 to 1 , more preferably from 5 to 1 such as 2.5.

By “water-immiscible solvent”, it is meant a solvent having a solubility in water at 20°C of 15g per lOOg of water or less, preferably of lOg per lOOg of water or less, more preferably ranging from 0,05g to lOg per lOOg of water, even more preferably ranging from 0,05g to 9 g per 100 g of water.

Preferably the extraction step (ii) is performed at a temperature of 15°C to 40°C, preferably 20°C to 30°C, more preferably 25°C to 30°C.

The water-immiscible organic solvent or the mixture of water- immiscible solvent of the invention preferably has a polarity index of 3.8 or more, more preferably ranging from 3.8 to 5, even more preferably ranging from 4 to 5, such as 4.4.

Solvents used for liquid-liquid partition are water-immiscible organic solvents which have a polarity index of 3.5 or more and are preferably selected from: i) chloroform, ii) (Ci-C₆)alkyl esters, such as those described below, preferably (Ci-C₆)alkyl acetate, more preferably ethyl acetate or butyl acetate, iii) (C4-Cio)alkyl alcohols such as n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, preferably (C4-Cs)alkyl alcohols, more preferably n-butanol.

The (Ci-C₆)alkyl esters have preferably the formula:

R’-C(0)-0-R” wherein R’ and R” each independently represents a C_\-Ce alkyl group, and more preferably the formula:

H C-C(0)-0-R” with R” representing a C_\-Ce alkyl group.

Liquid-liquid partition step (ii) is preferably carried out with (Ci-C₆)alkyl ester as defined above, such as (Ci-C₆)alkyl acetate, or (C4-Cs)alkyl alcohol, more preferably with ethyl acetate or n-butanol, even more preferably with ethyl acetate.

The extraction time may range from 1 minute to 24 hours, especially from 5 minutes to 5 hours, and more particularly from 10 to 60 minutes.

The extraction temperature may range from 5°C to 60°C, especially from 15°C to 40°C, and more particularly from 20°C to 35°C even more particularly from 25°C to 30°C such as at a temperature of 27-30°C.

In a preferred embodiment of the invention, the method for preparing the cosmetic henna extract comprises steps (io) , (i) and (ii).

In another embodiment of the invention, the method for preparing the cosmetic henna extract comprises steps (i) and (ii) and a filtration step after step (i) and before step (ii) .

According to one embodiment of the invention, after step (ii) of the method for preparing the henna extract, the solvent or mixture of solvents is eliminated, preferably evaporated and preferably at a temperature in the range of 10 °C to 50 °C, under vacuum. The crude henna extract can then be dried for example in a desiccator with P₂O₅ or silica gel. The invention is also directed to the henna extract obtainable with the method described above. Compositions

A further subject-matter of the invention is a composition, especially a cosmetic composition comprising the henna extract according to the invention and water or a mixture of water and of one or more organic solvent(s) or a mixture of organic solvent(s). In a preferred embodiment, the composition of the invention is a cosmetic composition comprising the henna extract according to the invention and water and no organic solvent.

The composition(s) of the invention is(are) cosmetic, i.e. they are cosmetically acceptable and therefore suitable for use for application to keratin fibers, especially human keratin fibers such as the hair.

The henna extract according to the invention is preferably present in said composition in an amount ranging from 0.1 % to 99% by weight, preferably ranging from 0.5% to 50% by weight, more preferably ranging from 0.8% to 25% by weight, even more preferably from 1 % to 20% such as 1 % by weight relative to the total weight of the composition.

Organic solvent(s) Organic solvent is understood to mean an organic substance capable of dissolving or dispersing another substance without modifying it chemically.

Examples of organic solvents that may be mentioned include C1-C4 alkanols, such as ethanol and isopropanol; polyols and polyol ethers and also aromatic alcohols. When the organic solvent(s) is(are) present, its(their) amount ranges from 0.1 % to 20% by weight, preferably from 0.5% to 10% by weight relative to the total weight of the composition. Sugar - Oligosaccharide(s) and polysaccharide(s)

According to one embodiment of the invention, the composition further comprises one or more sugars.

By “sugars” it is understood monosaccharides, oligosaccharides or polysaccharides.

According to one embodiment of the invention sugars are selected from oligosaccharides which are saccharide polymers containing a small number, typically 2 to 20, of simple sugars (monosaccharides). Examples of suitable sugars that may be mentioned include sucrose, glucose such as dextrose, galactose, ribose, fucose, maltose, fructose, mannose, arabinose, xylose and lactose, and derivatives thereof, especially alkyl derivatives, such as methyl derivatives, for example methylglucose.

Sugars may also be polysaccharides especially the ones chosen from starch hydrolysates with a dextrose equivalent (DE) of less than 20 and nonionic or anionic fructans. Preferably, said sugars are polysaccharides soluble in the composition. Even more preferably, said polysaccharides are water-soluble.

Starch hydrolysates are known (see Encyclopedia of Chemical Technology by Kirk-Othmer, 3rd Ed., Vol. 22, 1978, pp. 499 to 521 ) and are classified, according to their dextrose content, on the one hand as starch syrups, and on the other hand as maltodextrins.

Starch syrups are starch hydrolysates with a dextrose equivalent (DE) of greater than 20, and maltodextrins are starch hydrolysates with a DE of less than 20.

The DE is the number of grams of reducing sugars (considered as dextrose) per 100 g of product dry matter. The DE thus measures the degree of hydrolysis of the starch, since, the more the product contains small molecules (such as dextrose and maltose), the higher its DE. In contrast, the more the product contains large molecules (polysaccharides), the lower its DE.

In a preferred embodiment of the invention, sugars are selected from dextrose, oligosaccharide(s), and particularly maltodextrin.

In a particularly preferred embodiment of the invention, the composition comprises one or more oligosaccharide(s). When the sugars(s) is(are) present, its(their) amount ranges from 0.05% to 30%, preferably from 0.5% to 20%, more preferably from 1 % to 10%, even more preferentially from 5% to 7% by weight relative to the total weight of the composition.

Thickener( s )

The composition according to the invention may further comprise at least one organic thickener, preferably selected from anionic, cationic, nonionic, amphoteric organic polymer thickener(s) and mixtures thereof.

The composition of the invention preferably comprises at least one organic polymer thickener selected from: i) homopolymer of (A) R₂C=C(R)-C(0)-OH, ii) homopolymer of (B) R₂C=C(R)-C(0)-0-R’ and iii) crosslinked and non-crosslinked copolymer of (A) R2C=C(R)- C(0)-OH with R, identical or different, representing a hydrogen atom or a (C i - C4)alkyl group, and R’ representing a (Ci-C₆)alkyl group.

More preferably (A) represents (meth)acrylic acid and (B) is R₂C=C(R)-C(0)-0-R’ with R, identical or different, representing a hydrogen atom or a (Ci-C4)alkyl group, and R’ representing a (Ci- C₆)alkyl group, and better (B) represents a C1-C4 alkyl acrylate. The (A) acid residue is, for example, in an amount ranging from 20% to 80% by weight and further, for example, from 25 % to 70 % by weight and even further, for example, from 35% to 60% by weight relative to the total weight of the copolymer. The (B) is, for example, in an amount ranging from 15% to 80% by weight and further, for example, from 25% to 75% by weight and even further, for example, from 40% to 65% by weight relative to the total weight of the copolymer. It is chosen, for example, from methyl acrylate, ethyl acrylate and butyl acrylate residues. This copolymer is, for example, partially or totally crosslinked with at least one standard crosslinking agent.

The crosslinking agents are, for example, polyunsaturated compounds, such as ethylenically polyunsaturated compounds. These compounds are, for example, chosen from polyalkenyl ethers of sucrose and of polyols, diallyl phthalates, divinylbenzene, ally 1 (meth)acrylate, ethylene glycol di(meth)acrylate, methylenebisacrylamide, trimethylolpropane tri(meth)acrylate, diallyl itaconate, diallyl fumarate, diallyl maleate, zinc (meth)acrylate, and derivatives of castor oil and of polyols manufactured from unsaturated carboxylic acids. Crosslinking agents that may also be used include, for example, unsaturated monomer compounds comprising a reactive group capable of reacting with an unsaturation to form a crosslinked copolymer. The content of the crosslinking agent generally ranges, for example, from 0.01 % to 5% by weight and further, for example, from 0.03% to 3% by weight and even further, for example, from 0.05% to 1 % by weight relative to the total weight of the copolymer.

According to one embodiment of the present invention, the homopolymer or copolymer may be, for example, in the form of a dispersion in water. The number-average size of the particles of copolymer in the dispersion is generally, for example, from 10 to 500 nm, as measured by appropriate means known to those skilled in the art, and further, for example, from 20 to 200 nm and even further, for example, from 50 to 150 nm.

The organic thickener(s) are preferably crosslinked acrylic acid homopolymers, more preferably acrylic acid homopolymers crosslinked with ally 1 sucrose or ally 1 pentaerythritol. Examples of such polymers include Carbopol ® 980 sold by the company Lubrizol.

The organic thickener(s) may be selected from copolymers such as the ones described in international patent application WOOl/76552.

The organic thickener(s) amount may be from 0.01 % to 20%, preferably from 0.1 % to 10%, more preferably from 1 % to 5%, even more preferably from 3% to 4% by weight relative to the total weight of the composition such as 4% by weight relative to the total weight of the composition.

Additional dye(s)

The composition of the invention as defined previously may also contain one or more additional direct dye(s) other than Lawsone and THA. These direct dyes are chosen, for example, from those conventionally used in direct dyeing, and among which mention may be made of any commonly used aromatic and/or non-aromatic dye such as neutral, acidic or cationic nitrobenzene direct dyes, neutral, acidic or cationic azo direct dyes, natural direct dyes such as indigo, ortho diphenols, neutral, acidic or cationic quinone and in particular anthraquinone direct dyes, azine, triarylmethane, indoamine, methine, styryl, porphyrin, metalloporphyrin, phthalocyanine and methine cyanine direct dyes, and fluorescent dyes.

The composition of the invention may comprise one or more natural dye(s) other than lawsone and THA as defined previously. Among the natural direct dyes, mention may be made of indigo, juglone, isatin, curcumin, spinulosin, apigenidin, orceins, paradiphenols and orthodiphenols or polyphenols, preferably para- and ori/zo-diphenols

These natural dyes, besides their defined compound form (other than lawsone and THA), may be added in the form of extracts or of plant parts. The said defined compounds from extracts or from plant parts are preferably in the form of powders, in particular fine powders whose particles have sizes identical to that of the henna powder as defined previously.

The natural or non-natural direct dye(s), other than the lawsone and THA, in the composition according to the invention particularly represent from 0.001 % to 10% by weight relative to the total weight of the composition even more preferentially from 0.05% to 5% by weight relative to the total weight of the composition.

Preferably, the composition of the invention does not contain any synthetic direct dyes, i.e. dyes that do not occur in nature.

In a particular embodiment of the invention, the composition of the invention further comprises a water-soluble indigo compound.

By water-soluble indigo compound is meant a leucoindigo which has the following formula: wherein X is hydrogen or a alkali metal such as sodium.

The water-soluble indigo compound may be obtained by mixing an indigo extract with sodium dithionite, preferably in a ratio indigo extract/sodium dithionite ranging from 1 :0.1 to 1 :0.5.

The indigo extract is generally obtained from indigo-producing plants. As indigo-producing plants mention may be made of numerous species derived from the following genera:

- Indigofera such as Indigofera tinctoria, Indigo suffraticosa, Indigofera articulata, Indigofera arrecta, Indigofera gerardiana, Indigofera argenta, Indigofera indica, Indigofera longiracemosa,

- Isatis such as Isatis tinctoria ;

- Polygonum or Persicaria such as Polygonum tinctorium (Persicaria tinctoria);

- Wrightia such as Wrightia tinctoria ;

- Calanthe such as Calanthe veratrifolia, and

- Baphicacanthus such as Baphic acanthus cusia.

Preferably, the indigo-producing plant is of the genus Indigofera and more particularly is Indigofera tinctoria.

Use may be made of all or part (in particular the leaves especially for Indigofera tinctoria) of the indigo-producing plant.

The indigo-producing plant powder may be screened to obtain particles with upper limit sizes corresponding to the orifices or mesh sizes of the screen particularly between 35 and 80 mesh (US).

Indigo-producing plants used in the invention are preferably in the form of powder, and better still of particles.

According to a one embodiment of the invention, the size of the indigo-producing plant powder particles is fine. In particular, a particle size of less than or equal to 500 mhi is intended.

Preferentially, the powder consists of fine particles with sizes ranging from 10 to 300 mhi and even more preferably from 50 to 200 mhi. It is understood that the said indigo-producing plant particles preferentially have a moisture content of between 0 and 10% by weight relative to the total weight of the powders.

The composition as defined previously may also comprise one or more oxidation base(s) and/or one or more coupler(s) conventionally used for the dyeing of keratin fibers.

Mention may be made, among the oxidation bases, of para- phenylenediamines, bis (phenyl) alky lenediamines, para-aminophenols, bis-para-aminophenols, ortho-aminophenols, heterocyclic bases and their addition salts.

Mention may in particular be made, among these couplers, of meta-phenylenediamines, meta-aminophenols, meta-diphenols, naphthalene couplers, heterocyclic couplers and their addition salts.

The oxidation base(s) present in the composition(s) are each generally present in an amount of between 0.001 % and 10% by weight, of the total weight of the composition.

Preferably, the composition of the invention does not contain any oxidation dyes.

Adjuvants :

The composition of the invention may also contain various adjuvants conventionally used in hair dye compositions, such as anionic, cationic, nonionic, amphoteric or zwitterionic surfactants or mixtures thereof, mineral thickeners such as clays, antioxidants, penetrants, sequestrants, fragrances, fatty substances such as oils or butters, buffers, dispersants, conditioning agents other than the butters or oils as defined above, for instance ceramides, film-forming agents, preserving agents and opacifiers.

The above adjuvants are generally present in an amount for each of them of between 0.01 % and 40% by weight relative to the weight of the composition, and preferably between 0.1 % and 20% by weight relative to the weight of the composition under consideration.

Needless to say, a person skilled in the art will take care to select this or these optional additional compound(s) such that the advantageous properties intrinsically associated with the composition that is useful in the dyeing process in accordance with the invention is not, or is not substantially, adversely affected by the envisaged addition(s).

The composition may be in the form of a powder, a paste, a cream, an oil or a gel.

The composition of the invention may be prepared by mixing by hand or with a standard mixer and/or an extruder the components of the composition according to the invention.

Process for treating keratin fibers

Another subject-matter of the invention is a process for treating, more particularly for dyeing keratin fibers, and in particular human keratin fibers, such as hair, wherein the following steps are successively performed:

(a) mixing the henna extract of the invention with water, optionally wherein a water-soluble indigo compound is added;

(b) applying the mixture prepared in step (a), to the keratin fibers and leaving it on the said fibers preferably for a minimum time of 30 minutes, preferentially a time ranging from 30 minutes to 24 hours and better still ranging from 45mn to 12 hours;

(c) rinsing the keratin fibers with water, preferably without shampooing; and

(d) optionally drying the keratin fibers or letting them to dry naturally, without a hairdryer.

According to one variant of the process for treating keratin fibers, there is no step (a), and the step (b) is applying aqueous composition of the invention comprising the henna extract of the invention and optionally a water-soluble indigo compound as defined above.

According to an embodiment of the invention, the composition is mixed with water, at a temperature below 40°C, in particular between 15°C and 40°C in step (a).

In step (b), the application temperature for the composition may range from 15°C to 80°C, preferably from 15°C to 40°C, more preferably from 20°C to 30°C, even more preferably from 25°C to 30°C. Thus, after application of the composition according to the invention, the hair may advantageously be subjected to a heat treatment by heating to a temperature ranging from 30 to 60°C. In practice, this operation may be performed using a styling hood, a hairdryer, an infrared ray dispenser or other standard heating appliances.

According one embodiment of the invention, after applying henna extract on keratin fibers, said fibers are wrapped with a plastic film (cellophane sheet), preferably after step b) and before step c).

According to a particularly advantageous process, after step (c) (i.e. in step (d) ) , the keratin fibers are:

(d ’ ) either mechanically wiped with a towel or absorbent paper,

(d”) or dried by heat with a heat source (convection, conduction or radiation) by passing over, for example, a stream of a warm gas such as air.

Heat sources that may be mentioned include a hairdryer, hair drying hoods, a hair-straightening iron, an infrared ray dispenser and other standard heating appliances.

In a particular embodiment, an heating iron at a temperature ranging from 60 °C to 220 °C and preferably from 120 °C to 200 °C can be used after step (d) previously mentioned.

One particular embodiment of the invention is a dyeing process that is performed at a temperature ranging from 25°C to 30°C.

The process according to the invention may further comprise the following steps, when step (a) does not comprise the addition of a water-soluble indigo compound:

(a’ ) preparing separately a composition (A’ ) comprising a water- soluble indigo compound such as that defined above, and (b’ ) applying composition (A’ ) prepared in step (a’), to the keratin fibers and leaving it on the said fibers preferably for a minimum time of 30 minutes, preferentially a time ranging from 30 minutes to 24 hours and better still ranging from 45 minutes to 12 hours, wherein step (b’ ) is performed before or after step (b). The process according to the invention, comprising the use of a water-soluble indigo compound, either in the same composition (one- pot) as the henna extract, or in composition (A’) (which leads to a sequential layering), allows obtaining dark shades on keratin fibers.

Another subject-matter of the invention is the use of the cosmetic henna extract according to the invention, for dyeing keratin fibers, in particular human keratin fibers, for example hair.

The henna extracts, the compositions and processes for dyeing keratin fibers according to the invention have the advantage of dyeing keratin fibers, especially human keratin fibers, with intense, chromatic colorations that are resistant to washing, perspiration, sebum and light, and that are moreover long-lasting, without impairing the said fibers. Furthermore, the colorations obtained using the composition give homogenous colors from the root to the end of a fiber which corresponds to a little coloration selectivity.

Also, the dyeing processes according to the invention make it possible to obtain aesthetic colorations rapidly.

The treated keratin fibers have a very pleasant cosmetic aspect, and their integrity is respected. They have improved conditioning properties such as shine, smoothness and easy disentangling.

The evaluation of the coloration can be done visually or read on a spectrocolorimeter (such as Minolta CM2600d, illuminant D65, angle 10°, SCI values) for the L* , a*, b* colorimetric measurements. In this L*, a*, b* system, L* represents the intensity of the color, a* indicates the green/red color axis and b* indicates the blue/yellow color axis. The lower the value of L, the darker or more intense the color. The higher the value of a*, the redder the shade; the higher the value of b*, the yellower the shade. The variation in coloring between the colored locks of natural white hair (NW) which is untreated (control) and after treatment or coloration are defined by DE*, corresponding to the colour uptake on keratin fibers, according to the following equation:

In this equation, L*, a* and b* represent the values measured after dyeing the natural hair comprising 90% of white hairs and Lo*, ao* and bo* represent the values measured for the untreated natural hair comprising 90% of white hairs.

The greater the value of DE*, the greater the difference in color between the control locks and the dyed locks and the greater colour uptake is.

On the other hand for evaluating the selectivity of the color between the root and tip of the keratin fiber, measurement can be done on permed or sensibilised white hair (PW) and natural white hair, wherein the variation in coloring between the colored locks PW and the colored natural white hair are defined by DE**, corresponding to the selectivity of the colour, is calculated according to the following equation:

In this equation, L**, a** and b** represent the values measured after dyeing the natural hair comprising 90% of white hairs and Lo**, ao** and bo** represent the values measured after dyeing the permed or sensibilised hair. The lowest DE**, the best homogeneity of the hair color.

If the light fastness is investigated, DE* * is also calculated for the Lo**, ao**, bo** and L**, a**, b** measured of the locks before and after exposure to the light, respectively.

Chromaticity in the CIE L**, a**, b** colorimetric system is calculated according to the following equation:

The greater the value of C** , the greater the chromaticity is. The examples that follow serve to illustrate the invention without, however, being limiting in nature.

EXAMPLES

Example 1 - Preparation of henna extract

Dry henna leaf powder (1 kg) was extracted at a temperature of 27-30°C with 10 liters of water, whose pH is adjusted to 3 , using citric acid for 60 min. The aqueous extract obtained was filtered through a Buchner funnel containing cotton cloth (mesh size: 10 microns). The filtered extract was partitioned through liquid-liquid partition using three different types of water-immiscible solvents, two water- immiscible solvents according to the present invention, i.e. two water- immiscible solvents having a polarity index of 3.5 or more, namely butanol or ethyl acetate and a water-immiscible solvent different from the present invention, i.e. a water-immiscible solvent having a polarity index of less than 3.5, namely toluene. The extract obtained after lipophilic fractionation was concentrated under vacuum at 37°C. A brown amorphous powder was obtained. The dried henna extract comprises 2,3 ,4,6-tetrahydroxy acetophenone (THA) and 2-hydroxy- 1 ,4-naphthaquinone (lawsone).

The results are as follows:

The partition with ethyl acetate or with butyl alcohol gives an extract with the appropriate quantities of THA and lawsone and the appropriate ratio THA/ lawsone, especially the one with ethyl acetate. The stability of the henna extract 1 was tested at 40°C, 5 % of relative humidity for 2 months. No modification in the henna extract composition was observed.

Example 2

The following composition 1 was prepared.

Composition 1 :

Henna extract 1 of example 1 15.15 g Maltodextrine q.s. 100 g

Example 3

Composition 2 was prepared as indicated in the following experimental protocol:

Composition 2:

Henna extract of example 1 1.0 g

Maltodextrine 5.66 g

Carbopol® 980 (sold by Lubrizol) 4.0 g

Water q.s. 100 g

Experimental Protocol:

4g of Carbopol ® 980 was added slowly in a beaker comprising 100ml of warm water (50-60°C).

The mixture was stirred continuously and slowly using IKA stirrer until Carbopol ® 980 was completely dispersed in the water.

After cooling the gel, lg of Henna extract 1 of example 1 and 5.66g of maltodextrin were added in the Carbopol base till they were completely dispersed in the gel.

Example 4: Color measurements

Dyeing protocol:

Dyeing performance was also evaluated on natural grey hair swatches containing 90% of white hair (International Hair Importers & Products, Inc. Glendale, NY 11385, USA) using a Minolta CM2600d spectro colorimeter.

The variation in coloring between the dyed hair swatches is defined by DE*, corresponding to the colour uptake on keratin fibers, according to the following equation:

In this equation, L* , a* and b* represent the values measured after dyeing the hair swatches and Lo*, ao* and bo* represent the values measured for the untreated hair swatches. Each hair swatch was colored using the following protocol:

- X g of the composition was applied on lg of a natural grey hair swatch containing 90% of white hair using a soft hair brush;

- the hair swatch was then wrapped with a cellophane sheet;

- after a leave-on time of 1 hour at 27°C, the locks were first rinsed with water and then air-dried for 24h.

The dyeing performances of compositions 1 and 2 were compared with the dyeing performance of a comparative composition. The comparative composition was prepared by mixing 5g of henna leaves powder with 15 g of water using a brush to have a paste consistency.

Results

The compositions according to the present invention allow to obtain a very good color performance especially in terms of color intensity and color uptake.

Claims

1. Henna extract comprising:

• 10-50 % by weight of 2,3,4,6-tetrahydroxy acetophenone (THA) relative to the total weight of the extract; and

• 5-30 % by weight of 2-hydroxy- 1 ,4-naphthaquinone (lawsone) relative to the total weight of the extract; being understood that the weight ratio THA/Lawsone is higher than 1 , preferably higher than 1.5 and more preferably higher than 1.75.

2. Method for preparing the henna extract according to claim 1 comprising the following steps:

(i) hydrolysis of aqueous dispersion of henna at a pH ranging from 1 to 3.5, preferably for 1 minute to 24 hours, more preferably for 20 minutes to 24 hours then

(ii) extraction of the aqueous phase obtained in step (i) with a water- immiscible organic solvent or a mixture of water-immiscible organic solvents (liquid-liquid partitioning), wherein the water- immiscible organic solvent or the mixture of water-immiscible solvents has a polarity index of 3.5 or more, preferably with (Ci- C₆)alkyl esters or (C4-C10) alkyl alcohols, more preferably with ethyl acetate or n-butanol, even more preferably with ethyl acetate

3. Method according to claim 2, wherein the pH during the hydrolysis step (i) ranges from 1 to 3 , preferably from 2 to 3, more preferably from 2.5 to 3.

4. Method according to claim 2 or 3, wherein henna is decontaminated before step (i) (step (io)).

5. Henna extract prepared with the method according to any one of claims 2 to 4.

6. Composition comprising an extract according to claim 1 or 5, and water or a mixture of water and of one or more organic solvent(s) or a mixture of organic solvent(s).

7. Composition according to claim 6, wherein the henna extract is present in an amount ranging from 0.1 % to 99% by weight, preferably from 0.5 to 50% by weight relative to the total weight of the composition.

8. Composition according to claim 6 or 7, comprising one or more sugars, preferably dextrose and/or oligosaccharides, more preferably maltodextrin.

9. Composition according to any of claims 6 to 8, comprising at least one organic thickener, preferably selected from anionic, cationic, nonionic, amphoteric polymer thickener(s) and mixtures thereof.

10. Composition according to any of claims 6 to 9, comprising at least one organic thickener selected from: i) homopolymer of (A) R₂C=C(R)-C(0)-OH; ii) homopolymer of (B) R₂C=C(R)-C(0)-0-R’ ; and iii) crosslinked and non-crosslinked copolymer of (A) R2C=C(R)- C(0)-OH and (B) R₂C=C(R)-C(0)-0-R’ ; wherein:

- R, identical or different, represents a hydrogen atom or a (C i - C4)alkyl group; and

- R’ represents a (Ci-C₆)alkyl group; preferably, wherein (A) is (meth)acrylic acid and (B) is a C1-C4 alkyl acrylate.

11. Composition according to any of claims 6 to 10, comprising at least one organic thickener selected from crosslinked acrylic acid homopolymers, preferably acrylic acid homopolymers crosslinked with ally 1 sucrose or ally 1 pentaerythritol.

12. Composition according to any of claims 6 to 11 , comprising a water-soluble indigo compound which is a leucoindigo.

13. Process for dyeing keratin fibers, and in particular human keratin fibers, wherein the following steps are successively performed:

(a) mixing the extract according to claim 1 or 5 with water; and

(b) applying the mixture prepared in step (a) to the keratin fibers and leaving it on the said fibers preferably for a minimum time of 30 minutes;

(c) rinsing the keratin fibers with water, and

14. Process according to claim 13 , wherein a water-soluble indigo compound is added in step (a).

15. Process according to claim 13, further comprising the following steps: (a’ ) preparing separately a composition (A’ ) comprising a water- soluble indigo compound, and

(b’ ) applying composition (A’ ) prepared in step (a’), to the keratin fibers and leaving it on the said fibers preferably for a minimum time of 30 minutes, preferentially a time ranging from 30 minutes to 24 hours and better still ranging from 45 minutes to 12 hours, wherein step (b’ ) is performed before or after step (b).