Categories and components of soyasaponin in the Chinese wild soybean (Glycine soja) genetic resource collection

Soyasaponins, natural chemical compounds in soybean seeds, have important health benefits and also influence soyfood taste. A total of 3795 wild soybean (Glycine soja) accessions, collected from almost all the areas where wild soybean grows in China, were analysed using thin-layer chromatography to clarify saponin composition polymorphisms within Chinese wild soybeans. Twenty-three saponin components were distinguished, including four new components. The four new saponin components were a Sg-6 saponin K-αg [29–acetyl H-αg] in 18 accessions, an HAb-αg [29-hydroxy Ab] in an Ab type accession, an A-αg [3-O-(Glc-Gal-GlcUA)-soyasapogenol A (SS-A)] which is a biosynthetic precursor compound of the Aa and Ab types and its derivative KA-αg [29-O-acetyl A-αg] in the sg-7 mutant. Eight sg-10 variant accessions without the second sugar (xylose or glucose) at the C-22 position and one high-content group-E saponin Bd and one high-content group-A saponin Ae accessions were detected. Our present results can be expected to play vital roles in clarifying the biosynthetic pathway for soyasaponins. We suggest that the A-αg is the precursors for group-A and Bd components, and the Sg-6 saponin is biosynthesized from the Bd component in the relationship between the biosyntheses of group-A and Sg-6 saponins. The above new components and variants contribute to develop healthy and functional foods in soybean breeding programs.