ANTI-TYROSINASE ACTIVITY OF ETHANOL FROM GRAPES 231 Figure 4. Effect of pure phenolic compounds on mushroom tyrosinase activity using L-dopa (0.33 mg/ml) as the substrate. Mushroom tyrosinase (44 units/ml) reacted at room temperature for 10 min. Symbols: - - (no inhibitor) - - (ellagic acid 0.03 mg/ml) -▲- (gallic acid 0.03 mg/ml) - - (kuromanin chloride 0.03 mg/ml) -×- (catechin hydrate 0.03 mg/ml). Gallic acid has been identifi ed as a tyrosinase inhibitor from many plants, and it inhibits the diphenolase activity of mushroom tyrosinase (18,19). Since the gallic acid content in RGG-SEE was about twice that in KG-SEE and gallic acid showed high anti-tyrosinase activity, we suggested that gallic acid was the main compound affecting the anti-tyrosinase activity in the ethanol extracts from grape seeds. CONCLUSION Grape seeds had higher anti-tyrosinase activity than grape peels because grape seeds had higher total phenolic compounds. The profi le of phenolic compounds was also an impor- tant factor affecting anti-tyrosinase activity. It was suggested that gallic acid was the main compound affecting the anti-tyrosinase activity in the ethanol extracts from grape seeds. The inhibitory mechanism of the ethanol extracts from the grape seeds was a mix-type inhibition. Since grape seeds were the potential source of the tyrosinase inhibitor, they might serve as a skin-lighting agent. ACKNOWLEDGMENT This study was supported by the National Science Council (NSC 97-2313-B-468- 002-MY3), Taiwan, ROC. Their fi nancial support is greatly appreciated. REFERENCES (1) S. Y. Seo, V. K. Sharma, and N. Sharma, Mushroom tyrosinase: Recent prospects, J. Agr. Food Chem., 51, 2837–2853 (2003). (2) A. Sánchez-Ferrer, J. N. Rodríguez-López, F. García-Cánovas, and F. García-Carmona, Tyrosinase: A comprehensive review of its mechanism, Biochim. Biophys. Acta, 1247, 1–11 (1995).

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