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-hydroxy2,4,7-trimethoxy-9, 10-dihydrophenanthrene (2), 2,8-dihydroxy-3,4,7-trimethoxy-9, 10-dihydrophenanthrene (3), 2-hydroxy4,7-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.