Scutellaria baicalensis has been used topically to treat inflammatory
skin diseases in
traditional East Asian medicine. Because post-inflammatory
hyperpigmentation of the skin is difficult to manage, we investigated the effects of
baicalin, a major component of S. baicalensis, on
melanin synthesis in Mel-Ab cells. Our data showed that
baicalin significantly inhibited
melanin production and
tyrosinase activity in a dose-dependent fashion, but it did not directly influence
tyrosinase activity. Moreover,
baicalin treatment triggered decreases in both
mRNA and
protein levels of
microphthalmia-associated transcription factor (MITF) and
tyrosinase. Although
AMP-activated protein kinase (AMPK) and
extracellular signal-regulated kinase (ERK) activation were induced in
baicalin-treated Mel-Ab cells, they were not responsible for
baicalin-induced
hypopigmentation. Because the Akt pathway is also known to be involved in regulation of melanogenic
protein expression and
melanin synthesis, we examined the effects of
baicalin on the Akt pathway. Our results showed that
baicalin treatment stimulated Akt activation. Treatment with
LY294002, a specific Akt inhibitor, restored
baicalin-induced melanogenesis inhibition and abolished MITF and
tyrosinase downregulation by
baicalin. Taken together, our data suggest that Akt activation by
baicalin inhibits
melanin production via downregulation of MITF and
tyrosinase in Mel-Ab cells.