Effects of saponins on the water solubility of different model compounds

The influence of saponins on the water solubility of compounds having poor aqueous solubility was investigated with the model compounds digitoxin, rutin and aesculin. The saponins that were tested represent the most abundant structural types. Only slight effects on aqueous solubility were obtained for all the model compounds. These effects include both enhancements and reductions in aqueous solubility depending on the saponin, the concentration of the saponin solution and the model compound. Structure-activity relationships of general significance were not observed. Hence, saponins generally should not be regarded as solubilizers.