| Summary: | 碩士 === 國立陽明大學 === 生命科學系暨基因體科學研究所 === 101 === Studies on the bioactive chemical constituents of two Asteraceae medicinal plants
Preliminary in vitro cytotoxicity screenings on the EtOH extracts of Chinese herbal medicine against cancer cell lines revealed that Centipeda minima and Siegesbeckia orientalis were active against CEM and HT-29 cell lines at IC50s lower than 10 μg/ml, indicative of their high potential for development. Both C. minima and S. orientalis are annual herbs distributed in Oceania, Southeast Asia and China, and in Taiwan. They are often found at altitudes from 100 m to 1900 m. C. minima and S. orientalis contain abundant sesquiterpenes and other chemical constituents, and most of the known compounds were isolated in 1980s. Literature survey suggested that microhelenin B (CM-2) inhibits plate-activating factor receptor at an IC50 of 2.3 μg/ml. In this study, we discovered the crude extract of Centipeda minima show cytotoxic to MCF-7 cell line; the crude extract of Siegesbeckia orientalis show cytotoxic to H460 cell line. We also discovered the crude extract of Siegesbeckia orientalis show antiangiogentic activity. To trace the bioactive and new chemical constituents, isolation and purification of the EtOH extracts of C. minima and S. orientalis by Diaion HP-20 adsorption, silica gel column chromatography, MPLC and recrystallization a total of ten isolated compounds. Analyses of these compounds by techniques such as nuclear magnetic resonance, mass spectrometry etc. confirmed the structures of ten compounds, including four pseudoguaianolide type sesquiterpene (CM-1 ~ 4), one guaianolide type sesquiterpene (CM-6), one flavonol (SO-2), one germacrene type sesquiterpene (SO-3), one kaurane type diterpene (SO-1) and two pimarane type diterpene (SO-4 ~ 5). Among them, CM-3 and CM-5 inhibited cell growth of endothelial cells at IC50s of 3.0 and 1.5 μg/ml.
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