Study On The Correlation Between Root Structure And Active Components Of Platycodon Grandiflorum During Its Development

Platycodon grandiflorus(Jacq.)A.DC.belongs to Platycodon family and Platycodon genus.Chinese medicine Platycodon grandiflorum is the dry root of Platycodon grandiflorum.Platycodon grandiflorum contains abundant bioactive substances,which can be used for medicine,food and spectacle.In this study,Platycodon grandiflorum resources planted in Yuxian Traditional Chinese Medicine Base of Shanxi Province were studied.For the first time,optical microscopy was used to trace the transverse section of the root during the growth and development of Platycodon grandiflorum.The key enzyme activities in the biosynthesis of triterpenoid saponins were determined.The content of Platycodon D was determined by high performance liquid chromatography and the relationship between them was explored.The results of this study can provide theoretical basis for the harvesting time of Platycodon grandiflorum in this area,and also provide theoretical guidance for the development and utilization of Platycodon grandiflorum resources.The roots of Platycodon grandiflorum were harvested in the late days of March,April,May,June,July,August,September and October respectively,totally eight times.The cross section of the root of Platycodon grandiflorum can be observed by optical microscope.As a result,the root of Platycodon grandiflorum consists of periderm and vascular tissue.Microtubule cambium formed secondary phloem and secondary xylem with the growth of Platycodon grandiflorum,and the area ratio between xylem and phloem increased continuously.The number of pericortex is also increasing.The protective effect of cork layer cells on root was enhanced.The number of catheters increased,the pore size increased,and the nutrient transport capacity increased.Material accumulation increased significantly in September and October.The key enzymes in the biosynthesis of triterpenoid saponins in Platycodon grandiflorum roots were determined by enzyme labeling apparatus.The activities of key enzymes in the biosynthesis of triterpenoid saponins in Platycodon grandiflorum roots were determined by enzyme labeling apparatus: 3-hydroxy-3-methylglutaric acid monoacyl coenzyme A reductase(HMGR),1-deoxy-D-xylose-5-phosphate reductase isomerase(DXR),squalene cyclooxygenase(SE)and cytochrome oxidase(CYP450).The results showed that HMGR activity showed an upward-stable-downward trend;DXR and SE activity showed a stable fluctuation and began to rise in July;CYP450 activity was higher than the other three enzymes,and began to show an upward trend in July.These results indicate that MVA and MEP pathways of mevalonate and erythritose phosphate play an important role in the synthesis of triterpenoid saponins during the growth and development of Platycodon grandiflorum.Determining the activity of key enzymes in triterpenoid saponin synthesis can help us to understand the rate of triterpenoid saponin synthesis,the accumulation rule and amount of triterpenoid saponins,and also provide theoretical basis for the development and utilization of Platycodon grandiflorum resources.The content of Platycodon D in the root of Platycodon grandiflorum was determined by high performance liquid chromatography.The results showed that the content of Platycodon D in Platycodon grandiflorum roots was 6.130,9.740,11.280,5.070,7.560,5.830,2.690,2.580 and 1.220 in March-October and control respectively.The content of Platycodon D in Platycodon grandiflorum was significantly higher than that in the control group,indicating that the effective medicinal ingredients of Platycodon grandiflorum in this base were better,and the content of Platycodon D reached the highest in May,and tended to be stable in September and October.During the growth and development of Platycodon grandiflorum,there was a certain relationship between the root microstructure,the key enzyme activity of triterpene saponin synthesis and the content of Platycodon D.Especially in September and October,Platycodon grandiflorum accumulated more substances,enzymes activities were higher,triterpenoid saponins synthesized faster,and Platycodon D content was stable.Therefore,September and October are the best harvesting period for Platycodon grandiflorum.The results can provide theoretical basis for further efficient development and utilization of Platycodon grandiflorum resources.