Research Database

Author: Rao T.P. and Ozeki M. and Juneja L.R.

 

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Author: Lyon MR and Kapoor MP and Juneja LR

INTRODUCTION: The purpose of this study was to investigate the efficacy and safety of L-theanine as an aid to the improvement of objectively measured sleep quality in a population of 98 male children formally diagnosed with attention-deficit/hyperactivity disorder (ADHD). METHODS: A randomized, double-blind, placebo-controlled trial was conducted involving boys, ages 8-12 years, who had been previously diagnosed with ADHD. An experienced physician confirmed the diagnosis of ADHD in each subject. Randomization was stratified based upon current use of stimulant medication to ensure an equal distribution of stimulant/non-stimulant treated subjects into active and placebo treated groups. Participants consumed two chewable tablets twice daily (at breakfast and after school), with each tablet containing 100 mg of L-theanine (total 400 mg daily Suntheanine®, Taiyo Kagaku, Yokkaichi, Japan) or identical tasting chewable placebo for six weeks. Subjects were evaluated for five consecutive nights using wrist actigraphy at baseline, and again at the end of the six-week treatment period. The Pediatric Sleep Questionnaire (PSQ) was completed by parents at baseline and at the end of the treatment period. RESULTS: Actigraph watch data findings indicated that boys who consumed L-theanine obtained significantly higher sleep percentage and sleep efficiency scores, along with a non-significant trend for less activity during sleep (defined as less time awake after sleep onset) compared to those in the placebo group. Sleep latency and other sleep parameters were unchanged. The PSQ data did not correlate significantly to the objective data gathered from actigraphy, suggesting that parents were not particularly aware of their children's sleep quality. L-theanine at relatively high doses was well tolerated with no significant adverse events. CONCLUSIONS: This study demonstrates that 400 mg daily of L-theanine is safe and effective in improving some aspects of sleep quality in boys diagnosed with ADHD. Since sleep problems are a common co-morbidity associated with ADHD, and because disturbed sleep may be linked etiologically to this disorder, L-theanine may represent a safe and important adjunctive therapy in childhood ADHD. Larger, long-term studies looking at the wider therapeutic role of this agent in this population are warranted.

 

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L-Theanine Elicits an Umami Taste with Inosine 5′-Monophosphate

Author: Masataka NARUKAWA and Kanako MORITA and Yukako HAYASHI

We investigated the taste synergy between L-theanine and the flavour enhancer, inosine 5′-monophosphate (IMP), by using a human sensory evaluation. When L-theanine was added to IMP, only the umami taste was enhanced. We then investigated this synergistic effect of L-theanine in mice by gustatory nerve recording. We confirmed the synergism between L-theanine and IMP for the umami taste.

 

 

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Author: Masataka NARUKAWA and Kanako MORITA and Masahide UEMURA and Ryo KITADA and Seong-Hee OH and Yukako HAYASHI

Food contains various taste substances. Among them, umami substances play an important role with regard to the perception of the taste of food, but, few studies have examined the taste characteristics of representative umami substances other than monosodium L-glutamate (MSG). By conducting mouse behavioral studies (the 48-h 2-bottle preference test and the conditioned taste aversion test) and assessing gustatory nerve responses, we investigated the taste characteristics of unique umami substances, including sodium succinate, L-theanine, betaine, and the enantiomer of MSG, D-MSG. Furthermore, we examined the synergy of umami with inosine 5′-monophoshate (IMP). In the case of the mice, sodium succinate had an umami taste and showed strong synergy with IMP. L-Theanine showed synergy with IMP but did not have an umami taste without IMP. In contrast, betaine did not have an umami taste or synergy with IMP. D-MSG might have weak synergy with IMP.

 

 

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Author: Russ Mason

 

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Electron paramagnetic resonance studies of gamma-irradiated dl-alanine ethyl ester hydrochloride, l-theanine and l-glutamic acid dimethyl ester hydrochloride

Author: M. HalimBaşkan and Murat Aydın

 

Author: CASIMIR J and JADOT J and RENARD M

Separation and identification of N-ethyl-γ-glutamine from Xerocomus badius A derivative of glutamic acid has been found in the non protein nitrogen fraction of the mushroom Xerocomus badius. The compound was isolated by paper partition chromatography and was shown to be N-ethyl-γ-glutamine. The structure was confirmed by comparison with the synthetic compound. Different steps involved in the possible biogenesis of N-ethyl-γ-glutamine have been discussed.

 

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Author: Lekh Raj Juneja and Djong-Chi Chu and Tsutomu Okubo and Yukiko Nagato and Hidehiko Yokogoshi

Since ancient times, it has been said that drinking green tea brings relaxation. The substance that is responsible for a sense of relaxation, is theanine. Theanine is a unique amino acid found almost solely in tea plants and the main component responsible for the exotic taste of ‘green’ tea. It was found that L-theanine administered intraperitoneally to rats reached the brain within 30 min without any metabolic change. Theanine also acts as a neurotransmitter in the brain and decreased blood pressure significantly in hypertensive rats. In general, animals always generate very weak electric pulses on the surface of the brain, called brain waves. Brain waves are classified into four types, namely α,β,δ and θ-waves, based on mental conditions. Generation of α-waves is considered to be an index of relaxation. In human volunteers, α-waves were generated on the occipital and parietal regions of the brain surface within 40 min after the oral administration of theanine (50–200 mg), signifying relaxation without causing drowsiness. With the successful industrial production of L-theanine, we are now able to supply Suntheanine™ (trade name of L-theanine) which offers a tremendous opportunity for designing foods and medical foods targeting relaxation and the reduction of stress. Taiyo Kagaku Co., Ltd, Japan won the 1998 ‘Food Ingredient Research Award’ for development of Suntheanine™ at Food Ingredients in Europe (Frankfurt). The judges felt it was a particularly well-documented and fascinating piece of research.

 

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Author: Anna C Nobre PhD and Anling Rao PhD and Gail N Owen PhD

Tea is the most widely consumed beverage in the world after water. Tea is known to be a rich source of flavonoid antioxidants. However tea also contains a unique amino acid, L-theanine that may modulate aspects of brain function in humans. Evidence from human electroencephalograph (EEG) studies show that it has a direct effect on the brain (Juneja et al. Trends in Food Science & Tech 1999;10;199-204). L-theanine significantly increases activity in the alpha frequency band which indicates that it relaxes the mind without inducing drowsiness. However, this effect has only been established at higher doses than that typically found in a cup of black tea (~20mg). The aim of the current research was to establish this effect at more realistic dietary levels. EEG was measured in healthy, young participants at baseline and 45, 60, 75, 90 and 105 minutes after ingestion of 50mg L-theanine (n=16) or placebo (n=19). Participants were resting with their eyes closed during EEG recording. There was a greater increase in alpha activity across time in the L-theanine condition (relative to placebo (p<0.05). A second study replicated this effect in participants engaged in passive activity. These data indicate that L-theanine, at realistic dietary levels, has a significant effect on the general state of mental alertness or arousal. Furthermore, alpha activity is known to play an important role in critical aspects of attention, and further research is therefore focussed on understanding the effect of L-theanine on attentional processes.

 

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Author: Baptista, José and Lima, Elisabete and Paiva, Lisete and Andrade, Ana L. and Alves, Maria G.

The objectives of the present study were the determination of theanine (a specific amino acid of tea leaves with repercussion in human neuronal activity) by HPLC with o-phthaldialdehyde derivatisation prior analysis and comparison of its level in samples from different origins or from the same origin (Azores Islands) but with different processing conditions (fermentation, drying temperature and drying time) and shoot maturity. The results revealed a higher level of theanine in the Azorean green tea (3.10%), the only one produced in Europe, as compared with the Chinese, Japanese, Korean and Taiwan green teas that have an average theanine content of 1.52%, 1.34%, 0.89% and 2.76% of the dry weight (dw) of tea leaves, respectively. The fermentation for a longer period of time results in less theanine remaining (2.28% and 3.10% of dw for fermented and non-fermented tea, respectively). The drying temperature and time of the drying process have an inversely strong effect (4.45% and 5.65% of dw for dried at 55 °C during 8.50 h and at 40 °C during 7.10 h, respectively). The younger tea shoots have a higher theanine content than mature leaves (7.02% and 6.10% of dw, respectively). Our data suggested that a new type of Azorean theanine-rich tea may be produced by modifying the manufacturing processes of the younger tea shoots.

 

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