Stabilization of ferulic acid in cosmetic compositions

Details Stabilization of ferulic acid in cosmetic compositions Stabilization of ferulic acid in cosmetic compositions

2000-07-25

2003-10-14

Padmanabhan, Sreeni (Department: 1619)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Cosmetic, antiperspirant, dentifrice

C424S059000, C514S461000, C514S537000, C514S567000, C514S572000

Reexamination Certificate

active

06632444

ABSTRACT:

FIELD OF THE INVENTION
Cosmetic compositions containing ferulic acid in an aqueous phase.
BACKGROUND OF THE INVENTION
Ferulic acid has been described for use in cosmetic compositions as a skin lightener, a sunscreen, skin anti-wrinkling agent, and an anti-oxidant. See for instance JP 6413016, U.S. Pat. No. 5,824,326, U.S. Pat. No. 5,552,135, U.S. Pat. No. 5,817,299, JP 5310526 and JP 5255037. Incorporation of ferulic acid into cosmetic compositions, however, is highly problematic. Ferulic acid is soluble in water at neutral or alkaline pH (i.e., pH 7 and above) but then the solution discolors quickly on storage. At an acidic pH, ferulic acid precipitate into crystals, is deposited in the crystallized form onto skin and therefore cannot be delivered to skin. Thus, incorporation of ferulic acid into an aqueous phase of cosmetic compositions is problematic. On the other hand, ferulic acid is not easily incorporated into an oil phase of emulsions or anhydrous compositions, due to its limited solubility in cosmetically acceptable solvents other than water. Cosmetic compositions which do not discolor on storage and which are able to deliver dissolved ferulic acid to the skin are desirable.
SUMMARY OF THE INVENTION
The present invention includes a cosmetic composition comprising from about 10 to about 100% of an aqueous phase comprising from about 0.01 to about 10% of ferulic acid and from about 1 to about 90% of a non-volatile polyol, with the weight ratio of polyol to ferulic acid being at least 4:1, wherein the pH of the aqueous phase is from about 3 to about 5 and the half-life of the ferulic acid in the composition is at least 20 days at 50° C.
The inventive compositions are aesthetically pleasing, have improved storage ability and attain dissolution of ferulic acid upon application to skin.
DETAILED DESCRIPTION OF THE INVENTION
Except in the examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word “about”. All amounts are by weight of the composition, unless otherwise specified.
For the avoidance of doubt the word “comprising” is intended to mean including but not necessarily consisting of or composed of. In other words the listed steps or options need not be exhaustive.
The inventive compositions generally contain from 10 to 100% of an aqueous phase. The particular advantage of the inventive compositions is that ferulic acid can be stabilized in an aqueous phase. Thus, the inventive compositions may contain large amounts of water. Preferably, the water is present in an amount of at least 10%, most preferably from 40 to 95% of an aqueous phase. Aqueous phase may optionally contain other water soluble or water miscible solvents or ingredients.
The total aqueous phase is preferably at least 40%, most preferably at least 45%, by weight of the composition.
According to the present invention, the aqueous phase contains from 0.01 to 10%, preferably from 0.1 to 5%, most preferably from 0.5 to 2% of ferulic acid. It is to be understood that depending on the actual pH of the composition, salts of ferulic acid may also be present (e.g., sodium, potassium and ammonium salts).
The composition further contains a non-volatile polyol in an aqueous phase, as a solvent for ferulic acid. The term “polyol” as used in the present invention denotes a non-volatile compound containing more than one hydroxy group. The term “non-volatile” as used herein means that a compound either has a boiling point at 1 atmosphere greater than 130° C., preferably greater than 180° C. or is a solid having a melting point in the range of from 20 to 60° C., preferably 20 to 40° C. Suitable polyols typically have an average molecular weight below 10,000, most preferably below 1,000.
Suitable polyols include but are not limited to propylene glycol, butylene glycol, polyethylene glycol, glycerin, di-propylene glycol, polypropylene glycol, hydroxypropylene glycol, hexylene glycol, 1, 3 butylene glycol, 1,2,6-hexanetriol, ethoxylated glycerin, propyloxylated glycerin, and mixtures thereof. Most preferred non-volatile polyol is selected from polyethylene glycol and propylene glycol, optimally a mixture of the two used to maximize the solubility of ferulic acid and to attain the best sensory properties for the overall composition. When this mixture is employed, the ratio of polyethylene glycol to propylene glycol is in the range of from 5:1 to 1:10, most preferably in the range of from 2:1 to 1:5, with the optimum ratio being 1:2.
By virtue of including a non-volatile polyol solvent in the inventive compositions, dissolution of ferulic acid is achieved either in the composition or, at the very least, after application to skin. Even if the amount of polyol included in the composition is insufficient to dissolve ferulic acid in the composition, after application to the skin, water evaporates and ferulic acid dissolves in the non-volatile solvent left on skin. In the preferred compositions according to the invention, substantially all ferulic acid crystals are dissolved on drying at body temperature.
The amount of polyol in the inventive compositions ranges from 1 to 90%, preferably from 5 to 50%, most preferably from 5 to 30% of the composition, to obtain optimum aesthetic quality and ferulic acid stability and solubility.
The stability of the inventive compositions is achieved by maintaining the pH of the aqueous phase of the compositions in the range of from 3 to 5. Preferably, in order to optimize the stability of ferulic acid in the inventive emulsions, the pH is in the range of from 3 to 4.5, most preferably from 3 to 4. pH may be adjusted by adding acids and bases well known to the one of ordinary skill in the art.
The inventive compositions have a half-life of ferulic acid at least 20 days at 50° C., preferably at least 70 days, most preferably at least 30 days.
“Half-life” is defined as the time it takes for ferulic acid to degrade to half of its original concentration at a given temperature.
The inventive composition may be emulsions (oil-in-water or water-in-oil) or single-phase aqueous compositions (e.g., gels or toners, make-up removers, skin cleansers and aqueous sprays).
Optional Skin Benefit Materials and Cosmetic Adjuncts
The preferred compositions are oil-in-water emulsions, or single-phase aqueous compositions, since the particular advantage of the inventive compositions is the ability to stabilize ferulic acid despite large amounts of water.
If the composition is an oil-in-water emulsion, its oil phase contains oils and/or emollients, and emulsifiers or surfactants.
Suitable oils and/or emollients include but are not limited to silicone oil, vegetable oils, esters, fatty acids and alcohols, and hydrocarbons.
Esters may be mono- or di-esters. Acceptable examples of fatty di-esters include dibutyl adipate, diethyl sebacate, diisopropyl dimerate, and dioctyl succinate. Acceptable branched chain fatty esters include 2-ethyl-hexyl myristate, isopropyl stearate, isostearyl palmitate and isopropyl palmitate, and isopropyl myristate. Acceptable tribasic acid esters include triisopropyl trilinoleate and trilauryl citrate. Acceptable straight chain fatty esters include lauryl palmitate, myristyl lactate, and stearyl oleate. Preferred esters include coco-caprylate/caprate (a blend of coco-caprylate and coco-caprate), propylene glycol myristyl ether acetate, diisopropyl adipate and cetyl octanoate.
Suitable fatty alcohols and acids include those compounds having from 10 to 20 carbon atoms. Especially preferred are such compounds such as cetyl, myristyl, palmitic-and stearyl alcohols and acids.
Exemplary hydrocarbons which may serve as emollients are those having hydrocarbon chains anywhere from 12 to 30 carbon atoms. Specific examples include mineral oil, petroleum jelly, squalene, isoparaffins and squalane.
Oil-in-water emulsions contain from 40 to 99%, preferably from 50 to 95%, most preferably from 70 to 90% of an aqueous phase.
An emollient is in

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