[Bibenzyls from Dendrobium officinale]

Fifteen bibenzyls were isolated and purified from the ethyl acetate extract of the stems of Dendrobium officinale by macroporous resin, MCI, silica gel, Sephadex LH-20, and ODS column chromatographies, as well as preparative thin-layer chromatography and preparative HPLC. The structures of compounds were identified according to the spectra data of ~1H-NMR, ~(13)C-NMR, and MS, and the physical and physiochemical properties: dendrocandin X(1), 3,4'-dihydroxy-4,5-dimethoxybibenzyl(2), 6″-de-O-methyldendrofindlaphenol A(3), 3,4-dihydroxy-4',5-dimethoxybibenzyl(4), dendrosinen B(5), 3,4,4'-trihydroxy-5-methoxybibenzyl(6), 3,3'-dihydroxy-4,5-dimethoxybibenzyl(7), 3,4'-dihydroxy-5-methoxybibenzyl(8), moscatilin(9), gigantol(10), 4,4'-dihydroxy-3,5-dimethoxybibenzyl(11), 3,4',5-trihydroxy-3'-methoxybibenzyl(12), 3-O-methylgigantol(13), dendrocandin U(14), and dendrocandin N(15). Compound 1 was a novel compound. Compound 2 was isolated from Dendrobium species for the first time. Compounds 3-7 were isolated from D. officinale for the first time.