Two new nor -lignans, siamensinols A and B, from Selaginella siamensis Hieron. and their biological activities.

Two new nor -lignans siamensinols A-B ( 1 - 2 ) and seven known compounds agatharesinol ( 3 ), syringaresinol-glucoside ( 4 ), noreugenin ( 5 ), 8-methyleugenitol ( 6 ), melachromone ( 7 ), uncinoside A ( 8 ) and daucosterol ( 9 ) were isolated from Selaginella siamensis Hieron. The structures of the new compounds were elucidated on the basis of comprehensive spectroscopic methods, including 1 D, 2 D-NMR, HR-ESI-MS and CD spectrometry. Compounds 1-2 showed moderate inhibitory effect on MOLT-3 cells while 8-methyleugenitol ( 6 ) exhibited moderate inhibitory effect on three tumor cells (HepG2, A549 and HuCCA-1). Compounds 2-3 showed the potent cancer chemoprevention in DPPH, XXO, IXO and AIA assays.