Saponin and sapogenol. XXXIX. Structure of soyasaponin A1, a bisdesmoside of soyasapogenol A, from soybean, the seeds of Glycine max Merrill.

Five bioactive triterpene-oligoglycosides, named soyasaponins I, II, III, A1 (3), and A2 (2), were isolated from soybean, the seeds of Glycine max MERRILL (Leguminosae). By employing a photochemical degradation method and a lead tetraacetate degradation method, which are two of four selective cleavage methods available for the glucuronide linkage in oligoglycosides, the structure of soyasaponin A1 was elucidated to be 3-O [β-D-glucopyranosyl (1→2)-β-D-galactopyranosyl (1→2)-β-D-glucuronopyranosyl-22-O-[β-D-glucopyranosyl (1→3)-α-L-arabinopyranosyl]-soyasapogenol A (3).