VITAMIN C DELIVERY SYSTEM

Abstract: A cosmetic composition is provided which includes ascorbic acid (Vitamin C) stabilized by dimethyl isosorbide in a pharmaceutically acceptable carrier. Among the preferred carriers are polyols such as polyethylene glycol, propylene glycol and mixtures thereof. Aesthetic properties are improved by the presence of a cross-linked non-emulsifying siloxane elastomer and a volatile siloxane.

Description: VITAMIN C DELIVERY SYSTEM BACKGROUND OF THE INVENTION Field of the invention The invention relates to a cosmetic product that can stably store ascorbic acid and then deliver same to the skin. The Related Art Ascorbic acid, also known by its common name of Vitamin C, has long been recognized as an active substance benefiting skin appearance. Vitamin C reportedly increases the production of collagen in human skin tissue. Wrinkles and fine lines are thereby reduced. An overall healthier and younger-looking appearance results. Vitamin C has also found utility as an ultraviolet ray blocking or absorbing agent. Whitening or bleaching skin compositions have also employed Vitamin C utilizing its property of interference with the melanin formation process. There also is a belief that ascorbic acid interacts with the human immune system to reduce sensitivity to skin aggravating chemicals. Reduced levels of Vitamin C concentration on the skin have also been implicated with an increase in stress. From all of the foregoing perspectives, Vitamin C or ascorbic acid may provide significant benefit when topically applied. Unfortunately, Vitamin C is a very unstable substance. Although it is readily soluble in water, rapid oxidation occurs in aqueous media. Solubility of ascorbic acid has been reported to be relatively poor in nonaqueous media, thereby preventing an anhydrous system from achieving any significant level of active concentration. The art has sought to overcome the problem in a variety of ways. One approach is the preparation of ascorbic acid derivatives. These derivatives have greater stability than the parent compound and, through biotransformation or chemical hydrolysis, can at the point of use be converted to the parent acid. For instance, U.S. Patent 5,137,723 (Yamamoto et al) and U.S. Patent 5,078,989 {Ando et al) provide glycosylate and ester derivatives, respectively. U.S. Patent 4,818,521 (Tamabuchi) describes under the background technology a so-called two-pack type cosmetic wherein Vitamin C powder and other ingredients are separately packaged in different containers with mixing just prior to use of the cosmetic. The mixing procedure and expensive packaging were said to be drawbacks of this system. The patent suggests stable oil-in-water type emulsions that are weakly acidic and wherein ascorbic acid has been premixed with a stabilizing oil. Maintenance of pH below about 3.5 has also been suggested in U.S. Patent 5,140,043 (Darr et al) as a stabilization means for aqueous compositions of ascorbic acid. Water compatible alcohols such as propylene glycol, polypropylene glycol and glycerol have been suggested as co-carriers alongside water to improve stability. An illustration of this approach can be found in U.S. Patent 4,983,382 (Wilmott and Znaiden) . Therein a blend of water and water-miscible organic solvent are combined as a stabilizing system. At least about 40% of the organic solvent must be ethanol while the remainder may be selected from such alcohols as propylene glycol, glycerin, dipropylene glycol and polypropylene glycol . Japanese Patent 44-22312 (Shionogi) describes the stabilization of Vitamin C in a mainly aqueous medium by a variety of glycols. These include polyethylene glycol, ethylene glycol, diethylene glycol and even ethanol. These formulations are intended for mgestion U.S. Patent 4,372,874 (Modrovich) has reported incorporation of relatively large amounts of ascorbic acid in a polar water-miscible organic solvent such as dimethyl sulfoxide. Levels of water are kept below 0.5% through addition of a particulate desiccant to the carrier. Although highly polar systems such as dimethyl sulfoxide may be effective, this and related carriers are toxicologically questionable. Accordingly, it is an object of the present invention to provide a delivery system for ascorbic acid in which the compound is storage stable. Another object of the present invention is to provide a delivery system which assists the penetration of ascorbic acid into the human skin while avoiding irritation thereof. Still another object of the present invention is to provide a system for delivering ascorbic ac d that is aesthetically pleasing and imparts a soft and smooth skmfeel. These and other objects of the present invention will become more readily apparent through the following summary, detailed discussion and Examples. SUMMARY OF THE INVENTION A cosmetic composition is provided that includes: (1) from 0.001 to 50% by weight of ascorbic acid; (ii) from 0.5 to 20% by weight of dimethyl isosorbide; and (m) a pharmaceutically acceptable carrier present in an effective amount to deliver the ascorbic acid to skin. A method is also provided for stabilizing ascorbic acid involving adding dimethyl isosorbide in a stabilizing amount to the ascorbic acid in the presence of a pharmaceutically acceptable carrier. DETAILED DESCRIPTION OF THE INVENTION Now it has been discovered that ascorbic acid can be stabilized against decomposition through use of dimethyl isosorbide m a pharmaceutically acceptable carrier. Dimethyl isosorbide is known in Chemi cal Abstracts as 1,4:3,6 dιanhydro-2 , 5-dι-o-methyl-D-glucιtol . Commercially it is available from ICI Surfactants under the trademark Arlasolve DMI . Amounts of this material may range from 0.5 to 20%, preferably from 1 to 10%, optimally from 1.5 to 8% by weight . Ascorbic acid s available from several sources including Roche Chemicals. Amounts of this material may range from 0.001 to 50%, preferably from 0.1 to 10%, optimally from 1 to 10% by weight. Compositions of this invention will require a pharmaceutically acceptable carrier. Generally the carrier will be an ingredient present in highest amounts in the cosmetic composition. These amounts may range from 10 to 99.9%, preferably from 25 to 90%, optimally from 50 to 85% by weight. Pharmaceutically acceptable carriers may be selected from water, polyols, silicone fluids, esters and mixtures thereof. When present, water may range from 0.5 to 20%, preferably from 1 to 10%, usually from 2 to 6%, optimally less than 5% by weight of the composition. Advantageously one or more polyols are present as carriers in the compositions of this invention. Illustrative are propylene glycol, dipropylene glycol, polypropylene glycol, polyethylene glycol, sorbitol, hydroxypropyl sorbitol, hexylene glycol, 1,3-butylene glycol, 1 , 2 , 6-hexanetriol , glycerin, ethoxylated glycerin, propoxylated glycerin and mixtures thereof. Most preferably the polyol is a mixture of polyethylene glycol, molecular weight ranging from 200 to 2,000, and propylene glycol. Preferred weight ratios of polyethylene glycol to propylene glycol range from 5:1 to 1:10, preferably from 2:1 to 1:5, more preferably from 2:1 to 1:2, optimally 1:1 to 1:2. Amounts of the polyol may range from 1 to 50%, preferably from 10 to 40%, optimally from 25 to 35% by weight of the composition. Silicone oils may also be included as carriers in the compositions of this invention. These oils may be either volatile or nonvolatile. The term "volatile" as used herein refers to those materials which have a measurable vapour pressure at ambient temperature. Volatile silicone oils are preferably chosen from cyclic or linear polydimethylsiloxanes containing from about 3 to about 9, preferably from about 4 to about 5, silicon atoms. Cyclomethicone is the common name of the preferred volatile silicone oil and is available as a tetramer or pentamer. Amounts of the volatile siloxane will range from 10 to 80%, preferably from 20 to 70%, optimally from 30 to 65% by weight of the composition. Linear volatile silicone materials generally have viscosities less than about 5 centistokes at 25°C while cyclic materials typically have viscosities of less than about 10 centistokes. Examples of preferred volatile silicone oils useful herein include: Dow Corning 344, Dow Corning 345 and Dow Corning 200 (manufactured by Dow Corning Corp.); Silicone 7207 and Silicone 7158 (manufactured by the Union Carbide Corp.); SF 1202 (manufactured by General Electric) ; and SWS-03314 (manufactured by SWS Silicones, Inc.). The nonvolatile silicone oils useful in compositions of this invention are exemplified by the polyalkyl siloxanes, polyalklyaryl siloxanes and polyether siloxane copolymers. The essentially nonvolatile polyalkyl siloxanes useful herein include, for example, polydimethyl siloxanes with viscosities of from about 5 to about 100,000 centistokes at 25°C. Among the preferred nonvolatile silicones useful in the present compositions are the polydimethyl siloxanes having viscosities from about 10 to about 400 centistokes at 25°C. Such polyalkyl siloxanes include the Viscasil series (sold by General Electric Company) and the Dow Corning 200 series (sold by Dow Corning Corporation) . Polyalkylaryl siloxanes include poly (methylphenyl ) siloxanes having viscosities of from about 15 to about 65 centistokes at 25°C. These are available, for example, as SF 1075 methylphenyl fluid (sold by General Electric Company) and 556 Cosmetic Grade Fluid (sold by Dow Corning Corporation). Useful polyether siloxane copolymers include, for example, a polyoxyalkylene ether copolymer having a viscosity of about 1200 to 1500 centistokes at 25°C. Such a fluid is available as SF-1066 organoεilicone surfactant (sold by General Electric Company) . Cetyl dimethicone copolyol and cetyl dimethicone are especially preferred because these materials also function as emulsifiers and emollients. The former material is available from Goldsch idt AG under the trademark Abil EM-90. Amounts of the nonvolatile siloxane may range from 0.1 to 40%, preferably from 0.5 to 25% by weight of the composition. Esters may also be incorporated into the cosmetic compositions as pharmaceutically acceptable carriers. Amounts may range from 0.1 to 50% by weight of the composition. Among the esters are: (1) Alkyl esters of fatty acids having 10 to 20 carbon atoms. Methyl, isopropyl, and butyl esters of fatty acids are useful herein. Examples include hexyl laurate, isohexyl laurate, isohexyl palmitate, isopropyl palmitate, decyl oleate, isodecyl oleate, hexadecyl stearate, decyl stearate, isopropyl isostearate, diisopropyl adipate, diisohexyl adipate, dihexyldecyl adipate, diisopropyl sebacate, lauryl lactate, myristyl lactate, and cetyl lactate. Particularly preferred are C :1 -C 15 alcohol benzoate esters . (2) Alkenyl esters of fatty acids having 10 to 20 carbon atoms. Examples thereof include oleyl myristate, oleyl stearate, and oleyl oleate. (3) Ether-esters such as fatty acid esters of ethoxylated fatty alcohols. (4) Polyhydric alcohol esters. Ethylene glycol mono and di-fatty acid esters, diethylene glycol mono- and di-fatty acid esters, polyethylene glycol (200-6000) mono- and di-fatty acid esters, propylene glycol mono- and di-fatty acid esters, polypropylene glycol 2000 monooleate, polypropylene glycol 2000 monostearate, ethoxylated propylene glycol monostearate, glyceryl mono- and di-fatty acid esters, polyglycerol poly-fatty esters, ethoxylated glyceryl monostearate, 1,3-butylene glycol monostearate, 1,3-butylene glycol distearate, polyoxyethylene polyol fatty acid ester, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters are satisfactory polyhydric alcohol esters. (5) Wax esters such as beeswax, spermaceti, myristyl myristate, stearyl stearate. (6) Sterols esters, of which cholesterol fatty acid esters are examples thereof . Aesthetic properties and stabilization of emulsions incorporating the Vitamin C may be improved through addition of a crosslmked non-emulsifymg siloxane elastomer. Average number molecular weight of these elastomers should be in excess of 10,000, preferably in excess of 1 million and optimally will range from 10,000 to 20 million. The term "non-emulsifying" defines a siloxane from which polyoxyalkylene units are absent. Preferably the crosslmked non-emulsifymg siloxane elastomer is formed from a divmyl monomer reacting with Si-H linkages of a siloxane backbone. Illustrative of the elastomer is a material with the CTFA name of Crosslmked Stearyl Methyl- Dimethyl Siloxane Copolymer, available as Gransil SR-CYC (25-35% active elastomer) from Grant Industries, Inc., Elmwood Park, New Jersey. Supply of related elastomer may also be available from the General Electric Company. Amounts of the elastomer may range from 0.1 to 30%, optimally from 1 to 25%, most preferably from 10 to 20% by weight of the composition. Minor adjunct ingredients may also be included cosmetic compositions of this invention. These ingredients may be selected from preservatives, fragrances, anti-foam agents, opacifiers, colorants and mixtures thereof, each in their effective amounts to accomplish their respective functions. The following examples will more fully illustrate the embodiments of this invention. All parts, percentages and proportions referred to herein and in the appended claims are by weight unless otherwise indicated. EXAMPLE 1 Stabilization of ascorbic acid by dimethyl isosorbide was evaluated in the experimental and control formulations outlined under Table I. These formulations were placed in a temperature control oven at 110°F. The amount of remaining ascorbic acid was then measured at intervals of 2 , 4 and 8 weeks . TABLE I Test Formulations COMPONENT Example No. ( eight %) 1 1A (CONTROL) Cyclomethicone 42.0 42.0 Gransil SR CYL 18.0 18.0 Polyethylene Glycol 200 20.3 21.0 Dimethyl Isosorbide 10.0 — Ascorbic Acid 5.0 5.0 Cetyl Dimethicone 0.8 0.8 Copolyol Water balance balance Essentially no degradation of ascorbic acid occurred in the presence of dimethyl isosorbide. By contrast, the control formulation lost approximately 10% ascorbic acid over the eight week period. The data is shown in Table II. TABLE II Ascorbic Acid Storage Stability at 110°F COMPONENT Example No. (% Ascorbic Acid Remaining) 1 1A (CONTROL) Initial 100 100 2 Weeks 99 83 4 Weeks 99 93 8 Weeks 99 91 EXAMPLES 2-5 A series of further examples were prepared. Their compositions are outlined under Table III. These formulations provided good storage stability for the ascorbic acid and were judged to be aesthetically consumer acceptable . TABLE III COMPONENT Example No. (weight ) 2 3 4 5 Cyclomethicone 42.0 41.6 40.0 42.0 Gransil SR CYL 18.0 17.9 17.3 18.0 Propylene Glycol 16.8 14.8 17.5 15.0 Polyethylene Glycol 11.0 13.7 13.5 13.5 200 Ascorbic Acid 5.0 5.0 5.0 5.0 Dimethyl Isosorbide 2.0 2.0 2.0 2.0 Cetyl Dimethicone 0.8 0.8 0.8 0.8 Copolyol Water balance balance balanc balance e EXAMPLES 6-12 These series of Examples illustrate the scope of the present invention. Various concentrations and different glycol carriers are illustrated. TABLE IV COMPONENT Example No. (Weight %) 6 7 8 9 10 11 12 Cyclomethi36.0 36.0 36.0 40.0 40.0 45.0 32.0 cone Gransil SR 24.0 24.0 24.0 20.0 20.0 15.0 27.0 CYL Butylene 17.5 -- 17.5 -- -- -- 29.0 Glycol Glycerin — 17.5 Polyethy10.0 -- -- 17.5 12.0 10.0 10.0 lene Glycol 200 Polyethy10.0 10.0 10.0 12.0 10.0 -- lene Glycol 800 Dimethyl 2.0 2.0 2.0 4.0 8.0 10.0 1.0 Isosorbide Ascorbic 1.0 1.0 1.0 4.0 4.0 8.0 0.5 Acid Cetyl 0.8 0.8 0.8 0.8 0.8 -- -- Dimethicone Copolyol Water bal. bal. bal. bal. bal. bal. bal. The foregoing description and Examples illustrate selected embodiments of the present invention and in light thereof variations and modifications will be suggested to one skilled in the art, all of which are within the spirit and purview of this invention.

Claims: CLAIMS 1. A cosmetic composition comprising: (i) from 0.001 to 50% by weight of ascorbic acid; (ii) from 0.5 to 20% by weight of dimethyl isosorbide; and (iii)a pharmaceutically acceptable carrier present in an effective amount to deliver the ascorbic acid to skin. 2. The composition according to claim 1 wherein the carrier comprises a polyol in an amount from 1 to 50% by weight of the composition. 3. The composition according to claim 2 wherein the polyol is selected from the group consisting of propylene glycol, dipropylene glycol, polypropylene glycol, polyethylene glycol, sorbitol, hydroxypropyl sorbitol, hexylene glycol, 1,3-butylene glycol, 1,2,6- hexanetriol, glycerin, ethoxylated glycerin, propoxylated glycerin and mixtures thereof . 4. The composition according to claim 2 wherein the polyol is a mixture of polyethylene glycol and propylene glycol in a weight ratio of 2:1 to 1:2. 5. The composition according to any one of claims 1-4 wherein the carrier comprises water in an amount less than 5% by weight of the composition. 6. The composition according to any one of claims 1-5 wherein the amount of ascorbic acid ranges from 0.1 to 10% by weight of the composition. 7. The composition according to any one of claims 1-6 further comprising from 0.1 to 30% of a crosslinked non-emulsifying siloxane elastomer. 8. The composition according to claim 7 wherein the crosslinked non-emulsifying siloxane elastomer is formed from a divinyl monomer reacting with Si-H linkages of a siloxane backbone. 9. The composition according to any one of claims 1-8 further comprising from 10 to 80% of a volatile siloxane .

Inventors: CROTTY BRIAN ANDREW, JOHNSON ANTHONY WILLIAM, ZNAIDEN ALEXANDER PAUL, CROTTY, BRIAN, ANDREW, JOHNSON, ANTHONY, WILLIAM, ZNAIDEN, ALEXANDER, PAUL
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1997
Main classification: A61K7
IPC codes: A61K8, A61Q19