Phytochemical metabolites and their effects on in vitro and in vivo measures of oxidative stress

Phytochemicals, plant based non-nutrient compounds, are important components of the human diet and have been associated with many of the beneficial effects of fruit and vegetable consumption. Their potential ability to function as antioxidants and also to regulate cell signalling pathways and induce endogenous protective mechanisms is both an exciting and a complicated area of research. Currently it is known that phytochemicals can act to enhance cell survival in cells that are challenged with a cytotoxic stimulus, and it has recently been shown that the combination of different fruit extracts can have a synergistic enhancement on this cell survival. There have been numerous studies into the mechanisms behind this protection, indicating that some phytochemicals may have a direct binding effect on cell signalling molecules, some may act as chemical antioxidants that directly scavenge free radicals and some may induce an adaptive response by upregulation of the body‟s endogenous defence mechanisms. However, the majority of these studies have been conducted using dietary phytochemicals and have not examined the effects of the phytochemical‟s blood metabolites. In this thesis the effects of phytochemical blood metabolites on factors that regulate oxidative stress within the body are examined. It is shown that 3,4-dihydroxybenzoic acid (3,4-DHBA) pretreatment can induce an adaptive response by the upregulation of endogenous antioxidant enzymes and that this effects occurs in four different cell lines that originate from four distinct tissue types. Additionally, an animal experiment was conducted to determine if the results seen in vitro could be related to in vivo effects. The feeding of 3,4-DHBA to Sprague Dawley rats for two weeks at the nonphysiological dose of 100 mg per kg induced endogenous antioxidant expression in both intestine and liver of healthy young adult rats. While this effect is not directly applicable to levels of 3,4-DHBA seen in normal diets, it does highlight the potential for a high 3,4-DHBA or 3,4-DHBA precursor functional food and suggest that long term consumption of dietary levels of these compounds may induce a similar response.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Grantor

The University of Auckland

Year dc:date.issued

2011

Author dc:creator

• Walker, Edward

Advisors dc:contributor.advisor

• Print, C
• Skinner, M
• Sutherland, J
• Greenwood, J

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher.
• Whole document restricted until October 2012 but available by request. Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/6945

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/6945