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  • Title: [Separation and quantification of theanine enantiomers using high performance liquid chromatography coupled with chiral derivatization].
    Author: Li Y, Liu Z, Huang J.
    Journal: Se Pu; 2007 Sep; 25(5):719-22. PubMed ID: 18161325.
    Abstract:
    L-Theanine is a unique non-protein amino acid in tea, and shows many physiological functions. To directly extract L-theanine from tea is a lengthy and very costly process. Although the chemical synthesis of theanines is simple, the product is unfortunately a mixture of DL-enantiomers. A chiral derivatization method was developed for the separation and quantification of theanine enantiomers by reversed-phase high performance liquid chromatography (RP-HPLC). 1-Fluoro-2,4-dinitrophenyl-5-L-alanine amide (FDAA)was used as the chiral reagent. This method showed good linearity for both L-theanine (ranging from 1.732 x 10(-3) to 2.077 microg) and D-theanine (ranging from 1.696 x 10(-3) to 2.044 microg). The recoveries were in the range of 97.3% - 102.0% for L-theanine and 97.2% - 103.2% for D-theanine. This method also showed excellent limit of detection (approximately 5 x 10(-4) microg) and limit of quantification (approximately 1 x 10(-3) microg) for both L-theanine and D-theanine. The results demonstrated that this method is precise, accurate and can be used for the determination of theanine enantiomers.
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