Concentrations of polyphenols, caffeine and total free amino acid were determined with routine methods after extracted with deionised water in a boiling bath for 45 min with occasional hand shaking (Liang et al., 2003). The extract was immediately filtered and cooled to room temperature and measured for the concentrations of polyphenols and total free amino acid as previously described (Liang et al., 2003). Water extract was determined by an international standard method (ISO 9768:1994). Briefly, a volume of 50 mL of tea extract prepared as described above was evaporated in dish on boiling water bath to rough dry and further dried in an oven at 103 C to complete dryness and then weighted after cooling down to room temperature in a silicagel desiccator. The composition of free amino acids was measured by HPLC (Waters 600; Waters Corp., Milford, MA, USA) with AccQ Tag column (3.9 mm · 150 mm) and a fluorescence detector after derivatisation with AccQFluor ReagentKit following themanufacturer’sprotocol (Waters Corporation, 1996). Contents of total amino acid in the tea infusions were determined by a spectraphotometric method (Liang et al., 2007). The composition of caffeine and catechins in the extract was determined with a HPLC system (Waters 590; Waters Corp.) equipped with a Hypersil ODS2 C18 column (5 lm, 4.6 mm · 250 mm, 35 C) at 280 nm as previously described (Su et al., 2003). Solvents A (2% acetic acid)andB(acetonitrile)wereruninlineargradientswith A decreasing from 93% to 55% within 20 min and maintained for 5 min thereafter at a rate of 1.4 mL min)1. Concentrations of caffeine and catechins were quantified by their peak areas against those of standards prepared fromauthenticcompounds.Totalnitrogenwasmeasured by Kjeldahl digestion method (Liang et al., 2007).