Hydration Reaction Of Panaxadiol Ginsenosides Catalyzed By Metal Ions

In this paper,the hydration reaction of dehydration products Rk1 and Rg5 was studied.The effects of different condition factors on the hydration reaction were investigated and the components of the hydration products were analyzed.The reaction of ginsenoside Rb1 catalyzed by metal ions under anhydrous conditions was optimized.The optimum reaction conditions are as follows:absolute ethanol as solvent,Fe³⁺concentration 0.4 mol/L,reaction temperature 40℃,reaction time 14 h,substrate concentration 1.8%（W/V）.The reaction products are mainly Rk1 and Rg5,and the content is72.07%（W/W）.The results show that ginsenoside Rb1 mainly undergoes glycoside bond cleavage and C20 dehydration under anhydrous conditions are catalyzed by Fe³⁺.The hydration of ginsenosides Rk1 and Rg5 catalyzed by metal ions in alcohol-water system was studied.The content of 20（S,R）-25OH-Rg3,20（S,R）-Rg3,Rk1 and Rg5 are74.01%（W/W）,11.34%（W/W）and 7.26%（W/W）,respectively.The main product of hydration reaction is 20（S,R）-25OH-Rg3,and a small amount of 20（S,R）-Rg3 is produced.The results showed that ginsenosides Rk1 and Rg5 are hydrated at C20 and C24 sites under the catalysis of Fe³⁺under alcohol-water conditions.