A new 3, 28-bidesmosidic triterpenoid saponin was isolated from the ethanolic extract of the root of Dipsacus asperoides C. Y. cheng et T. M. Ai and its structure established as 3-O-[α-L-rhammopyranosyl (1→ 3)][-β -D-glycopranosyl (1→4)]-β-D-glycopranosyl (1→3)-α -L- rhammopyranosyl (1→2)-α -L-arabinopyranosyl-hederagenin-28-O-β-D- glycopranosyl (1→ 6)-β-D-glycopranoside. The results obtained showed that the chemical structure of oligosaccharide chains of the saponin could be elucidated by the combination of 1D-SEMDY, NOE difference spectroscopy in rotating frame and selective long-range DEPT techniques, without having recourse to chemical degradation or modification. Complete assignments of severely overlapping proton resonance of the sugar residues were made.

Key words: TRITERPENE, NMR SPECTROMETRY, PYRANE P, GLUCOSE