In vitro interactions of blueberry phenolics with protein, nucleic acids, and cells
LE3 .A278 2011
Master of Science
Research has revealed persuasive evidence that blueberry fruit (Vaccinium spp.) contain a variety of phytochemicals that could alone, or in combination, protect against certain cancers, cardiovascular disease, neurological disorders, diabetes, and obesity. Many questions exist about the in vivo bioactivity and distribution of blueberry phytochemicals (e.g., proanthocyanidins, anthocyanins, and flavonols), as well as the possible combinatorial effects of the constituent components. Human and animal studies are typically conducted by feeding whole-fruit or isolated flavonoids at physiologically irrelevant concentrations. To date, there have been no systematic investigations of the interactions between combinations of blueberry phenolic constituents and biological macromolecules and cells. This work seeks to bridge this gap by examining the interactions of biomolecules and cells with distinct compositions of blueberry phenolics, underscoring the importance of combinatorial effects in evaluating the biological activity of whole fruits. Five distinct fractions were isolated from lowbush blueberries, with attention to their concentrations in phenolics, anthocyanins, chlorogenic acid, and oligomeric and/or polymeric compounds. Biomolecular interactions with in vitro models of protein (human serum albumin) and nucleic acids (herring sperm DNA and plasmid DNA) were probed. Interactions with HL-60 cancer cells were also investigated in an attempt to elucidate the subcellular organelles involved in cell growth inhibition, which is vital information for understanding in vivo mechanisms of action. Key results presented in this thesis show that all of the blueberry phenolic mixtures demonstrated affinity to human serum albumin, a major finding that has implications for phenolic bioavailability in vivo. In plasmid DNA studies all of the phenolic mixtures acted as either anti-oxidants, in the presence of hydroxyl radicals, or pro-oxidants, in the absence of radical oxygen species. All of the phenolic mixtures inhibited HL-60 cell growth, and the xiv proanthocyanidin mixture showed a concentration-dependent increase in apoptotic cells with a concomitant decrease in mitochondrial membrane potential. The overall results suggest that between the two whole blueberry fractions, the total flavonoid mixture was the most potent, and of the three subfractions, the isolated proanthocyanidin mixture was the most active component. These results, and others, are detailed in this thesis.
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