Note: Descriptions are shown in the official language in which they were submitted.
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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
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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
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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 (VVllmott 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.
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.
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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 acid that is sufficiently transparent so as to render the system aesthetically
pleasing.
These and other objects of the present invention will become more readily
apparent through the following summary, detailed discussion and Examples.
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SUMMARY OF THE INVENTION
An anhydrous cosmetic composition is provided that includes:
(i) from about 0.001 to about 50% by weight of ascorbic acid; and
(ii) from about 0.10 to about 99.9% by weight of a pharmaceutically acceptable
carrier having the formula:
HO ( CH2cH2ot~H
wherein n is an integer ranging from 2 to 50.
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DETAILED DESCRIPTION OF THE INVENTION
Now it has been discovered that ascorbic acid can be stably dissolved in an
anhydrous composition containing a selected pharmaceutically acceptable carrier. The
carrier of this invention is polyethylene glycol having the formula:
HO ( CH2CH20t~H
wherein n is an integer ranging from 2 to 50, preferably from 4 to 20, more
preferably from 5 to 10.
Carbowax 400 and Carbowax 200 have been found to be the most useful
polyethylene glycols.
Generally the carrier will be an ingredient present in highest amounts of the
anhydrous composition. The amount can range from about 10 to about 99.9%,
preferably from about 25 to about 90%, optimally between about 70 and 85% by
weight.
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Lower alcohols such as ethyl alcohol may be present to assist the carrier.
However, the concentration of lower alcohol must be no higher than 40%, preferably
ranging from 0.1 to about 25% by weight.
Another essential element of the present invention is, of course, ascorbic acid.
The amount of ascorbic acid should range from about 0.001 to about 50%, preferably
from about 0.01 to about 10%, optimally between about 3 and 6% by weight of the
anhydrous composition.
Esters may also be incorporated into the anhydrous composition as emollients.
Among esters that may be utilized 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,2-C1s alcohol benzoate esters.
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(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.
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Emulsifiers may also be present in the compositions of this invention. These
emulsifiers may either be anionic, nonionic, cationic or amphoteric type. Nonionic
emulsifiers are particularly preferred, especially polyoxyalkylene polyol fatty acid esters
(which may also operate as ester emollients). Most preferred is polyethylene oxide
(15) trimethylolpropane isostearate. Levels of emulsifier may range anywhere from
about 0.1 to about 20%, preferably between about 1 and 5% by weight.
Silicone oils may also be included in the compositions of this invention. These
oils may be either volatile or nonvolatile. The term ~volatileU as used herein refers to
those materials which have a measurable vapor 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.
Linear volatile silicone materials generally have viscosities less than about 5
centistokes at 25C while cyclic materials typically have viscosities of less than about
1 0 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
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(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 25C. Among the preferred nonvolatile silicones useful in the present
compositions are the polydimethyl siloxanes having viscosities from about 10 to about
400 centistokes at 25C. 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 25C. 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 25C. Such a fluid is available as SF-1066
organosilicone surfactant (sold by General Electric Company). Cetyl dimethicone
copolyol and cetyl dimethicone are especially preferred because these materials also
function as emulsifiers and emollients.
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Among other skin benefit agents which may be present in the anhydrous
compositions of this invention are fatty acids having from 10 to 20 carbon atoms.
Suitable examples of the fatty acids include pelargonic, lauric, myristic, palmitic,
stearic, isostearic, hydroxystearic, oleic, linoleic, ricinoleic, arachidic, behenic, and
erucic acids. These materials may be present in amounts anywhere from about 0.1 to
about 20% by weight of the composition, preferably between about 2 and 10% by
weight of the anhydrous composition.
Acidifying agents may also be included in the anhydrous composition. These
may be either organic or inorganic and ranging in amount from about 0.1 to about
20%, preferably between about 1 and 10%, optimally between about 2 and 6% by
weight. The acids may include alginic acid, citric acid, malic acid, succinic acid, lactic
acid, glycolic acid, tartaric acid, sorbic acid, phosphoric acid, acid phosphate salt, acid
pyrophosate salt, bitartrate salt and metal acid citrate.
A preferred mode for utilization of the anhydrous cosmetic composition of the
present invention is as one phase of a dual-phase cosmetic product. The second
composition of the dual-phase product may be an aqueous composition containing an
alkaline material for increasing pH when blended with the anhydrous composition. A
multi-compartment dispenser is utilized for such product. A copending application
1 1
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having Attorney Docket No. 92-031 0-EA describes this further development in the
delivery of ascorbic acid.
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.
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EXAMPLE 1
An anhydrous composition according to the present invention is set forth in the
table below.
Component Wt. %
Carbowax 400 84.0
Ascorbic Acid (Vitamin C) 5.0
Ethyl Alcohol s.o
Anhydrous Citric Acid 3.0
Isostearic Acid 3.0
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EXAMPLE 2
Another anhydrous composition according to the present invention is set forth inthe table below.
Component Wt. %
Carbowax 200 82.0
Ascorbic Acid (Vitamin C) 5.0
Ethyl Alcohol 5.0
Anhydrous Glycolic Acid 3.0
Isostearic Acid 3.0
Dimethicone 2.0
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EXAMPLE 3
Another anhydrous composition according to the present invention is set forth inthe table below.
Component Wt. %
Carbowax 400 83.0
Ascorbic Acid (Vitamin C) 5.0
Glycerin 5.0
Anhydrous Lactic Acid 3.0
Linolenic Acid 2.0
Dimethicone Copolyol 2.0
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EXAMPLE 4
Another anhydrous composition according to the present invention is set forth inthe table below.
Component Wt. %
Carbowax 200 76.0
Ascorbic Acid (Vitamin C) 10.0
Ethyl Alcohol 5.0
Anhydrous Malic Acid 3.0
Oleic Acid 3.0
Polyoxyethylene 15 Trimethylolpropane Isostearate3.0
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EXAMPLE 5
Another anhydrous composition according to the present invention is set forth inthe table below.
Component Wt. %
Carbowax 400 80. 9
Isostearic Acid 7.0
Ascorbic Acid (Vitamin C) 5.0
Ethyl Alcohol 5.0
Polyoxyethylene 15 Trimethylolpropane Isostearate2.0
Anhydrous Citric Acid 0.1
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EXAMPLE 6
A variety of polyhydroxy compounds were evaluated as solvents for ascorbic
acid. Table I records solubility of ascorbic acid in these materials. The term
~'incompatibleU reflects a material that had visible signs of chemical reaction with
ascorbic acid. Those deemed to be insoluble did not solubilize enough ascorbic acid
to produce a stable two-phase product. From the table it is evident that only
polyethylene glycol provided suitable solubility and compatibility.
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TABLE I
SOLVENTS FOR ASCORBIC ACID
MATERIAL ASCORBIC ACID MAX. SOLUBILITY OBSERVATIONS
CONCENTRATION % W/W
GLYCERETH 4.5 5.0 -- INCOMPATIBLE
LACTATE
GLYCERETH 7 5.0 -- INSOLUBLETRIACETATE
GLYCERETH 75.0; 7.5; 10.0; 12.5; 20.0 12.50 INCOMPATIBLE
GLYCEREtH 26 12.50 ~` -- INSOLUBLE
PROPYLENE GLYCOL10.0; 15.0; 20.0; 25.0 10.00 INSOLUBLE
GLYCERETH 12 10.0 -- INSOLUBLE
BUTYLENE GLYCOL 5.0; 10.0 5.0 INSOLUBLE
GLYCERIN 10.0 -- INSOLUBLE
TRIETHYLENE GLYCOL 5.0 -- INCOMPATIBLE
HEXYLENE GLYCOL 5.0 -- INSOLUBLE
GLYCERIN/GLYCERETH-710.0; 15.0; 20.0 -- INCOMPATIBLE
(50/50)
TRIGLYCEROL 10.0 -- INCOMPATIBLE
HEXAGLYCEROL 10.0; 20.0 -- INCOMPATIBLE
DIGLYCEROL 10.0; 20.0; 25.0 -- INCOMPATIBLE
DECAGLYCEROL 10.0 -- INCOMPATIBLE
CARBOWAX 400 10.0 -- SOLUBLE
CARBOWAX 200 10.0 -- SOLUBLE
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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 in the spirit and purview of this invention.
