Two phenanthraquinones were isolated from the stems of Dendrobium monilifor
me. They were identified by interpretation of spectral data as 2,6-dimethox
y-1,4,5,8-phenanthradiquinone and 5-hydroxy-3,7diniethoxy-1,4-phenanthraqui
none, named moniliformin (1) and denbinobin (2), respectively. This is the
first report of compound 1, which possesses a novel 1,4,5,8-diquinone moiet
y in the phenanthraquinone skeleton. Compound 2 showed potent antiinflammat
ory effects in vitro.