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Issue 4, 2012
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Reactions of green and black teas with Cu(II)

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Abstract

Electron paramagnetic resonance (EPR) measurements of the products of reactions between Cu(II) and samples of green and black teas showed spectral components from at least six different Cu(II) complexes with both tea types. Several of these complexes were common to both teas in spite of major differences in their polyphenol compositions. The pH range observed for complex formation, and the total signal intensity in the pH range 4–8, were greatly different from those for the reactions of Cu(II) with (−)-epigallocatechin gallate and gallic acid, the main polyphenols responsible for the free radical signals observed during oxidation of these beverages. Components with spectral parameters similar to those of Cu(II) complexes with theanine, the major amino acid in tea, may contribute to two of the spectra recorded under acidic conditions. However, the initial complexes formed at the lowest pH values investigated are still unidentified. EPR spectra with parameters consistent with Cu(II) polyphenol complexes were only observed under alkaline conditions, thus suggesting that components of tea other than polyphenols might be more important in reactions with copper, and possibly other transition metals, in solutions under physiological conditions.

Graphical abstract: Reactions of green and black teas with Cu(ii)

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Publication details

The article was received on 29 May 2011, accepted on 12 Oct 2011 and first published on 13 Dec 2011


Article type: Paper
DOI: 10.1039/C1FO10086F
Food Funct., 2012,3, 399-409

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    Reactions of green and black teas with Cu(II)

    B. A. Goodman, J. F. Severino and K. F. Pirker, Food Funct., 2012, 3, 399
    DOI: 10.1039/C1FO10086F

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