We examined the effect of –tocotrienol on melanin content in mouse melanoma B16 cells. Melanin content was significantly reduced in cells reated with 50 and 100µM δ–tocotrienol, but not 10µM δ–tocotrienol. The activity and amount of tyrosinase also significantly decreased in cells treated with 10, 50 and 100µM δ –tocotrienol. Furthermore, the mRNA level of tyrosinase as measured using real-time PCR was significantly decreased compared to controls in cells treated with 100µM δ–tocotrienol, but not 10 or 50µM δ–tocotrienol. These results indicated that at first δ-tocotrienol caused tyrosinase degradation, and then caused further decrease in the tyrosinase protein level via both tyrosinase degradation and a decrease in the mRNA level of tyrosinase. We conclude that the decrease of melanin content in the cells by δ–tocotrienol was the result of the decrease of the protein level of tyrosinase (tyrosinase degradation is more important than the decrease of mRNA).
