Phenolic Glucosides from Dendrobium aurantiacum var. denneanum and Their Bioactivities

A new 8,4'-oxyneolignane glucoside 1 has been isolated from the stems of Dendrobium aurantiacum var. denneanum together with six known phenolic glucosides 2-7. The structure of the new compound, including its absolute configuration, was determined by spectroscopic and chemical methods as (-)-(7S,8R,7'E)-4-hydroxy-3,3',5,5'-tetramethoxy-8,4'-oxyneolign-7'-ene-7,9,9'-triol 7,9'-bis-O-beta-D-glucopyranoside (1). In the in vitro assays, compound 1 and (-)-syringaresinol-4,4'-bis-O-beta-D-glucopyranoside (2) showed evident activity against glutamate-induced neurotoxicity in PC12 cells. Shashenoside I (4) showed a selective cytotoxic activity with the IC50 value of 4.17 mu M against the acute myeloid leukemia cell line MV4-11, while it was inactive against 10 other human tumor cell lines.