Drug – bio-affecting and body treating compositions – Topical sun or radiation screening – or tanning preparations
Reexamination Certificate
2001-09-05
2003-03-04
Dees, Jose′ G. (Department: 1616)
Drug, bio-affecting and body treating compositions
Topical sun or radiation screening, or tanning preparations
C424S401000, C424S725000, C424S757000, C424S765000
Reexamination Certificate
active
06528043
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a composition comprising at least one sapogenin in a physiologically acceptable medium.
2. Description of the Background
Sapogenins are compounds resulting from the acid hydrolysis of saponosides, which are heterosides of very high molecular weight present in the plant kingdom. Examples of sapogenins include: diosgenin, hecogenin, smilagenin, sarsapogenin, tigogenin, yamogenin and yuccagenin.
These compounds have in common a steroidal structure comprising a variable number of hydroxyl and/or oxo substituents and/or a variable number of double bonds. They are known as natural chemical precursors of steroidal hormones and are described, in this respect. as constituents of choice for various cosmetic or pharmaceutical preparations. U.S. Pat. No. 5,827,884 also discloses the use of these compounds for their anti-inflammatory properties and as cell growth stimulants.
A preferred sapogenin is diosgenin, or spirost-5-en-3-beta-ol, which can be extracted from fenugreek or from various Dioscorea plants, for example from the root of wild yam.
However, it has been found that diosgenin is difficult to dissolve, and thus to formulate, in solvents that are physiologically acceptable for topical application to the skin, on account of its high melting point (close to 204-207° C.) and its tendency to recrystallize in these solvents.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a physiologically acceptable means for dissolving diosgenin and the other sapogenins of similar structure, in an amount which is sufficient to obtain the desired effect and for a period of time which is sufficient, at room temperature, to give the composition containing sapogenin a suitable shelf life.
The Inventors have now discovered that the use of a specific solubilizing system allows this object to be achieved.
Accordingly, the objects of the invention, and others, may be accomplished with a composition comprising, in a physiologically acceptable medium, at least one sapogenin and a solubilizing system comprising:
(a) at least one non-emulsifying ester of a fatty acid whose hydrocarbon-based chain contains at least 8 carbon atoms and/or of a fatty alcohol whose hydrocarbon-based chain contains at least 8 carbon atoms, or a plant oil, and
(b) at least one branched fatty alcohol whose hydrocarbon-based chain contains at least 8 carbon atoms and/or at least one lipophilic UV screening agent.
The inventors have demonstrated that, although emulsifying esters such as polysorbates do not dissolve sapogenins, certain non-emulsifying esters of fatty alcohols and/or of fatty acids, such as C
12-15
alkyl benzoate or castor oil, make it possible, by themselves alone, to dissolve an amount of sapogenin ranging up to 3% by weight, relative to the total weight of the sapogenin and solvent. However, the solution obtained recrystallizes after 3 days. It has also been demonstrated that an amount of sapogenin limited to 2% can be dissolved, without recrystallization for at least 7 days, in certain branched fatty alcohols, such as octyldodecanol, and in certain lipophilic UV screening agents, including octyl methoxycinnamate.
However, these first results were difficult to exploit for a commercial use of sapogenins. Moreover, although lipophilic UV screening agents and fatty alcohols are good sapogenin solvents per se, their use in large amount in products for topical application to the skin is not recommended. The reason for this is that the screening agents are relatively expensive. In addition, they have a strong influence on the rheology of the compositions containing them, such that they restrict the freedom of formulation of these compositions in terms of texture. Fatty alcohols, for their part, have a tendency to irritate and dry out the skin.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is based on the discovery that certain combinations of two of these solubilizing compounds offer synergism in the solubilization of sapogenin, in the sense that at least one of the following effects is obtained (relative to the compounds taken individually):
the dissolution temperature is lowered,
the crystallization is impeded, or even prevented, and
the amount of sapogenin dissolved is increased.
This synergistic effect was thus demonstrated for the combination of a plant oil or a non-emulsifying ester of a fatty alcohol and/or of a fatty acid with a branched fatty alcohol and for the combination of this ester with a lipophilic UV screening agent. These combinations also have the advantage of reducing the amount of fatty alcohol or of screening agent required to dissolve diosgenin, by replacing some of these compounds with an ester which offers the formulator full scope as regards the choice of the type of texture which may be envisaged for the composition. The nonemulsifying ester of a fatty alcohol and/or of a fatty acid also has good emollient properties and has the advantage of being relatively cost effective.
It is thus necessary and sufficient that the composition according to the invention should contain at least one of the pairs of compounds mentioned above. However, for cosmetic reasons, it will occasionally be advantageous to make use of a ternary mixture of these three solubilizing agents.
Thus, in one preferred embodiment, the composition according to the invention contains a solubilizing system comprising: (a) at least one nonemulsifying ester of a fatty acid and/or of a fatty alcohol whose hydrocarbon-based chain contains at least 8 carbon atoms, or a plant oil, (b) at least one branched fatty alcohol whose hydrocarbon-based chain contains at least 8 carbon atoms, and (c) at least one lipophilic UV screening agent.
The sapogenin may be chosen from: diosgenin, hecogenin, smilagenin, sarsapogenin, tigogenin, yamogenin and yuccagenin. However, the present invention relates more particularly to diosgenin. This compound can be extracted from Dioscorea tubers by a process comprising, successively: hydrolysis of the heterosides in a mineral acid medium (optionally after fermentation and drying of the tubers); and filtration of the insoluble fraction, which is then neutralized, washed and treated with an apolar solvent. However, other extraction processes can be used. Diosgenin is also commercially available from Sigma under the trade name Diosgenin.
The sapogenin can represent from 0.001% to 10% and preferably from 0.05% to 5% of the total weight of the composition according to the invention. These ranges for the amount of sapogenin in the composition include all specific values and subranges therebetween, such as 0.002, 0.005, 0.01, 0.02, 0.08, 0.1, 0.2, 0.5, 1, 1.5, 2, 3 and 4% of the total weight of the composition.
The constituents of the solubilizing system according to the invention will now be described in greater detail below.
Non-emulsifying Ester of a Fatty Acid and/or of a Fatty Alcohol
The ester forming the first component of the solubilizing system according to the invention can be a mono-, di- or triester obtained from a fatty acid whose hydrocarbon-based chain contains at least 8 carbon atoms and/or from a fatty alcohol whose hydrocarbon-based chain contains at least 8 carbon atoms. This ester has no emulsifying properties, i.e. it generally bears no polar groups such as oxyalkylenated groups or sulphate or phosphate functions, for example, which are liable to give it an amphiphilic nature.
Monoesters which are preferably used are a monoester of a branched fatty alcohol and/or of a branched fatty acid. It is even more advantageous for the fatty acid and the fatty alcohol both to be branched. Examples of such esters are: isononyl isononanoate, isodecyl neopentanoate, octyldodecyl neopentanoate, isostearyl isostearate and isocetyl stearate. As a variant, however, the fatty chain of the alc
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