Study On Biotransformation Of Ginsenoside And Its Metabolites

The studies are focused on microbial transformation of gisenosides, including total saponins and ginsenosides Rg3. The research aimes at screening for new ginseng saponins, including ginsenoside Rh2 which has strong antitumor activity. Three fungi strains (SYP2612, SYP1561 and SYP871) were found to have the ability of transforming ginseng total saponins by primary and secondary screening from 2856 fungi strains, and one fungus strain SYP2353 was selected for its positive transformation activity on conversion ginsenoside Rg3 to Rh2. Then the transformation products were extracted by organic solvents from the culture broth and purified by silica gel column chromatography and preparation HPLC. Structures of the target compounds were all determined by mass spectrometry (MS) and nuclear magnetic resonance (NMR). The final results were that the strain SYP2612 could transform ginseng total saponins to ginsenoside Rh4 as well as aglycon; the strain SYP2353 could transform ginsenosides Rg3 to ginsenoside Rh2 and aglycon PPD.The growth inhibition rate of human gastric adenocarcinoma (SGC), fibrosarcoma cells (HT) and mouth cancer cells (KB) in response to Rh4 as well as aglycon treatment for 48h and the cell survival rate of 24h and 48h were observed by MTT assay. It showed that ginsenoside Rh4 had strong cell proliferation inhibition activity with the value of IC50 at 0.040μmol/mL,0.049μmol/mL, 0.047μmol/mL respectively. The aglycon of ginsenoside Rh4 showed better antitumor activity with the inhibiting rates above 90% when the treatment concentration was at 100μg/mL(0.22μmol/mL).This experiment further examined the metabolites of strain SYP2612. The research indicates that the metabolite compound C-5 is a kind of cyclic pentapeptide, which includes two leucines, one valine, and other two unnormal amino acids, but its structure has not been identified yet.MTT assay was applied to determine the inhibition activity of cyclic pentapeptide on human gastric adenocarcinoma (SGC), fibrosarcoma cells (HT) and mouth cancer cells (KB). It showed very strong inhibitory effect with the value of IC50 at 0.011μmol/mL,0.014μmol/mL and 0.014μmol/mL, respectively, and when the treatment concentration reached 100μg/mL(0.19μmol/mL), the inhibiting rates achieved 98%.The strains SYP1561, SYP2612, SYP871 and SYP2353 were identified as Aspergillus niger, Aspergillus tubingensis, Gibberella avenacea and Myrothecium verrucaria respectively based on morphological characteristics of colonies, conidium and conidiophore, as well as ITS-5.8S sequences analysis.