Triterpenoid Saponins from the Roots of Sophora koreensis

抄録

From the roots of Sophora koreensis (Fabaceae), three new oleanene-type triterpene glycosides, echinosophorosides A₁ (1) and B (2), and acetyl-subproside II (5), were isolated as their methyl esters, together with the four known ones sophoraflavoside I, kudzusaponin SA₃, subproside II, and azukisaponin V. The structures of the new saponins were elucidated to be 3-O-α-L-rhamnopyranosyl(1→2)-α-L-arabinopyranosyl(1→2)-β-D-glucuronopyranosyl kudzusapogenol A 22-O-α-L-arabinopyranoside (1), 3-O-α-L-rhamnopyranosyl(1→2)-α-L-arabinopyranosyl-(1→2)-β-D-glucuronopyranosyl abrisapogenol C 22-O-α-L-arabinopyranoside (2), and 3-O-α-L-rhamnopyranosyl(1→2)-α-L-arabinopyranosyl(1→2)-β-D-glucuronopyranosyl kudzusapogenol A 22-O-acetate (5), respectively. It is noteworthy that two arabinopyranosyl moieties in the same molecule, echinosophoroside B (2), have different conformations. The conformation of the arabinopyranosyl moiety existing in the trisaccharide moiety was determined to be ¹C₄, whereas that of the arabinopyranosyl unit at C-22 was identified as ⁴C₁.