The composition of polyphenols and methylxanthines in teas and herbal infusions

The popularity of tea is increasing on the global aspect because of its role as a significant source of phenolic compounds in human diet. The purpose of this study was to determine and compare the phenolic and methylxanthine composition as well as the antioxidant capacity of white, green, Oolong and black teas, and chamomile and linden infusions depending on the extraction conditions (water temperature and multiple extractions). The content of total phenols and total flavonoids in teas and herbal infusions was determined by using UV/vis spectrophotometric methods, whilst individual polyphenols (phenolic acids and flavan-3-ols) and methylxanthines were identified and quantified by using high performance liquid chromatography coupled with photodiode array detection. In order to determine the antioxidant capacity of teas the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging assays were applied. The highest content of phenolic compounds was determined in green tea, which also demonstrated the highest antioxidant capacity, whilst herbal infusions were characterised with the lowest content of phenolic compounds, as well as the lowest antioxidant capacity. The highest content of caffeine, as the most abundant methylxanthine, was determined in black tea. Extraction at 100 degrees C is the most effective to extract the highest content of polyphenols and methylxanthines in all studied teas. (C) 2008 Elsevier Ltd. All rights reserved.