Int. J. Mol. Sci. 2009, 10(12), 5485-5497; doi:10.3390/ijms10125485
Article

Chelation of Cu(II), Zn(II), and Fe(II) by Tannin Constituents of Selected Edible Nuts

Received: 23 October 2009; in revised form: 24 November 2009 / Accepted: 21 December 2009 / Published: 22 December 2009
(This article belongs to the Special Issue Phenolics and Polyphenolics)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: The tannin fractions isolated from hazelnuts, walnuts and almonds were characterised by colorimetric assays and by an SE-HPLC technique. The complexation of Cu(II) and Zn(II) was determined by the reaction with tetramethylmurexide, whereas for Fe(II), ferrozine was employed. The walnut tannins exhibited a significantly weaker reaction with the vanillin/HCl reagent than hazelnut and almond tannins, but the protein precipitation capacity of the walnut fraction was high. The SE-HPLC chromatogram of the tannin fraction from hazelnuts revealed the presence of oligomers with higher molecular weights compared to that of almonds. Copper ions were most effectively chelated by the constituents of the tannin fractions of hazelnuts, walnuts and almonds. At a 0.2 mg/assay addition level, the walnut tannins complexed almost 100% Cu(II). The Fe(II) complexation capacities of the tannin fractions of walnuts and hazelnuts were weaker in comparison to that of the almond tannin fraction, which at a 2.5 mg/assay addition level, bound Fe(II) by ~90%. The capacity to chelate Zn(II) was quite varied for the different nut tannin fractions: almond tannins bound as much as 84% Zn(II), whereas the value for walnut tannins was only 8.7%; and for hazelnut tannins, no Zn(II) chelation took place at the levels tested.
Keywords: walnuts; hazelnuts; almonds; tannins; metal chelating capacity; Fe(II); Cu(II); Zn(II)
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MDPI and ACS Style

Karamać, M. Chelation of Cu(II), Zn(II), and Fe(II) by Tannin Constituents of Selected Edible Nuts. Int. J. Mol. Sci. 2009, 10, 5485-5497.

AMA Style

Karamać M. Chelation of Cu(II), Zn(II), and Fe(II) by Tannin Constituents of Selected Edible Nuts. International Journal of Molecular Sciences. 2009; 10(12):5485-5497.

Chicago/Turabian Style

Karamać, Magdalena. 2009. "Chelation of Cu(II), Zn(II), and Fe(II) by Tannin Constituents of Selected Edible Nuts." Int. J. Mol. Sci. 10, no. 12: 5485-5497.

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