New dimeric phenanthrene and flavone from Spiranthes sinensis.

From the whole plant of Spiranthes sinensis, one novel dimeric phenanthrene, 2,2'-dihydroxy-5,5',7,7'-tetramethoxy-9,9',10,10'-tetrahydro-3,3'-biphenanthrene (1) and flavone 5-hydroxy-3,7-dimethoxy-4'-(1-hydroxy-3-methylbut-3-en-2-yloxy)-flavone (2) were isolated along with three other known flavonoids, which are reported for the first time from this species. Their structures were established after an extensive analysis by 1D and 2D NMR spectroscopy (NOESY, HSQC, and HMBC) as well as HR-TOF-MS.