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Adding iron to green tea may decrease its antioxidant capacity in rats after an oral dose of the mixture

Kapsokefalou, M., Zhu, L., Miller, D.D.
Nutrition research 2006 v.26 no.9 pp. 480-485
green tea, phenolic compounds, food fortification, fortified foods, antioxidants, rats, animal models, nutrient availability, antioxidant activity, free radicals, free radical scavengers, blood serum, polyphenols
We tested in rats the hypothesis that adding iron to green tea diminishes the increase in antioxidant properties in plasma and red blood cells after tea ingestion. Thirty-two rats were divided randomly into 4 groups of 8 rats each. Rats were administered, by gavage, an infusion of green tea, iron citrate, a mixture of iron citrate and green tea infusion, or water. Blood was drawn under anesthesia from the jugular vein at 10, 30, 45, and 60 minutes after gavage. Antioxidant capacity was measured in plasma with the ferric-reducing ability of plasma and total radical trapping antioxidant parameter assays and in red blood cells (diacetyldichlorofluorescein assay). Phenolic compounds were determined in plasma with the modified Folin-Ciocalteau assay. The antioxidant capacity of plasma, measured with the total radical trapping antioxidant parameter assay, and the polyphenol content of plasma in rats that received tea increased at 30 minutes after gavage (P < .05) and subsequently dropped. When iron was introduced together with tea, the polyphenol content and the antioxidant capacity of plasma did not rise (P > .05), showing a similar profile with plasma of rats that received iron only or water. Results from the ferric-reducing ability of plasma assay in plasma and the diacetyldichlorofluorescein assay in red blood cells were not as clear. This study suggests that iron may modify the antioxidant properties of phenolic compounds. Further studies on the effect of iron on the bioavailability and the antioxidant capacity of phenolic compounds are required.