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.