WHITENING AND ANTIAGING EFFECT OF SESAMOL 75 with R2 = 0.9603. After considering the activity of each compound, sesamol exhibited a total antioxidant power (84.23 ± 4.59 μM FeSO4) greater than BHT (20.75 ± 3.62 μM FeSO4) and BHA (45.59 ± 15.30 μM FeSO4), but lower than α-tocopherol (165.75 ± 10.70 μM FeSO4), respectively (Table II). Taken together, our results on radical scaveng- ing, lipid peroxidation activities, and reducing power indicate that sesamol possessed antioxidant activity with multiple mechanisms. INHIBITORY EFFECT OF SESAMOL ON MUSHROOM TYROSINASE IN VITRO The antimelanogenic activity of sesamol was principally evaluated on its inhibition of mushroom tyrosinase activity in vitro. The results showed that sesamol and kojic acid inhibited tyrosinase activity in a dose-dependent manner. The respective IC50 values for sesamol and kojic acid were 0.33 μg/ml (1.6 μM) and 6.15 μg/ml (67.6 μM) (Figures 1A and 1B.). The other positive control (β-arbutin) did not show any tyrosinase inhibitory activity (data not shown), despite using a concentration as high as 1000 μg/ml (3673 μM), indicating that sesamol blocked the tyrosinase enzyme with the strongest activity than the known whitening compounds, kojic acid and β-arbutin. EFFECT OF SESAMOL ON CELLULAR TYROSINASE INHIBITION To confi rm the ability of sesamol on inhibition of tyrosinase enzyme in the cells, the cel- lular tyrosinase inhibitory activity was evaluated in the SK-MEL2 cell model. The con- centration used in the cell-based assay was higher than that used in the inhibitory study of mushroom tyrosinase in vitro to ensure suffi cient accumulation of the test compound in the cells. The result showed that 30 μg/ml (217 μM) sesamol inhibited cellular tyrosinase activity 23.55 ± 8.25%, whereas 600 μg/ml (4222 μM) kojic acid o nly inhibited tyrosi- nase 33.88 ± 1.43% (Figure 2). Although kojic acid was used at higher concentration (4222 μM) than sesamol (217 μM), kojic acid showed a tyrosinase inhibitory activity (33.88 ± 1.43%) not signifi cantly different than sesamol (23.55 ± 8.25%) (p = 0.243). By comparison, although β-arbutin was used as high as 3673 μM, it could only inhibit cel- lular tyrosinase enzyme at 8.26 ± 8.78% (Figure 2). These results indicate that sesamol has potential as a whitening agent and possesses better activity than the currently used whitening compounds, kojic acid and β-arbutin. Figure 1. Effect of (A) sesamol and (B) kojic acid on mushroom tyrosinase inhibition. Data are presented as mean ± S.D. (n = 3).

JOURNAL OF COSMETIC SCIENCE 76 EFFECT OF SESAMOL ON CELL CYTOTOXICITY To test the possibility of a clinical use for sesamol as a skin application, the cytotoxicity of sesamol was investigated in vitro in both normal (Vero) and melanoma (SK-MEL2) cell lines. The Vero cell line was used to represent normal cells. Cytotoxicity was evaluated using a colorimetric NR assay (20). Viable cells accumulate and bind neutral red within the lysosomes, but dead cells cannot because of the fragility of the lysosomal membrane and irreversible molecular alterations in the dead cells (21). Figure 3 shows that sesamol barely affected cell viability. Although as much as 800 μg/ml (5792 μM) sesamol was used, the cytotoxicity to Vero cell was only 22% after 48 h treatment. Similar non- cytotoxicity to the Vero cell line was observed for the positive control β-arbutin and kojic acid, which possessed a cytotoxicity of only 4% and 7%, respectively. The SK-MEL2 cell line was used to represent melanocytes. The cytotoxicity of the test compounds on the growth of SK-MEL2 was found to be non-cytotoxic when using concentrations up to 400 μg/ml (Figure 3). A 40% cytotoxicity was observed in the sesamol-treated SK-MEL2 cell line at concentration of 600 μg/ml (4344 μM) (Figure 3), while β-arbutin and kojic acid did not possess any cytotoxicity. Sesamol thus possesses a cytotoxicity IC50 value of 4406.5 μM in the SK-MEL2 cell line (Figure 3). Notwithstanding, the concentration used to create the tyrosinase inhibition effect in vitro was much lower than the concentra- tion used in this cellular assay. Sesamol therefore may not be cytotoxic at the effective whitening concentrations used in the melanoma cell line. Further experiment on the normal melanocyte cells should be conducted to confi rm non-toxicity of sesamol. Figure 2. Inhibition effects of kojic acid sesamol and β-arbutin on cellular tyrosinase enzyme. Data are pre- sented as mean ± S.D. (n = 3). Figure 3. Effect of sesamol, kojic acid and β-arbutin on cytotoxicity of the SK-MEL2 and Vero cell lines after 48 h treatment. Data are presented as mean ± S.D. (n = 3).