Saponin and Sapogenol. XLV. : Structures of Kaikasaponins I, II, and III from Sophorae Flos, the Buds of Sophora japonica L.

Abstract

Three new glucuronide-saponins, named kaikasaponin I (7), kaikasaponin II (8), and kaikasaponin III (9), were isolated from Sophorae Flos, the buds of Sophora japonica L. (Leguminosae), together with five known glucuronide-saponins soyasaponin I (6), soyasaponin III (4), azukisaponin I (2), azukisaponin II (3), and azukisaponin V (5). By use of the photochemical degradation method, which is one of selective cleavage-methods for the glucuronide linkage in glucuronide-saponins, and on the basis of chemical and spectral evidence, the structures of kaikasaponins I, II, and III have been determined as 3-O-[β-D-galactopyranosyl-(1→2)-β-D-glucuronopyranosyl]sophoradiol (7), 3-O-[α-L-rhamnopyranosyl-(l→2)-β-D-glucopyranosyl-(l→2)-β-D-glucuronopyranosyl]sophoradiol (8), and 3-O-[α-L-rhamnopyranosyl-(1→2)-β-D-galactopyranosyl-(1→2)-β-D-glucuronopyranosyl]sophoradiol (9), respectively. In the course of ^<13>C nuclear magnetic resonance spectral analysis of these kaikasaponins, it has been noticed that some chemical shifts of carbohydrate carbons close to the sapogenol are affected by the presence of a hydroxyl group in the sapogenol nearby the glucuronide linkage.