Purification and identification of 25-OH-Rg2 from ginsenosides by enzymatic transformation

In order to isolation, purification and structural identifying unknown saponins of ginsenoside Re conversion products, the products were prepared by enzymatic conversion method, then separated and purified by silica gel column chromatography, crystallization and recrystallization, and identified by nuclear magnetic resonance ( NMR) structure. The product of the enzyme preparation consisted of 20 ( S, R) -Rg2, a small amount of Rg4 and Rg6. And unknow chiral isomer saponin with a bimodal peaks of HPLC, which conversion rate was 65.5% ( w/w) . Using the silica gel column chromatography and the crystallization recrystallization method, obtained 0.33 g of unknown saponins with purity of 99.7%. The unknown saponins were identified as20 ( R) -25-OH-Rg2 by nuclear magnetic resonanc NMR, and its systematic name was 3β, 12β, 20 ( R) , 25-tetrahydroxydammar-6-O-α-L-rhamnopyranosyl- ( 1 →2) -β-D-glucopyranoside, and another unknown saponins were indentified as 20 ( S) -25-OH-Rg2, the systematic name was 3β, 12β, 20 ( S) , 25-tetrahydroxydammar-6-O-α-L-rhamnopyranosyl- ( 1→2) -β-D-glucopyranoside.