Preparation Of Ginsenoside Rh2 By Catalytic Transformation Of Panaxadiol Saponins By Two-Step Method

The ginseng rare saponin Rh2 has good anti-cancer,anti-thrombotic,anti-inflammatory and immune-enhancing functions,and is beneficial to the development of health foods,cosmetics and new drugs.In this thesis,the ginsenoside Rh2 isomers（including 20（S,R）-Rh2,20（S,R）-25-OH-Rh2,Rk2 and Rh3）were prepared by enzyme conversion and metal ion catalysis.The enzymatic conversion reaction conditions of PPD and the process of hydrolysis of ginsenoside F2 by Fe³⁺in alcohol-water phase were studied,and the catalytic conversion products were separated and purified.First,the optimal fermentation conditions for A.niger g.848 were determined as follows:the inducer was sassafras,the optimal inducer was 20%,and the fermentation time was 6 days.Using ginsenoside PPD as substrate,the optimal reaction conditions for enzymatic conversion of PPD were:ethanol concentration of 10%,substrate concentration of 2.5%,reaction temperature of 40°C,and reaction time of 1.5 h.The enzyme conversion yield was 69.8%.Secondly,the reaction of Fe³⁺catalyzed ginsenoside F2 was studied.Ethanol was selected as the solvent system.The optimal conditions were:ethanol concentration 50%,substrate concentration 1.3%,reaction temperature 50°C,Fe³⁺solution concentration 0.8mol/L,reaction time 17 h.The yield of the final reaction to form the Rh2 group isomer was72.4%.It was found by HPLC that six kinds of catalytic reaction products were found in the crude product of Fe³⁺catalyzed ginsenoside F2,which were 20（S,R）-Rh2,20（S,R）-25-OH-Rh2,Rk2 and Rh3,respectively.The main product was 20（S,R）-Rh2 with a content of 43.8%.