Solubilizing Properties of Glycyrrhizin and Its Derivatives : Solubilization of Saikosaponin-a, the Saponin of Bupleuri Radix

抄録

Licorice root is often co-prescribed with Bupleuri Radix (Bupleurum root) for decoctions used in oriental traditional medicine. It was found that the water solubility of saikosaponin-a, the active principle of Bupleurum root, was increased in the presence of the water extract or the saponin fraction of licorice root and this solubilizing effect was due to glycyrrhizin, the major active saponin of this plant drug. A solubilizing effect on saikosaponin-a was also observed with the 30-β-glucoside ester and 30-β-glucuronide ester of glycyrrhizin. The 30-β-glucoside ester improved the solubilizing property of glycyrrhizin. Aqueous solutions of the 30-β-glucoside ester and the 30-β-glucuronide ester solubilized dl-α-tocopherol and oleanolic acid, both of which are almost insoluble in water.