COMPARISON OF DIFFERENT PEARL POWDERS 137 reducing power. A higher absorbance indicates a higher reducing power. Ginkgo and dandelion were used as positive controls and diluted to 1, 5, and 10 mg/ml for further use. (A concentration of P-w, P-n, ginkgo, and dandelion exceeding 20 mg/ml would lead to sedimentation.) Free-radical scavenging activity of DPPH. A method described by Shimada et al. (1992) was used to detect the DPPH radical scavenging activity (18). To start, 2 ml of each test solu- tion, including three kinds of pearl powders, ascorbic acid, and ginkgo solutions, was mixed with 2 ml of 0.2 mM freshly prepared DPPH methanolic solution. The mixture was shaken vigorously and left to stand for 30 minutes in the dark. Absorbance was then measured at 517 nm against a blank solution. Ascorbic acid and ginkgo solutions were used as positive controls for comparison to P-μ and P-n diluted to 1, 5, and 10 mg/ml, as well as for comparison to P-w diluted to 1, 5, 10, 20, and 50 mg/ml. The percentage of DPPH scavenging activity is expressed as [1 (test sample absorbance/blank sample absorbance)] × 100 (%). Ferrous ion chelating ability. Chelating ability was determined according to the method proposed by Dinis et al. (19). Each sample dilution (1, 5, 10, and 20 mg/ml in water or DMSO) was mixed with 0.1 ml of 0.1 mM FeCl2 and 0.2 ml of 5 mM ferrozine solutions. After ten minutes at room temperature, the absorbance of the solution was determined at 562 nm and the values were measured and recorded. The percentage of ferrous ion chelat- ing ability is expressed as [1 (test sample absorbance/blank sample absorbance)] × 100 (%). EDTA and BHA were used as positive and negative controls. SAMPLING AND STATISTICAL ANALYSIS The results were obtained from three or more individual examinations. Values were ex- pressed as means ± SEM. Group means were compared by one-way ANOVA followed by Scheffe’s test. Probability values less than or equal to 0.05 or 0.01 were considered sig- nifi cant or very signifi cant, respectively. RESULTS THE EFFICACY OF PEARL POWDER MOISTURIZING The time course of TEWL is shown in Figure 1A. For both TEWL and the hydration mois- turizing test, 1% Hya diluted with 30%, 50%, 80%, and 30% of glycerite was used. The results showed that 50% Hya had a better moisturizing effect than that of 30% or 80% Hya, which was similar to that of 30% glycerite. Fifty percent Hya was considered as the positive comparison for the experimental group, and 10 mg/ml Spi was considered as the negative comparison. Pearl powders were diluted with DI water as the blank. The P-μ (sieve size = 8000) and the P-w were used at 1 mg/ml and 10 mg/ml for the test, and the results showed that from fi ve to 30 minutes after application of the samples, the P-μ and the P-w had almost the same moisturizing performance as that of soluble Hya. The three groups showed signifi cant differences ( p 0.01 and 0.001) compared with the blank and the Spi. The effect of hydration on skin is shown in Figure 1B. There were no distinct differences between the test substances in the fi rst 15 minutes. From 15 to 30 minutes, there were dis- tinct differences among the 1 mg/ml or 10 mg/ml P-μ and the 50% Hya, the blank, and
JOURNAL OF COSMETIC SCIENCE 138 the Spi ( p 0.01 and 0.001). However, there were no differences among the P-w, the blank, and the Spi. INHIBITORY EFFECTS OF TYROSINASE ACTIVITY Ange-da and arbutin were originally adopted as positive comparisons in the test. How- ever, it was found that the seaweed had a low ability to resist activation of tyrosinase. The three kinds of pearl powders were diluted to 5, 10, and 20 mg/ml, as shown in Figure 2. It can be observed that the three pearl powders at 5 mg/ml have a higher capacity for tyrosinase resistance than Ange-da. At the concentration of 20 mg/ml, the tyrosinase resistance of these three kinds of pearl powders was the same as that of Ange-da and Figure 1. (A,B) Transepidermal water loss (TEWL) and effect of hydration on skin over time. Values repre- sent the means ± SEM for three separate experiments. ***Signifi cantly different from blank and Spiraea for- mosana, p 0.001. **p 0.01 (one-way ANOVA followed by Scheffe’s test).
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