| Free radical formed during oxidation processes occurring in various products and living organisms. The oxidation caused by free radicals was not only closely related with the occurrence of various diseases, but also accelerated the damage to food, health and aging. As a result, Antioxidants are always widely concerned because of the harmfulness, Consequently, antioxidants, especially those known as primary, natural and nontoxic antioxidants, have become an essential part of preservation technologies and contemporary health care. In order to screen natural, non-toxic and highly active antioxidants, the development of a fast and effective method for screening is very important. Currently, the method of Screening antioxidants due to cumbersome and difficult to control experimental conditions, time-consuming effort, and require expensive equipment and reagents is difficult to spread. In this paper, On line HPLC-DPPH screening method is established for rapid screening antioxidants form extract of Chinese herb, and then the antioxidants were identified by UV, MS and NMR technology after separation and purification. The greatest benefit of the method is that it is immediately clear which constituent possesses radical scavenging activity without purify every single constituent for off-line assays, So the method is simple and fast, intuitive and clear, accurate, simple operation and good reproducibility.This study has mainly finished the following work:1:An analytical method was developed for the determination of baicalein in the ten different habitats Scutellariae by HPLC-UV, The method is simple sample pre-treatment, fast, accurate and good reproducible, So it can be used for the quality control and evaluate. Then a line HPLC-DPPH Screening System was established, the system is used for screening antioxidants form extracts of Scutellariae, and Comparing antioxidantive difference of Scutellaria root, stem, leaf and the ten habitats. The antioxidants were identified by UV, MS and NMR technology after separation and purification. The result is that the Baicalein, Baicalin, dihydrostreptomycin, wild-dihydro-baicalin and Scutellarin have antioxidant capacity.2:An analytical method was established for the simultaneous determination of quercetin, quercetin-3-O-a-L-rhiamnoside, pinocem-birn-7-O-β-D-glucoside in Penthorum chinense Pursh by HPLC. The chromatography column is Spherigel ODS C18(4.6×200mm,5μm), Mobile phase is phosphoric acid in water and acetonitrile(pH=3), The gradient HPLC flow is 1mL/min. This method has good precision, reproducibility and stability. Then Screening antioxidants from exract of Penthorum chinense Pursh by on line HPLC-DPPH method, Comparing the differences in parts of root, stem, leaf and different habibats of Penthorum chinense Pursh, The significance is to provide an important reference to the cultivation of Penthorum chinense Pursh in order to ensure that medicinal efficacy. Purification and identification of antioxidants form Penthorum chinense Pursh after screening. The purpose is to study the pharmacological effects and quality assurance in Penthorum chinense Pursh.3:Study of the relationship between flavonoids structure and capacity of antioxidant activity by on line HPLC-DPPH method.Discuss the impact of the structure of flavonoid compounds, hydroxyl position, number, glycosides and antioxidant capacity. The Significance is how to choose primary and high efficient antioxidants as additive agent in food and drug. Moreover the another advantage is that extract antioxidants Prioritily from the high content of chinses herbal. The reserch can help us to modify molecular of flavonoids in order to increase the antioxidant capacity. And to guide the Synthetic of antioxidant. So more and more natural antioxidants additive in pharmaceuticals and food was extensive applied.
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