Antifibrotic phenanthrenes of Dendrobium nobile stems.

Two new phenanthrenes ( 1 and 6) and four new dihydrophenanthrenes ( 2- 5) were isolated from a methanolic extract of Dendrobium nobile stems, along with 13 known phenanthrenes and dihydrophenanthrenes ( 7- 19). By spectroscopic analysis, the structures of compounds 1- 6 were determined as 2,8-dihydroxy-3,4,7-trimethoxyphenanthrene ( 1), 3-hydroxy-2,4,7-trimethoxy-9,10-dihydrophenanthrene ( 2), 2,8-dihydroxy-3,4,7-trimethoxy-9,10-dihydrophenanthrene ( 3), 2-hydroxy-4,7-dimethoxy-9,10-dihydrophenanthrene ( 4), 2,2'-dihydroxy-3,3',4,4',7,7'-hexamethoxy-9,9',10,10'-tetrahydro-1,1'-biphenanthrene ( 5), and 2,3,5-trihydroxy-4,9-dimethoxyphenanthrene ( 6), respectively. Antifibrotic activity of compounds 1- 19 was evaluated employing HSC-T6, an immortalized rat hepatic stellate cell line, as an in vitro assay system by assessing cell proliferation.