Extract of Oplopanax elatus Adventitious Roots Inhibits Melanogenesis in B16F10 Cells by Regulating cAMP/MAPK Pathways

Oplopanax elatus Nakai is an endangered perennial shrub of the Araliaceae family with various bioactive compounds, but its practical application is limited by the shortage of plant resource. Adventitious root (AR) culture is a novel approach for obtaining plant materials; thus, this study used the extract from bioreactor cultured O. elatus ARs (OAE) as experimental material and investigated the effect of OAE on inhibiting melanin synthesis of mouse melanoma cells (B16-F10) to utilize the ARs in production of related products in the future. The results showed that tyrosinase activity and melanin content of B16-F10 cells were inhibited by the treatments of 12.5, 25, and 50 μg/mL OAE, but those did not significantly decrease at 6.25 μg/mL OAE, indicating the anti-melanin effect of OAE (≥12.5 μg/mL). OAE down-regulated the expressions of microphthalmia-associated transcription factor, tyrosinase, and tyrosinase-related proteins-I or -II. Furthermore, phosphorylation of cyclic adenosine monophosphate (cAMP) response element-binding protein was inhibited by OAE. Meanwhile, phosphorylation of mitogen-activated protein kinases (MAPKs) of p38 and c-Jun N-terminal kinase was also inhibited by OAE, whereas that of extracellular regulated protein kinases was promoted. These findings demonstrated that the anti-melanin effect of OAE is probably caused by the regulation of the cAMP and MAPK signaling pathways. In conclusion, O. elatus ARs possess good anti-melanin effect and could be used in production of whitening products.