Extract of Enzyme-Hydrolyzed Green Tea Seed as Potent Melanin Synthesis Inhibitor

Melanogenesis is the process of melanin synthesis and distribution by a cascade of enzymatic and chemical reactions in melanocytes. The role of melanin is to protect the skin from the harmful effects of ultraviolet light and scavenging free radicals. However, increased levels of epidermal melanin synthesis can darken the skin and produce various dermatologic disorders, such as melasma, age spots or liver spots, and actinic damage. Recently, the application of naturally occurring products as melanin synthesis inhibitors in cosmetics has attracted much interest. For example, plant polyphenols have been the target of several studies, resulting in repeated reviews of their classification, occurrence, structural aspects, reactivity, biochemistry, and biogenesis. Extensive literature is available on the screening of tyrosinase inhibitors, among phenolics of plant origin, and polyphenols are currently the target of numerous studies. Tea [Camellia sinensis (L.) O. Kuntze, Theaceae] has been cultivated widely in Asia for centuries. Recently, as the popularity of green tea has increased, the production of green tea seed (GTS) has also increased. GTS contains many biologically active compounds such as saponins, flavonoids, vitamins, and oils. It exhibited a broad spectrum of biological activities such as antitumor activities and weight reducing activity. Several studies have reported the potential of enzyme treatments for enhancing the activity levels and number of antioxidants in order to increase the content of functional components in food products. We previously reported that the several kaempferol glycosides can be produced from GTS extract (GTSE) by enzymatic hydrolysis. However, the depigmentation effect of GTS by enzyme treatment was not studied. In the present study, tyrosinase and melanin synthesis inhibitory effect of GTSE was investigated before and after subjecting the extract to enzymatic hydrolysis. Enzyme treatment was applied to GTSE for 1 h with stirring at 27 °C. After incubation, each aliquot was extracted with ethanol. Prepared samples were evaluated for melanin synthesis activity. Figure 1 shows inhibitory effect of GTSE and Enzyme treated GTS extract (ET-GTSE) on melanin synthesis. ETGTSE reduced α-Melanocyte-stimulating hormone (α-MSH) stimulated mouse melanocyte/keratinocyte (melan-a/SP-1) co-culture assay in Figure 1(a). The melanin contents of melan-a cells also were suppressed by treatment of ET-GTSE in a dose-dependent manner in Figure 1(b). However, GTSE showed no inhibitory activity at tested concentration. To investigate the possible mechanisms of ET-GTSE underlying the inhibition of melanogenesis, the effects of the ET-GTSE on tyrosinase inhibition activity as well as the expression of tyrosinase were examined. Tyrosinase inhibitory activity was evaluated with mushroom tyrosinase (Table 1). GTSE