Structure and Cytotoxicity of Diterpenoids from Isodon eriocalyx

A new ent-atisanoid, eriocatisin A (1), six new ent-abietanoids, eriocasins B−E (2−4, 7), 3-acetyleriocasin C (5), and 3β-acetoxyeriocasin D (6), and seven new ent-kauranoids, maoesins A−F (8, 10−14) and 3α-acetoxy-maoesin A (9), together with 21 known compounds, were isolated from the aerial parts of Isodon eriocalyx. The structures of 1−14 were determined by spectroscopic data interpretation. All compounds isolated were evaluated for their in vitro growth inhibitory activity against the HT-29, BEL-7402, and SK-OV-3 human cancer cell lines. Compounds 17, 18, and 20 showed inhibitory effects for all three tumor cell lines used, with IC50 values in the range 2.1−7.3 μM.