Preparation of Rare Ginsenoside Rh1 Group Isomers by Two-step Method

The aim of this thesis was to prepare ginsenoside Rh1 by catalytic transformation of protopanaxatriol type saponin Re with two-step method including enzymatic conversion and metal ion catalysis. The catalytic reaction conditions in each step were researched,and the products were purified and analyzed. The results showed that,Absidia sp.P39r strain could catalyze Re to Rg1,the optimum reaction conditions were determined as:Buffer pH5.0,reaction temperature 40 ℃,substrate concentration 1.2%,reaction time 16 h,ethanol concentration 10%. Under these conditions,the mass fraction of Rg1 obtained was the highest,up to 70.5%. Next,Rg1 was used as the substrate,the mass fraction of 20(S,R)-Rh1 was determined to be the highest in reaction conditions under metallic ion Fe³⁺ catalysis. The optimum reaction conditions were as follows:Ethanol concentration 50%,reaction temperature 50 ℃,substrate concentration 1.7%,Fe³⁺ solution concentration 1.4 mol/L,reaction time 14 h,the mass fraction of 20(S,R)-Rh1 was 61.83%,and the sum mass fractions of Rk3 and Rh4 were 27.34%. Under the above conditions,20 g ginsenoside Re was reacted with the enzyme solution. And after the reaction was completed,14.1 g Rg1-containing product was obtained by separation with AB-8 macroporous adsorption resin and dried. Then,10.2 g Rg1 obtained by the reaction was reacted with Fe³⁺ solution. After drying,the mass of the final ginsenoside Rh1 group isomers was 8.18 g,with a conversion rate of 80.2%,in which the contents of 20(S)-Rh1 was 37.71%,20(R)-Rh1 was 24.12%,Rk3 was 7.27%,Rh4 was 20.07%.