WO1991010421A1

WO1991010421A1 - Use of n-acyl derivatives of homocysteine to modify the structure of keratin and cosmetic compositions containing these derivatives

Info

Publication number: WO1991010421A1
Application number: PCT/EP1991/000128
Authority: WO
Inventors: Hervé Tournier; Hubert Delagneau; Philippe Bussat; Roland Hyacinthe
Original assignee: Reckitt & Colman
Priority date: 1990-01-16
Filing date: 1991-01-12
Publication date: 1991-07-25
Also published as: PT96499A; IE910124A1; AU7055391A

Abstract

The use of N-acyl derivatives of homocysteine of formula (II), where R is substituted or unsubstituted, saturated or unsaturated, straight-chain or branched CO-alkyl radical of more than 4 carbon atoms, for lasting modification of keratinous materials, in particular as agents for waving hair or as depilatory agents, keratolytic compositions and derivatives of formula (II).

Description

Use of N-acyl derivatives of homocvsteine to modify the structure of keratin and cosmetic compositions containing these derivatives.

The present invention relates to the treatment of materials of organic origin based on keratin, in particular horn, bristles, nails, hair, wool, silk and other analogous biosubstances, in order permanently to modify their shape and structure. This treatment consists in attacking the sulfur bonds constituting crosslinking bridges in their polypeptide skeleton.

The invention also relates to cosmetic compositions, for example for use on the hair to wave straight hair or to straighten curly hair, or depilatory compositions to remove superfluous hair. The term "permanent modification" is here intended to refer to a treatment leading to a more or less pronounced restructuring, deformation or degradation of the keratin due to the more or less complete breakage of the thioether or disulfide (cysteine type) bonds of the polypeptide. Thus, such a modification, when it is very extensive, causes the irreversible disintegration of the keratinous polymer, that is to say the depilatory effect where hair is concerned.

The invention relates in particular to the use of some N-acyl derivatives of homocysteine and its water- soluble salts, the formula of which derivatives will be specified below, to effect such a permanent modification.

It has long been known that some sulfur- containing organic compounds, in particular thiols, are chemically active towards keratin and able permanently to modify its shape and its structure. Such a property applies to the treatment of hair (straightening and permanent waving) and, as a depilatory cosmetic, to remove superfluous hair from certain parts of the body. In the document US-A-4,121,904, it is explained that this effect is due to the weakening, the rupture or the destruction of the thioether or disulfide bonds of cystine molecules. This rupture of bonds ends by degrading the material of the hair, to such a point that it is then possible to remove said hair by brushing or rinsing. The document US-A-4 121 904 also specifies that the sulfur- containing reagent is able to act either as free thiol or, if the pH is alkaline, as thiolate anion in accordance with the following equations, where A-SH denotes the active thiol and B denotes the non-sulfur-containing portion of the keratin chain.

(1) A-SH + B-SS-B A-SS-B + A S~ + H⁺

(2) A-S~ + B-SS-B ^*> BS~ + A-SS-B

It is therefore seen that an increase in the pH promotes the attack on the sulfur bridges and increases the rate of degradation and, consequently, the depilatory effect.

Amongst the sulfur-containing organic compounds having a keratolytic action which are commonly used to modify the structure of keratin, the following may be mentioned as examples : lower mercaptocarboxylic acids of formula HS-(CH₂)_n-COOH, where n is an integer no higher than about 4 to 5, for example thioglycolic acid and thiolactic acid and their alkali metal, alkaline earth metal and ammonium salts.The sulfur-containing glycols may also be mentioned, for example thioglycol, thioglycerol and aminothioglycol.

Cysteine, cysteamine and the glyceride esters of thioglycolic acid are also mentioned (see EP-A-302,265) .

Dithiothreitol and dithioerythritol (see DE-A- 2, 131,630) and l,4-dimercaptobutane-2,3-diol (see US-A- 3,865,546) are also mentioned.

The keratolytic action of homocysteine and some of its derivatives is also known. Thus, the Japanese document JP 61-165.316 (HADA KESHOHIN KAGAK) describes depilatory compositions containing, as principal in- depilatory compositions containing, as principal in¬ gredient, homocysteine or its thiols esters, in particular in the form of alkali metal salts and organic amines, and also hydrochloride. The document EP-A-236,533 (SUMITOMO) describes a preparation for permanent waving containing homocysteine or its esters with lower aliphatic alcohols ( C± to C₆) . According to this document, it is alleged that homocysteine is more effective than cysteine and its effect is longer lasting. Moreover, the proportion of homocystine (inactive) naturally present in homocysteine is well below the proportion of cystine present in cysteine.

This document also provides for the use of homocysteine in the form of its salts with inorganic or organic bases.

The N_.-acyl derivatives of homocysteine thiolactone are also known for their keratolytic activity. Thus, the document US-A-3,533,417 (UNILEVER) describes a technique intended to modify the structure of human hair, for example to wave the hair, by contact with an alkaline (pH 11) solution of homocysteine thiolactone derivatives substituted on the nitrogen. Such compounds have the following formula :

where R denotes an alkanoyl C-^ to C group, benzoyl, toluoyl and ethylbenzoyl. However, the document US-A-

3,533,417 does not indicate that such compounds can be used as depilatories.

In this regard, it will be noted that the N- acyl derivatives of homocysteine do not all have a keratolytic action. Thus, for example, the document FR-A-

2,265,355 (BLUM) describes in very broad terms a variety of cal and cosmetic properties. This document indicates, in particular, that N-(3,4,5-trimethoxy benzoyl)-homocysteine has hypnotic properties ; N -(carboxymethylacetyl)- homocysteine is said to be mucolytic and N,£3-diacetyl homocysteine has trophic properties for the skin and hair, whereas N-( (chromon-2-yl) carbonyl)-homocysteine is cicatrization accelerator and a hair protector. It however discloses in the family of aliphatic N-acyl derivatives of homocysteine only the N-propionyl (C₃) derivative. Knowing the above, it is all the more surpri¬ sing to have discovered that the N-acyl homocysteines of formula (II)

HS-(CH₂)₂-CH(NHR)-COOH (II) where R denotes a substituted or unsub- stituted, saturated or unsaturated, straight-chain or branched acyl radical, comprising more than 4 carbon atoms, have keratolytic properties which are similar to or even more pronounced than those of known N-acyl derivatives_^ By virtue of this fact, their use as principal or sub- sidiary ingredients in depilatory formulations or formula¬ tions for waving hair is very valuable.

The present invention has therefore as its object the use of N-acyl-derivatives of homocysteine of formula HS-(CH₂)₂-CH-COOH (II)

NHR where R is substituted or unsubstituted, saturated or unsaturated, straight-chain or branched CO-alkyl radical of more than 4 carbon atoms, for lasting modification of keratinous materials, in particular as agents for waving hair or as depilatory agents

In the formula (II) , R can be (a) an indepen¬ dent single radical or, (b) can constitute a recurring unit in a polymer as will be seen below. In general, in case (a) the number of carbons in R is limited to 24 ; however, the C₅ to C₁₆, particularly C₆-C₁₂, and more particularly the ^c ₆ ^-c _l° compounds, are preferred because it is within this range that the effectiveness of the derivatives (II) is the most satisfactory. The precise reasons why chains of a certain length are the most effective are not known, but it could be a question of the hydrophilic/lipophilic proper¬ ties balance (amphipathic factor) between the HS and COOH groups on the one hand and the hydrocarbon chain on the other hand. In other words, the most efective derivatives are those which have an optimum combination of hydrophilic and lipophilic properties.

Consequently, the derivatives (II) are used in aqueous solution or dispersion, such solutions or disper¬ sions also being able to contain other ingredients customarily used in cosmetology for depilatory formulations or for formulations for permanent waving of the hair. Such ingredients are well known to those skilled in the art and are widely mentioned in the prior art.

In this regard it should be noted that the derivatives (II) can be used individually or as mixtures or in combination with other known organic or inorganic sulfur-containing keratolytic compounds. In some cases, in particular with the thioglycolates and thioglycerol, a keratolytic synergistic effect is obtained with such combinations. The aqueous phase can advantageoulsy comprise a lipophilic phase with which the derivative or derivatives (II) are combined ; this lipophilic phase can consist of vegetable or mineral oil or fatty matter, or of dispersion of liposomes, for example. It should be noted that, in this latter case, because of the lipophilic chain of the derivatives (II) the latter are incorporated easily in the liposome membrane, which increases their keratolytic activity.

When the derivatives (II) are used in composi- tions for permanent waving or for straightening curly hair, their concentration in the aqueous phase is generally of the order of 0,5 to 10 % by weight depending on wether they are or are not combined with other known keratolytic agents such as thioglycolate, thioglycerol, thioglycol, 3-mercaptopropionic acid, N-hydroxyethy1)-mercaptoacetami- de, N-methylmercaptoacetamide, β - mercaptoethylamine (cys- teamine) , mercaptopropionamide, 2-mercaptoethanesulfonic acid, dimercaptoadipic acid, dithiothreitol, homocysteine thiolactone and inorganic sulfides such as lithium, sodium, potassium, caesium, magnesium, calcium, strontium and barium sulfides (see for example, "Cosmetics" in Science and Technology (Ed. M.S. Balsam & E. Sagarin) Vol. 2 (1972)). The pH of these compositions is obtained by addition of inorganic or organic bases, in particular alkali metal or alkaline earth metal hydroxides or organic amines.

The pH of the aqueous phase is preferably between 7 and 8,5, but it is possible to go outside these limits for some special applications. The rates of reactions are, in fact, lower at the lower power pHs, but pHs which are too high could cause too severe an attack on the hair if the action is prolonged. A compromise must therefore be achieved depending on the type of application intended.

These compositions can also contain other ingredients, such as thickeners, agents for increasing the viscosity, surfactants, buffers, swelling agents, colour¬ ants, perfumes, opacifying agents, etc. A great deal of information on such ingredients is found in the general prior art, in particular in the following documents : DE-A- 1,917,433 ; FR-A-1,503,640.

When the derivatives (II) are used in the aqueous depilatory compositions, their concentration is generally somewhat higher than in the compositions for use in treatment of the hair, in particular of the order of 1 to 15 % by weight, depending on whether they act on their own or in combination with other keratolytes. However, it is in particular on the increase in the pH that reliance is placed to lead to an effective disintegration rather than a simple deformation of the keratin. The pH is generally of the order of 10 to 12, 5, but these values can be modified in certain cases. In general, it is sought to establish a compromise between the effectiveness of the depilatory (high pH) and its harmlessness to the skin (pH as low as possible, but adequate rate of treatment) . The N-acyl derivatives of homocysteine are very active at pHs which are relatively not very high (of the order of 10 to 11) , which makes them particularly valuable for these applica¬ tions.

The depilatory compositions of the present invention generally comprise, in addition to the active depilatory agents, thickeners enabling "body" to be given to the composition during its application to the skin, wetting agents (surfactants) to improve the contact with the skin, and softening fillers such as clay, MgO, bentonite, talc, etc., as well as other adjuvants, in particular perfumes. Amongst the thickeners, those which may be mentioned are the natural gums (guar, xanthan, tragacanth, karaya, etc.) and some hydrophilic polymers such as carboxymethylcellulose, hydroxyethy1cellulose, polyvinyl alcohol, swelling hydroxyacrylates and dextrins. The surfactants can be anionic (soaps, alkyl- and alkyl- aryl-sulfonates and mixed sulfates of fatty alcohols and alkali metals) ; cationic (quaternary alkyl-arylalkyl- or aryl-ammonium compounds) ; nonionic (polyoxyethylenated fatty alcohols, polyoxyalkylenated alkylphenols, etc.) and amphoteric (sulfo- and phosphobetaines) .

In some embodiments of such compositions according to the invention, the formulations comprise at least one polymer which, on drying, forms films at the surface of the skin onto which the depilatory composition has been applied. As the drying time is calculated to correspond to the time necessary for the depilatory to act on the keratin of the hairs to be epilated, the film thus formed can then simply be removed, this film then painless¬ ly bringing away the hairs degraded by the depilatory. A film-forming polymer of this type can be, for example, PVA (polyvinyl alcohol) , PVP (polyvinylpyrrolidone) , polyacryl- a ide, polyacrylic acid and others in the form of polyacry- lic solutions, dispersions or latex and also the latexes of poly(1,4-cis-isoprene) having molecular weights which can reach and exceed 10⁶ daltons (see for example, the document EP-A-196,896, which describes depilatory films containing such polymers and, as depilatory, thioglycolic acid) . It is also possible to use a polymer consisting of a succession of alkylene units, some of which comprise an acyl group linked to the amino group of homocysteine. Such a polymer, one embodiment of which is illustrated by the formula (III) below, corresponds to the derivatives (II) (case b) in which the group R (also substituted by other appended hydrophilic functions) represents a monomer unit repeated n times. —[CH(COOH)-CH-CH₂-CH(OCH₃) ] _n

CONH-CH(COOH)-(CH₂)₂-SH (HI)

Such a polymer can be produced, for example, by reaction of homocysteine thiolactone with a polymer comprising anhydride or acylchloride functions. A suitable polymer for this reaction is the polymer termed GANTREZ AN-

119 (marketed by GAF Corp.) of formula

- [ CH CH—CH₂ - CH(0CH₃) ] - _n (IV)

OC CO

It will also be noted that, like the com¬ positions for the treatment of the hair, the present depilatory compositions can contain a variety of adjuvants, such as gelling agents, emollients, swelling agents, agents for increasing the viscosity, thickeners, surfactants, perfumes, softeners, etc. , all well known to those skilled in the art and being mentioned in the prior art mentioned below, as well as plasticizers, in particular, glycerol, polyglycerol, polyglycerides and polyols, such as polyethy¬ lene glycol (PEG) . Amongst other plasticizers which are suitable, the following may be mentioned in particular : diethylene glycol, triethylene glycol, triethanolamine, butane-l,3-diol, Carbowax-2000, triethanolamine acetate and ethanol-acetamide. The compositions can also contain epilation accelerators (see, for example, EP-A-96,521 (PROCTER & GAMBLE)), i.e. urea guanidine, thiourea and thiocyanate. The portion by weight of these accelarators is preferably between 0.5 to 10 %. A number of documents reflecting the general prior art in the field of depilatory compositions are cited below :

FR-A-824,804 ; 1,161,038 ; 1,405,939 1,411,330 ; 1,469,512 ; 1,578,008 ; 2,077,895 ; 2,038,196 ; 2,585,566 ;

US-A-3,154,470 ; 2,352,524 ; 3,865,546 ; DE-A-2,215,122 ;2, 131, 630 ; 2,122,293 2,614,723 ; 2,253,117 ;

GB-A-1,296,356 ; 1,142,090 ; EP-A-95 916 ; 287,773

The compounds of formula II are obtained easily by reaction of homocysteine in the lactone form with an acyl halide or anhydride RCOX or RCO-O-OCR in accordance with the known techniques (for example described in detail in the document FR-A-2,265,355), followed by opening of the lactone ring in in an alkaline medium.

The present invention has at least as its object the N-acyl derivatives of homocysteine as well as their salts characterized in that they correspond to the general formula HS-(CH₂)₂-CH-COOH (II)

NHR in which R represents an aliphatic acyl group containing from 5 to 24 carbon atoms, notably the derivatives of formula II wherein R is a Cg-Cn_^O radical, and particularly the derivatives described as examples and more particularly the examples which follow and illustrate the invention in more detail.

1. Measurement of the keratolytic activity This method consists in the spectrophometric measurement, in solution, of the concentration of

2-thiopyridine formed by reaction of 2.2*-dithiopyridine with the free thiol functions of a standard sample of keratin (lock of hair) treated beforehand (under standard conditions) with a compound for which it is desired to test the activity.

110 mg of hair of Asiatic origin (supplied by Valeda, Alencon) cut into fragments about 1 cm long are immersed for exactly 5 minutes in 5 or 10 ml of the depilatory agent to be assessed, which has previously been brought to a pH of 12.5. The hair is then immediately filtered off on a sintered glass filter connected to a water pump and washed using the same device by circulating 1500 ml of demineralized water. The drained hair is then placed in a vessel containing :

- 12 ml of ethanol

- 8 ml of TRIS-EDTA buffer at pH 8.5, prepared from 24.2 g of TRIS diluted in 100 ml of a 0.2 M solution of EDTA (tetrasodium salt) and then made up to 1 liter and then adjusted to a pH of 8.2

- 8.5 ml IN HC1

- 0.25 ml of a 50g/l solution of 2.2 '-dithiodi- pyridine (DTDP) in ethanol.

The hair is allowed to react for exactly l hour in the vessel, which is closed or preferably under a blanket of nitrogen, and the optical density* is measured at 353 nm against a blank sample obtained after the hair has been attacked in a sodium hydroxide solution at pH 12,5 without depilatory agent. The optical density values obtained are used directly for comparison (comparison with 3 - 5 % calcium thioglycolate or thioglycerol solutions at pH 12,5) to assess the degree of attack associated specifically with the depilatory agents concerned.

* If the optical densities exceed a values of 2 it is preferable to carry out a dilution by a factor of 5 or 10.

2. Preparation of N-acyl homocysteines

36 g of sodium bicarbonate are dissolved in 800 ml of water and 30 g (0,1953 mole) of homocysteine thiolactone hydrochloride are then added in 5 g portions

(effervescence) . Stirring is continued for 15 minutes at ambient temperature (temperature in the mixture = 15° C) .

38,4 g (0,2583 mole) of heptanoyl chloride in solution in

400 ml of chloroform are then added dropwise (rapidly) . The temperature rises to 25° - 26° C.

After the addition (15 - 20 min) , stirring is continued for 4 hours at ambient temperature. The chloro¬ form phase is then separated off. The aqueous phase saturated with NaCl and extracted with 4 x 100 ml of CHC1₃. The chloroform phases are collected, washed with 2 x 50 ml of saturated aqueous salt solution and dried over Na₂S0 .

After filtering, the solvent is evaporated and a yellow oil is obtained which dissolved at about 50° C in a minimum of isopropyl ether. A crystallization is observed on cooling. After one night in the refrigerator, the mixture is filtered and the crystals are washed with petroleum ether. The white solid obtained is dried in a vacuum oven at 30° C.

Mass collected : 38.18 g. Theoretical mass : 44.8 g. Yield : 85.2 %.

The product can optionally be recrystallized from ethanol. During the reaction, formation of ethyl heptanoate takes place, the chloroform being stabilized with 1 % of ethanol. This prevents immediate crystalliza¬ tion of the product in ethanol. The cylic compound was then opened by dissol¬ ving in aqueous 2N NaOH.

The same procedure was used with other acid chlorides in stoichiometrically equivalent amount and the following N-acyl derivatives (II) were prepared : Derivative Meltin oint R

Acetyl

Heptanoyl

Octanoyl

Decanoyl Dodecanoyl

Palmitoyl

The keratolytic activity of these derivatives was measured in aqueous solution (1 - 4% ; pH 12.5) using the abovementioned test. It was found that the activity of the C_η and C₈ compounds was about 30 - 40 % higher than that of of the C^ derivative ; the reactivity then decreases progressively when the chain length increases above C₉ to C ⁰

3. Influence of the concentration on the keratolytic activity

The keratolytic activity of N-heptanoylhomocys- teine (pH 12,5) at various concentrations by weight was compared. The same comparison was made for a control, calcium thioglycolate, a conventional depilatory. The results (in arbitrary relative values) are given in the table which follows. It is found that the activity of the control levels off above 4 %, which is not the case for the η , derivative II. C e tration Activit %

The activity of a solution containing 3.6 (SH) equiv. % of N-heptanoylhomocysteine was measured at various pH values (control : calcium thioglycolate at the same

It is found that at pH 11 the activity of the compounds of the invention is virtually identical to that of the control at pH 12 - 12.5. The derivatives of the invention therefore allow better protection of the skin to be epilated than the known products. 5. The use of accelerators

The keratolytic effect of 3,1 % solutions of thioglycerol to which various accelerators had been added, including, in some cases (labelled X) , 1 % of N-heptanoyl¬ homocysteine was measured. The results, in terms of comparative activity are given in the table below. In this table, the first line corresponds to the activity of thioglycerol on its own. The second line corresponds to the addition of 1 % of homocysteine only.

Accelerator

Urea (3,1) Urea (3,1) Guanidine (4,8) Guanidine (4,8) Thiourea (3,8) Thiourea (3,8) NaSCN (4,2) NaSCN (4,2)

It is found that the (C₇) derivative II behaves as a very effective depilation accelerator and does so in the presence of other known accelerators. The other derivatives (II) behave in a similar way.

6. Depilatory films

A polymer of formula (III) containing grafted homocysteine groups was prepared by reaction stoichiome- trie amounts (molecular equivalents) of GANTREZ AN -119 polymer (manufactured by GAF Corp.) and of homocysteine thiolactone (free base) in THF. The THF was evaporated, the residue dissolved in ethanol and the desired polymer precipitated by adding ether (yield 85 %) . Aqueous film-forming compositions were prepared containing concentrations by weight of 2 to 10 % of the abovementioned polymer to which 2 to 10 % of polyvinyl alcohol (PVA, MW 100 000) had been added. Variable amounts (from 1 to 4 %) of derivatives (II) (C₇ to C₁₂) ^were also added to some samples. These compositions were used as depilatory in thin layers and it was found that after a drying time of about 15 - 20 minutes it was possible easily to pull off the films thus formed, the hairs to be removed being removed simultaneously with the film.

Analogous results were obtained using composi¬ tions containing a non-keratolytic polymer (for example PVA or polyvinylpyrrolidone) and a concentration of 1 to 4 % derivatives (II) .

7. Depilatory liposomes

7.1 SUV⁺ liposomes (Small Unicellular Vesicles) The following lipids :

- 2,100 mg of hydrogenated lecithin (NC 95H from Nattermann Chemie)

- 880 mg of cholesterol

- 160 mg of stearylamine are added to 50 ml of an aqueous sodium hydroxide solution at pH = 12.5 and the whole is subjected to the action of ultrasonic sound (Branson Sonifier) for 15 minutes at 55° C. 50 ml of a 10 % aqueous solution of N-heptanoylhomocysteine at pH = 12.5 (NaOH) is then added and the mixture is left to incubate for an hour, stirring gently, at 37° C. N-heptanoylhomocysteine then incorporates into the liposome membrane to a large extent by virtue of its heptanoyl chain.

7.2 REV⁺ liposomes (Reverse Evaporation Vesicles)

The following lipids :

- 2,940 mg of hydrogenated lecithin (NC 95H from Nattermann Chemie)

- 1,230 mg of cholesterol - 225 mg of stearylamine are dissolved at 50° C in 210 ml of a chloro- form/diisopropyl ether (v/v : 1/1) mixture.

70 ml of an aqueous sodium hydroxide solution at pH = 12.5 is then added and the whole is subjected to the action of ultrasonic sound (5 x 1 minutes ; Branson sonifier) at 50° C. The organic solvents are then evapora¬ ted at 50° C under reduced pressure in a rotary evaporator. A homogeneous suspension of liposomes is thus obtained which is adjusted to a final volume of 50 ml. 50 ml of 10 % aqueous solution of N-heptanoylhomocysteine at pH = 12.5 (NaOH) are then added and the mixture is left to incubate for one hour, with gentle stirring, at 37° C.

The keratolytic activity of the above SUV⁺ and REV*^" liposomes is then tested in comparison with that of a 5 % by weight solution of derivative (II) (C₇) at pH = 12.5. The results are given below.

Composition Activity

Derivative (II) 5% 100

SUV^4" (II) 99

REV^4" (II) 108

It is seen that the incorporation of the depilatory agent in the liposomes does not reduce their effectiveness but even improves this slightly in one case, which further adds to the value of having a depilatory in the form of liposomes and benefiting from the emollient and softening effect of the latter.

Depilatory compositions Example 8

A depilatory cream was prepared by mixing the following ingredients (parts by weight) at 75° C (mixture A) :

Ingredients Parts by weight

Ethoxylated cetyl alcohol (20 molecules of ethylene oxide) 1 Cetyl alcohol 6 Stearyl alcohol 6 Liquid paraffin oil

(viscosity at 20°C, 70 mPas) 3

Water 48

30% aqueous sodium lauryl sulphate 2.5 In addition, a mixture (mixture B) of the following ingredients was prepared, the ingredients being added in the given sequence :

Ingredients Parts by weight

Water 18.5 Thioglycolic acid

(80% aqueous solution) 3

Ca (OH)₂ 4

30% sodium hydroxide solution 1 Guanidine 2 N-heptanoylhomocysteine 1

CaC0₃ 3

Mixture B was added to mixture A at 45 - 50° C and then, after having cooled to 30° C, one part by weight of perfume (rose essence) was added. After resting, a depilatory cream of high effectiveness, although remarkably soft for the skin, was thus obtained. Example 9

A mixture (the ingredients being indicated by weight) of 7.5 parts of stearyl alcohol, 5.5 parts of cetyl alcohol and 4 parts of ethoxylated cetyl alcohol (contai¬ ning 10 units of ethylene oxide) was incorporated at 75 - 80° C into 68.5 parts of water. The following ingredients were then incorporated , in the sequence given, at 40 - 45° C : 3 parts of - monothioglycerol, 3 parts of N-heptanoylhomocysteine, 5 parts of Ca(0H)₂ and 3 parts of urea. Then, after having brought the temperature to 30° C, 0.5 part of perfume (orange flower) was also added. This perfectly homogenized mixture provided a particularly effective epilatory cream, the odour (sulphur-containing products) of which was not very pronounced compared with the products of the prior art. Example 10

25 parts by weight of ethoxylated (by 50 units of ethylene oxide) cetyl alcohol were dissolved at 45°- 50° C in 40 parts of water, and 5 parts of mercaptopropio- nic acid and 3 parts of N-heptanoylhomocysteine were then added, with stirring. The pH was then adjusted to between 10.5 and 12.5 using a (50 %) aqueous KOH solution and, at 30° C, 1.5 parts of perfume (floral note) and a dose of biocompatible pink colourant were added and the mixture was made up to 100 parts with water.

A depilatory composition was thus obtained which was in form of a gel having thixotropic properties during its application to the skin to be epilated. After a few minutes¹ application (3 to 5 minutes) , the depilatory effect being obtained, the gel was removed by simple washing with water. Example 11 2 parts by weight of hydroxyethylcellulose (NATROSOL 250 HHR from Hercules Co.) were intimately mixed at ambient temperature into 60 parts by weight of water and the following were added (all in parts by weight) : 5 of sorbitol, 10 of potassium thioglycolate (30 % aqueous solution) and 1 part of N-octanoylhomocysteine. The pH was then adjusted to 12 - 12.5 using a

30 % sodium hydroxide solution to which 0.25 part of a soluble perfume (mint) had been added, and the mixture was made up to 100 parts with an aqueous solution of bioaccep- table colourant. Spread on the skin, the above composition formed a stable hydrophilic gel having improved depilatory properties and a weak sulfur odour and capable of being rinsed off easily with water after use.

Example 12

An active concentrate for aerosols was prepared by intimatly mixing the following ingredients :

Ingredients Parts by weight

Water 60

Sodium polyethoxy-lauryl sulphate (containing 2.5 molecules of ethylen oxide) 5

Na metasilicate pentahydrate 2

K thioglycolate (30% aqueous solution) 8 Na₂S.H₂0 1 N-heptanoylhomocysteine 1

30% aqueous NaOH to give pH 11 - pH 12.5

0.8 parts of a perfume (rose fragrance) was then added and the mixture was then made up with water to give 100 parts by weight. 80 parts of the above concentrate and 20 parts of propellant gas (Freon 12-114) were introduced into an aerosol container.

On actuating the valve of the spray container, a depilatory foam which is highly effective although gentle to sensitive skin, was projected onto the skin.

Example 13

6 parts by weight of white petroelum jelly (m.p

- 50° C) , 3 parts of stearyl alcohol and 3 parts of ethoxylated cetyl alcohol (containing 20 ethylene oxide units) were intimately dispersed in 60 parts by weight of water at 75° C.

After having cooled to 40 - 45° C, 4 parts by weight of monothioglycerol, 2 parts of N-octanoylhomocys- teine and 1.5 part of Ca(OH) were added. The pH was then rendered alkaline to pH 12 - 12.5 using a 30 % sodium hydroxide solution, 0.5 part of perfume was also added and the mixture was made up to 100 parts by weight with water.

The above active concentrate was then packed in an aerosol container in a proportion of 92 g of concentrate per 8 g of butane under 3.2 bars. This formulations also provided a depilatory foam which was effective although gentle to the skin.

Compositions for treatment of the hair Example 14

A composition for permanent waving was prepared by intimately mixing 60 parts by weight of water, 5 parts of ammonium thioglycolate (60 % solution of thioglycolic acid neutralized with ammonia) , 2 parts by weight of 28 % aqueous solution of ammonium lauryl sulphate and 2 parts by weight of N-heptanoylhomocysteine and then adjusting the pH to 8.5 - 9.5 using 28 % aqueous NH₄0H.

While stirring vigorously, a solution of 0.5 part by weight of perfume in ethoxylated nonylphenol (containing 15 molecules of ethylene oxide) was then added and the mixture was made up to 100 parts with water.

This composition was succesfully used for waving hair using the techniques customary in hairdressing salons.

Example 15

A gel for permanent waving was prepared in the following way (parts by weight) : 0.5 part of carboxyme- thylcellulose (CMC-7M from Hercules and Co.) was dispersed in 60 parts of water and, at 75° C, a mixture, brought to 75° C, comprising 1 part of liquid paraffin oil (viscosity at 20° C, 70 mPa s) , 0.2 part of cetyl alcohol and 5 parts of ethoxylated (by 10 molecules of ethylene oxide) cetyl alcohol was added to this dispersion, with stirring.

The mixture was then cooled to 45 - 50° C and 4 parts of a α - monothioglycerol and 4 parts of N-decanoyl- homocysteine were added thereto and the pH was adjusted to 8.5 - 9.5 by adding monoethanolamine. The composition was then made up with 0.5 part of a perfume product and with water to give a total of 100 parts by weight. A composition for permanent waving was thus obtained which is effective and releases only a slight odour during its use in a hairdressing salon.

Claims

1. The use of N-acyl-derivatives of homocys¬ teine of formula

HS-(CH₂)₂-CH-COOH (II)

NHR where R is substituted or unsubstituted, saturated or unsaturated, straight-chain or branched CO-alkyl radical of more than 4 carbon atoms, for lasting modification of keratinous materials, in particular as agents for waving hair or as depilatory agents.

2. The use as claimed in claim 1, wherein the alkyl portion of the group R comprises at most 24 carbon atoms.

3. The use as claimed in claim 1 or 2, wherein the alkyl portion of R is a recurring substituted poly- methylene member in a moiety forming the framework of a polymer in which the substituents are, at least in part, homocysteine radicals.

4. The use as claimed in claim 2, wherein the compound (II) is in solution or in suspension in aqueous phase.

5. The use as claimed in claim 4, wherein the aqueous phase comprises, in emulsion or dispersion, a lipophilic phase with which the compound (II) is combined.

6. Ths use as claimed in claim 5, wherein the lipophilic phase consists of a dispersion of liposomes.

7. The use as claimed in claim 4, 5 or 6, wherein the aqueous phase contains, in addition, a polymer which forms a flexible film on the skin during application, which film is then pulled from the area to be epilated.

8. The use as claimed in any one of claims 2, and 4 to 7, wherein R denotes a hexanoyl, heptanoyl, octanoyl, decanoyl, dodecanoyl or palmitoyl group.

9. The use as claimed in claim 4, 5 or 6, wherein the aqueous phase also contains a depilation accelerator chosen from urea, guanidine, thiourea and thiocyanate.

10. An aqueous composition having a keratolytic action and intended lastingly to modify the shape of the hair or to produce a depilatory effect which is non- irritant for the skin, which composiiton contains, as keratolytic organic compound, at least one N-acyl derivati¬ ve of homocysteine of formula

HS-(CH₂)₂-CH-COOH (II)

NHR where R is saturated or unsaturated, straight-chain or branched, aliphatic acyl group compirsing more than 4 carbon atoms.

11. The composition as claimed in claim 10, wherein the hydrocarbon portion of the radical R is either an independent alkyl group comprising at most 24 carbon atoms or recurring alkylene unit, the repetition of which constitutes a polymer chain.

12. The composition as claimed in claim 10 or 11, intended to produce a depilatory effect, which composition also contains one more organic and/or inorganic keratolytic agents chosen from thioglycolic acid, thiolac- tic acid, thiopropionic acid, aminothioethanol, thioglycol, thioglycerol, β -mercaptopropionic acid, N-(hydroxyethyl) - mercaptoacetamide, N-methyl mercaptoacetamide, β -mercaptoethylamine (cysteamine) , mercaptopropionamide, 2-mercaptoethanesulfonic acid, dimercaptoadipic acid, dithiothreitol, homocysteine thiolactone and lithium, sodium, potassium, caesium, magnesium, calcium, strontium and barium sulfides, and other similar substances. 13. The composition as claimed in claim 12 or

13, which contains one or more film-forming components, so as to form, by application to the area to be epilated, a film which, once dry, pulls away easily, bringing away the hair to be removed.

14. The composition as claimed in claim 12, which contains, in addition, epilation accelerators chosen from urea, guanidine, thiourea and thiocyanate.

15. The N-acyl derivatives of homocysteine as well as their salts characterized in that they correspond to the general formula

HS-(CH₂)₂-CH-COOH (II) NHR in which R represents an aliphatic acyl group containing from 5 to 24 carbon atoms.

16. The N-acyl derivatives of homocysteine as well as their salts, as defined in claim 15, characterized in that R represents an aliphatic acyl group containing from 6 to 10 carbon atoms.

17. Any one of the derivatives corresponding to the general formula II of which the names follow :

- N-heptanoyl homocysteine

- N-octanoyl homocysteine

- N-decanoyl homocysteine

- N-dodecanoyl homocysteine - N-palmitoyl homocysteine

18. A use, composition or derivative substan¬ tially as described herein, with reference to the examples.