Selective Hydrolysis Of Glycyrrhizin And Effect Of Ionic Liquid On β-glucuronidase

Glycyrrhizin (GL), a major ingredient of liquorice, has various pharmacological activities such as anticancer, anti-inflammation, anti-ulcer and antiviral, and is also widely used in food industry. GAMG is a metabolite of GL with similar biological activities as GL and higher merit as sweetener. Our research is focused on selective hydrolysis of GL to produce GAMG and primary study on pharmacologic mechanism of GL, and we got some constructive results as follows: 1. Selection and purification ofβ-glucuronidaseThe hydrolysis reaction conducted withβ-glucuronidase extracted from different animals and GL was monitored by HPLC though calculating GAMG-yield to compare the enzyme activity. Selectβ-glucuronidase and purify it though autolysis, differential centriguation, thermal denaturation and NH4SO4 precipitation. We find thatβ-glucuronidase extracted from domestic duck shows the highest activity compared to other animals; after purification the specific activity ofβ-glucuronidase is 23255U/g, the purification fold is 170, the activity recovery is 48.78%. 2. Effects of ionic liquid on P-glucuronidaseThe activity, stability and selectivity of (3-glucuronidase can be enhanced in [Bmim]Br. GAMG-yield in [Bmim]Br is higher than any other reaction systems under the same condition; the enzyme activity is increasing with [Bmim]Br ranging from 0.01mol/l to 0.06mol/l andβ-glucuronidase was most activated at 0.06mol/l; the optimal temperature ofβ-glucuronidase is 45℃,decreased by 10℃compared to PBS and the thermal stability of enzyme is enhanced; when the reaction is carried out at 0.06mol/l and 45℃for 5 hours, GL can be completely converted to GAMG, with the yield up to 99.60% , and the GAMG-yield was relatively stable during 24 hours. 3. Primary study on pharmacologic mechanism of glycyrrhizinThe pharmacology of GL may be that it can inhibit viral absorption and infection though forming molecular complex with sialic acid (SA). DTA,'HNMR and UV analysis is applied to characterize the molecular complex, and we find that after GL incubating with SA, the initial melting temperature of SA was distinctly enhanced, the chemical shift of methyls in GL was transferred downfield and UV absorption of SA suffered an obvious blue shift. These findings suggest that GL and SA had formed molecular complex in solutions after incubation.