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ABSTRACT
Polyphenols in plants such as tea may offer many health benefits. The leaf and bottled teas available on the market today are advertised with a strong emphasis on their antioxidant properties. In this study, we have quantified the total polyphenol, flavonoid, and theaflavin concentrations by simple colorimetric methods, measured the reactivity of polyphenols using direct and indirect oxidation methods, and identified specific polyphenols present using high-performance liquid chromatography in a variety of commercially available teas. We find that, per given volume, freshly brewed teas are richer in polyphenols and reactivity by a factor five or more compared to bottled teas. Within the brewed and bottled categories, white and green teas are richer in antioxidants than oolong and black teas although the differences are less than a factor of two. We also find that the presence of additives causes changes in antioxidant properties such as an enhancement in Cranberry Orange tea and a reduction in Earl Grey tea. Since we verified our results using several overlapping techniques, we are able to evaluate the analytical tools commonly used in antioxidant studies. We find that the Folin–Ciocalteu method of quantifying polyphenols is a good indicator of the relative antioxidant reactivity of teas.