Two new hydroxylated ent-kauranoic acids from Pteris semipinnata

Two new hydroxylated ent-kauranoic acids, pterisolic acid G (1) and pterisolic acid H (3), together with five known ent-kaurane-type diterpenoids (2 and 4-7) were isolated from the whole plant of Pteris semipinnata L. The structures of compounds 1-3 were elucidated on the basis of HR-MS, 1D and 2D NMR analysis, and the absolute configuration of compounds 1 and 2 were determined by the results of single crystal X-ray diffraction experiment. Compounds 1-4 and 6-7 were evaluated in vitro cytotoxicity against the A549, CT26.WT, and Hep G2 cells, and compounds 4 and 6 possessed varying degrees of activity.