136 NATURALS
the cell walls by alkaline washing/enzymatic treatment. Its properties are white to light yellow powder
(Figure 1). The main component, a complex polysaccharide, contains about 40% β1,3-1,6 glucan, which is known for its cellular activating action, and about 30% mannan and other polysaccharides. The torula yeast polysaccharide is a new cosmetic ingredient, thus the INCI name, ‘Hydrolyzed Cyberlindnera Polysaccharides’.
Safety evaluation Since torula yeast, the raw material of the torula yeast polysaccharide, has already been used as a food ingredient for a long time, we believe that it is safe enough. However, since the torula yeast polysaccharide is a new cosmetic ingredient, we decided to conduct safety tests for the development of cosmetic ingredients. No animal studies were conducted
to evaluate the safety of the torula yeast polysaccharide which was done using in vitro tests and human studies. Safety evaluation was confirmed by AMES
test, in vitro skin irritation test, in vitro eye irritation test, human patch test, and RIPT (human cumulative irritation) test, all results were negative.
Characteristics of the torula yeast polysaccharide and comparison with sodium hyaluronate The free water and bound/non-freezing water of this polysaccharide were measured using a differential scanning calorimeter, and it was found to have approximately 10% bound/ non-freezing water, suggesting that it has moisture retention properties similar to sodium hyaluronate (Figure 2A). Different from common polysaccharide aqueous solutions, the torula yeast polysaccharide’s aqueous solution has almost no viscosity and is therefore very pleasant to the touch (Figure 2B). Furthermore, when an equal amount of
1% torula yeast polysaccharide solution was added to the coloured mineral oil and stirred to observe the interface, a cloudiness appeared at the interface. This observed cloudiness
A
■ Ice-free water ■ Bound water ■ Free water
100 p<0.01 75 50 C 25
Sodium Hyaluronate Solution
Gluca Moist Solution
B
0
Gluca Moist
Hyaluronic acid
Sodium Hyaluronate Solution
Mineral Oil
Figure 2: Comparison of Gluca Moist with sodium hyaluronate, a polysaccharide commonly used as a moisturizer. A: Content of bound/non-freezing water. B: Properties of aqueous solution. C: Gluca Moist has a weak emulsifying effect
was thought to be due to the polysaccharide complex of the torula yeast polysaccharide having hydrophilic and hydrophobic structures (Figure 2C). Since this phenomenon is not observed with sodium hyaluronate, it can be said that the torula yeast polysaccharide has a higher affinity with sebum on the skin surface than sodium hyaluronate, and is an ingredient that retains moisture and is well spread on the skin.
Clinical trial for skincare Moisture retention test Clinical trials were conducted on three healthy Japanese males who agreed to accept the study design. A 10% torula yeast polysaccharide solution was prepared and then diluted twofold to prepare an aqueous solution containing
TRANSEPIDERMAL WATER LOSS (TEWL)
100% 93% 85% 78% 70%
0% 3% 5% 8% Concentration of Gluca Moist Figure 3: Moisture retention test results for Gluca Moist aqueous solution (n=3) PERSONAL CARE April 2024
www.personalcaremagazine.com 10%
120% 90% 60% 30% 0%
0% 3%
1.25-10% torula yeast polysaccharide. The inner forearms of three subjects were acclimatized for 15 minutes after washing with soap. Then, 20uL of each concentration of solution
was applied to a 15mm square test section and applied to the skin using fingers and dried. After acclimatization for 10 minutes, transepidermal water loss (TEWL) and stratum corneum water content were measured in each test section. The results showed a concentration-dependent decrease in TEWL. The stratum corneum water content
increased in a concentration-dependent manner up to a 2.5% solution, but a plateau was observed above 5%. This observation was thought to be due to the film-forming ability of the polysaccharide, which prevents the electrode from contacting the skin (Figure 3).
STRATUM CORNEUM WATER CONTENT
Gluca Moist Solution
Apparent decrease due to film formation
5% 8% Concentration of Gluca Moist 10%
TEWL (Control=100%)
Skin texture volume ratio (µm3
/mm2
/100)
Stratum corneum water content
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