Antimelanogenic Effect of an Oroxylum indicum Seed Extract by Suppression of MITF Expression through Activation of MAPK Signaling Protein

In this study, the antimelanogenic effect of an ethyl acetate fraction of Oroxylum indicum Vent. seeds (OISEA) and its underlying mechanisms in melan-a cells were investigated. Antimelanogenesis activity was confirmed by assessing inhibition of tyrosinase activity and melanin content in the cells. Both transcriptional and translational expression of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase related protein-1 and 2 (TYRP-1 and TYRP-2), were also examined. The results depicted that pretreatment of OISEA significantly inhibits not only tyrosinase activity, but melanin production and intracellular tyrosinase activity. By repressing the expression of tyrosinase, TYRP-1, TYRP-2, and MITF, OISEA interrupted melanin production. Additionally, OISEA interfered with the phosphorylation of p38, extracellular signal-regulated kinase 1/2 (ERK1/2), and c-Jun N-terminal kinase (JNK), with the reversal of OISEA-induced melanogenesis inhibition after treatment with the specific inhibitors SB239063, U0126, and SP600125. Overall, these results suggest that OISEA can stimulate p38, ERK1/2, JNK phosphorylation, and subsequent suppression of melanin, leading to the inhibition of melanogenic enzymes and melanin production, possibly owing to the presence of polyphenolic compounds.