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Isolation of the effective components from selected natural products and characterization of their bioactivities

Authors Zhang, Jingnan
Issue Date 2009
Summary Natural products especially traditional Chinese medicines (TCMs) are important sources for the discovery and development of novel drugs and health care supplements. However, the separation of the bioactive components from the selected natural products, and the evaluation of the quality and efficacy of the resulting products have been the key challenges. In this study, a general procedure has been proposed to meet these challenges. It includes four steps of feed preparation, extraction, separation and bioassays. Separation is the key step. Antisolvent crystallization is often chosen in the separation step, and the selection of solvent and antisolvent is pivotal. In order to ensure the quality and efficacy of the resulting products, appropriate bioassays should be used to characterize their bioactivities. Then two projects were studied using the above strategy. In these projects, specific bioactive components were isolated following the proposed procedure and their bioactivities were characterized by different bioassays, providing good examples for applying the above conclusion. The first project was on soybean isoflavones which are used for relieving menopausal symptoms and other estrogen-deficient diseases. Here soybean isoflavones were purified by antisolvent crystallization and their estrogenic activities were characterized by E-Screen bioassay. The extraction and purification parameters of the manufacturing procedure were all optimized to give a high yield of total isoflavones. In addition, the effective and safe concentrations of isoflavones in estrogenic therapy were discussed. The second project is on a TCM formula of Sheng Mai San. First of all, the antioxidant components of SMS were explored. With bioassay results being combined with the composition analysis, an inference was drawn that the protective effect of SMS against cellular oxidative injury is due to the combined action of the components, at least including several specific ginsenosides and 5-HMF. Then a new manufacturing procedure was developed. The three herb ingredients were processed together as a whole, and antisolvent crystallization was identified to be effective for purifying both ginsenosides and 5-HMF. HPLC analysis showed that the main components of SMS decoction were conserved and concentrated, and the bioassay results supported that our extracts had strong protective effect, suggesting our proposed procedure gained success for the second time and the selection of solvent and antisolvent was suitable. Then further study was performed on the derivations of the active components. The importance of Radix Ginseng (RG) was reemphasized, and the ingredient Fructus Schisandrae (FS) was found to play multiple important roles in the SMS decoction, which was not mentioned in the traditional theory of Chinese medicines. In addition, the other bioactivities of SMS will be studied in future. Based on the derivation study and bioassays, an important inference was drawn that the better way for studying TCMs is to focus on the whole recipe and the interactions between the herb ingredients.
Note Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2009
Language English
Format Thesis
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