stimulated
p38 mitogen-activated protein kinase (MAPK), which
would phosphorylate upstream transcription factor that
would bind to the tyrosinase promoter(10).
Although lots of mechanistic points can be targeted,
tyrosinase inhibition is still the most common approach
to achieve skin whitening. Tyrosinase inhibitors have
been reviewed by Seo et al.(22). Several hypopigmenting
products have been developed; however, those from
natural sources are still considered more desirable and
will predominate in the cosmetics market. Growing
active compounds such as phenols, flavonoids, coumarins
and other derivatives have been identified from natural
sources and have recently been reviewed by Solano et
al.(23) and Parvez et al.(24). Natural whitening products
inhibiting tyrosinase can be roughly divided into two
categories, simple phenols and polyphenols. In addition,
some depigmenting agents blocking the upstream of
melanogenesis were discussed.
NATURAL WHITENING PRODUCTS
BLOCKING TYROSINASE
I. Phenols
(I) Arbutin and Derivatives
Arbutin (hydroquinone-O-beta-D-glucopyranoside
(Figure 3) isolated from the fresh fruit of the California
buckeye(25), Aesculus californica, was reported by
various researchers to inhibit the oxidation of L-DOPA
catalyzed by mushroom tyrosinase and was effective in