HPLC ANALYSIS OF FREE AMINO-ACIDS AND CAFFEINE IN GREEN TEA CULTIVATED BY HYDROPONICS

Free amino acids and caffeine in green tea cultivated by hydroponics were analyzed by an HPLC system using UV detector. Standard solution containing amino acids or green tea fresh extracts were labeled with Edman's method, and formed phenylthiocarbamoyl derivatives. Amino acids derivatives were separated on a Wakopack WS-PTC column (200 x 4.0 mm i.d.) using a linear-gradient of 0-70% (0-15 min) acetonitrile/60 mM: sodium acetate buffer pH 6.0 (60 : 40 v/v) in acetonitrile/60 mM sodium acetate buffer pH 6.0 (6 : 94 v/v) and an isocratic separation (15-20 min) with acetonitrile/60 mM sodium acetate buffer pH 6.0 (60 : 40 v/v). In this method, 14 kinds of amino acids and caffeine were detected in tea extract. Accuracy of this method was ensured with 0.30 similar to 6.97% of coefficient of variation and 95.0 similar to 105.9% of recovery. The main free amino acid in fresh green tea was theanine in five organs, and the concentration of theanine, arginine, and threonine were high in roots, stems, and younger leaves. Caffeine was also plentiful in younger leaves, but not detected in roots. The components of free amino acids was slightly difficult in five organs. Total free amino acids content was rich in younger leaves than more developed ones, and the level in roots was about four times as high as that in buds and first leaves.