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Bioassay-guided isolation, characterization and mechanistic study of bioactive components from oldenlandia diffusa and androsace umbellata for anti-proliferative effect on human hepatoma cells. / CUHK electronic theses & dissertations collection

Eleven known compounds were separated from Oldenlandia diffusa using the bioassay-guided methods. Among which, heptatriacontane and stearic acid (SA) were isolated from this herb for the first time. The anti-proliferative activities of ursolic acid (UA) and SA, as well as the anti-proliferative and immunomodulatory activities of quercetin, kaempferol, quercetin-3-O-D-glucoside, kaempferol-3-O-D-glucoside and kaempferol-3-O-D-galactoside, are responsible for the anti-hepatomatic effect of OD, to which UA might be the major contributor due to relatively high content in OD and potent cytotoxicity. / In conclusion, our findings provided a better elucidation on phytochemical basis responsible for the anti-cancer activities of OD and AU, and also suggested the potential of UA, SB and SD as new chemotherapeutic agents for the treatment of liver cancer in further studies. / Mechanistic study indicated that anti-proliferative effects of SB and SD due to induction of apoptosis on both HepG2 and R-HepG2 cells were established by sub-G1 accumulation in cell cycle profile and cell population with PS externalization, which were confirmed by activation of apoptosis mediators PARP and caspase-3. The induction of apoptosis was suggested to be mediated by both extrinsic and intrinsic pathways, as evidenced by activation of caspase-8 and -9, up-regulation of Bcl-XS, dysfunction of mitochondria and release of cytochrome c during SB and SD treatment. Besides, Bcl-2 and Bax expression levels were notably different on SB/SD-treated HepG2 and R-HepG2 cells, which implied that Bcl-2 and Bax might play a role in SB and SD modulation of drug resistance on R-HepG2 cells. / Motivated by the serious health hazard worldwide caused by hepatoma and side effects of chemotherapeutic agents in clinical treatment, we have initiated a research project to isolate and characterize bioactive compounds from Oldenlandia diffusa (OD) and Androsace umbellata (AU) as well as to study the molecular mechanisms of their anti-proliferative effects on human hepatoma cells. / On the other hand, phytochemical study of Androsace umbellata led to isolation of two novel triterpenoid sapogenins and five known compounds (3-O-D-glucosyl-(1→2)-L-arabinosyl cyclamiretin A, primulanin, saxifragifolin B, saxifragifolin C and saxifragifolin D). Their anti-tumor effects were firstly reported here, where saxifragifolin B (SB) and saxifragifolin (SD) showed the most potent cytotoxicities on human hepatoma cells. Structure-activity relationship study revealed that introduction of glucosyl moiety might be useful for the enhancement of cytotoxicity of this chemotype. / The action mechanism of UA has been intensively investigated. Our results showed that UA was not a substrate of p-glycoprotein, and it could bypass multidrug resistance of R-HepG2 cells. Furthermore, UA treatment also resulted in apoptotic cell death which was indicated by cell morphology observation, cell cycle analysis, DNA fragmentation and Annexin V-FITC/PI double staining assay. UA-induced apoptosis was associated with the extrinsic (death receptor-mediated) pathway, which was suggested by increase of FasL expression, activation of caspase-8 and caspase-3 as well as cleavage of PARP. Besides, changes implying the intrinsic (mitochondria-mediated) apoptotic pathway, including up-regulation of p53 and Bax, down-regulation of Bcl-2, cleavage of Bid, collapse of Deltapsi m, leakage of cytochrome c and AIF as well as activation of caspase-9, were also observed on R-HepG2 cells after UA treatment. Moreover, elevation of cytosolic calcium concentration, generation of reactive oxygen species and activation of MAPKs pathway were involved in UA-induced apoptosis. Proteomic analysis exhibited significant changes in the expression level of twelve proteins which were involved in tumor cell proliferation, invasion and apoptosis. / Zhang, Dongmei. / "September 2007." / Adviser: Kwok-Pui Fung. / Source: Dissertation Abstracts International, Volume: 69-08, Section: B, page: 4744. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (p. 239-263). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

Identiferoai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344144
Date January 2007
ContributorsZhang, Dongmei, Chinese University of Hong Kong Graduate School. Division of Biochemistry.
Source SetsThe Chinese University of Hong Kong
LanguageEnglish, Chinese
Detected LanguageEnglish
TypeText, theses
Formatelectronic resource, microform, microfiche, 1 online resource (xxiv, 263 p. : ill.)
RightsUse of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/)

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