title: [Separation and quantification of theanine enantiomers using high performance liquid chromatography coupled with chiral derivatization].
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.
authors.affiliation: Institute of Natural Products, Hunan Agricultural University, Changsha 410128, China.
authors.forename: Yinhua
authors.initials: Y
authors.lastname: Li
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Liu
authors.forename: Jian'an
authors.initials: J
authors.lastname: Huang
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005971:Glutamates / Q000737:chemistry* / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D015203:Reproducibility of Results; D013237:Stereoisomerism
chemical_list: D005971:Glutamates; C026166:theanine