Generation mechanism of radical species by tyrosine-tyrosinase reaction.
Alleviated melanin formation in the skin through inhibition of tyrosine-tyrosinase reaction is one of the major targets of cosmetics for whitening ability. Since melanin has a pivotal role for photoprotection, there are pros and cons of inhibition of melanin formation. This study applying electron spin resonance (ESR)-spin trapping method revealed that (•)H and (•)OH are generated through tyrosine-tyrosinase reaction. When deuterium water was used instead of H(2)O, the signal of 5,5-dimethyl-1-pyrroline N-oxide (DMPO)-H (a spin adduct of DMPO and (•)H) greatly decreased, whilst DMPO-OH (a spin adduct of DMPO and (•)OH) did not. Thus, it is suggested that (•)H was derived from H(2)O, and (•)OH through oxidative catalytic process of tyrosine to dopaquinone. Our study suggests that tyrosinase inhibitors might contribute to alleviate the oxidative damage of the skin by inhibiting (•)OH generation via the enzyme reaction.
Tada
Mika
M
New Industry Creation Hatchery Center, Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.
Kohno
Masahiro
M
Kasai
Shigenobu
S
Niwano
Yoshimi
Y