Two novel phenanthraquinones with anti-cancer activity isolated from Bletilla striata.

7-Hydroxy-2-methoxy-phenanthrene-3,4-dione and 3',7',7-trihydroxy-2,2',4'-trimethoxy-[1,8'-biphenanthrene]-3,4-dione, two novel compounds and four known compounds were isolated from Bletilla striata. The structures of the compounds were established on the basis of extensive spectroscopic analysis. The two compounds exhibited antiproliferative effects using the MTT test; these effects may be due to cell cycle arrest and inducing ROS generation.