Abstract: A new 3,28-bidesmosidic triterpenoid saponin was isolated from the ethanolic extract of the root of Dipsocus asperoides C.Y.Cheng et T.M.A. and its structure established as 3-O-[α-L-rhammopyranosyl(1→3)][-β-D-glycopranosyl(1→4)]-β-D-glycopranosy(1→3)-α-L-rhammopyranosyl (1→2)-β-L-arabinopyranosyl-hederagenin-28-O-β-D-glycopranosyl (1→6)-β-D-glycopranoside. The sites of glycosylation and the sequence of sugars in the glycoside can be determined unambiguously and total assignment of severely overlapping proton resonance of sugar residues were achieved by a combined use of the 1D SEMDY, NOE difference spectroscopy in rotating frame and selective long-range DEPT techniques.

Key words: ¹H NMR sepectrum of sugar residue, Dipsocus asperoides, 3,28-bidesmosidic triterpenoid saponin, Structural determination of Oligosaccharide Chains, ROE difference spectroscopy, Selective long-range DEPT, 1D-SEMDY