Three new bibenzyl derivatives fromDendrobium nobile

Three new bibenzyl derivatives have been isolated from the stems of Dendrobium nobile Lindl. (Orchidaceae). Their structures were established as 4,5-dihydroxy-3,3',alpha-trimethoxybibenzyl (1), 4,4'-dihydroxy-3,3',5,alpha-tetramethoxybibenzyl (2) and 4-hydroxy-3,3',4',5,alpha-pentamethoxybibenzyl (3) on the basis of spectroscopic analysis.