A new dihydrophenanthrene from Cymbidium finlaysonianum and structure revision of cymbinodin-A.

1-(4-Hydroxybenzyl)-4,6-dimethoxy-9,10-dihydrophenanthrene-2,7-diol (13), a new dihydrophenanthrene, was isolated along with ferulic acid esters (1), eight phenanthrene derivatives (2, 3, 6-11) and three bibenzyls (4, 5, 12) from an epiphytic orchid, Cymbidium finlaysonianum. The molecular structure of cymbinodin-A (2) was revised based on spectroscopic data and comparison with the literature. Compounds 2, 3, and 6-13 were evaluated and shown to be cytotoxic against human small cell lung cancer (NCI-H187) cell line. Cymbinodin-A displayed the highest cytotoxicity with an IC50 value of 3.73 µM.