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Coupling Chromatographic Techniques For Preparative Isolation Of Tea Ingredients And Its Detection On Antioxidant Activity

Posted on:2015-03-22Degree:MasterType:Thesis
Country:ChinaCandidate:F F ChenFull Text:PDF
GTID:2254330428963723Subject:Medicinal chemistry
Abstract/Summary:PDF Full Text Request
Rapid separation and detection of complex active ingredients were difficult problems in the natural products research. In this work, three on-line liquid chromatography tandems were developed for one-step preparative separation of components and screening of individual antioxidants from the tea water extractFirstly, according to the different separation mechanism between the molecular exclusion chromatography and reversed-phase chromatography, a new two-dimensional medium pressure liquid×preparative HPLC (2D-MPLC x prep-HPLC) was constructed. The Sephadex LH-20medium-pressure column was applied as the first dimension and the C18preparative column as the second one. One-step preparative separation of18compounds,16of which were identified by MS,1H-NMR and even by less-sensitive13C-NMR, could be achieved using this system, exhibiting great advantages in analytical efficiency.Secondly, on the basis of a switching interface with a switching valve as well as two equivalent holding columns, an on-line two-dimensional chromatography coupling of counter-current chromatography and high-performance liquid chromatography (2D CCC×prep-HPLC) was developed. The CCC acted as the first dimensional isolation column with an aqueous two-phase solvent system of isopropanol and16%sodium chloride aqueous solution(1:1.2, v/v), and a preparative column packed with C18had been employed as the second dimensional separation for effluents pre-fractionated. Under the optimum separation conditions, the present integrated system was successfully applied in a one-step preparative separation of11pure compounds from the water extract of tea.9compounds were identified by NMR and MS. The results demonstrated that the on-line2D CCC×LC method was very efficient for the preparative separation of the ingredients from the tea water extract.Finally, a fast and efficient online HPLC-FRAP equipment system for screening of antioxidants from the six kinds tea water extract was developed. Based on the known compounds which were achieved by the above two-dimensional chromatography,8antioxidants were identified from tea the water extract of Tie Guan Yin, of which catechins (EC) and epigallocatechin gallate (EGCG) were the main antioxidants.
Keywords/Search Tags:MPLC×prep-HPLC, CCC×prep-HPLC, HPLC-FRAP antioxidant activityscreening
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