Electrogenerated bromine as a coulometric reagent for the estimation of the bioavailability of polyphenols |
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Authors: | A M Nizamova G K Ziyatdinova G K Budnikov |
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Institution: | 1.Butlerov Chemical Institute,Kazan (Volga Region) Federal University,Kazan,Russia |
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Abstract: | A method is proposed for the estimation of the bioavailability of polyphenols using electrogenerated bromine as a coulometric
titrant. The titration of model solutions of casein and bovine serum albumin (BSA) shows that casein does not interact with electrogenerated bromine, while BSA reacts with the titrant in the ratio 1: 63.
The proteins bind rutin and quercetin (from 14 to 90%) at a high rate and thus reduce the bioavailability of polyphenols.
The concentration of free polyphenol is reduced with an increase in the concentration of protein in the mixture. The total
antioxidant capacity (AOC) of tea is determined. Green tea is shown to possess higher AOC than the black one because of the partial oxidation of polyphenols
to respective thearubigins and theaflavins at the fermentation step in the production of green tea. The total AOC of tea drops
from 7 to 85%, in proportion to the increase in the amount of milk in the mixture. Milk proteins bind tea polyphenols into
complexes because of intermolecular interactions and thus reduce their bioavailability. The observed effect of milk is independent
of the brand of black tea. The degree of reduction of the total AOC of tea in going from one tea to another remains virtually
constant. |
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