Structure and hemolytic activity relationships of triterpenoid saponins and sapogenins

We evaluated the hemolytic activity of 41 commercially available triterpenoid saponins and sapogenins derived from three types of structural skeletons. Structure-activity relationships were established by comparing the structural characteristics of both the aglycone and sugar moieties among the tested compounds. The majority of oleanane-type sapogenins had stronger hemolytic effects than those of the ursane and dammarane types. The presence of polar regions on sapogenins, such as a carboxyl (COOH) at position 28, an alpha-hydroxyl (alpha-OH) at position 16, and/or a beta-hydroxyl (beta-OH) at position 2, significantly enhanced hemolysis. Meanwhile, the introduction of an alpha-OH at position 2 or a methyl hydroxyl (CH2OH) at positions 23 or 24 was closely associated with reduced activity. Our findings suggest that not only the complexity of sugar moieties but also the types and stereochemical configurations of functional groups at different positions, as well as the skeleton types, are important structural features affecting hemolytic potential. Our results provide a baseline in terms of the toxicity of saponins and sapogenins to erythrocytes, which holds promise for drug development.