Cytotoxic Diterpenoids from the Roots of Aralia melanocarpa.

Five new diterpenoids (1-5) were isolated from the roots of Aralia melanocarpa, together with four known compounds, 7β-hydroxy-ent-pimara-8(14),15-diene-19-oic acid (6), 18-norpimara-8(14),15-dien-4-ol (7), ent-16βH,17-isovalerate-kauran-19-oic acid (8), and ent-16α,17-dihydroxykauran-19-oic acid (9). Based on the MS, IR, and NMR spectral analysis, the structures of the five new diterpenoids (1-5) were elucidated. The cytotoxic activities of compounds 1-9 were assayed, and compounds 1 and 2 showed cytotoxicity in four cancer cell lines with IC50s from 4.2 to 8.2 µM.