Three New Diterpenoids from the Leaves of Thuja orientalis

Three new diterpenoids, 18-formyloxy-8 beta-hydroxysandaracopimar-15-ene (1), 15(R)-n-butoxypinusolidic acid (2), and 15,16-dihydro-15,16-dimethoxylambertianic acid (3), along with twelve known compounds (4-15) were isolated from MeOH extracts of leaves of Thuja orientalis L. The structures of the three new compounds were elucidated on the basis of spectroscopic analyses, including extensive 2D-NMR data. The absolute stereochemistry of compound 2 was clarified by a CD spectroscopic study. The isolated compounds were evaluated for cytotoxicity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines in vitro using the sulforhodamin B (SRB) bioassay.