Determination of Theanine, GABA, and Other Amino Acids in Green, Oolong, Black, and Pu-erh Teas with Dabsylation and High-Performance Liquid Chromatography

Kai-Yang Syu, Chih-Li Lin, Hsiu-Chen Huang and Jen-Kun Lin*
Graduate Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei, Taiwan
J. Agric. Food Chem., 2008, 56 (17), pp 7637–7643
DOI: 10.1021/jf801795m
Publication Date (Web): July 25, 2008
Copyright © 2008 American Chemical Society
* Address correspondence to this author at the Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Section 1, Jen-ai Road, Taipei, Taiwan [telephone (886)-2-2356-2213; fax (886)-2-2391-8944; e-mail jklin@ha.mc.ntu.edu.tw].

Abstract

Dabsyl chloride (dimethylaminoazobenzene sulfonyl chloride), a useful chromophoric labeling reagent for amino acids and amines, was developed in this laboratory in 1975. Although several methods have been developed to determine various types of amino acids, a quick and easy method of determining theanine, GABA, and other amino acids has not been developed in one HPLC system. In this paper are analyzed the free amino acid contents of theanine and GABA in different teas (green tea, black tea, oolong tea, Pu-erh tea, and GABA tea) with a dabsylation and reverse phase high-performance liquid chromatography (HPLC) system coupled with a detector at 425 nm absorbance. Two reverse phase columns, Hypersil GOLD and Zorbax ODS, were used and gave different resolutions of dabsyl amino acids in the gradient elution program. The data suggest that the tea source or the steps of tea-making may contribute to the theanine contents variations. High theanine contents of high-mountain tea were observed in both green tea and oolong tea. Furthermore, the raw (natural fermented) Pu-erh tea contained more theanine than ripe (wet fermented) Pu-erh tea, and the GABA contents in normal teas were generally lower than that in GABA tea.

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History

  • Published In Issue September 10, 2008
  • Article ASAPJuly 25, 2008
  • Received: June 11, 2008
    Accepted: June 24, 2008

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