Immunosuppressive Bibenzyl-phenylpropane Hybrids from Dendrobium devonianum

Two new bibenzyl-phenylpropane hybrids, dendrophenols A and B (1 and 2), along with nine known bibenzyls, were isolated from the aerial part of Dendrobium devonianum Paxt. Their structures were determined by extensive spectroscopic methods and methylation. Bioassays revealed that compounds 1-9 were specifically immunosuppressive to T lymphocytes with IC50 values ranging from 0.41 to 9.4 mu M, of which compounds 1 (IC50=1.62 mu M) and 2 (IC50=0.41 mu M) were promising immunosuppressive agents for T lymphocytes with the selectivity indices of 19.9 and 79.5, respectively.