Studies on the Constituents of Thladiantha dubia BUNGE. II. : Structures of Dubiosides D, E and F, Neutral Saponins of Quillaic Acid Isolated from the Tuber

抄録

Three neutral 3, 28-O-bisdesmosidic glycosides of quillaic acid, named bubiosides D, E and F, were isolated from the tuber of Thladiantha dubia BUNGE (Cucurbitaceae). Their structures were elucidated on the basis of chemical and spectral evidence.All dubiosides have a common prosapogenin structure, 3-O-[O-β-D-glucopyranosyl-(1→3)-[O-β-D-galactopyranosyl-(1→2)]-β-D-glucopyranosyl]-quillaic acid, and differ only in the structures of the estr-linked sugar moieties. Dubioside D is a 28-[O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl] ester, dubioside E, a 28-[O-β-D-xylopyranosyl-(1→4)-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl] ester and dubioside F, a 28-[O-β-D-xylopyranosyl-(1→3)-O-β-D-xylopyranosyl-(1→4)-O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyl] ester of the prosapogenin.