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Biological properties of selected flavonoids of rooibos (Aspalathus linearis).Snijman, Petra Wilhelmina. January 2007 (has links)
<p>Bioactivity-guided fractionation was used to identify the most potent antioxidant and antimutagenic fractions contained in the methanol extract of unfermented rooibos (Aspalathus linearis), as well as the bioactive principles for the most potent antioxidant fractions. The aim of this thesis was to investigate whether the same flavonoids are responsible for both the potent antioxidant and antimutagenic properties of unfermented rooibos.</p>
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Structural characterization of isomeric flavonoid glycosides and metabolites by metal complexation and electrospray ionization tandem mass spectrometryDavis, Barry D., January 1900 (has links)
Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.
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Structural activity relationship of flavonoids on endothelial nitric oxide expressionCheung, Hoi-tak. January 2008 (has links)
Thesis (M. Med. Sc.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 38-50)
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GABA[subscript A] receptor subtype selectivity underlying selective behavioral profiles of neuroactive flavonoids /Wang, Feng. January 2008 (has links)
Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references (leaves 99-119). Also available in electronic version.
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The effect of plant UV-B absorbing compounds on life history traits and reproductive performance in variable UV-B environmentsCooke, Susan Jill. January 1999 (has links)
Thesis (Ph. D.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains x, 130 p. : ill. Vita. Includes abstract. Includes bibliographical references.
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Structural activity relationship of flavonoids on the expression and activity of cyclooxygenaseLeung, Pui-hong. January 2009 (has links)
Thesis (M.Med.Sc.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 44-54).
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Flavonoid chemotaxonomic studies in Cnidoscolus section Calyptrosolen (Euphorbiaceae, Crotonoideae, Manihoteae)Kolterman, Duane August. January 1982 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 244-261).
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Biological properties of selected flavonoids of rooibos (Aspalathus linearis)Snijman, Petra Wilhelmina January 2007 (has links)
Magister Scientiae - MSc / Bioactivity-guided fractionation was used to identify the most potent antioxidant and antimutagenic fractions contained in the methanol extract of unfermented rooibos (Aspalathus linearis), as well as the bioactive principles for the most potent antioxidant fractions. The aim of this thesis was to investigate whether the same flavonoids are responsible for both the potent antioxidant and antimutagenic properties of unfermented rooibos. / South Africa
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Studies related to natural products : part I selected electrophilic substitution reactions of 3-methylfuran part II structural elucidation of oxygen heterocycles from Zeyhera tuberculosaHanssen, Harald Wilhelm January 1970 (has links)
Part I describes an investigation of the following electrophilic substitution reactions of 3-methylfuran. Acylation under Friedel-Crafts conditions yielded 3-methyl-2-acetylfuran (8) and 3-methyl-5-acetylfuran (9) in the ratio 65:35. Vilsmeier and Gatterman formylation procedures yielded 3-methylfurfural (10) and 3-methyl-5-furfural (11) in the same ratio, 93.5:6.5. Mercuration of 3-methylfuran yielded only the 2-mercuro derivative.
Part II describes the isolation and structural elucidation of two major oxygen heterocyclic compounds C and D occurring in the leaves of Zeyhera tuberculosa Bur. et Verlot (Bignoniaceae). Compound C is assigned the structure 5,6,7,8-tetramethoxyflavone (25) on the basis of spectroscopic evidence. Compound D is shown to possess the structure 5,6,7-trimethoxyflavone (35). In this latter instance spectroscopic and chemical evidence could be obtained in support of the structural assignment. In particular, alkaline hydrolysis of D yielded 2,3,4-trimethoxy-6-hydroxyacetophenone (34), the identity of which was established by an unambiguous synthesis.
In the synthesis of the acetophenone derivative (34), the key intermediate is 2,6-dimethoxyhydroquinone diacetate (31) which was subjected to Fries rearrangement conditions, followed by acid hydrolysis, to give 2,4-dimethoxy-3,6-dihydroxyacetophenone (33). Partial methylation of (33) yielded (34). / Science, Faculty of / Chemistry, Department of / Graduate
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The synthesis and electrochemical studies of chalcones and flavanones: an investigation of their antioxidant activityBaugaard, Carlo January 2013 (has links)
>Magister Scientiae - MSc / Flavonoids, one of the biggest classes of secondary metabolites, are found abundantly in
nature in a broad range of fruits, vegetables and beverages such as tea, coffee, beer, wine and fruit drinks. Flavonoids have been reported to exert multiple biological functions as well as tremendous pharmacological activity, including anticancer activity, protection, antioxidant activity, cardiovascular protection, antibacterial, antifungal and antiviral activity. The antioxidant activity of flavones is reported to be associated with those bearing hydroxyl functions. In the present study, several reaction steps have been carried out to synthesize three sub classes of flavonoids namely; chalcones, dihydrochalcones and flavanones with various substituents attached. The first step involved protection of hydroxyl groups of acetophenone and benaldehyde as starting materials. Thereafter the Clasien Schmidt condensation reaction, under basic conditions, was performed to afford chalcone intermediates. Treatment of these chalcones with sodium acetate, under reflux, afforded flavanones as a single product in high yields. Thereafter all protecting groups where removed to yield the final products. All products and intermediates where purified by column chromatography and were characterized by Nuclear Magnetic Resonance Spectroscopy (NMR) (1H NMR and 13C NMR). An electrochemical analysis on all flavonoid compounds was performed by Cyclic
Voltammetry (CV) and Square Wave Voltammetry (SWV) to give information on the
accessible redox couples identified by their oxidation potentials. Oxidation potentials,
which gave valuable information about reducing ability and hence the antioxidant activity, where used to compare all compounds. The antioxidant activity was observed to increase with the addition of hydroxyl groups on the B-ring. Compounds with a combination of hydroxyl groups on the A-ring and methoxy groups on the B-ring showed increased antioxidant activity when compared to those with only hydroxyl groups on the base structure. 2, 5, 4’-trihydroxy dihydrochalcone showed moderate antioxidant ability. However the 2, 5, 4’-trihydroxychalcone, containing the α, β unsaturated double bond, proved to have the greatest antioxidant ability.
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