Effect Of Drying On Composition Change And Hepatoprotective Activity Of Active Substances In Rheum Palmatum L

The medicinal parts of rhubarb are roots and rhizomes,dry processing of rhubarb after harvesting is very important to the quality and quantity.Rheum palmatum is a genuine medicinal material in Gansu Province,where the local common drying method of Rheum palmatum is smoke-drying.Therefore,an efficient modern drying method,which has such characteristics as environmental protections,simple operation,rapid drying and higher natural constituents content,has not been found to ensure the healthy and sustainable development of rhubarb industry.Based on the above scientific problems,exploring the safe,efficient and high-quality drying methods of R.palmatum is important.This paper draws the following conclusions through drying and hepatoprotective active systematic research :1.Drying time,sensory evaluation and active component content are in evaluating the traditional drying methods(sun drying,shade drying,smoke drying methods)and modern drying methods(oven drying,vacuum drying,heat pump drying,vacuum freeze drying methods).It was found that the sun shed drying method(SD)and hot air drying method(HAD)aquired shorter drying time and the higher active component content.The anthraquinone(AQ)content of R.palmatum which keeping the peel was significantly higher than removing the peel and the AQ content increased with the segment length.And the AQ content of four-year-old plants were significantly higher than that in three-year-old plant.The appearance of R.palmatum was the best when using the drying method of smoke-drying combined with hot air drying(SMD-HAD),and when the diameter was 4 cm and the temperature was 50℃,three-year-old R.palmatum presented the best appearance,and the content of effective components got the highest.2.By comprehensive analysis of drying kinetic characteristics,color characteristic,appearance and microscopic characteristics of R.palmatum,it was found that the Logarithmic,Logistic and Boltzmann models can simulate and predict the moisture loss of the three drying methods,respectively.The initial drying rate is fast and it starts to slow down in the middle period and continues to slow down in the late period by SD and HAD.The moisture content of SMD decreased relatively slowly in the early stage,and decreased rapidly in the middle and late stage.The brighter color and the higher total AQ content of R.palmatum were obtained by HAD method.The color of R.palmatum drying by SMD-HAD presented reddish brown or yellowish brown,and the free AQ content was higher.The changes of microstructure of R.palmatum dried by SD and HAD methods were not conducive to the extraction of effective substances,while the changes of microstructure of R.palmatum dried by SMD-HAD were conducive to the extraction of active components.The comprehensive analysis shows that the combination of SMD-HAD method can be used as the best drying method for R.palmatum.3.The AQ content of R.palmatum was dynamic monitored,The AQ content showed a trend of "decrease-increase-decrease" accompained with the decrease of moisture content.When the moisture content was 40%,free and total AQ content reached to peaks.Metabolomic study indicated that flavonoids,phenolic acids,stilbene and anthraquinones were the main chemicals affecting the quality of R.palmatum with the reduction of moisture content in the drying process.Continuous reduction of moisture content significantly promote the content of phosphoenolpyruvate and D-erythrose-4-phosphate,these two compounds are the important precursors to synthesize the secondary metabolites of anthraquinone,phenolic acid,flavone and stilbene.The results indicated that glycolysis and pentose phosphate were the key pathways to affect the quality of R.palmatum during reduction of moisture content.Phosphoenolpyruvate and D-erythrose-4-phosphate were the key precursors for the production and transformation of active substances in R.palmatum.4.Animal experiments were conducted to compare the effects of drying treatments on the liver protection activity of R.palmatum.The results showed that the moisture content of 40% showed the best liver protection activity.A total of 17 differential metabolites of anthraquinone compounds with different moisture content were obtained by using widely targeted metabolomics.Five antifibrosis active ingredients were screened by network pharmacology : 1,5-Dihydroxy-2-methylanthraquinone,2,6-Dihydroxyanthraquinone,Aurantio-obtusin,Emodin bianthrone and palmidin A.The contents of these 5 different metabolites were the highest in the MC40 group,which was the possibly hepatoprotective active substance basis in MC40 group.Further studies showed that the above five metabolics regulate PI3K-Akt pathway to produce synergistic liver protection by possibly acting on SRC,PIK3 CA,CTNNB1,ESR1,HSP90AA1,RELA,NOS2 and MMP2 targets,respectively.The results of this study indicate that R.palmatum has the characteristics of multi-pathway,multi-target and multi-component synergistic action in the treatment of liver fibrosis,and the difference of AQ metabolites in the drying process has a significant influence on its hepatoprotective activity.This study provides theoretical basis for the establishment of modern drying method and the development of anti-hepatic fibrosis drugs based on the unification of "dryness,composition and efficacy" of R.palmatum.