Biotransformation Of Ginsenoside Rb1by Aspergillus Niger Sp. J7

Ginsenosides are the essential components responsible for the pharmaceuticalactivities of ginseng. About forty kinds of different ginsenosides have been isolatedfrom different parts of ginseng in recent studies. Some rare ginsenosides such as Rg3,Rh2and C-K exhibited various biological and pharmacological activities, includinganti-tumor, anti-hyperglycemic, and anti-aging effects. However, these rareginsenosides existed in very low content or even did not naturally present in ginsengand its processed products for application. The preparation of rare ginseng saponins isbecoming a hot spot of current research. The rare ginsenosides, which had sameginsengenin as the high-content ginsenosides, could therefore be prepared byhydrolyzing the glycosyl in high-content ginsenosides. In this study, a novel fungalstrain which could be used in microbial transformation was used in the hydrolysis ofhigh-content ginsenosides to prepare minor ginsenosides. The main results are asfollows:1. To be superior than conventional TLC, an improved PMD （programmedmultiple development） method that could be used to isolate ginsenosides Rb1, Rb2,Rc, Rd and Re with CHCl₃-MeOH-H₂O （65:35:10, v/v/v, lower phase） andn-BuOH-EtOAc-H₂O （4:2:1, v/v/v） as solvents.10g roots ginsenosides had been toseparate into Re （0.739g）, Rd （0.283g）, Rc （0.534g）, Rb2（0.215g） and Rb1（0.384g） by silica-gel column chromatography method in two times withCHCl₃-MeOH-H₂O （65:35:10, v/v/v, lower phase） and n-BuOH-EtOAc-H₂O （4:2:1,v/v/v） as eluents.2. Nine fungal strains were isolated from the agricultural soil. A fungus, sp. J7,which was found to be able to transform ginsenoside Rb1into rare ginsenoside C-Kwith high activity and no by-product, the transformation pathways could beRb1â†'Rdâ†'F2â†'C-K. The strain was identified to be Aspergillus niger bymorphology and ITS sequencing, named Aspergillus niger sp. J7.3. The glucosidase activities of A. niger sp. J7reach maximum after72hfermentation in V8liquid medium. The conditions for C-K production by A. niger sp.J7were optimized, as well. Following optimization conditions were obtained: pH,5.0;temperature,28oC; concentration of Rb1,0.5mg/mL.4. When amplified the reaction systems by increasing dosage of substrate to200mg, A. niger sp. J7transformed total Rb1to final metabolite, ginsenoside C-K in 60h, the metabolite was identified and characterized by TLC, HPLC and¹³C-NMR.The pathways are as following: Rb1â†'Rdâ†'F2â†'C-K.