Isolation Of Glycyrrhetic Acid 3-O-mono-b-D-glucuronide

Glycyrrhizic acid (or glycyrrhizin, GL) is a major ingredient of licorice (gancao in Chinese) which is one of the most widely used medicinal herbs in China. Besides being a popular food additive because of its sweetness that is about 170 folds of sucrose, GL is also known for its physiological activities, such as anti-inflammation, antitumor, anti-allergy and antivirus effects. Glycyrrhetic acid 3-O-mono-β-D-glucuronide (GAMG) is an important derivate of GL. It displays the similar (or stronger) anti-allergic and anti-inflammation effects with (or than) GL, and it has the evident antitumor effect. The sweetness of GAMG is about 5 folds of GL. From above, it is anticipated that GAMG could be used as a new food additive and a therapeutic agent. Now, direct bio-transformation from GL to GAMG is becoming a hot spot. This paper studied the preparation and purification of GAMG. The main studies of this paper were as follows:1) A new method of reversed-phase high performance liquid chromatography (RP-HPLC) was developed for the simultaneous determination of GL and GAMG in the enzymatic transformation system. The analysis adopted a fixed phase which was Apollo C18 column, a mobile phase which was V(methanol) : V(water) : V(acetic acid ) = 75:25:5 at a flow rate of 1.0 mL/min, and UV detection at 254 nm. The linear ranges of GL and GAMG were all at 0.2~20μg. The recoveries of GL and GAMG were 97.47%~99.32% and 92.68%~98.44%, and the relative standard deviations were at the range of 0.88% ~3.78% and 1.07%~3.95% (n=3) respectively. The method is accurate, simple, rapid and cheap for simultaneous determination of GL and GAMG in the enzymatic transformation system.2) Two kinds of preparation methods of rude GAMG were studied in this paper. On the one hand, bio-transformation of GL to GAMG used solid enzyme. After extraction by organic solvent and evaporation out of the solvent, rude GAMG was obtained; On the other hand, free state enzyme and membrane immobilization reaction assemblage were utilized to bio-transformation GL and preparation GAMG. After spray drying, rude GAMG was obtained.