Comparison of the inhibitory effects of vitamin E analogues on melanogenesis in mouse B16 melanoma cells.
The effect of eight vitamin E analogues (d-alpha-, dl-alpha-, d-beta-, d-gamma-, and d-delta-tocopherols, d-alpha- and dl-alpha-tocopheryl acetates) and 2,2,5,7,8-pentamethyl-6-hydroxychroman (PMC) on melanogenesis were compared in mouse B16 melanoma cells. D-beta-tocopherol at 250 mug ml(-1) inhibited not only 28% of melanin synthesis in B16 cells, but also 34% of the tyrosinase activity, a very important cascade enzyme involved in the synthesis of melanin in melanoma cells. D-gamma-tocopherol also strongly inhibited up to 39% of melanin synthesis and 45% of the tyrosinase enzyme activity at the same concentration. The inhibitory activity of both d-beta- and d-gamma-tocopherols was observed without cytotoxicity up to a concentration of 250 mug ml(-1). Weak activity was also observed with d-delta-tocopherol at 8 mug ml(-1) and with PMC at 16 mug ml(-1), with 19% and 25% inhibition of melanin synthesis, respectively. However, PMC did not directly inhibit tyrosinase, as was observed with d-beta-, d-gamma-, and d-delta-tocopherols. Analysis by reverse transcription-polymerase chain reaction showed that the mechanism of melanogenesis inhibition by d-beta- and d-gamma-tocopherols in cells might be attributed to reduced expression of tyrosinase and tyrosinase related protein-2 mRNA in addition to direct inhibition of the tyrosinase. These findings suggest that both d-beta-tocopherol and d-gamma-tocopherol might be useful as effective ingredients in whitening cosmetics with lower skin toxicity to prevent or improve skin pigmentation such as skin spots and freckles caused by UV exposure.
Kamei
Yuto
Y
Coastal Bioenvironment Center, Saga University, 152-1 Shonan-cho, Karatsu, Saga, 847-0021, Japan, kameiy@cc.saga-u.ac.jp.
Otsuka
Yuri
Y
Abe
Kouichi
K