Patent Application
20050048017
The present invention relates to the use of surfactants with a ratio of hemolysis value to denaturation index of greater than or equal to 1 for obtaining or increasing the selectivity of cosmetic or dermatological cleansing preparations.
Even cleansing of the skin using a simple waterbath—without the addition of surfactants—initially causes the horny layer of the skin to swell. The degree of this swelling depends inter alia on the bathing time and temperature. At the same time, water-soluble substances are washed off or out, such as, for example, water-soluble constituents of dirt, but also substances endogenous to the skin which are responsible for the water-binding capacity of the horny layer. In addition, as a result of surface-active substances which are endogenous to the skin, fats in the skin (surface and barrier lipids) are also dissolved and washed out to a certain degree.
While the combined removal of surface dirt and surface lipids which primarily originate from the sebaceous glands and are decisively responsible for the appearance of greasy skin is entirely desirable in cosmetic terms, the washing-out of barrier lipids can impair the function of the skin barrier, which is associated with a loss of moisture from the skin. This is accompanied by a sporadic increase in the transepidermal water loss (TEWL) and a sporadic reduction in skin moisture. Primarily for products for the cleansing of sensitive facial skin and here particularly in the case of products for greasy skin, as selective as possible a removal of surface dirt, make-up and skin sebum is particularly important for the consumer. On the other hand, the facial skin in particular requires particularly gentle cleansing.
In healthy skin, the disturbances caused by washing are generally limited in terms of time since the protective mechanisms of the skin are able to readily compensate for such slight disturbances to the upper layers of the skin. However, even in the case of nonpathological deviations from the norm, e.g. as a result of wear damage or irritations caused by the environment, photodamage, aging skin etc., the protective mechanism of the surface of the skin is impaired. In some instances, it is then no longer able by itself to fulfill its function and has to be regenerated by external measures. There has therefore been no lack of attempts to find suitable cleansing preparations for better and more rapid regeneration of the skin which help the skin to retain its natural balance.
Known compositions for the cleansing and simultaneous care of the skin are, for example, oil-containing cleansing preparations or cleansing preparations comprising various refatting agents or skin moisturizers, which are intended to refat or remoisturize the skin at the same time as cleansing it. For this purpose, the prior art recognizes, for example, oilbath preparations of various types and also shower oils, cleansing creams and the like.
The main disadvantage of such preparations is that some of the barrier lipids are initially removed and the skin is then refatted with the help of the added oil components. In addition, such cleansing preparations are washed off following application, meaning that only small amounts of the additives used remain on the skin.
It was therefore an object of the present invention to provide cosmetic or dermatological preparations which significantly improve the condition of the skin, in particular reduce the roughness of the skin, and which are characterized by a selectivity of the cleansing performance.
It was surprising and could in no way have been foreseen by the person skilled in the art that
Selective cleansing preparations within the meaning of the present invention wash significantly more surface or sebum lipids out than barrier lipids. Thus, if the ratio of washed out surface or sebum lipids to washed out barrier lipids is defined, then this is significantly greater than 1 for preparations comprising surfactants used according to the invention with a ratio L/D of greater than or equal to 1, preferably greater than or equal to 3, with particular preference greater than or equal to 5. The increase in the selectivity of a cleansing preparation can be determined according to the invention, for example, relative to water. According to the present invention, it is possible to formulate products which remove dirt and excess sebum with high selectivity and in so doing conserve the lipids endogenous to the skin which are essential for preventing the skin from drying out.
The ratio L/D represents the relationship between hemolysis value (L) and denaturation index (D) and is determined by means of the standard RBC test.
The standard RBC test serves for estimating in vivo ocular mucosa irritation potentials of surfactants and surfactant products. The method is based on the fact that surfactants interact strongly with cell membranes and proteins. Both effects are determined photometrically by analyzing the natural blood dye oxyhemoglobin (HbO2). In contrast to other cell-based systems the RBC test is capable of differentiating between damage to the cell membrane (hemolysis) and protein denaturation (denaturation index).
Fresh samples of calf blood are obtained direct from the abattoir. The red blood cells are repeatedly washed and centrifuged in order to separate off the white blood cells and to remove all residues of plasma.
1. Hemolysis:
A defined aliquot of isolated calf erythrocytes is incubated with shaking at RT for 10 minutes with a series of increasing concentration of the specimens containing the washing-active substances under analysis (stock solution for raw materials containing 0.1% by weight of the washing-active substance in PBS). PBS is a customary standard phosphate buffer (pH 7.4) whose composition is as follows:
The incubation period is ended by rapid high-speed centrifuging. After centrifuging, the supernatants recovered are analyzed photometrically for the amount of liberated hemoglobin (HbO2) therein at 530 nm. The relative degree of hemolysis, based on 100% hemolysis, is calculated from this, and the L value [μl/ml] (generally also referred to as the H50 value) is determined as a parameter from the concentration/response curve. This L value indicates the concentration of the test sample at which 50% of the hemoglobin is released.
2. HbO2 Denaturation Index:
A defined aliquot of isolated calf erythrocytes is incubated with shaking at room temperature for 10 minutes with a fixed concentration of the test sample (in the case of surfactants: 0.1% of active substance in PBS) and then centrifuged rapidly. The change in the spectral absorption at 575 nm and 540 nm is measured in comparison to the native HbO2. From the ratio of the absorption values to one another the denaturation index D [%] is calculated. Na lauryl sulfate (0.1% active substance) serves as 100% standard.
L/D Ratio:
The ratio represents the relationship between the parameters of hemolysis (L) and denaturation index (D) and is used for classifying and characterizing the test samples.
The method is also recorded in the INVITTOX database for the recording of alternatives to animal experimentation, under protocol No. 37, and is further described in the following references:
The surfactant or surfactants for use in accordance with the invention are advantageously chosen from the group of surfactants having a ratio L/D of hemolysis value (L) to denaturation index (D) of greater than or equal to 3, with particular preference greater than or equal to 5.
With particular advantage the surfactant or surfactants for use in accordance with the invention are chosen from the group consisting of sodium N-alkylylglutamates, sodium alkylsarcosinates, sodium alkylsulfosuccinates and sodium salts of ethoxylated and carboxylated triglycerides.
Particular preference for the purposes of the present invention is given to the use of one or more of the following surfactants: sodium cocoylglutamate, sodium lauroyl-sarcosinate, disodium lauryl polyglycol ether sulfosuccinate, sodium PEG-7 olive oil carboxylate.
The total amount of one or more surfactants used according to the invention in the finished cosmetic or dermatological preparations is advantageously chosen from the range from 0.1 to 10.0% by weight, preferably 0.5 to 5.0% by weight, in each case based on the total weight of the preparations.
The cleaning compositions comprising surfactants used according to the invention can have the customary composition and serve for the cosmetic and/or dermatological cleansing of the skin and/or the hair and as a make-up product for decorative cosmetics.
For use, the compositions comprising surfactants used according to the invention are applied to the skin and/or the hair in a sufficient amount in the manner customary for cosmetics.
The cleansing preparations for the purposes of the present invention advantageously comprise one or more washing-active surfactants in the following four groups A to D:
A. Anionic Surfactants
Anionic surfactants to be used advantageously are
Cationic surfactants which can be used advantageously are
Quaternary surfactants contain at least one N atom which is covalently bonded to 4 alkyl or aryl groups. Irrespective of the pH, this leads to a positive charge. Benzalkonium chloride, alkylbetaine, alkylamidopropylbetaine and alkylamidopropyl-hydroxysultaine are advantageous.
C. Amphoteric Surfactants
Amphoteric surfactants which can be used advantageously are
Nonionic surfactants which can be used advantageously are
The cleansing preparations for the purposes of the present invention particularly advantageously comprise one or more washing-active surfactants according to the invention from the group of surfactants which have an HLB value of more than 25, very particularly those which have an HLB value of more than 35.
It is advantageous for the purposes of the present invention when the content of one or more washing-active surfactants in the cosmetic or dermatological cleaning preparation is chosen from the range from 1.5 to 20% by weight, very particularly advantageously from 2.0 to 15% by weight, in each case based on the total weight of the preparation.
The compositions for the purposes of the present invention further advantageously comprise water and optionally the additives customary in cosmetics, e.g. preservatives, preserving aids, bactericides, perfumes, dyes, pigments which have a coloring effect, moisturizing and/or humectant substances, fillers which improve the feel on the skin, fats, oils, waxes or other customary constituents of a cosmetic or dermatological formulation.
Advantageous preservatives for the purpose of the present invention are, for example, formaldehyde donors (such as, for example, DMDM hydantoin, which is available, for example, under the trade name Glydant™ from Lonza), iodopropyl butylcarbamates (e.g. those available under the trade names Glycacil-L, Glycacil-S from Lonza and/or Dekaben LMB from Jan Dekker), parabens (i.e. p-hydroxybenzoic alkyl esters, such as methyl-, ethyl-, propyl- and/or butylparaben), phenoxyethanol, ethanol, benzoic acid and the like. According to the invention, the preservative system usually also advantageously comprises preserving aids, such as, for example, octoxyglycerol, glycine soya etc.
The water phase of the preparations for the purposes of the present invention can advantageously comprise customary cosmetic auxiliaries, such as, for example, alcohols, in particular those of low carbon number, preferably ethanol and/or isopropanol, diols or polyols of low carbon number, and ethers thereof, preferably propylene glycol, glycerol, ethylene glycol, ethylene glycol monoethyl or monobutyl ether, propylene glycol monomethyl, monoethyl or monobutyl ether, diethylene glycol monomethyl or monoethyl ether and analogous products, polymers, foam stabilizers, electrolytes, dihydroxyacetone, and in particular one or more thickeners which can advantageously be chosen from the group consisting of silicon dioxide, aluminum silicates, polysaccharides and derivatives thereof, e.g. hyaluronic acid, xanthan gum, hydroxypropylmethylcellulose, particularly advantageously from the group of polyacrylates, preferably a polyacrylate from the group of so-called Carbopols, for example Carbopol grades 980, 981, 1382, 2984, 5984, in each case individually or in combination. Moisturizers can also preferably be used.
Moisturizers is the term used to described substances or mixtures of substances which, following application or distribution on the surface of the skin, confer on cosmetic or dermatological preparations the property of reducing the moisture loss by the horny layer (also called transepidermal water loss (TEWL) and/or have a beneficial effect on the hydration of the horny layer.
Advantageous moisturizers for the purposes of the present invention are, for example, glycerol, lactic acid and/or lactates, in particular sodium lactate, butylene glycol, propylene glycol, biosaccharide gum-1, glycine soya, ethylhexyloxyglycerol, pyrrolidonecarboxylic acid and urea. In addition, it is particularly advantageous to use polymeric moisturizers from the group of polysaccharides which are soluble in water and/or swellable in water and/or gellable using water. Particularly advantageous are, for example, hyaluronic acid, chitosan and/or a fucose-rich polysaccharide, which is listed in Chemical Abstracts under the registry number 178463-23-5 and is available, for example, under the name Fucogel® 1000 from SOLABIA S.A.
Particularly advantageous preparations are also obtained when antioxidants are used as additives or active ingredients. According to the invention, the preparations advantageously comprise one or more antioxidants. Favorable, but nevertheless optional, antioxidants which may be used are all antioxidants customary or suitable for cosmetic and/or dermatological applications.
For the purposes of the present invention, water-soluble antioxidants may be used particularly advantageously, such as, for example, vitamins, e.g. ascorbic acid and derivatives thereof.
Preferred antioxidants are also vitamin E and derivatives thereof, and vitamin A and derivatives thereof.
The amount of antioxidants (one or more compounds) in the preparations is preferably 0.001 to 30% by weight, particularly preferably 0.05 to 20% by weight, in particular 0.1 to 10% by weight, based on the total weight of the preparation.
If vitamin E and/or derivatives thereof are the antioxidant or the antioxidants, it is advantageous to choose their respective concentrations from the range from 0.001 to 10% by weight, based on the total weight of the formulation.
If vitamin A or vitamin A derivatives, or carotenes or derivatives thereof are the antioxidant or the antioxidants, it is advantageous to choose their respective concentrations from the range from 0.001 to 10% by weight, based on the total weight of the formulation.
It is particularly advantageous when the cosmetic preparations according to the present invention comprise cosmetic or dermatological active ingredients, preferred active ingredients being antioxidants which can protect the skin and/or the hair against oxidative stress.
Further advantageous active ingredients for the purposes of the present invention are natural active ingredients and/or derivatives thereof, such as, for example, alpha-lipoic acid, phytoene, D-biotin, coenzyme Q10, alpha-glucosylrutin, carnitine, carnosine, natural and/or synthetic isoflavonoids, creatine, taurine and/or β-alanine.
The examples below are intended to illustrate the present invention. The numerical values in the examples are percentages by weight, based on the total weight of the respective preparations.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10147049.5 | Sep 2001 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP02/09420 | 8/23/2002 | WO |
