One bi-bicyclic and two bi-tricyclic derivatives of coumarin-benzofuran, phenanthrene-phenanthrene and phenanthrene-phenanthraquinone, along with seven known compounds, were isolated from stems of Dendrobium thyrsiflorum Rchb.f. (Orchidaceae). On the basis of chemical, NMR (H-1 C-13, HMQC, HMBC and NOESY) and mass spectrometry data, their structures were elucidated as denthyrsin [3 - (5', 6'-dimethoxybenzofuran-2'-yl)-6,7-dimethoxy-2H-chromen-2-one; 1], denthyrsinol (4,5'-dimethoxy-[1,1']biphenanthrenyl-2,5,4',7'-tetraol; 2), and denthyrsinone (7,4',7'-trihydroxy-2,2',8'-trimethoxy-[5,l']biphenanthrenyl-1,4-dione; 3). Compounds 1-3 and denthyrsinin (1,5,7-trimethoxyphenanthrene-2,6-diol; 4) showed significant cytotoxic activities against Hela (13.5, 9.3, 9.9 and 2.7 mu M, respectively), K-562 (0.45, 1.6, 6.0 and 2.3 mu M, respectively) and MCF-7 (18.1, not tested, 3.5 and 4.8 mu M, respectively) cell lines. (c) 2005 Elsevier Ltd. All rights reserved.
(8.0+极速模式)