COMPARISON OF DIFFERENT PEARL POWDERS 139 arbutin, even reaching a tyrosinase resistance of 90-100%. In comparison, seaweed had a tyrosinase resistance of only 18.7 ± 2.3%. ANTIOXIDANT ACTIVITY Reducing power. The reducing powers of the three kinds of pearl powders compared with ginkgo and Tara are shown in Figure 3A. Gingko and Tara were adopted as positive com- parisons. The three kinds of pearl powders (P-w, P-μ, P-n) have a stronger reducing power with increasing concentration. From the bar diagram, Figure 3B, it can be ob- served that the Tara at 10 mg/ml has a stronger reducing power than ginkgo but that P-μ and P-n have a stronger reducing power nearly equal to that of ginkgo. Meanwhile, at concentrations of 5 mg/ml and 10 mg/ml, P-μ, P-n, ginkgo, and Tara all have a signifi - cantly ( p 0.01) stronger reducing power than P-w. Determination of free-radical scavenging activity by DPPH. Ascorbic acid and ginkgo were adopted as positive comparisons. As shown in Figure 4A, the ability of P-μ and P-n to scavenge the DPPH free radical is observed, whereas P-μ does not increase with increas- ing concentration. Though rather weak, the P-w free-radical scavenging capacity also rises with increasing concentration at 50 mg/ml, its DPPH free-radical scavenging ca- pacity can reach 58.2 ± 0.9%. From the bar diagram in Figure 4B, it can be seen that at 1 mg/ml, the DPPH free-radical scavenging capacities of P-μ and P-n are 33.8 ± 4.6%, and 34.4 ± 6.1%, respectively, which are even stronger than the 24.4 ± 0.2% of ginkgo (positive comparison). At the three different concentrations (1, 5, and 10 mg/ml), except for P-μ at 10 mg/ml, P-μ, P-n, and ginkgo have a distinctly stronger DPPH free-radical scavenging capacity than P-w ( p 0.001). Ferrous ion chelating ability. The three kinds of pearl powders, as well as EDTA for positive comparison and BHA for negative comparison, were diluted to various concentrations according to the above-mentioned method. As shown in Figure 5, the chelating ability of Figure 2. Inhibitory effects of water-soluble pearl powder, ultra-micro pearl powder, and ultra-nano pearl powder on tyrosinase activity with L-tyrosine as a substrate.

JOURNAL OF COSMETIC SCIENCE 140 Figure 3. (A,B) Reducing power of the P-w, P-μ, and P-n compared with ginkgo and Tara. All samples were diluted fi ve times with DMSO and distilled (DI) water before absorbance measurement. Values represent the means ± SEM for three separate experiments. ***Signifi cantly different from P-w, p 0.001. **p 0.01 (one-way ANOVA followed by Scheffe’s test). 1 mg/ml EDTA is 68.8 ± 3.3%, lower than that of any of the three pearl powders (at 78.3 ± 1.7–79.5 ± 1.4%). However, the three pearl powders at other concentrations (5, 10, and 20 mg/ml) have almost the same chelating ability as EDTA, which is between 75% and 80%. When compared with the solutions of 1–20 mg/ml of BHA in 96% eth- anol, their chelating abilities are only 0.2% and 2.0%. DISCUSSION In general, analysis of skin quality should include at least two parameters: the lipid content and the moisturizing capacity of the skin. The lipid content of normal skin can not only make the skin glossy and beautiful, but can also help in retaining the water content of the skin (20,21). It is very important to maintain a certain amount of water in the corneum, as it provides the skin with healthy softness, smoothness, plasticity, and fi ne barrier functions. The water-holding capacity of the skin signifi cantly declines as the skin ages (22,23).