[Two new bibenzyl derivatives from Dendrobium nobile and their anti-tumor activities]

Guided by anti-tumor activity, components with anti-tumor effects were tracked and isolated from the leaves of Dendrobium nobile using silica gel column chromatography, gel column chromatography, medium-pressure preparative chromatography, and high-performance liquid chromatography. The structures of the purified monomer compounds were identified by comprehensive spectroscopic techniques including NMR and HR-ESI-MS. Five bibenzyl derivatives were isolated and identified from the leaves of D. nobile: crepidatuol C(1),(S)-4,5,9-trihydroxy-2-methoxy-9,10-dihydrophenanthrene(2), crepidatuol B(3), 4,5-dihydroxy-2-methoxy-9,10-dihydrophenanthrene(4), and 3',4,5'-trihydroxy-3-methoxybibenzyl(5). Among them, compounds 1 and 2 are new compounds, while compounds 3-5 were isolated from the leaves of D. nobile for the first time. The five identified bibenzyl derivatives were tested for in vitro anti-tumor activity, and results showed that compounds 1-5 exhibited selective inhibitory effects against four tumor cell lines, i.e., HeLa, MCF-7, A549, and MGC-803.