| Huang-qi(Radix Astragali),derived from the root of medicinal plant Astragalus membranaceus(Fisch.) Bge.var.mongholicus(Bge.) Hsiao or A.membranaceus (Fisch.) Bge.,is one of the most widely used Chinese herbs at present either as a single herb or as a collection of herbs in a complex prescription.Studies on pharmacology and clinical practice have demonstrated that Huang-qi possesses many biological functions, including hepatoprotective,neuroprotective effect against ischemic brain injury, immunological properties,cardiotonic and antiaging activities,strengthening of the superficial resistance,promotion of the discharge of pus and the growth of new tissues. As a commonly used traditional Chinese medicine(TCM),it has been utilized for the treatment of nephritis,diabetes,cancer,etc.for centuries.The literatures published at present concerning quality control and evaluation of Radix Astragali are mainly focused on determination of some marker components,which insufficiently represent overall pharmacological activities.The chromatographic fingerprint of Radix Astragali,just established on one solvent extraction part for comparison,can only characterize chemical components contained and cannot explain the role of every component in pharmacological activities.The relationship between chromatographic fingerprint and efficacy of Radix Astragali has not been studied so far.With development of analytical techniques,chemometfic methods,showing powerful performance,have been widely used and are becoming essential approaches for data process in quality control and evaluation of TCMs.In the present work, Chemometric methods were used to analyze the HPLC fingerprint and a novel correlative characteristic fingerprint was proposed and applied to discrimination of Radix Astragali according to geographical origin.IR spectroscopy combined with chemometric method was also applied to identifying habitat and detecting adulteration of Radix Astragali.The significant variables having great contribution to Radix Astragali discrimination based on geographical origin and its adulteration detection were selected successfully;Relationship between chromatographic fingerprints of Radix Astragali injections and scavenger activity against DPPH free radical were modeled by chemometric methods.Thereafter,contribution of chromatographic peaks to scavenger activity was evaluated.Chemometric method could be regarded as a new effective approach to explore fingerprint-efficacy relationship.Our present research work on Radix Astragali mainly includes the following three parts:Firstly,Radix Astragali samples from 5 different geographical origins were collected,and then HPLC chromatographic fingerprint based on efficacious solvent extraction part was established.Chemometric methods were used to select significant variables(chromatographic peaks) for discrimination of Radix Astragali according to different geographic origins.The selected significant chromatographic peaks were employed to construct characteristic fingerprint related to discrimination of Radix Astragali depending on geographical origins.As compared with the original chromatographic fingerprint,the characteristic fingerprint has an improved discrimination.In order to identify the structure of components corresponding to selected significant chromatographic peaks in fingerprints,HPLC/MS technique combined with characteristic UV spectra was employed to study and identify the structure of selected components.And the selected components were elementarily identified as follow:peak 4 is Genistin;peak 9 is Ononin;peak 10 is 9,10-dimethoxypterocarpan-3-O-β-D-glycoside;peak 11 is 2'-hydroxy - 3',4'-dimethoxyisoflavan -7- O-β-D-glycoside.Secondly,an evaluation method for selecting appropriate solvent to extract samples as a pretreatment method to obtain distinct characteristics of IR spectra was proposed. As the result shown,the solution of cluster analysis based on constitutes in butanone extract has the best similarity to real class categorized by geographical origin,so we selected butanone as an appropriate solvent for extraction.Then,samples of Radix Astragali from different geographical regions were discriminated with Fourier transform infrared spectroscopy(FT-IR) and discriminant partial least squares(DPLS) method.The significant wavenumbers for classification in IR spectra were also selected. The results manifested that Radix Astragali samples from different geographical origins were successfully discriminated with FT-IR spectroscopy and DPLS method.The correct rate of discrimination was 100%for samples in test set.The significant wavenumbers containing useful information for classification were found in IR spectra. Meanwhile,the possibility of using IR spectroscopy combined with chemometric method to detect adulteration of Radix Astragali was also explored.To detect adulteration of Radix Astragali,Mahalanobis distance was attempted and demonstrated to be a feasible method to detect adulteration.The useful informative regions of IR spectra were also investigated.The results showed that the most informative region was the functional group region(4000～1300 cm-1),and all the adulterated samples,except for 1%sample,were detected correctly.Finally,HPLC fingerprints of 10 batches of Radix Astragali injections were established,and DPPH free radical scavenging model was selected to evaluate the antioxidant activity of Radix Astragali injections.Partial least squares(PLS) method was employed to model the relationship between the HPLC fingerprint and DPPH free radical scavenging activity.The results shown:both the HPLC fingerprints and DPPH free radical scavenging activity from 10 batches of Radix Astragali injection were obviously different.According to model based on PLS method,some important peaks were found.Among 14 chromatographic peaks,eight peaks were positively relevant to DPPH free radical scavenging activity.However,other six peaks were negatively related to DPPH free radical scavenging activity. |
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