Melanin plays an important role in protection the skin
against ultraviolet light injury and is responsible for
skin color. However, overproduction and accumulation
of melanin result in several skin disorders including
freckles, melasma, age spots and other hyperpigmentation
syndrome [1]. Tyrosinase (monophenol, L-dihydroxyphenylalanine
(L-DOPA): oxygen oxidoreductase EC
1.14.18.1) is the key enzyme in the first two steps of
melanin biosynthesis, in which L-tyrosine is hydroxylated
to L-DOPA (o-diphenol product), and L-DOPA is further
oxidized into the corresponding o-quinone [2]. It has
been reported that microphthalmia-associated transcriotion factor (MITF) and other enzymes such as tyrosinase
related protein-1 (TRP-1) and tyrosinase related protein-2
(TRP-2) also contribute to the production of melanin
[3-5]. Recently, melanogenesis inhibitors have been increasingly
applied in skin care cosmetics for the prevention
of hyperpigmentation [6]. In addition, melanogenesis
is reported to produce hydrogen peroxide (H2O2) and
other reactive oxygen species (ROS) which makes the melanocytes
under high-grade oxidative stress. It is well
known that ROS play a significant role in the regulation of
the melanogenesis, while ROS scavengers and inhibitors of
ROS generation may down-regulate UV-induced melanogenesis
[7]. Therefore, antioxidants such as ascorbic derivatives
and reduced glutathione (GSH) have been applied
as inhibitory agents of melanogenesis