Biotransformation Of Panaxadiol Saponins By Two Phytopathogenic Fungi

Ginseng is a traditional Chinese herbal medicine. Its major active components are ginsenosides. More than 40 kinds of ginsenosides have been isolated and identified from ginseng. It was found that some minor ginsenosides, such as Compound K, Rg3, Rh2, have remarkable pharmacological activities. Ginsenoside Rd has the ability to prevent thrombosis and enhance the differentiation of neural stem cells. Since their contents in ginseng are quite low, it is difficult to extract the minor ginsenosides from ginseng. A possible pathway for preparation of the minor ginsenosides is biotransformation from structurally related major ginsenosides. This method has many advantages such as mild conditions, high specificity, less by-products and no pollution. In this paper, two phytopathogenic fungi were identified and used to transform major protopanaxadiol-type saponins. The results are as follows:1. Ginsenosides were extracted from dried ginseng roots by hot water and the supernatant containing ginsenosides was subject to macroporous resin chromatography. Through this procedure, the yield of total ginsenosides from dry ginseng root was 4.6%. The protopanaxadiol-type saponins were separated into Fraction-I and Fraction-II by silica gel column chromatography. The components of Fraction-I were identified to be Rb1, Rb2, Rc and a little Rd, and the major component Fraction-II was identified to be Rd by both TLC and HPLC method.2. Two pathogenic fungi, isolated from diseased tissues of eggplant, were named 1.68 and 1.69, respectively. These two fungi were morphologically identified. Strain 1.68 was identified as Carpenteles Langeron and strain 1.69 was Thielavia Zopf.3. The transformation of protopanaxadiol type saponins containing Rb1, Rb2 and Rc by strain 1.68 and 1.69 was studied. The results indicated that both fungi can transform protopanaxadiol-type saponins by their extracellular enzymes. The main transformation products were identified to be Rd and F2 by both TLC and HPLC method. Comparing the two fungi, the biotransformation by strain 1.68 was more efficient and specific than strain 1.69. What's more, ginsenoside Rb1 can be converted by strain 1.68 rather than 1.69. So strain 1.68 would be more suitable for ginsenoside Rd and F2 production in pharmacological industry.