Study On Microbial Transformation Of Glycyrrhetinic Acid

Objective: To study on the microbial transformation of Glycyrrhetinic acid(GA) by microorganism and its enzyme, and evaluate the pharmacological activity in vitro of GA and its separated and purified derivatives, in order to obtain a series of derivatives of GA with novel structure and or pharmacological activity. Methods: Screening and rescreening experiments of microbial transformation of GA was carried out by 52 kinds of microorganisms that are preserved in our laboratory now. Extracted samples in screening and rescreening experiments was detected by thin layer chromatography and high performance liquid chromatography and found that GA was converted into different products by 10 fungi strains. A filamentous fungus, named Cunninghamella blakesleeana CGMCC 3.970 was cultured to be used for scaling-up experiment of microbial transformation, by which results of two screening transformation experiments were consistent and the number of conversion products was more than others. After incubation with cell cultures of C. blakesleeana CGMCC 3.970 at 25 ℃ for 7 days on a rotary shaker operating at 135 r·min-1, the products were extracted and purified by solvent extraction, macroporous adsorbent resin and silica gel column chromatography, and semi-preparative liquid chromatography. Their structures were identified by the analyses of LC-MS, 1H-NMR and 13C-NMR spectroscopic data respectively. GA and its derivatives were screened through the establishment of the inhibition model of microglia release inflammatory factors to evaluate neuroprotective activity in vitro respectively. Results: GA was converted into 18 derivatives. Among them, 12 were new compounds. Conclusion: These results suggest that C. blakesleeana CGMCC 3.970 has the capability of selective ketonization, hydroxylation and acylation for GA. The results of pharmacological activity screening experiments show that neuroprotective activity in vitro of compound 1 is the strongest, of which the IC50 value is 0.00045 μmol·L-1, even stronger than that of GL.