Three new sesquiterpene glycosides from Dendrobium nobile with immunomodulatory activity

Dendroside A (1) and dendronobilosides A and B (2 and 3), three new sesquit erpene glycosides, have been isolated from the stems of Dendrobium nobile, a plant used in Chinese traditional medicine. Their structures and stereoch emistry were determined as 10 beta ,12,14-trihdroxyalloaromadendrane 14-O-b eta -D-glucopyranoside (1), 10,12-dihydroxypicrotoxane 10,12-di-O-beta -D-g lucopyranoside (2), and 6a,10,12-trihydroxypicrotoxane 10-O-beta -D-glucopy ranoside (3), respectively, on the basis of spectroscopic and chemical meth ods. Quantum chemistry calculations were used in support of the structural determination of 1. Compounds 1 and 2 were found to stimulate the prolifera tion of murine T and B lymphocytes in vitro, while compound 3 showed inhibi tory activity in this same assay.