Sensitive Enzymatic Method for the Quantification of Theanine, a Principal Umami Component of Commercial Tea Beverages

Shimizu, Yoichiro; Imaoka, Masashi; Yano, Shigekazu; Sawaragi, Yosuke; Takagi, Kazuyoshi; Wakayama, Mamoru

doi:10.3136/fstr.19.909

Cited by 2 publications

(2 citation statements)

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“…With L-THE lacking a chromophore group, the use of chromatographic methods for its estimation requires pre or post-column derivatisation to allow high sensitivity for ultraviolet (UV), visible, fluorometric, or electrochemical detection. However, such methods generally require expensive instrumentation and reagents [44]. On the other hand, ECC involves the application of different voltages across buffer filled capillaries to separate colloids based upon their differences in electrophoretic mobility.…”

Section: Analytical Methods For the Determination Of L-the Levelsmentioning

confidence: 99%

“…A relatively simple colorimetric assay using enzymes (an environmentally friendly and low cost approach) has also been reported. It involves the coupled reaction of Pseudomonas nitroreducens NBRC 12694 (PnGGT, involved in catalysing theanine synthesis from glutamine and ethylamine effectively by a transfer reaction) and an amine dehydrogenase from Paracoccus denitrificans NBRC 12442 (PdADH, involved in catalysing the oxidative deamination of primary amines as well as aromatic amines, and shows a strict substrate specificity toward amines) [44]. The micellar electrokinetic capillary chromatography technique has also been reported for quantification of L-THE.…”

Section: Analytical Methods For the Determination Of L-the Levelsmentioning

confidence: 99%

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l-Theanine as a Functional Food Additive: Its Role in Disease Prevention and Health Promotion

et al. 2016

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Tea has been consumed for thousands of years and is an integral part of people's daily routine, as an everyday drink and a therapeutic aid for health promotion. Consumption of tea has been linked to a sense of relaxation commonly associated with the content of the non-proteinogenic amino acid theanine, which is found within the tea leaves. The aim of this review article is to outline the current methods for synthesis, extraction and purification of theanine, as well as to examine its potential benefits related to human health. These include improvements in cognitive and immune function, cancer prevention, reduced cardiovascular risk and its potential usefulness as a functional food product.The relative concentration of L-THE in the Camellia sinensis plant varies between the plant's structures, over maturation and through the growth period. Recent studies have indicated that L-THE is distributed across the entirety of the plant with concentrations ranging between 1.2 and 6.2 mg/g fresh weight, with higher concentrations being expressed in the roots (6.2-13.7 mg/g). The biosynthesis of L-THE is proposed to occur in the roots of the plant and it is then transported towards the leaves [11]. The shading treatment and nitrogen fertilisation have been shown to influence the L-THE levels and the total free amino acid content in the Camellia sinensis plant [12]. Although most often related to GT, L-THE is present at similar levels in other types of teas made from the plant, including black, white and oolong teas [13]. Chemical, Physical and Flavour PropertiesL-THE is a water soluble non-proteinous amino acid [14] containing a glutamine backbone within the core of L-THE as well as existing as an ethylamide derivate of glutamate [15]. It is stable in acidic conditions but yields glutamic acid and ethylamine during base hydrolysis [8,16]. L-THE is insoluble in organic solvents such as chloroform and methanol, which facilitates the easy separation of L-THE from caffeine, catechins and other lipophilic tea constituents [8]. Aqueous L-THE solutions (1% (w/v)) stabilised at pH 5-6, were found to be stable (>1 year) under normal environmental conditions [8,16,17] and have a boiling point higher than that of water (range 214-216˝C) [8]. Furthermore, its systematic nomenclature is described as (2S)-2-amino-5-(ethylamino)-5-oxopentanoic acid (C 7 H 14 N 2 O 3 , M.W. = 174.2 g/mol) [18]. and L-glutamic acid-gamma-ethylamide have also been used to denote L-THE and it is also available under the proprietary name Suntheanine ® [5,19]. Similar to other amino acids in nature, theanine is a chiral species and occurs predominantly as the L-(S) enantiomer (Figure 1), whereas a synthetically derived theanine is typically a racemic mix of L-and D-enantiomers. As such, the use of synthetically derived theanine may not necessarily exhibit the same physiological effects as theanine found "naturally" occurring in foods [8].

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Section: Analytical Methods For the Determination Of L-the Levelsmentioning

confidence: 99%

Section: Analytical Methods For the Determination Of L-the Levelsmentioning

confidence: 99%