Biosynthesis of ginsenosides in Panax ginseng

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Extracts of Panax ginseng roots (Ginseng) are used as health promoting drugs in traditional Oriental medicine. In recent time, however, Ginseng has gained importance in Western medicine as an anti-aging drug with an increasing market value. The drug is now produced from the roots of P. ginseng plants cultivated in the field by laborious and long-lasting procedures. The root extracts contain ginsenosides, a small family of triterpenoid saponins in approximate amounts of 20 mg/g dry weight roots. Although the mechanisms of Ginseng on human metabolism and health are not well understood, bioactivity is assigned to the presence of ginsenosides in the extracts. It is the major goal of this project to elucidate the ginsenoside biosynthetic pathway in whole plants of Panax ginseng. For this purpose, growing plants at various ages (1 – 7 years old) shall be labelled with 13CO2 in the field. The isotopologue distribution in the target compounds (triterpenes) and additional metabolic products (e.g. amino acids) shall be analysed by NMR spectroscopy and mass spectrometry. In a retrobiosynthetic approach, the isotopologue profiles shall assign and quantify biosynthetic pathways and metabolic flux from the basic photosynthates to ginsenosides under field conditions. The data shall also be correlated with metabolite profiles in the extracts of leaves and roots. The project can be considered as a model study to challenge 13CO2-based isotopologue profiling as an innovative method to study plant metabolism under physiological conditions. It should also be noted that the optimized methodology can be applied, without major modification, to the analysis of metabolic pathways and flux in green plants, including nutritional plants.