Melanogenesis inhibitory bisabolane-type sesquiterpenoids from the roots of Angelica koreana.

Bioactivity-guided isolation of the methanolic extract of the roots of Angelica koreana led to the isolation of four new bisabolane-type sesquiterpenoids, osterivolones A-D (1-4) together with four known compounds, bisabolangelone (5), decursinol angelate (6), psoralen (7), and falcarindiol (8). Their structures were elucidated on the basis of spectroscopic data interpretation, especially 2D NMR spectra such as HMQC, HMBC, and NOESY. All compounds were evaluated for their inhibitory effects of the melanogenesis against α-melanocyte stimulating hormone (α-MSH)-activated B16 melanoma cells.