Use of nanoscale sterols and sterol esters

Details Use of nanoscale sterols and sterol esters Use of nanoscale sterols and sterol esters

1999-10-14

2001-11-13

Page, Thurman K. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Particulate form

C424S426000, C424S400000, C424S401000, C424S070100

Reexamination Certificate

active

06316030

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to nanoparticles and more particularly to the use of nanoscale sterols and sterol esters in cosmetics.
Prior Art
Sterols and sterol esters are important raw materials both for cosmetics and pharmaceutical products and for the food industry. For example, it is known that sterols, especially vegetable representatives (“phytosterols”), are incorporated in the basal membrane of the skin and pass to the skin surface through the differentiation of the skin cells. This would explain the caring and protecting effect of phytosterols in skin cosmetics. The topical application of sterols also leads to an increased skin moisture level and to an increased lipid content. This improves the desquamation behavior of the skin and reduces any erythemas present. According to more recent studies, sterols (again preferably phytosterols) act on the arachidonic acid cascade by reducing the leucotriene level. However, high concentrations of leucotrienes in the skin are always accompanied by inflammatory reactions, as is the case for example with atopical dermatitis, psoriasis and UV erythemas. Accordingly, sterols also have an inflammation-inhibiting effect. In the field of skin care, sterol-containing preparations produce an improvement in combability and tear strength, especially in the case of bleached hair. Overviews on the properties of sterols and sterol esters in cosmetics have been published, for example, by R. Wachter in Parf. Kosm. 75, 755 (1994) and in Cosm. Toil. 110, 72 (1995). Reference is also made to German patent application DE-A1 19522822 (Henkel) which proposes mixtures of sterols and fatty alcohols for cosmetic applications. The antimicrobial effect of sterols and sterol derivatives is known, for example, from European patent application EP-A1 0 838 155 (Beiersdorf).
The effect of sterols and sterol esters is always associated with the rate at which the compounds are incorporated or absorbed. So far as the substances available at present are concerned, there is considerable potential for improvement in this regard. Accordingly, the problem addressed by the present invention was to accelerate the absorption of topically applied sterols and sterol esters by presenting them in new forms.
DESCRIPTION OF THE INVENTION
The present invention relates to the use of nanoscale sterols and/or sterol esters with particle diameters of 10 to 300 nm for the production of cosmetic and/or pharmaceutical preparations.
It has surprisingly been found that the absorption of sterols and sterol esters, particularly those based on vegetable raw materials, can be significantly increased if they are present in the form of nanoparticles, i.e. particles with a mean diameter of 10 to 300 and preferably 50 to 150 nm.
Sterols and Sterol Esters
Sterols (also known as stenols) are animal or vegetable steroids which only contain a hydroxyl group but no other functional groups at C-3. In general, sterols contain 27 to 30 carbon atoms and one double bond in the 5/6 position and occasionally in the 7/8, 8/9 or other positions. Besides these unsaturated species, other sterols are the saturated compounds obtainable by hydrogenation which are known as stanols and which are also encompassed by the present invention. One example of a suitable animal sterol is cholesterol. Typical examples of suitable phytosterols, which are preferred from the applicational point of view, are ergosterols, campesterols, stigmasterols, brassicasterols and, preferably, sitosterols or sitostanols and, more particularly, &bgr;-sitosterols or &bgr;-sitostanols. Besides the phytosterols mentioned, their esters are preferably used. The acid component of the ester may go back to carboxylic acids corresponding to formula (I):
R
1
CO—OH  (I)
in which R
1
CO is an aliphatic, linear or branched acyl group containing 2 to 22 carbon atoms and 0 and/or 1, 2 or 3 double bonds. Typical examples are acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, 2-ethyl hexanoic acid, capric acid, lauric acid, isotridecanoic acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, isostearic acid, oleic acid, elaidic acid, petroselic acid, linoleic acid, conjugated linoleic acid (CLA), linolenic acid, elaeosteric add, arachic acid, gadoleic acid, behenic acid and erucic acid and the technical mixtures thereof obtained, for example, in the pressure hydrolysis of natural fats and oils, in the reduction of aldehydes from Roelen's oxosynthesis or as monomer fraction in the dimerization of unsaturated fatty acids. Technical fatty acids containing 12 to 18 carbon atoms, for example cocofatty acid, palm oil fatty acid, palm kernel oil fatty acid or tallow fatty acid, are preferred. It is particularly preferred to use esters of &bgr;-sitosterol or &bgr;-sitostanol with fatty acids containing 12 to 18 carbon atoms. These esters may be prepared both by direct esterification of the phytosterols with the fatty acids or by transesterification with fatty acid lower alkyl esters or triglycerides in the presence of suitable catalysts, for example sodium ethylate or, more particularly, enzymes [cf. EP-A2 0195311 (Yoshikawa)].
Production of Nanoparticles
One process for the production of nanoparticles by rapid expansion of supercritical solutions (RESS) is known from the article by S. Chihlar, M. Türk and K Schaber in Proceedings World Congress on Particle Technology 3, Brighton, 1998. To prevent the nanoparticles from agglomerating, it is advisable to dissolve the starting materials in the presence of suitable protective colloids or emulsifiers and/or to expand the critical solutions into aqueous and/or alcoholic solutions of the protective colloids or emulsifiers or into cosmetic oils which may in turn contain redissolved emulsifiers and/or protective colloids. Suitable protective colloids are, for example, gelatine, casein, gum arabic, lysalbinic acid, starch and polymers, such as polyvinyl alcohols, polyvinyl pyrrolidones, polyalkylene glycols and polyacrylates. Accordingly, the nanoscale sterols and/or sterol esters preferably used are those which are surrounded by a protective colloid and/or an emulsifier. The protective colloids or emulsifiers are normally used in quantities of 0.1 to 20% by weight and preferably in quantities of 5 to 15% by weight, based on the sterols or sterol esters.
Another suitable process for the production of nanoscale particles is the evaporation technique. Here, the starting materials are first dissolved in a suitable organic solvent (for example alkanes, vegetable oils, ethers, esters, ketones, acetals and the like). The resulting solutions are then introduced into water or another non-solvent, optionally in the presence of a surface-active compound dissolved therein, in such a way that the nanoparticles are precipitated by the homogenization of the two immiscible solvents, the organic solvent preferably evaporating. O/w emulsions or o/w microemulsions may be used instead of an aqueous solution. The emulsifiers and protective colloids mentioned at the beginning may be used as the surface-active compounds. Another method for the production of nanoparticles is the so-called GAS process (gas anti-solvent recrystallization). This process uses a highly compressed gas or supercritical fluid (for example carbon dioxide) as non-solvent for the crystallization of dissolved substances. The compressed gas phase is introduced into the primary solution of the starting materials and absorbed therein so that there is an increase in the liquid volume and a reduction in solubility and fine particles are precipitated. The PCA process (precipitation with a compressed fluid ant-solvent) is equally suitable. In this process, the primary solution of the starting materials is introduced into a supercritical fluid which results in the formation of very fine droplets in which diffusion processes take place so that very fine particles are precipitated. In the PGSS process (particles from gas saturated solutions), the starting materials are melted by t

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