EUTECTIC MIXTURES IN COSMETIC COMPOSITIONS

Abstract: The present invention relates to a liquid, substantially anhydrous eutectic mixture comprising a principal acid component, such as a hydroxy acid, and at least one other component selected from the group consisting of a carbohydrate, a polyol, an amino acid, and a carboxylic acid. The mixtures remain liquid at room temperature, are relatively non-irritating, and can be used to deliver higher levels of the principal acid than would ordinarily be possible. The invention also provides a method of making such a mixture comprising heating the component having the lowest melting point to the temperature at which it melts, dissolving the remaining component or components in the melted component, and allowing the mixture to cool.

Description: EUT TIC MIXTURES IN COSMETIC COMPOSITIONS Field of the Inventio n The invention relates to cosmetic compositions. More I specifically, tne invention relates to cosmetic compositions containing relatively high levels of active components that cause suostantially no irritation to the skin. Background of the Invention 10 The presence of biologically active ingredients m cosmetics has become commonplace today. Such materials provide the consumer with considerable benefits, such as exfoliation, lightening of ahnormal pigmentation, lipid barrier repair, and the like, in addition to the more traditional benefits of moisturizing. With the l c biological benefits, however, sometimes comes the problem of irritation. While most potential users can readily appreciate the advantages of tnese materials with no problem, certain active ingredients can cause discomfort to individuals with particularly sensitive skin, thereby depriving that segment of the population of 20 the benefits of these products. One of the most common groups of compounds to which a certain segment of the population reacts is acids, particularly hydroxy acids, or retmoic acid, which have provided enormous benefits to those who are not sensitive to them. These compounds are highly 25 effective keratolytic agents, that effectively bring about exfoliation of dead keratmocytes , reducing the appearance of fine lines and wrinkles, and conferring a smooth, glowing look to the facial skin. However, because of the possibility of irritation, particularly at higher concentrations, these compounds have not 0 reached their full potential m cosmetic compositions, generally having to be used at lower levels than would oe optimum for activity. Thus, there continues to be a need for formulations that will permit the exploitation of these compounds to their fullest potential. The present invention fulfills such a need. 5 Summary of the Invention The present invention relates to eutectic mixtures of a principal acid component and at least one other component selected from the group consisting of a carbohydrate, a polyol, a carbonylic 0 compound, an ammo acid, and a carboxylic acid. The mixtures of the invention are used m anhydrous cosmetic compositions that, when applied to the skin, slowly release the acid in the presence of the , substantially without any irritation. The invention also relates to a method for preparing a eutectic mixture of an acid component and at least one other component selecteα from the group consisting of a carbohydrate, a polyol, a carbonylic compound, an a ino acid, or a carboxylic acid, the method comprising heating the component having tne lowest melting point to the temperature at whicn it melts, dissolving the remaining component or components m the melted component, and allowing the mixture to cool. While the components of the mixtures are solid before combination, when heated and dissolved as described, they remain as a homogeneous liquid when returned to room temperature. Detailed Description of the Invention The mixtures of the invention provide a non-irritatmg base for delivery of potentially irritating acids. The mixtures are non- aqueous, so that the acidic character of the acid component, whicn is only realized in an aqueous environment, is not present m the mixture. In essence, the acid component cannot ionize, so remains undissociated m the mixture, until the mixture is exposed to tne moisture of the skin, at which time it is slowly converted to the acid form and released to the skin to provide the benefits achieved by such acids. The mixtures of the invention are referred to as "eutectic mixtures" which for purposes of the present application and claims means an equilibrium phase between two or more components, which equilibrium phase, or mixture, does not have any of the physical characteristics of the individual components. Eutectic mixtures are known in various chemical areas are known, but are ordinarily difficult to create, and to the best of the inventors' knowledge, have not previously been used in cosmetics or pharmaceuticals . It has now been unexpectedly discovered that it is possible to create such cosmetically and pharmaceutically acceptable eutectic mixtures with biologically active acid components, when they are combined with specified other components under certain conditions. In the present case, the components of the mixture are all solid at room temperature prior to creation of the mixture, but after melting and dissolution of the components, an anhydrous solution results which remains liquid at room temperature without crystallization of the individual components. This is all achieved, in most cases, m the absence of any additional solvent that dissolves both compounds. To be successfully combined, the individual components must be compati e, i.e., eac compoun must orm an mtermo ecu ar interaction with the other, so that this interaction will counteract tne usual forces that tend to arrange the individual components into their individual crystalline forms. This result is only obtainable, however, when the components are mixed on the molecular level. In the present mixtures, while not wishing to be bound by any particular theory, it is believed that a complex forms between the two or more components, due to hydrogen bonds, or Van der Waals interactions, between the solutes, interfering with each compound's ability to recrystallize, i.e., to return to the solid state, thereby resulting m a liquid mixture of two normally solid compounds at room temperature. Since this is preferably achieved m the absence of the usual solvent, i.e., water, or at least after the removal of water from the mixture, the mixture is substantially anhydrous, and therefore does not produce the lonization conditions needed to release ri ions . It will be recognized that tne term "acid" in the present specification and claims is used, for convenience, to refer to both the non-ionized, substantially inert structural acid m the initial mixture, as well as the active, dissociated molecule that exists when the mixture contacts moisture on the skin. The acid that constitutes the principal acid component (referred to as "principal" to distinguish it from the second component which m some cases may also be an acid) of the mixture can be any pharmaceutically or cosmetically acceptable acid, and is preferably one that exhibits some type of biological activity on the skin. Examples of useful acids for the present purpose include, but are not limited to, alpha hydroxy acids, such as glycolic acid, lactic acid, citric acid, malic acid, tartronic acid, tartaπc acid, beta hydroxy acids, such as salicylic acid, and retmoic acid. The second component which forms part of the mixture is a component selected from the group consisting of a carbohydrate, a polyol, a carbonylic compound, an ammo acid, and a carboxylic acid. Compounds from each of these groups have been shown to form the desired type of mixture with acids, and while not wishing to be bound by any particular theory, it is believed that, while chemically diverse, compounds these groups all have the ability to form mtermolecular hydrogen bonds, which provide a solvent-type environment conducive to retaining the liquid state of the mixture upon cooling. Examples of useful carbohydrates include, but are not limited to, monosacchaπdes , such as glucose, galactose and fructose; disacchaπdes , such as saccharose, lactose, maltose, and trehalose; an po ysacc ari es , suc as ow mo ecu ar weig ex rms, so u e starch, amyiopectm a^d amylose . Preferably, the polysaccharides are selected from those nav g no more than twenty carbohydrate units. Polyols, such as sorcitol, 1-thιosorbιtol , ositol, mannitol, ana = polyvmyl alcohol, can also be employed. The second component can also be a caroonylic compound, for example, ketones or aldehydes, such as dihydroxyacetone or erytnrulose, or any ammo acid (natural or synthetic), for examole, glycme, alanme, valme, norval e, leucine, norleucme, aspartic acid, glutamic aci, asparag e, ±C glutamme, argmme, lysme, serme, threonme, prolme, tyros e, cyste e, cystine, methionme, phenylalanme, histid e, tryptophan, dihydroxyphenylalan e, and methionme, as well as a small peptide, such as a reduced glutathione. The second component can be another acid component such as a carboxylic acid. Examples of carboxylic i: acids include the alona and beta hydroxy acids noted above, as well as oxalic, malonic, succmic or ercaptosuccmic, or glutaπc acid The mixtures are prepared relatively simply. Tne chosen component having the lowest melting point is heated, with conventional systems or microwaves, to that temperature. When the 20 first component is liquified, the second component (s) can be mixed m and dissolved the melted first component. It will be understood that the combining of the components can take place before the melting of the first component, and the second component simply blended when the first component is liquefied, or the second 25 component can be added to the first after the first has been melted. Once the components are dissolved, the resulting mixture is transparent and homogeneous; upon cooling, the mixture retains its liquid nature and transparent, homogeneous appearance. The mixtures will only solidify, without crystallizing, at very low temperatures, 30 e.g., below 0°C, at which point they form transparent solid glasses. The solidification and melting process can be repeated indefinitely. The foregoing method can be applied to all combinations m which the components are thermostable, i.e. stable at the lowest melting point of a component. In a case m which one or more 5 components are not heat-stable, it is possible to conduct the heating step in the presence of an auxiliary solvent, such as water, or any other solvent with a suitably low boiling point. The solutes are dissolved the solvent, then the solvent removed by evaporation at reduced pressure, leaving a liquid phase containing only solutes. 0 For a successful creation of a eutectic mixture, certain ranges of the components must be employed. As a general rule, the principal acid component will be used in an amount between about 40 to about y weig t o t e mixture, more pre era y etween a out o about 90% . The actual amount of principal acid used will depend upon the identity of the second component. As a general rule, the amount of principle acid employed will be at the lower end of this range when the second component is one having functional groups capable of forming large numbers of hydrogen bonds, for example, for example, mono- and disaccharides . In contrast, the amount of principle acid used will increase as the molecular weight of the second component increases, for example, with soluble starch or polyvmyl alcohol. It will be recognized that more than one of each type of component can be used in the mixture. A particularly preferred combination is a mixture containing at least one hydroxy acid, preferably an alpha hydroxy acid, and a carbohydrate. A preferred carbohydrate such a combination is a disaccharide, most preferably the disaccharide trehaiose. The latter is a particularly preferred choice because of its own peneficial effects on the skin, particularly its weil-establisheα ability to protect biological structures. Mixtures of this type can be used in exfoliation of the skin, reduction of the appearance of lines and wrinkles, and any other therapeutic purpose for which these acids are ordinarily used. The advantage of these mixtures is that much higher levels of acid, for example as high as 85-90%, can be used, thereby increasing their efficacy, while still remaining substantially non-irritating or at least significantly less irritating than a comparable mixture containing water. In fact, mixtures of this type, containing no water, or even an amount of water less than about 5%, does not have a measurable pH, showing the low level of acidity. However, once on the skin, over a period of time, the mixture will effectively achieve the desired exfoliation or other beneficial effect with little or no adverse effect. The mixtures of the present invention can be used directly on the skm, but more frequently will be employed in a pharmaceutically or cosmetically acceptable carrier. The form may be a cream, lotion, gel, mousse, or the like. Preferably, the formulation contains substantially no water, and in any case, should contain no more than 5% water. The mixture can simply be added to the carrier in an amount sufficient to give the desired concentration of acid in the final formula. Because of the relative safety of the mixtures, however, the range of concentration of the acid can be much higher than in an ordinary acid-in-water-containing formulation; therefore, the amount of acid in the final formulation may be as high as about 70% by weight, and as low as about 0.01%. The actual amounts used the final formulation will depend upon the intended end use, for example, higher levels of acio will be used to accomplish a chemical peel, whereas lower levels can oe used to achieve gentle exfoliation and wrinkle reduction. Because the irritation level of these compositions is so low, nowever, it is possible to use the acid at a higher level than would normally be used for its intended purpose, and at the same time reduce the frequency of application. For example a composition containing a 70:30 glycolic acid : trehalose mixture can be applied to achieve exfoliation, substantially without causing any erythema. The mixtures of the invention can also be combined with other actives, and in fact certain actives may be enhanced by their combination within the mixture per se . Examples of actives that may oenefit by combination with or within the mixture are self-tanning agents such as DHA or lmidazole or erythrulose, or whitening agents/tyrosmase inhibitors, such as ko]ic acid, licorice extract and components thereof, or arbutm, or resveratrol and its derivatives . The invention will oe further illustrated by the following non- limiting examples. EXAMPLES Example 1 This example illustrates the preparation of a glycolic acid/carbohydrate solution. Solutions of glycolic acid and mono-or polysaccharides are prepared, using different concentrations of components, by melting the glycolic acid component at 85°C using conventional heating metnods . In the liquid glycolic acid, the selected carbohydrate is dissolved. The liquid solution is cooled to room temperature and its chemical and physical characteristics are analyzed. The results are as follows: (a) glycolic acid/glucose: Solutions are prepared containing from 50% to 70% by weight of glycolic acid. At concentrations of glycolic acid over 70%, metastable solutions that tend to crystallize are obtained; below 50%, an amorphous solid is obtained. For the stable solutions, the viscosity decreases as the concentration of the acid increases. At 25°C, the viscosity of the 60% solution is over 8000 cps . (b) glycolic acid/trehalose : Solutions are prepared containing from o y weig o g yco c ac . concen ra ions over acid, a metastable solution that tends to crystallize is formed and below 50%, an amorphous solid is obtained. The viscosities of the stable solutions are as follows: 50%, >8000 cps; 60%, 8000 cps; 70%, 6000 cps. (c) glycolic acid/starch: Solutions are prepared containing from 75 to 90% by weight of glycolic acid. In excess of 90%, a metastable solution that tends to crystallize is obtained, and below 75%, an amorphous solid is obtained. Viscosities of stable solutions are as follows: 75%, 6800 cps; 80%, 3450 cps; 90%, 1,200 cps. Example 2 This example illustrates solutions made with glycolic acid and polyols . The solutions are prepared as described m Example 1. The results are as follows: (a) glycolic acid/sorbitol : Concentrations of glycolic acid ranging from 40 to 90% are used. In excess of 90%, a metastable solution that tends to crystallize is obtained, and below 75%, an amorphous solid is obtained. Viscosities of stable solutions are as follows: 50%, >8000 cps; 70%, 2000 cps; 85%, 1500 cps; 90%, 800 cps. (b) glycolic acid/polyvmyl alcohol: Concentrations of between 90-95% by weight of glycolic acid are used, m combination with either 25 or 75 KDa polyvinyl alcohol. Viscous stable solutions result at these concentrations. Over 95% acid, a metastable solution that tends to crystallize is obtained, and below 90%, an amorphous solid is obtained. The viscosity of the solutions decreases as the concentration and molecular weight of the polyvinyl alcohol decreases . Example 3 This example illustrates the preparation of glycolic acid/hydroxyacid solutions. The solutions are prepared as described in Example 1. The results are as follows: (a) glycolic acid/tartaric acid: Solutions are prepared containing from 50 to 90% by weight of glycolic acid. At concentrations over 90% acid, a metastable solution that tends to crystallize is formed and below 50%, an amorphous solid is obtained. The viscosities of the stable solutions are as follows: 60%, >8000 cps; 70%, 6500 cps; 80%, 3000 cps , 90 % , 1 , 100 cps . (b) glycolic acid/citric acid: Solutions are prepared containing from 40 to 90^ oy weight of givcolic acid. At concentrations over 90% ς acid, a metastable solution that tends to crystallize is formed and below 40%, an amorphous solid is obtained. The viscosities of the stable solutions are as follows: 50%, >8000 cps; 70%, 4100 cps; 80^, 2000 cps; 90%, 850cps. 0 Example 4 This example illustrates the preparation of glycolic acid/carboxylic acid solutions. The solutions are prepared as described Example 1. Tne results are as follows: 5 (a) glycolic acιd/2-mercaptosuccmιc acid: Solutions are prepared containing from 80 to 95% oy weight of glycolic acid. At concentrations over 95% acid, a metastable solution that tends to crystallize is formed ano below 80%, an amorphous solid is obtained. Ir the stability range, the viscosity is about 600 cps. 0 Example 5 This example illustrates the preparation of glycolic acid/ammo acid solutions. The solutions are prepared as described m Example 1. The results are as follows: 5 Solutions of 80% glycolic acid and various L-amino acids are prepared. The viscosities of the stable solutions depend upon the identity of the ammo acio: glycme, 6000 cps; alanine, 5800 cps; valme, 5500 cps; methionme, 1700 cps; glutamic acid, 300 cps; 0 arginme, 8700 cps; asparagme, 1200 cps. Example 6 This example illustrates the preparation of solutions containing glycolic acid and DHA. DHA has a melting point of about 80°C. The solutions are prepared as described m Example 1. The chemical and physical properties are then analyzed. The results are as follows: the viscosity at 25°C of DHA/glycolic acid (10:90) is 1150 cps.

Claims: What we claim is : 1. A liquid, substantιa__y anhydrous eutectic mixture comprising a principal acid component and at least one other component selected from the group consisting of a caroohydrate, a polyol, a carbonylic compound, an ammo acio, and a carboxylic acid. 2. The mixture of ciair 1 m which the principal acid is selected from the group consisting of an alpha hydroxy acid, a beta hydroxy acid, and ret oic acid. 3. The mixture of claim _ wh ^ ch the other component comprises a carbohydrate . 4. The mixture of claim 3 which the carbohydrate is selected from the group consisting of monosacchandes , disacchaπdes, and polysaccharides . 5. The mixture of claim 1 which comprises an alpha hydroxy acid as the principal acid, and a carbohydrate as the second component. 6. The mixture of claim 5 m which the hydroxy acid is glycolic acid and the carbohydrate is a disaccharide. 7. The mixture of claim 6 m which the disaccharide is trehalose. 8. The mixture of claim 1 which comprises from about 40 to about 95% by weight of the principal acid component. 9. The mixture of claim 5 which comprises from about 50 to about 90% of a principal acio component. 10. The mixture of claim 6 which comprises from about 50 to about 70% of a principal acid component. 11. A cosmetic or pharmaceutical composition comprising the mixture of claim 1 and a cosmetically or pnarmaceutically acceptable carrier. 12. A cosmetic or pharmaceutical composition comprising the mixture of claim 5 and a cosmetically or pharmaceutically acceptable carrier. 13. A cosmetic or pharmaceutical composition comprising the mixture of claim 6 and a cosmetically or pharmaceutically acceptable carrier. 14. A cosmetic or pharmaceutical composition comprising the mixture of claim 9 and a cosmetically or pharmaceutically acceptable carrier. 15. A cosmetic or pharmaceutical composition comprising tne mixture of claim 10 and a cosmetically or pharmaceutically acceptable carrier . 16. A method for making a liquid, substantially anhydrous eutectic mixture containing a principal acid component and at least one other component selected from the group consisting of a carbohydrate, a polyol, an ammo acid, and a carboxylic acid, the method comprising heating the component having the lowest melting point to the temperature at which it melts, dissolving the remaining component or components the melted component, and allowing the mixture to cool. 17. The method of claim 16 m which the principal acia component is an alpha hydroxy acid and the other component is a caroohydrate . 18. The method of claim 17 m which the principal acid component is employed in an amount of about 40% to about 95% by weight of the mixture . 19. The method of claim 17 m which the carbohydrate is a monosaccharide, disaccharide, or polysaccharide, and the principal acid component is employed m an amount of from about 50% to about 90% by weight of the mixture. 20. The method of claim 19 in which the carbohydrate is a monosaccharide or disaccharide, and the principal acid component is employed m an amount of from about 50% to about 70% by weight of the mixture . 21. The method of claim 19 m which the principal acid component is glycolic acid and the carbohydrate is trehalose. 22. A eutectic mixture prepared according to the method of claim 16. 23. A eutectic mixture prepared according to the method of claim 17 24. A eutectic mixture prepared according to the method of claim 18 25. A eutectic mixture prepared according to the method of claim 19. 26. A eutectic mixture prepared according to the method of claim 20. 27. A eutectic mixture prepared according to the method of claim 21. 28. A cosmetic composition comprising the mixture of claim 22. 29. A cosmetic composition comprising the mixture of claim 23. 30. A cosmetic composition comprising the mixture of claim 24. 31. A cosmetic composition comprising the mixture of claim 25. 32. A cosmetic composition comprising the mixture of claim 26. 33. A cosmetic composition comprising the mixture of claim 27. A. CLASSIFICATION OF SUBJECT MATTER IPC 7 A61K7/48 A61K47/12 A61K47/26 According to International Patent Classification (IPC) or to both national classification and IPC B. FIELDS SEARCHED Minimum documentation searched (classification system followed by classification symbols) IPC 7 A61K Documentation searched other than minimum documentation to the extent that such documents are included in the fields searched Electronic data base consulted during the international search (name of data base and, where practical, search terms used) WPI Data , PAJ , EPO-Internal , CHEM ABS Data , MEDLINE , EMBASE C. DOCUMENTS CONSIDERED TO BE RELEVANT Category ° Citation of document, with indication where appropriate of the relevant passages Relevant to claim No WO 99 26617 A (YAMANOUCHI EUROPE ) 1-33 3 June 1999 ( 1999-06-03 ) the whol e document A , P WO 00 33877 A (JOHNSON AND JOHNSON 1-33 CONSUMER COMPANIES ) 15 June 2000 (2000-06-15 ) the whol e document W0 00 15202 A ( IPR ) 1-33 23 March 2000 (2000-03-23 ) the whol e document W0 00 15179 A ( UNILEVER ) 1-33 23 March 2000 (2000-03-23 ) the whol e document -/- Further documents are listed in the continuation of box C Patent family members are listed in annex ' Special categories of cited documents "T" later document published after the international filing date or pnonty date and not in conflict with the application but 'A' document defining the general state of the art which is not cited to understand the principle or theory underlying the considered to be of particular relevance invention Ε" earlier document but published on or after the international "X" document of particular relevance the claimed invention filing date cannot be considered novel or cannot be considered to 'L' document which may throw doubts on pnonty claιm(s) or involve an inventive step when the document is taken alone which is cited to establish the publication date of another "Y" document of particular relevance, the claimed invention citation or other special reason (as specified) cannot be considered to involve an inventive step when the '0' document referring to an oral disclosure, use, exhibition or document is combined with one or more other such docuother means ments, such combination being obvious to a person skilled 'P* document published prior to the international filing date but in the art later than the priority date claimed '&' document member of the same patent family Date of the actual completion of the international search Date of mailing of the international search report 28 September 2001 09/10/2001 Name and mailing address of the ISA Authorized officer European Patent Office, P B 5818 Patentlaan 2 NL - 2280 HV Rijswηk Tel (+31-70) 3 4 0-20 4 0, Tx 31 651 epo nl, Fax (+31-70) 3*40-3016 Fi scher , J . P . Form PCT/ISA/210 (second sheet) (July 1992) page 1 of 2 C.(Contmuation) DOCUMENTS CONSIDERED TO BE RELEVANT Category ° Citation of document, with indication.where appropriate, of the relevant passages Relevant to claim No EP 0 747 061 A (II. R. A.) 1-33 11 December 1996 (1996-12-11) the whol e document Form PCT/ISA/210 (continuation of second sheet) (July 1992) page 2 of 2 mation on patent ami y mem ers PCT/uS 01/05296 Patent document Publication Patent family Publication cited in search report date member(s) date WO 9926617 A 03-06-1999 AU 1965999 A 15-06-1999 BG 104470 A 30-03-2001 BR 9815016 A 03-10-2000 CN 1280495 T 17-01-2001 O 9926617 Al 03-06-1999 EP 1032378 Al 06-09-2000 HU 0100066 A2 28-08-2001 NO 20002649 A 24-07-2000 PL 340679 Al 12-02-2001 WO 0033877 A 15-06-2000 US 6238683 Bl 29-05-2001 AU 1841200 A 26-06-2000 BR 9907666 A 19-12-2000 CN 1292707 T 25-04-2001 EP 1051193 Al 15-11-2000 WO 0033877 Al 15-06-2000 W0 0015202 A 23-03-2000 AU 5404399 A 03-04-2000 O 0015202 A2 23-03-2000 WO 0015179 A 23-03-2000 US 6022896 A 08-02-2000 AU 2836499 A 11-10-1999 AU 4259799 A 03-04-2000 BR 9913589 A 05-06-2001 CN 1293566 T 02-05-2001 WO 9947110 Al 23-09-1999 O 0015179 A2 23-03-2000 EP 1061896 Al 27-12-2000 EP 1109527 A2 27-06-2001 EP 747061 A 11-12-1996 IT MI951224 Al 09-12-1996 EP 0747061 A2 11-12-1996 US 5733559 A 31-03-1998 Form PCT/ISA/210 (palent family annex) (July 1992)

Inventors: DEROSA MARIO, ROSSI MOSE, DEROSA, MARIO, ROSSI, MOSE
Applicants: E L MANAGEMENT CORP, E-L MANAGEMENT CORPORATION
Application year: 2001
Main classification: A61K7
IPC codes: A61K8, A61K9, A61K47, A61Q19