Process for obtaining an aqueous composition based on a sennoside, strong base and acid

Abstract

Process for obtaining an aqueous composition based on a sennoside, a strong base and an acid The present invention relates to a process for preparing a cosmetic composition comprising at least one compound of formula (I) as defined below, or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of an organic or mineral base or solvates such as hydrates; at least one strong base; at least one acid; and water, said composition having a pH of between 5.5 and 7.0. It also relates to the composition capable of being obtained by this process. Figure for the abstract: none

Description

Title of the invention: Process for obtaining an aqueous composition based on a sennoside, strong base and acid

[0001] The present invention relates to a process for preparing a cosmetic composition comprising at least one compound of formula (I) as defined below, or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of organic or mineral base or solvated such as hydrates; at least one strong base; at least one acid; and water, said composition having a pH of between 5.5 and 7.0. It also relates to the composition capable of being obtained by this process.

[0002] Human skin is made up of two compartments, namely a deep compartment, the dermis, and a superficial compartment, the epidermis. The epidermis is in contact with the external environment, and its role is in particular to protect the body from dehydration and from external, chemical or mechanical attacks.

[0003] There is always a need for new cosmetic compositions having interesting properties, particularly on the skin.

[0004] Sennosides can be interesting active ingredients for this purpose. Indeed, this type of active ingredient is known in cosmetics, for example from application JP2002-255733.

[0005] However, sennosides are partially soluble in certain solvents such as methanol or acetone (which are not cosmetically acceptable solvents), and are not soluble in water, particularly at room temperature. They therefore do not allow, as such, the formulation of stable cosmetic compositions applicable to the skin.

[0006] The formulator is therefore looking for compositions comprising a sennoside such as sennoside A which are stable and applicable in particular topically (i.e. on the skin and / or mucous membranes).

[0007] Such compositions must further comprise a certain amount of water, in order to be able to formulate a sennoside such as sennoside A in a wide range of cosmetic carriers including lotions, gels or emulsions.

[0008] In this context, the inventors have surprisingly discovered that particular bases allow the solubilization of a sennoside such as sennoside A, and are compatible with a formulation in an aqueous medium at a given pH.

[0009] The invention therefore aims to provide a cosmetic composition which responds to all these problems.

[0010] Indeed, in this case, sennoside A is insoluble in water at its native pH, i.e. around 4.3. It is known that by raising the pH of a molecule beyond its last pKa (i.e. highest pKa), it becomes soluble. However, since sennoside A has 4 pKa and its last pKa is equal to 8.2, such a pH leads to the solubilization of sennoside A beyond 8.3, which is incompatible with topical cosmetic application, particularly on the skin and / or mucous membranes. Indeed, topical cosmetic compositions, particularly those applicable to the skin and / or mucous membranes, must have an acceptable physiological pH, i.e. between 5.0 and 7.0.

[0011] Surprisingly, as demonstrated in examples, the Applicant has discovered that by adjusting the pH first with a strong base and then with an acid, it is possible to obtain a clear solution.

[0012] Thus, the present invention relates to a process for preparing a cosmetic composition (“process according to the invention”) comprising the following steps: i. the mixture of at least one compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of organic or mineral base or its solvates such as hydrates, with water; ii. adding at least one strong base to the mixture obtained in (i), until a pH greater than the highest pKa of the compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts or solvates is obtained; then iii. adding at least one acid to the mixture obtained in (ii), until a composition having a pH between 5.5 and 7.0 is obtained.

[0013] The present invention also relates to a composition capable of being obtained by this process.

[0014] The present invention also relates to a cosmetic composition comprising: a. at least one compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of organic or mineral base or its solvates such as hydrates, b. at least one strong base, c. at least one acid, and d. water,

[0015] said composition having a pH between 5.5 and 7.0.

[0016] Preferably, the present invention relates to a cosmetic composition consisting of: a. at least one compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of organic or mineral base or its solvates such as hydrates, b. at least one strong base, c. at least one acid, and d. water,

[0017] said composition having a pH between 5.5 and 7.0.

[0018] For the purposes of the present invention, and unless otherwise indicated: an “alkyl” radical is a saturated, linear or branched hydrocarbon radical, in particular C1-C6, preferably C1-C4; a "sugar" radical is a monosaccharide or disaccharide radical. Examples of sugar radicals include: sucrose (or saccharose), glucose, galactose, ribose, fucose, maltose, fructose, mannose, arabinose, xylose or lactose; by "monosaccharide" is meant a monosaccharide sugar comprising at least 5 carbon atoms of formula CX(H2O)X, with x being an integer greater than or equal to 5, preferably x is greater than or equal to 6, in particular x is inclusively between 5 and 7, preferably x = 6. They may be of D or L configuration, and of alpha or beta anomer, as well as one of their salts or their solvates such as hydrates; by "disaccharide" is meant a di-osidic sugar which is a compound consisting of two oses linked together by O-osidic bonds, said compounds being composed of two monosaccharides (also called mono-osidics) as defined above, said monosaccharide units comprising at least 5 carbon atoms, preferably 6, particularly the mono-osidic units are linked together in 1,4 or 1,6, in anomer α (alpha) or [3 (beta), each osidic unit being able to be of L or D configuration, as well as one of its salts or its solvates such as hydrates. A disaccharide is more particularly a polymer formed from two oses (or monosaccharides) having the general formula: -[Cx(H2O)y)]2- or -[(CH2O)x]2-, with x being an integer greater than or equal to 5, preferably x is greater than or equal to 6, in particular x is inclusively between 5 and 7, preferably x = 6, and y is an integer which represents x - 1; by "organic or mineral base salt" is meant a salt of a base or alkaline agent such as alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, ammonia, amines, alkanolamines or salts of so-called "basic" amino acids such as lysine or arginine; “skin” means the skin of the face and / or body, the scalp; “appendages” means eyelashes, eyebrows, nails, and hair, in particular eyelashes and hair; - in what follows, and unless otherwise indicated, the limits of a domain of values ​​are included in this domain, in particular in the expressions “between” and “ranging from ... to ..."; - furthermore, the expression “at least one” used in this description is equivalent to the expression “one or more”.

[0019] The invention also relates to a method for caring for the skin and / or mucous membranes comprising the application of the composition according to the invention to the skin and / or mucous membranes.

[0020] The invention also relates to the use of a composition according to the invention for the care of the skin and / or mucous membranes.

[0021] The invention also relates to a final cosmetic composition comprising, in a cosmetically acceptable medium, at least 50% by weight, preferably from 60% to 99%, and more preferably from 70% to 95% relative to the total weight of the composition of a composition as described above (i.e. comprising ingredients a) to d)). This final composition corresponds in particular to the final commercialized cosmetic product. Method according to the invention

[0022] The method according to the invention comprises the following steps: i. the mixture of at least one compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of organic or mineral base or its solvates such as hydrates, with water; ii. adding at least one strong base to the mixture obtained in (i), until a pH greater than the highest pKa of the compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts or solvates is obtained; then iii. adding at least one acid to the mixture obtained in (ii), until a composition having a pH between 5.5 and 7.0 is obtained.

[0023] Each of the ingredients of the process (as well as their contents in the composition) is described below.

[0024] Preferably, the compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of organic or mineral base or its solvates such as hydrates is sennoside A or one of its salts.

[0025] Preferably, the strong base is a strong mineral base.

[0026] Preferably, the acid is an organic acid.

[0027] In step (i), at least one compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of organic or mineral base or its solvates such as hydrates, is mixed with water. This mixing is typically done while stirring.

[0028] Then, in step (ii), at least one strong base is added to the mixture obtained in (i), until a pH greater than the highest pKa of the compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts or solvates is obtained.

[0029] Preferably, in the case where the compound of formula (I) is sennoside A, its last pKa (highest pKa) being equal to 8.2, step (ii) comprises the addition of at least one strong base in the mixture obtained in (i), until a pH greater than 8.3 is obtained.

[0030] Typically, the quantity of strong base added to the mixture obtained in (i) is, in active material, between 0.01% and 1% by weight relative to the total weight of mixture (i), preferably between 0.02% and 1% by weight, preferably between 0.03% and 0.6% by weight.

[0031] Then, in step (iii), at least one acid is added to the mixture obtained in (ii), until a composition having a pH between 5.5 and 7.0 is obtained.

[0032] Typically, the amount of acid added to the mixture obtained in (ii) is, in active material, between 0.001% and 0.1% by weight relative to the total weight of mixture (ii), preferably between 0.001% and 0.01% by weight, preferably between 0.003% and 0.008% by weight. Compound of formula (I)

[0033] The composition according to the invention comprises at least one compound of formula (I) or one of its optical isomers, cis-trans isomers (such as an alpha or beta anomer), tautomers or one of its salts, in particular of organic or mineral base, or one of its solvates such as hydrates:

[0034] [Chem.l] R”. OO (i)

[0035] in which:

[0036] - R' and R' ' are identical or different, preferably identical, and represent a H or a monosaccharide or a polysaccharide comprising up to 20 sugar units, preferably up to 6 sugar units, in pyranose and / or furanose form and of L and / or D series, said mono- or polysaccharide possibly being substituted by a hydroxyl group which must be free, and optionally one or more amine function(s) which may be protected, and said monosaccharide or polysaccharide being optionally substituted on its -CH2OH group by a -C(O)-CO2 H group;

[0037] - R represents H or -C-(O)-O-Ri or -Alk-X-Rl, preferably -C-(O)-O-Ri or Alk- O-Ri,

[0038] with X being O, S or -NRb, preferably O; Ri being H or a saturated or unsaturated hydrocarbon chain, preferably saturated in C1-C6, more preferably RI corresponds to H, and Alk corresponds to a C1-C6 alkylene group, preferably -CH2-,

[0039] Advantageously, R' and R” are identical or different and represent a monosaccharide or a polysaccharide containing up to 6 sugar units, in pyranose and / or furanose form and of L and / or D series, said mono- or polysaccharide having at least one hydroxyl function which is obligatorily free and / or optionally one or more amine functions which are obligatorily protected.

[0040] Advantageously, the monosaccharide is chosen from D-glucose, D-galactose, D-mannose, D-xylose, D-lyxose, L-fucose, L-arabinose, L-rhamnose, D-glucuronic acid, D-galacturonic acid, D-iduronic acid, N-acetyl-D-glucosamine and N-acetyl-D-galactosamine. The monosaccharide advantageously denotes D-glucose, L-rhamnose, D-xylose, N-acetyl-D-glucosamine or L-fucose, and more preferably D-glucose.

[0041] Advantageously, the polysaccharide containing up to 6 sugar units is chosen from D-maltose, D-lactose, D-cellobiose, D-maltotriose, a disaccharide combining a uronic acid chosen from D-iduronic acid or D-glucuronic acid with a hexosamine chosen from D-galactosamine, D-glucosamine, N-acetyl-D-galactosamine, N-acetyl-D-glucosamine, a disaccharide combining L-rhamnose and D-galactose, an oligosaccharide containing at least one xylose which may be advantageously chosen from xylobiose, methyl-[3-xylobioside, xylotriose, xylotetraose, xylopentaose and xylohexaose and in particular xylobiose which is composed of two xylose molecules linked by a 1-4 bond.

[0042] More preferably, R' and R' ' are identical and represent a monosaccharide chosen from D-glucose, D-xylose, L-fucose, L-rhamnose, D-galactose and D-maltose, preferably D-glucose.

[0043] The monosaccharide or polysaccharide of R' and / or R” may be substituted on one or more hydroxymethyl residue(s) by a -C(O)-COOH group.

[0044] Preferably, the compound of formula (I) or one of its optical isomers, cis-trans isomers (such as an alpha or beta anomer), tautomers or one of its salts, in particular of organic or mineral base or one of its solvates such as hydrates, is chosen from sennosides A, B, C, D, E and F, preferentially it is chosen from sennosides A and B, even more preferentially the compound of formula (I) is sennoside A or one of its salts.

[0045] The compound of formula (I) or one of its optical isomers, cis-trans isomers (such as an alpha or beta anomer), tautomers or one of its salts, in particular of organic or mineral base or one of its solvates such as hydrates, preferably sennoside A or one of its salts is present in solubilized form in the composition. By "in solubilized form" is meant that said compound does not form crystals visible to the naked eye in the composition.

[0046] Sennoside A (C42H38O20) (or acid (9R)-9-[(9R)-2-carboxy-4-hydroxy-10-oxo-5-[(2S,3R,4S,5S,6R)-3,4,5-trihydroxy-6-(h ydroxymethyl)oxan-2-yl]oxy-9H-anthracen-9-yl]-4-hydroxy-10-oxo-5-[(2S,3R,4S,5S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)oxan-2-yl]oxy-9H-anthracene-2-carboxylic acid (IUP AC) is the chemical compound of formula (I') below:

[0047] [Chem.2] (D

[0048] Its CAS number is 81-27-6. It is a derivative of anthraquinone, found in plants of the genus Senna. It typically appears as a very hygroscopic yellow powder.

[0049] Sennoside A has 4 pKa, whose values ​​are pKal = 3.3, pKa2 = 3.9, pKa3 = 7.5 and its last pKa (pKa4) is equal to 8.2.

[0050] The compound of formula (I), preferably sennoside A, may also be in salt form. By "salt" is meant a cosmetically acceptable salt, i.e. compatible with application to the skin, mucous membranes and / or appendages. The salt of the compound of formula (I), preferably the salt of sennoside A, may be an alkali metal salt or alkaline earth, preferably a calcium, magnesium, sodium or potassium salt.

[0051] Typically, the salt of the compound of formula (I), preferably the sennoside salt such as sennoside A salt, may exist once the compound is introduced into the composition. Indeed, the compound of formula (I) is introduced in non-salified form into the composition.

[0052] Sennoside A is for example marketed by INTERCHIM under the name Sennoside A.

[0053] Preferably, the composition comprises between 0.1 and 5% by weight of the compound of formula (I) or one of its optical isomers, cis-trans isomers (such as an alpha or beta anomer), tautomers or one of its salts, in particular of organic or mineral base or one of its solvates such as hydrates, relative to the total weight of the composition, preferably between 0.2 and 4% by weight, preferably between 0.3 and 3% by weight, preferably between 0.4 and 1% by weight.

[0054] Preferably, the composition comprises between 0.1 and 10% by weight of sennoside A or one of its salts relative to the total weight of the composition, preferably between 0.2 and 5% by weight, preferably between 0.3 and 3% by weight, preferably between 0.4 and 1% by weight. Strong base

[0055] The composition according to the invention comprises at least one strong base. A strong base is a base which dissociates completely in water.

[0056] By “strong base” is meant a base belonging to an acid-base pair with a pKa greater than 14.

[0057] The strong base can be mineral or organic.

[0058] As strong mineral bases, mention may be made of alkali or alkaline-earth metal hydroxides, such as for example sodium hydroxide (NaOH), potassium hydroxide (KOH) or calcium hydroxide (Ca(OH2)).

[0059] Preferably, the strong base is chosen from strong mineral bases, preferably alkali metal hydroxides, such as sodium hydroxide (NaOH) or potassium hydroxide (KOH).

[0060] The composition according to the invention may comprise at least one strong base in an active material content ranging from 0.01% to 1% by weight, relative to the total weight of the composition, in particular from 0.02% to 1% by weight, preferably ranging from 0.03% to 0.6% by weight. Acid

[0061] The composition according to the invention comprises at least one acid.

[0062] Said acid may be an organic or mineral acid. It may be strong or weak.

[0063] Preferably, the composition according to the invention comprises at least one organic acid, preferably at least one carboxylic acid. Preferably, the acid is a (poly)(hydroxy) (C1-C6) alkyl (poly)carboxylic acid. By "(poly)(hydroxy) (C1-C6) alkyl" is meant a C1-C6, preferably C1-C4, alkyl radical, optionally substituted by one or more hydroxy radicals, preferably substituted by 1 to 4 hydroxy groups, more particularly 1 to 3.

[0064] Preferably the acid is a C1-C4 hydroxy (poly)carboxylic acid, preferably an alpha hydroxy acid (AHA).

[0065] By alpha hydroxy acid is meant according to the present invention a carboxylic acid having at least one hydroxy function (-OH) occupying an alpha position on said acid (carbon adjacent to a carboxylic acid function). This acid can be present in the final composition in the form of free acid and / or in the form of one of its associated salts (salts with an organic base or an alkali in particular).

[0066] The α-hydroxy acids (alpha hydroxy acids or AHAs) are for example chosen from citric acid, lactic acid, methyllactic acid, glucuronic acid, glycolic acid, pyruvic acid, 2-hydroxybutanoic acid, 2-hydroxypentanoic acid, 2-hydroxyhexanoic acid, 2-hydroxyheptanoic acid, 2-hydroxyoctanoic acid, 2-hydroxynonanoic acid, 2-hydroxydecanoic acid, 2-hydroxyundecanoic acid, 2-hydroxydodecanoic acid, 2-hydroxytetradecanoic acid, 2-hydroxyhexadecanoic acid, 2-hydroxyoctadecanoic acid, 2-hydroxytetracosanoic acid, 2-hydroxyeicosanoic acid, mandelic acid, phenyllactic acid, gluconic acid, galacturonic acid, aleuritic acid, ribonic acid, tartronic acid, tartaric acid, malic acid, fumaric acid, their salts and their mixtures.

[0067] According to a preferred embodiment, the acid is chosen from citric acid, lactic acid, malic acid, tartaric acid and their salts. More particularly, the acid is chosen from citric acid, lactic acid, their salts and their mixtures.

[0068] Preferably, the acid is citric acid.

[0069] Preferably, the composition comprises between 0.001% and 0.1% by weight of active matter of organic or mineral acid, preferably organic acid, relative to the total weight of the composition, preferably between 0.001% and 0.01% by weight, preferably between 0.003% and 0.008% by weight. Water

[0070] The composition according to the invention comprises water.

[0071] The water used may be sterile demineralized water and / or a floral water such as rose water, cornflower water, chamomile water or linden water, and / or a natural thermal or mineral water such as VITTEL water, LUCAS water or from LA ROCHE POSAY.

[0072] The composition preferably comprises at least 30% by weight of water relative to the total weight of the composition, preferably at least 50% by weight, preferably at least 60% by weight, preferably at least 70% by weight. pH of the composition

[0073] The composition according to the invention has a pH between 5.5 and 7.0.

[0074] The strong base and acid are used to adjust the final pH of the composition between 5.5 and 7.0.

[0075] Preferably, the present invention relates to a cosmetic composition comprising: a. sennoside A or one of its salts, b. at least one strong base, preferably at least one strong mineral base, c. at least one acid, preferably at least one organic acid, and d. water,

[0076] said composition having a pH between 5.5 and 7.0.

[0077] Preferably, the present invention relates to a cosmetic composition consisting of: a. sennoside A or one of its salts, b. at least one strong base, preferably at least one strong mineral base, c. at least one acid, preferably at least one organic acid, and d. water,

[0078] said composition having a pH between 5.5 and 7.0.

[0079] The composition according to the invention may also comprise at least one hydrophilic gelling agent, in particular a hydrophilic gelling polymer. By "hydrophilic polymer" is meant according to the invention a polymer soluble or dispersible in water at 25°C.

[0080] Any hydrophilic agent usable in cosmetics is suitable for the present invention.

[0081] Preferably, the hydrophilic gelling agent is chosen from at least partially neutralized non-superabsorbent acrylic acid homo- and copolymers, 2-acrylamido-2-methyl propane sulfonic acid homo- and copolymers or one of its salts, and mixtures thereof.

[0082] The term "superabsorbent polymer" means a polymer which is capable in its dry state of spontaneously absorbing at least 20 times its own weight of aqueous fluid, in particular water and in particular distilled water. Such superabsorbent polymers are described in the work "Absorbent polymer technology, Studies in polymer science 8" by L. BRAN NON-PAPPAS and R. HARLAND, published by Elsevier, 1990. In the context of the invention, a non-superabsorbent polymer is a polymer which does not meet the definition given above for superabsorbent polymers.

[0083] The non-superabsorbent acrylic homopolymers suitable for the invention may be present in the composition in particulate or non-particulate form.

[0084] When they are in a particulate form, their average size in the hydrated state is preferably less than or equal to 10 pm, and even more preferably less than or equal to 5 pm. Their average size in the dry or non-hydrated state is preferably less than or equal to 2 pm, preferably less than or equal to 1 pm.

[0085] Preferably, the at least partially neutralized non-superabsorbent acrylic acid homopolymer according to the invention is present in non-particulate form.

[0086] Preferably, a non-superabsorbent acrylic acid homopolymer that is at least partially neutralized is used. The homopolymer used according to the invention is in particular chosen from sodium polyacrylates and potassium polyacrylates. Sodium polyacrylate is preferably used.

[0087] Examples of these non-superabsorbent acrylic homopolymers already neutralized before their use include:

[0088] - sodium polyacrylates such as those marketed under the name Cosmedia SP® containing 90% dry matter and 10% water, or Cosmedia SPL® in inverse emulsion containing approximately 60% dry active matter, an oil (hydrogenated polydecene) and a surfactant (PPG-5 Laureth-5), both sold by the company Cognis;

[0089] - partially neutralized sodium polyacrylates, in particular found in form of an inverse emulsion comprising at least one polar oil, for example that sold under the name Luvigel® EM by the company BASF; and

[0090] - their mixtures.

[0091] It is also possible to use a non-superabsorbent acrylic acid homopolymer which has not been previously neutralized, which is then neutralized before use by any suitable means, in particular by adding sodium hydroxide. Sodium polyacrylates are thus obtained. Potassium polyacrylates are also suitable for the present invention.

[0092] On the other hand, for some of them, neutralization is inherent to the raw material. This is the case in particular for Luvigel® EM and the products called Cosmedia® SP and SPL which are already partially neutralized. The neutralization step, for example by sodium or potassium counterions, is important to give the acid polymers their gelling properties and therefore to stabilize the composition. Said acrylic polymers are converted into corresponding acrylate polymers during this neutralization step. The acrylic monomers of the acrylic polymer according to the invention can be neutralized at a rate of 5 to 100%, and in particular 5 to 80%. Thus, preferably, an acid homopolymer is used. neutralized acrylic at a rate ranging from 5 to 100%, in particular ranging from 5 to 80%.

[0093] According to a particular embodiment, the acrylic acid homopolymer may be in the form of a water-in-oil emulsion, called an inverse emulsion. This inverse emulsion may, for example, be obtained by inverse emulsion polymerization.

[0094] According to a particular embodiment of the invention, the homopolymer used is a partially neutralized sodium polyacrylate in the form of an inverse emulsion comprising at least one polar oil. Among the oils, mention may be made of fatty acid esters. Examples of these fatty acid esters are isopropyl esters of fatty acids, such as isopropyl palmitate or isopropyl myristate, or polyglycerides of fatty acids, in particular mixtures of fatty acids comprising at least 50% capric and / or caprylic acids. Such water-in-oil emulsions are described in document US 6,197,283.According to this embodiment, the oily phase may consist of one or more fatty acid esters, one or more fatty acid polyglycerides based on a mixture of polyglycerides, which contains diglycerides and triglycerides, with mixtures of fatty acids, which contain caprylic acid and / or capric acid, preferably at a rate of at least 50% by weight relative to the total weight of fatty acids. According to one embodiment of the invention, the oil content of the inverse emulsion is between 15 and 70% by weight, in particular between 20 and 35% by weight relative to the total weight of the inverse emulsion. In this respect, mention may be made in particular of Luvigel® EM, the oily phase of which comprises 26% of oil phase consisting of C8-10 triglycerides, namely the fatty acids of which are a mixture of capric and caprylic acid. Furthermore, the water-in-oil emulsion may contain from 0.25 to 7% by weight, preferably 0.5 to 5% by weight, of a surfactant.The at least partially neutralized acrylic homopolymer may be present in the inverse emulsion in a content varying from 20% to 70% by weight, in particular from 20 to 65% by weight, for example from 20 to 62% by weight relative to the total weight of the inverse emulsion. In particular, according to one embodiment, the acrylic homopolymer may be present in the inverse emulsion in a content varying from 20 to 30% by weight relative to the total weight of the inverse emulsion. According to yet another embodiment, the acrylic homopolymer may be present in the inverse emulsion in a content varying from 50 to 62% by weight relative to the total weight of the composition.

[0095] The hydrophilic gelling polymer may also be chosen from homo- and copolymers of 2-acrylamido-2-methyl propane sulfonic acid or one of its salts. These are water-soluble, water-dispersible or water-swellable polymers.

[0096] Preferably, the AMPS® polymers (Lubrizol monomer) used in accordance with the invention can be partially or completely neutralized by an inorganic base (such as sodium hydroxide, potassium hydroxide, or aqueous ammonia) or an organic base such as mono-, di-, or triethanolamine, an aminomethylpropanediol, N-methylglucamine, or basic amino acids such as arginine and lysine, or mixtures of these compounds. They are generally neutralized. In the present invention, the term "neutralized" is intended to refer to polymers that have been completely or almost completely neutralized, i.e., at least 90% neutralized.

[0097] The AMPS® polymers (Lubrizol monomer) used in the composition of the invention generally have a number-average molecular mass ranging from 1,000 to 20,000,000 g / mol, preferably ranging from 20,000 to 5,000,000, and even more preferably from 100,000 to 1,500,000 g / mol.

[0098] When the polymers are crosslinked, the crosslinking agents can be chosen from olefinically polyunsaturated compounds commonly used for crosslinking polymers obtained by radical polymerization. Crosslinking agents that may be mentioned include, for example, divinylbenzene, diallyl ether, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trimethylolpropane triacrylate, methylenebisacrylamide, methylene-bismethacrylamide, triallylamine, triallyl cyanurate, diallyl maleate, tetraallylethylenediamine, tetraallyloxyethane, trimethylolpropane diallyl ether, allyl(meth)acrylate, allyl alcohol ethers and allyl esters of phosphoric acid derivatives and / or vinylphosphonic acid derivatives, or mixtures of these compounds.According to a preferred embodiment of the invention, the crosslinking agent is chosen from methylene-bis-acrylamide, allyl methacrylate or trimethylol propane triacrylate (TMPTA). The crosslinking rate generally varies from 0.01 to 10% by mole, and more particularly from 0.2 to 2% by mole, relative to the polymer.

[0099] More particularly preferred AMPS® homopolymers comprise, randomly distributed, units of the following general formula (III):

[0100] [Chem.3] H^. yz CH (III)

[0101] in which X+ denotes a proton, an alkali metal cation, an alkaline earth cation or the ammonium ion, at most 10 mol% of the X+ cations being able to be H+ protons;

[0102] and crosslinking units originating from at least one monomer having at least two olefinic double bonds.

[0103] The homopolymers used according to the invention and more particularly preferred comprise from 90 to 99.9% by weight and preferably from 98 to 99.5% by weight of units of formula (I), and from 0.01 to 10% by weight, preferably from 0.2 to 2% by weight of crosslinking units, the proportions by weight being defined relative to the total weight of the polymer.

[0104] As a homopolymer of this type, mention may in particular be made of the crosslinked and neutralized homopolymer of 2-acrylamido 2-methylpropane sulfonic acid, marketed by the company Clariant under the trade name Hostacerin AMPS® (INCI name: Ammonium Polyacryldimethyltauramide).

[0105] The hydrophilic gelling agent may be present in the composition of the invention in an active material content ranging for example from 0.01 to 1% by weight, preferably from 0.1 to 0.8% by weight, preferably ranging from 0.2 to 0.6% by weight relative to the total weight of the composition.

[0106] The composition according to the invention may also contain ingredients usual in the cosmetic field, such as preservatives, perfumes, fillers, oils, waxes, pasty fatty substances, sun protection filters or UV filters, odor absorbers, coloring matters, sequestering agents or active ingredients.

[0107] The quantities of these different ingredients are those conventionally used in the field considered, and for example from 0.01 to 20% of the total weight of the composition. These ingredients, depending on their nature, can be introduced into the fatty phase and / or into the aqueous phase.

[0108] Of course, those skilled in the art will take care to choose the possible compound(s) to be added to the composition according to the invention and their quantities in such a way that the advantageous properties intrinsically attached to the composition in accordance with the invention are not, or not substantially, altered by the envisaged addition.

[0109] The composition in accordance with the invention can be obtained in a conventional manner by a person skilled in the art.

[0110] The invention also relates to a final cosmetic composition comprising, in a cosmetically acceptable medium, at least 50% by weight relative to the total weight of the composition of a composition as described above (i.e. comprising ingredients a) to d)), preferably from 60 to 99% by weight, more preferably from 70 to 95% by weight. The final composition corresponds in particular to the final commercialized cosmetic product, based on sennoside. By cosmetic medium- Technically acceptable means an environment compatible with the skin and / or its appendages.

[0111] The invention also relates to a method for caring for the skin and / or mucous membranes comprising the application of the composition according to the invention or of the final composition according to the invention to the skin and / or mucous membranes.

[0112] The invention also relates to the use of a composition according to the invention or of the final composition according to the invention for the care of the skin and / or mucous membranes.

[0113] The following examples will allow a better understanding of the invention, without however being limiting in nature. The raw materials are named by their chemical or INCI name. The quantities indicated are in % by weight of raw materials relative to the total weight of the composition (% w / w), unless otherwise stated. Examples

[0114] Example 1: Preparation of a composition according to the invention and evaluation in relation to comparative compositions

[0115] A composition according to the invention is compared with a counterexample. Operating mode

[0116] The composition according to the invention of Table 1 below is prepared as follows:

[0117] In a beaker under magnetic stirrer, the powdered sennoside A is placed, then the water, the mixture is not homogeneous (1st column).

[0118] The pH is adjusted by first adding 0.04% by weight of active matter of NaOH (strong base) (2nd column), then another 0.0053% by weight of active matter of NaOH is added (i.e. 0.0453% by weight relative to the total weight of liquid, 3rd column): a liquid of pH = 9.3 is obtained (pH value above the pKa4 of sennoside A).

[0119] Stir for a while to stabilize the pH.

[0120] Then 0.006% of active ingredient citric acid (strong acid) is added (4th column): a perfectly clear solution of pH = 6.2 is obtained, stable over time and with a pH suitable for skin application (see table 1).

[0121] In the case of the counterexample:

[0122] The pH adjustment is extremely difficult to achieve: when the pH is for example 5.8 (i.e. with 0.035% NaOH), sennoside A is not completely solubilized (1st column of the counter-example). A very small pH variation, for example 0.1 to obtain solubilization (i.e. with 0.0403% NaOH or a pH of 5.9), does not allow reproducibility (2nd column of the counter-example).

[0123] [Tables 1] Method and example according to the invention (aqueous solution of sennoside A at 0.5% w / w - pH increase then decrease) Counterexample (aqueous mixture of sennoside A at 0.5% w / w - direct pH obtained) Sennoside A 0.5 - - - 0.5 - NaOH - 0.04% MA 0.0453% MA - 0.035% MA 0.0403% MA Citric acid - - - 0.006% MA - - pH 4.3 6.0 9.3 6.2 5.8 5.9 Observations Insolubl e Opaque yellow Partially soluble, but not clear Color change (redder). Partially Soluble but not perfectly clear Perfectly clear Cloudy color always pale yellow Clear transparent but not reproducible Note The pH adjustment is easily done and is reproducible. Adjusting the pH is extremely difficult to achieve: when the pH is, for example, 5.8, sennoside A is not completely solubilized. A very small pH variation, i.e. 0.1 to obtain solubilization, does not allow not reproducibility.

[0124] MA = active ingredient

[0125] In the example according to the invention, it can be observed that sennoside A is dispersed in water at a native pH which fluctuates between 4.3 and 4.5. The solution is opaque yellow.

[0126] When the pH is increased to between 8 and 10, the color becomes reddish brown, and the solution becomes more transparent but not perfectly clear. When the pH is lowered, the solution becomes clear-transparent, as expected.

[0127] In the counterexample, when the pH is adjusted directly from native pH to pH close to 6.0, the sennoside A solution obtained is clear, but this step is very uncertain and not reproducible from one test to another.

[0128] The solubility margin is very variable: we can have perfect solubilization at pH = 5.9, but cloudy at pH = 5.8. The margin of error for measuring pH being + / - 0.3, this direct solubilization route is not reliable.

[0129] We can therefore conclude that the solubilization of sennoside A must involve a rise and then a fall in pH.

[0130] Example 2: preparation of a composition according to the invention in gel form

[0131] A composition according to the invention in gel form is prepared as follows:

[0132] • sennoside A is dissolved in water. Sodium hydroxide is added until pH = 8.0, then citric acid is added to bring the pH back down to pH = 6.2 while stirring;

[0133] • the AMPS gel is added with light Rayneri stirring, heating to a temperature temperature below 55°C to facilitate mixing;

[0134] • then, once the mixture is homogeneous, the sodium polyacrylate is added still under agitation rayneri.

[0135] We obtain a fairly yellow and fairly thick gel.

[0136] [Tables2] INCI Gel according to the invention (% w / w) NaOH (soda) 0.0453 Water Qsp 100 AMMONIUM POLYACRYLOYLDIMETHYL TAURATE (AMPS) 1.5 Sodium polyacrylate (Cosmedia SP) 0.5 (=0.45% MA) Citric acid 0.006 SENNOSIDE A 0.5 Controls T24h: pH = 5.8 M3: 21 poises T0 Stable after 2 months at 4°C, TA and 45°C

[0137] TA = room temperature (approximately 20°C)

[0138] MA = active ingredient

[0139] The viscosity is measured using a Rheomat RM180, mobile 3 (M3). The value is recorded after 30 seconds (T0) and 10 minutes. CONCLUSION

[0140] It is known that a solution of sennoside A is totally insoluble in water at native pH.

[0141] Perfect and stable solubility over time of 0.5% sennoside A can be obtained by varying the pH of this solution. At a pH of 5.5 to 7.0, the sennoside A solution is clear and stable over time. However, to obtain this solubility, it is necessary to go through a rise and then a fall in pH, to reach values ​​above the pKa4 then reduce the pH to between 5.5 and 7.0.

[0142] Obtaining a solution of sennoside A by going directly to a pH = 6.0 is not reproducible and difficult for scaling up.

Claims

1. Claims Process for preparing a cosmetic composition comprising the following steps: (i) the mixture of at least one compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of organic or mineral base or its solvates such as hydrates, with water: [Chem.l] (I) in which: - R' and R' ' are identical or different, preferably identical, and represent an H or a monosaccharide or a polysaccharide comprising up to 20 sugar units, preferably up to 6 sugar units, in pyranose and / or furanose form and of L and / or D series, said mono- or polysaccharide possibly being substituted by a hydroxyl group which must be free, and optionally one or more amine function(s) which may be protected, and said monosaccharide or polysaccharide being optionally substituted on its -CH2OH group by a -C(O)-CO2H group; - R represents H or -C-(O)-O-Ri or -Alk-X-Rl, preferably -C-(O)-OR! or Alk-O-Rj, with X being O, S or -NRb, preferably O; RI being H or a saturated or unsaturated hydrocarbon chain, preferably saturated in C1-C6, more preferably RI corresponds to H, and Alk corresponds to a C1-C6 alkylene group, preferably -CH2-, (ii) the addition of at least one strong base to the mixture obtained in (i), until a pH higher than the highest pKa of the compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts or solvates is obtained; then (iii) adding at least one acid to the mixture obtained in (ii), until a composition having a pH between 5.5 and 7.0 is obtained.

2. Process according to claim 1, in which the quantity of strong base added to the mixture obtained in (i) is comprised, in active material, between 0.01% and 1% by weight relative to the total weight of mixture (i), preferably between 0.02% and 1% by weight, preferably between 0.03% and 0.6% by weight.

3. Process according to claim 1 or 2, in which the quantity of acid added to the mixture obtained in (ii) is comprised, in active material, between 0.001% and 0.1% by weight relative to the total weight of mixture (ii), preferably between 0.001% and 0.01% by weight, preferably between 0.003% and 0.008 by weight.

4. Method according to one of the preceding claims, in which the compound of formula (I) is such that R' and R” are identical and represent a monosaccharide chosen from D-glucose, D-galactose, D-mannose, D-xylose, D-lyxose, L-fucose, L-arabinose, L-rhamnose, D-glucuronic acid, D-galacturonic acid, D-iduronic acid, N-acetyl-D-glucosamine and N-acetyl-D-galactosamine, preferably chosen from D-glucose, L-rhamnose, D-xylose, N-acetyl-D-glucosamine and L-fucose, and more preferably D-glucose; preferably the compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of organic or mineral base or one of its solvates such as hydrates, is chosen from sennosides A, B, C, D, E and F, preferably it is chosen from sennosides A and B.

5. A method according to any preceding claim, wherein the compound of formula (I) is sennoside A or one of its salts.

6. Method according to one of the preceding claims, in which the composition which comprises between 0.1 and 10% by weight of compound of formula (I) relative to the total weight of the composition, preferably between 0.2 and 5% by weight, preferably between 0.3 and 3% by weight, preferably between 0.4 and 1% by weight.

7. Method according to one of the preceding claims, in which the strong base is mineral or organic, preferably chosen from hy- alkali or alkaline earth metal oxides, preferably from sodium hydroxide, potassium hydroxide and calcium hydroxide.

8. A method according to any preceding claim, wherein the acid is an organic acid, preferably a (poly)(hydroxy) (C1-C6) alkyl (poly)carboxylic acid, preferably an alpha hydroxy acid, preferably selected from citric acid, lactic acid, methyl lactic acid, glucuronic acid, glycolic acid, pyruvic acid, 2-hydroxy butanoic acid, 2-hydroxypentanoic acid, 2-hydroxyhexanoic acid, 2-hydroxyheptanoic acid, 2-hydroxyoctanoic acid, 2-hydroxy nonanoic acid, 2-hydroxydecanoic acid, 2-hydroxyundecanoic acid, 2-hydroxydodecanoic acid, 2-hydroxytetradecanoic acid, 2-hydroxy hexadecanoic acid, 2-hydroxyoctadecanoic acid, 2-hydroxytetracosanoic acid, 2-hydroxyeicosanoic acid, mandelic acid, phenyllactic acid, gluconic acid, galacturonic acid, aleuritic acid, ribonic acid, tartronic acid, tartaric acid, malic acid,fumaric acid, their salts and their mixtures; preferably the acid is chosen from citric acid, lactic acid, malic acid, tartaric acid and their salts.,

9. Method according to one of the preceding claims, in which the composition comprises at least 30% by weight of water relative to the total weight of the composition, preferably at least 50% by weight, preferably at least 60% by weight, preferably at least 70% by weight.

10. Method according to one of the preceding claims, in which the composition comprises at least one hydrophilic gelling agent, preferably the hydrophilic gelling agent is chosen from at least partially neutralized non-superabsorbent acrylic acid homo- and copolymers, 2-acrylamido-2-methyl propane sulfonic acid homo- and copolymers or one of its salts, and mixtures thereof.

11. Composition obtainable by the process according to one of claims 1 to 10.

12. Cosmetic composition comprising, preferably consisting of: a. at least one compound of formula (I) or one of its optical isomers, cis-trans isomers, tautomers or one of its salts, in particular of organic or mineral base or its solvates such as than hydrates, preferably sennoside A or one of its salts, b. at least one strong base, preferably at least one strong mineral base, c. at least one acid, preferably at least one organic acid, and d. water, said composition having a pH between 5.5 and 7.

0.

13. Final cosmetic composition comprising, in a cosmetically acceptable medium, at least 50% by weight, preferably from 60 to 99% by weight, more preferably from 70 to 95% by weight relative to the total weight of the composition of a composition according to one of claims 11 or 12.

14. A method of caring for the skin and / or mucous membranes comprising the application of the composition according to one of claims 11, 12 or 13 to the skin and / or mucous membranes.

15. Use of a composition according to one of claims 11, 12 or 13 for the care of the skin and / or mucous membranes.