Soyasaponins and Related Glycosides of Desmodium canadense and Desmodium illinoense

Seed extracts of Desmodium canadense (L.) DC., a native Canadian legume, were examined by HPLC and electrospray ionization mass spectrometry (LC/MS) for the presence of triterpenoid saponins of the oleanene type. An aqueous methanol extract, fractionated by use of a DiaionTM HP-20 macroporous resin, was found to possess soyasaponin III (soyasaponin Bb ́) and the 2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one conjugate of soyasaponin III (DDMP S-III) as major saponin components. Minor components were identified by LC/MS as C-24 aldehyde (sandosapogenol) derivatives, S-III al and DDMP S-III al. Soyasaponin I (soyasaponin Bb), soyasaponin VI (soyasaponin g) and dehydrosoyasaponin I (soyasaponin Be) were also found as minor components. These components were also detected in extracts obtained by Soxhlet extraction with water followed by partitioning into n-butanol. Extracts from foliage of greenhouse and field origins were essentially free of these saponins. Soyasaponin VI was the main seed saponin of Desmodium illinoense A. Gray whereas soyasaponin III and DDMP S-III were found as minor components. Components corresponding in molecular mass to C-22 glycosides of soyasaponin I and soyasaponin III were also detected in saponin-enriched extracts. Neither species was a good source of alkaloids.