Pterosins from Pteris multifida

A new C(14) pterosin sesquiterpenoid, named (2R)-pterosin P (1), and a new natural product, named dehydropterosin B (3), were isolated from the aerial parts of Pteris multifida Poir., along with nine known compounds (2, 4-11). By chiral HPLC, compounds 1 and 2 were isolated as a pair of enantiomeric pterosin sesquiterpenoids. The planar structure of 1 was elucidated on the basis of NMR spectroscopy analysis, and the absolute configuration was established by the CD spectrum. In addition, the absolute structure of 1 was further confirmed by single-crystal X-ray diffraction (CuK alpha). Compounds 3, 5, and 6 showed potent cytotoxicity against PANC-1 (human pancreatic cancer) and NCI-H446 (human small-cell lung cancer) cell lines, with IC(50) values in the range of 4.27-14.63 mu M.