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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

A study of amperometric biosensors of phenolic compounds

Cummings, Edward A. January 2000 (has links)
No description available.
22

Studies on the antioxidant activity and immunomodulatory properties of black tea

Amarakoon, A. M. T. January 1997 (has links)
No description available.
23

Antioxidant effects of phytochemicals in conditions of oxidative stress : impact on endothelial cell survival and function

Deakin, Sherine Jane January 2010 (has links)
Two dietary polyphenols, delphinidin and resveratrol, were selected for this study; delphinidin, an anthocyanin flavonoid, was found to elicit cardioprotective properties from a pilot study and resveratrol, a stilbene flavonoid, one of the most studied of the polyphenols and was chosen as a worthy comparator. <i>In vitro</i> studies using cultured endothelial cells exposed to a variety of reactive oxygen species (ROS) were used to determine if delphinidin and resveratrol could protect these cells from oxidative damage. It was found that physiological concentrations of delphinidin protected these cells from hydroxyl-radical damage. However, resveratrol failed to show any protective effects. Oxidative stress was induced in porcine coronary artery using diethyldithiocarbamate (DETCA), an inhibitor of the superoxide dismutase (SOD). Sensitivity to nitric oxide (NO) was preserved in endothelium-denuded vessels that were pre-treated with delphinidin, but not with resveratrol. However, studies where a balloon catheter was used to induce injury to the endothelium, delphinidin pre-treatment did not preserve sensitivity to NO in these vessels. Taken together, these results suggest that delphinidin, but not resveratrol, has potential to protect the endothelium from oxidative stress by preserving/protecting NO bioavailability and by acting directly as an antioxidant or indirectly upregulating antioxidant systems.
24

Resveratrol and procyanidin content in select Missouri red wines

Ortinau, Laura, Grün, Ingolf, January 2009 (has links)
The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on December 29, 2009). Thesis advisor: Dr. Ingolf Gruen. Includes bibliographical references.
25

Protective effects of natural polyphenols in reactive carbonylspecies/lipid peroxidation-induced toxicity

Zhu, Qin, 朱芹 January 2011 (has links)
Oxidative degradation of lipids, not only leads to the quality deterioration in foodstuffs but also associates with a multitude of physiological processes. One of the causations involved in these damaging effects is the generation of reactive carbonyl species (RCS) in lipid peroxidation process. RCS are notorious toxins that possess reactivity towards biological nucleophiles (such as proteins and DNA) with potential functional alternation in these biomolecules. Therefore, the exogenous intervention is required to inhibit the toxicity related to RCS/lipid peroxidation. In present study, the screening for effective natural polyphenols to trap two representative RCS, acrolein (ACR) and 4-hydroxy-trans-2-nonenal (HNE), was performed with mechanism elucidation. It was found that the polyphenols from the categories of flavan-3-ols, theaflavins, cyanomaclurins and dihydrochalcones were effective scavengers of ACR/HNE. Subsequently, facilitated by HPLC, LC-MS/MS and NMR analysis, the characterization of polyphenols’ as sacrificial nucleophiles towards these two electrophiles products was accomplished. Michael addition at A ring of polyphenols’ to the C=C bond of ACR/HNE was suggested to be responsible for trapping of these two RCS and thus render their active sites unavailable to covalently modify critical biomolecules. Further investigation of phloretin’s effect to attenuate ACR-induced modification on lysine residue and proteins was carried out. Phloretin’s protective effect against ACR’s toxicity was clearly reflected by its inhibition of the formation of Nε-(3-formyl-3,4-dehydropiperidino) lysine (FDP-lysine), blocking the electrophilic site in FDP-lysine, lowering protein carbonylation in bovine serum albumin (BSA) and lessening protein oligomerization in bovine pancreas ribonuclease A. Such protection might be mediated by phloretin’s directly trapping of ACR and consequently deactivation of ACR in covalent modification of amino acids and proteins. The biological relevance of polyphenols’ trapping activity of ACR was explored in a cell culture model. Natural polyphenols including phloretin, EGCG and quercetin were proved to be active to inhibit ACR-induced cytotoxicity in human neuroblastoma SH-SY5Y cells. The cytoprotection of phloretin (as the most potent one in alleviation of ACR stress) was suggested to be achieved through the reduction of the increased cellular protein carbonyl level as revealed by Western blotting analysis. In the final part of this study, an in vitro system containing metal-catalyzed fatty acids and BSA was established to study the modification on protein induced by lipid peroxidation and possible inhibitory effects conferred by some natural polyphenols. The protective effects of these polyphenols against lipid peroxidation-induced modification on BSA was manifested by the observation of reduced levels of high-molecular-weight proteins, MDA-related fluorescent substances and protein carbonylation. However, poor correlations were found between such protection and antioxidant activities, suggesting alternative mechanisms were existed such as carbonyl-scavenging. In conclusion, findings from the present study highlighted certain kinds of natural polyphenols as promising agents in counteracting RCS/lipid peroxidation-induced toxicity in amino acid, protein and cell models. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy
26

Anti-inflammatory and Cytotoxic Activities of Mango (Mangifera indica L. var Keitt) Polyphenols in Cancer and Non-cancer Breast Fibroblasts in Vitro

Arbizu Berrocal, Shirley Heidi 16 December 2013 (has links)
Breast cancer is the leading cause of cancer death among women worldwide and polyphenols are under investigation as an alternative to conventional treatment approaches of breast cancer. The anti-inflammatory and anti-proliferative activities of polyphenols have been demonstrated in many studies, yet cellular targets and the underlying cellular mechanisms remain unclear. The overall goal of this study was to investigate the anti-inflammatory and cytotoxic properties of polyphenol compounds extracted from the mango variety Keitt in MCF-12A breast non-cancer and MDA-MB231 breast cancer cells by assessing the modulation of signaling pathways involved in inflammation and carcinogenesis. Mango polyphenols were identified by HPLC-MS analysis. The generation of reactive oxygen species was performed using fluorescence intensity in the DCFH-DA assay. Gene expression was analyzed by qRT-PCR, and protein expression was conducted by Western Blotting and Multiplex Bead assay analysis. Bioactive compounds identified in the mango pulp by HPLC-MS included a great variety of polyphenols such as gallic acid, galloyl glucosides with different degree of polymerization and other polyphenols. The anti-inflammatory activities of mango polyphenols were evaluated in MCF-12A non cancer breast fibroblasts. An inflammatory microenvironment for MCF-12A breast cells was induced with tumor necrosis factor alpha (TNF-α). The generation of reactive oxygen species was suppressed significantly compared to cells induced with TNF-α, where there was no significant difference between the concentrations of mango polyphenol extract. Results showed a significant down-regulation of mRNA and protein expression of inflammatory genes involved in the PI3K/AKT pathway and related downstream targets such as NF-κB and mTOR involved in biological processes including cell growth, proliferation and survival. Moreover, mango polyphenols had a significant impact on the miRNA-126-PI3K/AKT axis which plays an important role in inflammation and carcinogenesis, suggesting a potential anti-inflammatory underlying mechanism. The cytotoxic effects of mango polyphenols were investigated in MDA-MB231 breast cancer cells. Mango polyphenols decreased the production of reactive oxygen species; however no significant differences were found between the tested concentrations of mango polyphenols. The gene expression of proapoptotic factors involved in the intrinsic mitochondrial pathway such as cytochrome C and caspase-3 were significantly regulated after mango polyphenol treatment. In addition, the suppression of the PI3K/AKT/mTOR pathway and downstream effectors such as HIF-1α and VEGF as well as the disruption of the miRNA-21-PTEN/AKT axis were identified as potential underlying mechanism of the cytotoxic properties of mango polyphenols. Overall, findings from this study show that mango polyphenols counteract inflammatory and cancerous cell signaling processes; therefore the potential of mango polyphenols in the prevention of breast-cancer focusing on the PI3K/AKT/mTOR-axis should be further investigated.
27

Bitterness modifying properties of hop polyphenols

McLaughlin, Ian R. 20 September 2005 (has links)
Graduation date: 2006
28

Trapping of methylglyoxal by dietary compounds in vitro

Tan, Di. January 2007 (has links)
Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Food Science." Includes bibliographical references (p. 84-90).
29

Sugarcane polyphenol oxidase /

Bucheli, Carolyn. January 1900 (has links) (PDF)
Thesis (Ph. D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1995. / Copy of author's previously published article inserted. Includes bibliographical references (leaves 180-195).
30

Select Procyanidins induce gammadelta T cell activation and proliferation

Holderness, Jeffrey Scott. January 2008 (has links) (PDF)
Thesis (MS)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Mark Jutila. Non-Latin script record Includes bibliographical references (leaves 105-131).

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