Biosynthesis of ginsenosides in Panax ginseng

人参提取物(Ginseng)在传统东方医学中被用作保健药物。然而，近年来，人参作为一种市场价值越来越高的抗衰老药物在西医中变得越来越重要。现在，这种药物是从田间栽培的人参植物的根中通过艰苦而持久的程序生产的。根提取物含有人参皂苷，这是一个小家族的三萜皂苷，其含量约为20毫克/克干重的根。虽然人参对人体新陈代谢和健康的作用机制尚不清楚，但生物活性归因于人参提取物中人参皂苷的存在。阐明人参皂苷在整个植物中的生物合成途径是本课题的主要目标。为此，不同树龄(1-7年生)的生长植物应在田间标记13CO2。目标化合物(三萜类)和其他代谢产物(如氨基酸)中的同位素分布应用核磁共振谱和质谱仪进行分析。在反生物合成方法中，同位素图谱应指定和量化田间条件下从基本光合作用产物到人参皂苷的生物合成途径和代谢通量。这些数据还应与叶和根提取物中的代谢物特征相关联。该项目可以被视为一个模型研究，挑战基于13CO2的同位素图谱作为一种创新方法来研究植物在生理条件下的代谢。还应该指出的是，优化的方法可以应用于包括营养植物在内的绿色植物的代谢途径和通量的分析，而不需要进行重大修改。

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.