| Rhubarb is a typical representative of commonly used Chinese herbal medicines.With the increasing domestic demand and foreign demand,excessive excavation leads to a significant reduction of wild resources and it could not meet the demand in these days,so the rhubarb is mainly from cultivar.The clinical efficacy may be affected by the different provenance or ecological condition of the cropped location.Material basis of pharmacological effect for rhubarb is a variety of efficacy components.The efficacy component varying with geographic variation is one of the causes of the unstable clinical efficacy of rhubarb cultivar.It is necessary to further resolve the geographic variation pattern and its formation mechanism of the efficacy components.In order to realize the accurate medication for the rhubarb,it is necessary to selected a particular harvest processing besides selecting specific provenance and exceptional cultural environment.In this research,the most widely distributed and the most-found cultivated Rheum palmatum L.and Rheum tanguticum Maxim.ex Balf.were taken as materials for systematic analysis of geographical variation of the three traditional active ingredients.Then,the genetic and environmental mechanism of geographical variation of active ingredients was studied with the molecular phylogeography methods and ecological factor analysis.Based on the study above,the suitable seed source and origins were selected.Further,the proper collection time,processing method and sampling location were determined in reference to those of Rheum tanguticum Maxim.ex Balf.Results have shown that:(1)Study of the geographical variation pattern of active ingredients of rhubarb has found that active ingredients of both the Rheum palmatum and Rheum tanguticum Maxim have geographical variation.To be specific,dianthrone glucosides in Rheum palmatum varied longitudinally and latitudinally,with the trend that within a geographical range,the content of dianthrone glucosides gradually rose from east to west,from north to south.The total free anthraquinones mainly varied longitudinally,with the trend that within a geographical range,the content of total free anthraquinones gradually rose from west to east.In Rheum tanguticum Maxim,phenolic acids mainly varied longitudinally,with the trend that within a geographical range,the content of phenolic acids gradually rose from west to east.The total free anthraquinones mainly varied latitudinally,with the trend of gradual rise from south to north.(2)Study of the genetic mechanism for geographical variation of active ingredients in rhubarb has shown that in Rheum palmatum,samples with the haplotypes HRP1 and HRP5 of chloroplast matK had the highest content of phenolic acids,samples with haplotype HRP4 had the highest content of dianthrone glucoside,samples with haplotypes of HRP1,HRP8,HRP6 and HRP9 had the highest content of total free anthraquinones,samples with haplotypes HRP2 and HRP5 had the highest content of total combined anthraquinones,and samples with haplotypes HRP2 and HRP5 had the highest content of total anthraquinones.In Rheum tanguticum Maxim,samples with haplotype HRT13 had the highest content of phenolic acids and dianthrone glucosides,samples with haplotype HRT14,HRT11,HRT13 had the highest content of total free anthraquinones,samples with haplotype HRT10 had the highest content of total combined anthraquinones and samples with haplotype HRT10 and HRT11 had the highest content of total anthraquinones.This indicates that different haplotypes have different contents of active ingredients.The nuclear gene ITS cloned homozygotes were grouped by active ingredient,with results as follows:in Rheum palmatum,samples with cloned homozygotes RP4 and RP7 had the highest content of phenolic acid,samples with the cloned homozygote RP8 had the highest content of dianthrone glucosides,samples with cloned homozygotes RP4,RP6 and RP5 had the highest content of total free anthraquinones,samples with cloned homozygotes RP7 and RP9 had the highest content of total combined anthraquinones and total anthraquinones.In Rheum tanguticum Maxim,samples with cloned homozygotes RT4,RT11 and RT10 had the highest content of phenolic acids,samples with cloned homozygotes RT2 and RT9 had the highest content of dianthrone glucosides and total free anthraquinones,and samples with cloned homozygote RT4 had the highest content of total combined anthraquinone and total anthraquinone.(3)Study of the ecological mechanism for geographical variation of active ingredients of rhubarb has shown that the content of active ingredients in Rheum palmatum from eight seed sources had negative correlation with longitude and latitude and positive correlation with annual precipitation and annual moisture content.The content of active ingredients of Rheum tanguticum Maxim from six seed sources had negative correlation with longitude,latitude,average temperature in July and annual sunshine hours and positive correlation with annual precipitation and annual moisture content.This indicates that if the content of active ingredients is taken as a criterion,both the Rheum palmatum and Rheum tanguticum Maxim will grow better at the lower longitude,lower latitude,fewer annual sunshine hours,higher annual precipitation and higher annual average moisture content.(4)Study of applicable medicinal location,processing method and collection time in the specially-planted medicinal materials of special efficacy has shown that different locations have different contents of active ingredients,with the greater-diameter roots having the highest content of active ingredients and the 1cm-2cm roots having similar content of active ingredients as the rhizome.Contents of activities ingredients varied among different processing methods,with the gezi drying in shade method having higher content of dianthrone glucosides and phenolic acids,drying at 60℃-70℃ having higher content of combined anthraquinones,and both the gezi drying in shade and gezi smoke drying having higher content of total free anthraquinone.Also,contents of active ingredients varied among different collection time,with the best collection time happening in September for the 6-year plant if calculated based on the phenolic acid content and per mu yield,in July for the 6-year plant if calculated based on the dianthrone glucoside content and per mu yield,in May for the 4-year plant if calculated based on the total free anthraquinone content and per mu yield and in July for the 4-year plant if calculated based on the total combined anthraquinone content and per mu yield.This study has laid a theoretical and practical foundation for directive breeding of medicinal materials of special efficacy,improving quality of man-cultivated rhubarb,clinical selection of rhubarb drugs,guaranteeing more accurate clinical drug application in traditional Chinese medicine and enhancing curative effect of TCM.In addition,it can provide reference for like studies on other medicinal plants. |
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