Maysoon Al-Hafez - Polyphenols, flavonoids and (-)-epigallocatechin gallate in tea leaves and in their infusions under various conditions

Document created by Maysoon Al-Hafez on Apr 15, 2016Last modified by Maysoon Al-Hafez on Apr 15, 2016
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– The purpose of this paper was to determine total   polyphenols (TP), total flavonoids (TF) and (-)-epigallocatechin   gallate (EGCG) in five   commercial tea extracts and in their infusions at various   temperatures (95-60°C) and brewing times (5-30 min).
– TP was determined by the Folin–Ciocalteu method, TF by   the aluminium chloride colorimetric method andEGCG by   HPLC method.
– The results showed that White tea – Silver needle had the   highest content of TP and EGCG when   extracted, but its infusions had very poor concentrations of   these compounds. Green tea infusion was better source of TP   and EGCG than   white or black tea, although its extract did not contain a very   high amount of TP compared to the latter two types. Black tea   extract had a relatively high content of TP and TF in its   extract. Its infusions as well contained higher concentrations of   TP than white tea, but lower concentrations of EGCGthan all   studied teas.
– Increasing infusion time and temperature does not   necessarily increase the concentration, according to the results.   To the authors’ knowledge, this is the first report on comparing   these types of tea, especially the white tea, with other   well-known teas under various infusion conditions. The extraction   of the white tea leaves was also not found in previous works.

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