Biotransformation Of Ginsenoside Rb1for Ginsenoside Rd Preparation By Bacillus Massiliens No.24

Biotransformation is a powerful tool in the pharmaceutical industry. Many natural products were converted into pharmaceutically active compounds by biotransformation. Ginsenosides are the major active components in ginseng. Up to now, more than40kinds of ginsenosides have been isolated and characterized from ginseng roots. It is noticed that the separation of ginsenoside Rd from ginseng was difficult because of its low concentration and to prepare it by chemical synthesis because of its complex structure. A possible pathway for preparation of Rd is through transforming structurally related compounds to it. The amount of the major ginsenoside Rbl is high in ginseng, and it has the same aglycone (protopanaxadiol) as Rd. Rb1has one more sugar residue at the C-20position than Rd. Theoretically; Rd can be obtained by hydrolysis of Rb1with removing the outer glucosidic residue at position C-20. Chemical transformation usually has poor selectivity and generates more environmental pollution. Biotransformation has more potential for conversion because of its high specificity and environmental compatibility. Some studies have looked for suitable microbes or enzymes that can transform Rb1into Rd. However, most of them showed poor specificity and can further transform Rd into other metabolites, such as ginsenoside F2, compound K, Rg3and Rh2, which resulted in a low yield of Rd. In this research, I report a high specificity transformation of Rbl to Rd by Bacillus massiliensis No.24.Bacterium Bacillus massiliensis No.24was tested for its ability to transform the major ginsenosides Rb1. The transformed product was identified by TLC and HPLC, and its further structural features were determined by NMR analysis. B. massiliensis No.24was found to transform the major ginsenoside Rbl to Rd as the sole product. The optimal conditions for the transformation of Rbl by B. massiliensis No.24were determined to be: the substrate concentration3mg/ml, temperature34℃, pH10, the time of substrate addition48h, cells concentration0.30×109cells/ml, and biotransformation period3days. The maximum yield of ginsenoside Rd under optimal conditions was97%. Further, a preparative scale transformation with B. massiliensis No.24was performed at a dose of150mg of Rb1by a yield of79%. This bacterium has potential to be applied in the preparation for Rd in pharmaceutical industry.