Antidepressant principles of the roots of Polygala tenuifolia.

[(125)I]RTI-55-membrane binding assay-guided fractionation and separation of a water-soluble extract of the roots of Polygala tenuifolia gave five new oligosaccharide derivatives, polygalatenosides A-E (1-5). The structures of these new oligosaccharides were established on the basis of spectroscopic evidence. Polygalatenosides A and B (1 and 2) showed significant inhibitory activity, with IC(50) values of 30.0 and 6.04 microM, respectively, in this membrane binding assay and acted as norepinephrine reuptake inhibitors through blocking norepinephrine transport.