NATURALS TDS10011150
50 45 40 35 30 25 20
0.00 0.02 0.04 0.06 0.08 PCA mg / 3cm x 3cm (5 pieces total)
Figure 2: Relationship between the amount of PCA in the stratum corneum and skin capacitance
(manufactured by Ajinomoto, product name: Ajidew™ NL-50). Figure 1 shows the structural formula of PCA Na. Because PCA Na has high water solubility,
it can be incorporated into various water- containing formulations and is commonly used as a humectant in emulsion systems such as milky lotions and creams, and cleansing formulations such as hair shampoo and body wash. Figure 2 shows the relationship between pyrrolidone carboxylic acid (PCA) and the amount of water in the stratum corneum. After measuring skin capacitance at the
inner side of the forearm, the stratum corneum was collected from the same site using tape stripping method, and PCA was extracted from the stratum corneum for quantitative analysis. There is a positive correlation between the amount of PCA in the stratum corneum and the amount of skin moisture. Figure 3 shows the results of comparing the
moisture absorption properties of PCA Na and other humectants. The measurement method is as follows. After measuring the initial moisture
8 7 6 5 4 3 2 1
0 0.4% 3.5% Application concentration of sample (% active)
PCA Na ■ Glycerin ■ Sodium Hyaluronate* ■ * Molecular weight: 1,200,000˜1,300,000 35%RH
65%RH 80% r=0.550 60% 40% 20% 0.10 0% 0 7 14 Days Figure 3: Moisture absorption properties of each wetting agent
content of each sample using the Karl Fischer method, the sample was weighed in a weighing bottle (initial weight). Next, the sample was left in a constant
temperature and humidity chamber at 25°C and 65% RH, and the change in weight was recorded for 14 days. Subsequently, the weight was similarly recorded for 14 days under conditions of 25°C and 35% RH. The moisture content relative to the theoretical solid content was determined as the moisture content (%) using the following formula. ■ Moisture content (%) = (Change weight - theoretical solid content) / (theoretical solid content) x 100 ■ Theoretical solid content (g) = initial weight x (1-moisture content) As a result, PCA Na showed higher
hygroscopicity under high humidity and higher moisture retention under low humidity compared to glycerin and sodium hyaluronate. This shows that PCA Na is a humectant with high moisturizing properties. Next, using PCA Na and glycerin, we
PCA Na ■ Glycerin ■ n=4
TDS10010582 1
0.8 0.6 0.4 0.2 0
0.4% 3.5% Application concentration of sample (% active) Figure 4: Moisturizing properties of PCA Na and glycerin (left) and absorption into the stratum corneum (right)
www.personalcaremagazine.com June 2024 PERSONAL CARE
show the change in skin capacitance when an occlusive patch is applied to human skin (Figure 4, left). The quantitative values of PCA Na and glycerin in the stratum corneum were collected from the same site using the tape stripping method are also shown (Figure 4, right).
The skin capacitance value was measured
after rinsing the inner part of the forearm with water and acclimating for 30 minutes under constant temperature and humidity conditions and was used as the initial value. Next, 450uL of the evaluation sample of each concentration was applied as an occluded patch for one hour. After that, the test site was gently wiped
and allowed to acclimatize for 30 minutes under the same constant temperature and humidity conditions, after which skin capacitance was measured and the stratum corneum was collected using the tape-tripping method. PCA and glycerin in the collected stratum corneum were quantified by HPCE and HPLC respectively.
* Difference from the non-treated area, sum of the 5 stripped layers
PCA Na ■ Glycerin ■ n=4
TDS10010870 21 28
43
Difference in capacitance before and after application
Skin capacitance (a.u.)
PCA or Glycerin (mg) / insoluble protein (mg)
Increment*, Weight increasing ration (%)
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