The Root Structure And The Dynamic Accumulation Of Main Composition For Bozhou Asters

Chinese herb aster comes from the root and rhizome of aster tataricus L.f.,a Compositae perennial herbaceous plant.Aster has several functionalities including moistening lung,expelling phlegm and relieving cough.In recent years,pharmacological research shows that aster has the effects of anti-oxidation,antitumor,antivirus,antibacteria,diuresis and antiulcer,etc.Although aster,a local Chinese medicinal herb of Bozhou,has a planting history of over 300 years and has been extensively planted by farmers,the research and report about it up to now is rare.Previous research mostly focused on chemical and pharmacologicl apects of aster.However,no literature was reported on aster's growth period,variation in the number of organs,structure of root,accumulation parts of main medicinal ingredients and quality evaluation.A research shows that the lowe part of aster roots in the market are often cut off,which has no scientific explanation.Pharmacopoeia regulates that aster is harvest in the spring and autumn,but the best harvest season of aster has not been reprted.This study used a series of methods including field experiment,morphologic observation and data analysis,with a combination of plant anatomy,histochemistry,analytical chemistry and modern instrument analytical technique.We look systematically into the growth and development characteristics of aster,the dynamic change of the organ's quantitative characters,the root anatomic structure,the relationship between the accumulation position and structure of main medicinal components(aster ketone,kaempferol,quercetin)and their accumulation,and dynamic content variation of the three main medicinal components in different phrases,which provide theoretical guidance and practical basis for improving herb quality,guiding field cultivation and improving the evaluation of commodity specifications.The results showed that in the growth of aster,seedlings are grown out of buds on the stem nodes of the parent roots,and then the stem base expand and form rhizomes where fibrous roots are grown.July to September is the crucial nutrition accumulation period for aster.The microscopic structure of aster root is similar to ordinary dicotyledonous plant roots.From the outside to inside the structures are as follows: epidermis,cortex and vascular cylinder.The contents of three medicinal ingredients in the roots are dozens of times higher than that in the rhizomes.By using 5% vanillin glacial acetic acid and perchloric acid as color-developing agent,primary phloem of the roots and medial prefrontal cortex(accounting for about half of the diameter of the cortex)were stained in deep color,while the pith and cortex lateral were significantly lighter.Flavonoid compounds were stained yellow to orange by using 5% NaOH solution,and the roots' cortex,phloem and medullary parenchyma cells were all colored yellow.The content of aster ketone,a characteristic component of aster,was determined to be 0.171%~0.248% in root and 0.017~0.071% in rhizome.In both parts,the aster ketone contents reached the highest in December,and then decreased gradually.For quercetin and kaempferol,the active ingredients of aster,their contents in the roots both peaked in the next February after the cultivation,with the value of 0.185% and 0.283% respectively.In contrast,the contents of these two components in the rhizomes peaked in December,with 0.016% and 0.029% respectively.According to these experimental results,it can be concluded that:(1)Parent roots' and rhizomes' quality,segment length and bud number will affect aster's later growth.July to September is the critical period for aster planting in Bozhou and people should pay attention to field management;(2)Asters with different diameters have the same basic structure,the difference lies in the number of cortical parenchyma cell layers,number of phloem bunches,number of secretion pathways and whether it has pith in the center;(3)The histochemistry result showed: the color of Triterpenoid saponins was darker near parenchyma cells and phloem of vascular organization,while the color was lighter near the outside parenchyma cells.Light flavonoids was colored yellow in the whole cortex and parenchyma cells of the pith and the color was evenly distributed.(4)Asters roots with different diameters contain different amount of ketone,with the ketone content order of diameter 1 mm > diameter 1-2 mm > diameter 2-3 mm.The relationship of quercetin content versus the root diameter showed an opposite pattern with that of ketone,while the kaempferol content showed no obvious pattern.The pharmacopoeia specifies that the aster quality assessment should be based on single-ingredient aster ketone.Therefore according the results obtained in this study,the practice in herb markets to cut off the bottompart of the aster roots is unreasonable.This study suggests keeping the bottom thin roots during aster processing,to meets the goal of scientific and reasonable utilizing herb resources.(5)The contents of the three medicinal ingredients in different parts of the aster root are as below: their contents in roots were all obviously greater than those in rhizomes.Their contents in the aster root were several to tens times of the contents in rhizomes,suggesting thatthe ratio of roots to rhizomes could be used as a criteria to assess the aster quality.Moreover,the aster ketone content in aster's mother root comply with pharmacopoeia regulations.Considering the nutrients and quantity of aster in different months,we suggest that December should be the best aster harvest month in Bozou.