Japanese Beauty appeared in the market as a strong defender of preventive rather than corrective solutions, with innovative developments and high-quality products with long-term reliability. This concept has had a big impact in our Western lifestyle, as it helps us to balance our stressful routines and brings us scientifically proven results. This article presents two ingredients developed by Kao Corporation for skincare. An emulsifier for W/O emulsions specially designed to avoid a sticky feel and easily spreadable, and an extremely moisturizing emollient with a skin biomimetic structure and non-greasy feel.
The world of cosmetics has recently pleased with its diversity and variety of popular marketing trends. The inspiration is the cultural traditions of different countries: this is K-Beauty based on the Korean culture of self-care and traditional Chinese medicine as the conceptual source of the C-Beauty trend. New and interesting concepts from different regions and countries are also emerging, such as A-Beauty, which focuses on a healthy lifestyle with natural and environmentally friendly ingredients from Australia, and J-Beauty, which embodies conservative care, aimed more at prevention rather than correction of cosmetic problems. New cosmetic brands based on these concepts are popular all over the world, not only with the local consumer. The demand for them has naturally increased against the backdrop of globalization, an increased interest in foreign culture and travel abroad, while the inscription “made in” means more than ever today.
Kao Chemicals Europe, as a member of the KAO Group, introduced some innovative ingredients from Kao Japan in June 2020 to bring J-Beauty closer to the Western lifestyle. Japanese cosmetics are usually associated with efficiency, high quality and beneficial properties. A distinctive feature of this concept is a preventive action based on innovative developments and highly effective products that provide long-term results. In this article, two ingredients from this product line will be introduced in detail. PENETOL GE-IS is a non-ionic W/O type emulsifier designed specifically to provide non-tacky application and easy spreading products. EXCEPARL ISCE-A is a biomimetic cholesterol ester with a low melting point and is non-irritating to the skin. This ether shows characteristic emulsifying properties and excellent moisturizing effect.
HIGH PERFORMANCE WATER-IN-OIL EMULSIFIER
Emulsion is the most common form of product in the cosmetics market. Emulsions with oil as an external phase tend to feel more oily or greasy upon application, which is perceived as very nourishing skin care. This consumer property can be useful in products such as sun protection products, where the presence of occlusion gives the feeling of better protection. Kao’s innovative approach to reverse emulsifier technology allows the creation of W/O emulsions that give a more elegant feel on the skin and are more aesthetically pleasing to the consumer.
Fig. 1 Structure of isostearylglycerol ether
PENETOL GE-IS is an α-monoalkylglycerol ether whose hydrophobic component is the isostearic group and the hydrophilic component is glycerol (Fig. 1). This emulsifier, which has a very low HLB level of 2, can stabilize inverse emulsions with a high aqueous phase because it creates a liquid crystal structure in the emulsion system. PENETOL GE-IS forms a hydrophobic reverse hexagonal liquid crystal phase over a wide range of temperatures and concentrations (Fig. 2).
Fig. 2 Binary phase diagram PENETOL GE-IS/water
An angular profile was found using a polarizing microscope, which confirms that this phase is liquid crystal with a hexagonal structure. Due to this, a kind of three-dimensional crystal network is created in the emulsion, which affects its rheology and stability. This structure, in turn, prevents the movement of water droplets, preventing their coalescence [1].
1 Comparative characteristics of emulsions
Formation of the liquid crystal phase allows the creation of light, non-oily inverse emulsions. In addition, the dynamism and fluidity of this network contribute to the sensory characteristics of the emulsion when applied to the skin.
PENETOL GE-IS can be used to create stable high concentration inverse emulsions internal phase walkie talkie, also known as HIPEs (High Internal Phase Emulsions). Emulsions in which the volume ratio of the dispersed phase is greater than or equal to 0.74 (maximum packing density for monodisperse spheres) are called emulsions with a high internal phase concentration. They have a large area-to-volume ratio and viscoelastic rheological properties. Moreover, well-defined hydrophobic and hydrophilic regions of the disperse system allow the use of molecules of different nature. HIPE emulsions containing Penetol GE-IS create a light texture without the typical stickiness and oiliness characteristic of inverse emulsions, while maintaining the effect of maintaining skin hydration and elasticity (Table 1) [2]. The higher the water content in the reverse hexagonal structures, the greater the feeling of lightness and freshness when applying the emulsion to the skin.
BIOMIMETIC CHOLESTEROL ETHER Cholesterol plays an important role in many physiological processes. Intercellular lipids in the stratum corneum help maintain healthy skin by regulating water-holding capacity and its barrier function [3]. The lipid composition of the stratum corneum is shown in Figure 3. Cholesterol can react with fatty acids to form the corresponding cholesterol esters.
Fig. 3 Composition of intercellular lipids in the stratum corneum
Cholesterol esters, as shown in the diagram in Figure 3, are one of the structural components of intercellular lipids that play a key role in maintaining skin hydration levels. Of particular interest is the use of these lipids as an oil component in cosmetic emulsions. Most natural cholesterol esters contain a fatty acid alkyl chain with a high melting point. EXCEPARL IS-CE-A is a natural biomimetic emollient with a melting point of 28-35°C that supports the physiological functions of the skin through the same mechanisms as intercellular lipids in the stratum corneum. It is a branched ester of cholesterol and isostearic acid (Fig. 4) with an extremely low irritant effect on the skin.
Fig. 4 Structural formula of cholesteryl isostearate
This product exhibits excellent moisturizing properties and characteristic co-emulsifier properties of cholesterol, allowing it to be used in a wide range of cosmetics, both in skin care and in shampoos and hair conditioners.< /p>
When using EXCEPARL IS-CE-A as a component of an emollient system in a lamellar emulsion, the skin surface texture improves and the water-retaining capacity of the stratum corneum is restored (Table 2). In this case, EXCEPARL IS-CE-A stabilizes the lamellar structure through intermolecular interactions, thereby increasing the content of bound water.
Table 2 Water-retaining properties (total amount of water
that can be absorbed per gram of emollient)
The surface of healthy skin is smooth and soft due to the properly hydrated stratum corneum, an extremely thin and soft barrier membrane created by the underlying normal epidermis. On the contrary, the skin surface on pathologically affected areas shows dryness and flaking, and the stratum corneum shows poor barrier function.
Fig. 5 Restoration of skin moisture and reduction
damages after exposure to acetone and application of
W/O cream containing EXCEPARL IS-CE-A. IM cream: 2% Penetol GE-IS,
3% petrolatum, 5% squalene and 10% octyldodecyl myristate
The water-retaining capacity of the stratum corneum was quantified using skin conductivity measurements [4]. Figure 5 shows the moisturizing power of EXCEPARL IS-CE-A at two concentrations compared to an inverse emulsion without EXCEPARL IS-CE-A. The same amount of emulsions was applied to the corresponding areas skin and measured one and two days after application. The reaction of the skin, including peeling, was studied on the third day after the treatment with acetone/ether, under the same conditions as the skin conductivity measurement. Peeling was rated as follows: no peeling – 0, slight peeling – 1, moderate peeling – 2, severe peeling – 3.
3 Stability of direct and reverse emulsions containing EXCEPARL IS-CE-A as an emulsifier
Topical application of a cream with EXCEPARL IS-CE-A on dry skin obtained with a special acetone treatment, compared to the base cream, showed a significant restoration of moisture-retaining properties, which in turn affects the reduction peeling.
Another property of EXCEPARL IS-CE-A is its use as a co-emulsifier for forward and reverse emulsions, producing very stable emulsions with cholesterol ilecithin [5]. To obtain stable emulsions, a combination of EXCEPARL IS-CE-A and cholesterol in a weight ratio of 90:10 to 10:90 can be used. When preparing an emulsion, it is useful to use lecithin to stabilize it. Testing was carried out as follows: 45% olive oil, 2% emulsifier mixture and 53% distilled water were taken. The aqueous and oil phases were heated to 70° C. and mixed. The results are shown in Table 3.
W/O CREAM WITH HIGH WATER CONTENT
To obtain a W/O type cosmetic emulsion that can be used to protect and treat dry skin, it is recommended to use EXCEPARL IS-CE-A at concentrations from 0.1 to 10% in conjunction with PENETOL GE-IS in an amount of 0.5 to 25% [6].
The high water W/O cream formula shown in Table 4 is a prime example of combining high quality, effective ingredients with beneficial properties, which embodies the J-Beauty concept to the maximum.
PENETOL GE-IS and EXCEPARL IS-CE-A are ingredients from Kao Corporation that enable the creation of a variety of emulsion skin care products in the J-Beauty concept. These ingredients are recommended in dry and mature skin care products, and can also become effective “working” ingredients for special care products for atopic skin, cosmetics for children, products for sensitive skin, etc.
4 Recipe for W/O cream with high water content
SOURCES
[1] Yuji Suzuki and Hisao Tsutsumi. Emulsifying Characteristics of α-monoalkyl glyceryl ether. Ukagaku, 36, 588 (1987)
[2] Noboru Nagatani. Application of W/O Emulsions to Cosmetic Foundations. J. Soc. Cosmetic. Chem.Jpn 35(4) 289–297 (2001)
[3] Toshiyuki Suzuki, Hidetaka Iwai. Formation of Lipid Emulsions and clear gels by Liquid Crystal Emulsification. IFSCC Magazine-vol.9, no3/2006
[4] G. Imokawa, S. Akasaki, A. Kawamata, S. Yano and N. Takaishi. Water-retaining function in the stratum corneum and its recovery properties by synthetic pseudoceramides. J. Soc. Cosmetic. Chem. 40, 273–285 (1989)
[5] Kouichi Urata, Naotake Takaishi. Cholesteryl ester compounds containing alkyl brancehs acyl grous – their preparation, properties and Applications. Fett/Lipid 99 (1997), Nr.9. S. 327–332 [6] Mizuyama, K. and E. Iijima, Cosmetic W/O emulsion for dry skin containing glycerl ether and colesterol ester: Jpn. Tokkyo Koho 9006729 (1990), Kao Corp.
Subirats Neu, Kao Chemicals Europe
Yulia Popova, Revada LLC
