Investigation of the presence and significance of theanine in the tea plant

Theanine was determined in black teas and tea plants by a combination method of thin-layer chromatography (t.l.c.) and densitometry. It was shown that in 20 samples of black tea from different qualities and sources the amount varied from 0.33 to 1.59 g 100 g^?1 dry wt. The highest quality black teas possessed the lowest amount of theanine, but it is subject to chemical degradation during black tea manufacture. The investigation of physiological function of theanine in the tea plant showed that during germination the theanine level reached a maximum after 45 days. This indicates that at this period of the growth of the tea plant theanine acted as a source of nitrogen and as a starting point for the synthesis of the carbon skeletal compounds of the tea plant. Theanine was found to exist in all parts of the tea plant but it accumulated more in young and active tissues and also in younger plants, which emphasises its metabolic role in the tea plant. The distribution of theanine in the shoots indicated that the first leaf was the principal site for the synthesis of polyphenolic compounds from theanine.     

Green tea from purple leaf coloured tea clones in Kenya- their quality characteristics

The Kenyan tea industry wishes to diversify its tea products, and in line with this, anthocyanin – rich teas were developed at the Tea Research Foundation of Kenya. These teas have purple-coloured leaves and the green colour is masked. In total, 12 accessions of the purple leaf coloured teas and 2 standard tea varieties were studied. Clones Hanlu and Yabukita are Chinese and Japanese tea varieties, respectively, known for good green tea, and they were used as reference standards. Little if any research had been done to characterize the quality of these purple leaf coloured teas and this study investigated their total polyphenols (TPP), catechins, caffeine, gallic acid and theanine. These are the major green tea quality parameters. Results showed that the new Kenyan tea clones had higher total polyphenols than had the reference standard tea varieties, which had 17.2% and 19.7% while the lowest among the Kenyan clones was 20.8%. On catechin quality index, K-purple and TRFK 91/1 showed high index values of 15.9 and 13.3, respectively, while clones TRFK 83/1 and 73/5 showed low index values of 0.74 and 1.0, respectively. Hanlu had the highest caffeine level with 2.42% while clones TRFK KS 3, TRFK KS 2 and TRFK 83/1 had relatively high caffeine levels among the purple leaf coloured teas, with 2.33%, 2.22% and 2.21%, respectively. Clone TRFK 73/5 had the lowest caffeine content, with 1.16%. Theanine analysis showed that most purple leaf coloured teas had more theanine than had the reference standard clones, except TRFK 83/1 and K-purple, which were lower than the reference standard clones. The implication of the green tea chemical quality parameters is also discussed. It is concluded that all the studied clones/varieties have above the minimum 14% of total polyphenols. Clones K-purple and TRFK 91/1 showed high green tea quality indices with the latter doubling with high levels of theanine; hence its highly recommended for green tea manufacture.     

Comparison of the main compounds in Fuding white tea infusions from various tea types

The purpose of this study was to compare the main components, and particularly catechins, caffeine, theanine, free amino acids, and water extracts, in Bai Hao Yin Zhen, Bai Mu Dan, and Shou Mei Fuding white tea infusions brewed at different temperatures, and their contributions to taste were estimated by dose-over-threshold value. Infusion temperature had a distinct effect on the main components extracted, and 100 °C was found to be optimal for extracting catechins and caffeine. However, the effect of temperature on theanine, free amino acids, and water extracts varied with tea type. Bai Mu Dan and Shou Mei yielded a higher content of the major compounds than did Bai Hao Yin Zhen. Thus, infusion temperature had a large effect on extracting the main compounds, and the differences in content between the three white teas presumably reflected differences in the harvest time, processing method or leaf shape.     

茶鲜叶萎凋时期乙烯利溶液对游离氨基酸组分的影响

探究萎凋过程中乙烯利溶液对离体茶鲜叶游离氨基酸含量的影响。以贵州省自主培育品种“黔茶1号”为试材,设置对照组、喷施乙烯利组及喷施乙烯抑制剂组。采用邻苯二甲醛（o-phthalaldehyde,OPA）法、9-芴甲基氯甲酸酯（9-fluorenylmethyl chloroformate,FMOC）法进行高效液相色谱在线衍生检测游离氨基酸。结果表明,鲜爽味氨基酸含量随萎凋时间延长而减少,甜味、苦味氨基酸含量随时间推移呈上升趋势。3类呈味氨基酸含量在萎凋期间对喷施乙烯处理响应不同。萎凋期间,鲜味氨基酸含量受乙烯诱导上调,差异显著发生在4、8 h;甜味氨基酸含量在各处理间总体差异不显著;各处理组苦味氨基酸含量在4、8 h无显著变化,12、20、24 h含量有所下降,差异不显著。鲜味氨基酸以茶氨酸为主,除谷氨酸含量在4 h时各处理间无显著差异外,茶氨酸、天冬氨酸及谷氨酸含量受乙烯诱导上调。甜味氨基酸中丝氨酸、脯氨酸含量不受乙烯调控,甘氨酸含量受乙烯诱导上调,丙氨酸含量不完全受乙烯调控。苦味氨基酸中组氨酸、酪氨酸、缬氨酸、异亮氨酸及亮氨酸含量受乙烯诱导上调。因此,萎凋期间喷施乙烯利溶液可以显著提高部分游离氨基酸含量。     

Analysis of free amino acids in Chinese teas and flower of tea plant by high performance liquid chromatography combined with solid-phase extraction

An effective liquid chromatographic method that involved precolumn derivatisation with o-phthaladehyde combined with solid-phase extraction has been developed for the determination of free amino acids in tea. Firstly, tea infusion was treated by C18 cartridge before derivatisation, resulting in great improvement of separation by Zorbax Eclipse XDB-C₁₈ column. Then, the contents of free amino acids in Chinese green, black, and Oolong teas and the flower of plant Camellia sinensis have been determined. The results showed that theanine was the most abundant amino acid in teas, and green tea contained much higher amounts of free amino acids than fermented ones. While the contents and composition of free amino acids in tea flower were quite different from those of teas. The tea flower contained much higher content of free amino acids. Furthermore, although theanine was the most abundant amino acid in tea flower as tea, histidine became the second one.     

Seasonal variations in theaflavins,thearubigins, total colour and brightness of Kangra orthodox tea (Camellia sinensis (L) O Kuntze) in Himachal Pradesh

Variations in theaflavins, thearubigins, total colour and brightness of orthodox black tea were studied for four consecutive years (1993–1996) with a view to evaluating the effects of changing weather conditions on the quality of Kangra tea. A degree of withering of 600–650 mg g⁻¹ during the first, second and fourth seasons was optimal for the development of significantly higher brightness and total colour characteristics. The quality of rainy season teas suffered owing to high chlorophyll content and low degree of withering. Hot air circulation through the withering troughs to assist evaporation of leaf moisture increased the brightness and total colour of rainy season teas. High atmospheric demand during the dry season assisted loss of green leaf moisture, but withering and brightness exhibited significant negative correlations with high relative humidity and rainfall. Summer season teas were superior in their total colour and brightness. © 2000 Society of Chemical Industry     

茶叶加工过程对咖啡叶化学成分和抗氧化活性的影响

本研究采用茶叶加工方法对咖啡叶进行加工,探索茶叶加工步骤（包括萎凋、揉捻、发酵、干燥）对不同叶龄咖啡叶的基础成分、植物化学成分和抗氧化活性的影响。结果表明,加工步骤和叶龄对基础成分、植物化学成分和抗氧化活性有不同程度的影响。咖啡叶中水浸出物的含量在整个加工步骤中总体呈下降趋势;可溶性糖的含量在前三个步骤中呈下降趋势,但是干燥后其含量有所上升;萎凋使咖啡幼叶中的游离氨基酸含量提高,然而从发酵步骤开始降低。咖啡因含量在幼叶中呈降低趋势但在成熟叶中变化不显著;芒果苷和芦丁含量在萎凋时升高,揉捻和发酵时降低,干燥时升高;绿原酸含量在发酵步骤结束之前呈下降趋势,干燥时又升高;总酚和总黄酮含量以及抗氧化活性的基本变化趋势与绿原酸相似。鲜咖啡幼叶的水分含量、可溶性糖、可溶性蛋白、植物化学成分和抗氧化活性均显著高于成熟叶且在相同步骤下其含量在幼叶与成熟叶中存在显著性差异。发酵2 h的基础成分含量、植物化学成分含量和抗氧化活性高于48 h。不同茶叶加工步骤对咖啡叶的植物化学成分和抗氧化活性具有不同的影响,其中发酵的时间对除了水分之外的基础成分和植物化学成分的影响最为显著。     

几种茶叶生化成分及其抗氧化活性分析

目的:比较白茶与绿茶、红茶生化成分的差异,探讨生化成分与抗氧化活性的关系。方法:以寿眉、安吉白茶及白琳工夫分别为白茶、绿茶、红茶代表,分析茶叶成分,测定茶汤抗氧化活性,并对二者进行相关性分析。结果:总黄酮含量与年份呈正相关关系,而咖啡碱则相对稳定;白茶茶多酚及儿茶素含量均低于绿茶,但其酯型儿茶素所占比重显著高于绿茶,且游离氨基酸、茶氨酸及总黄酮含量也显著高于其他两种茶类;EGC所占比重与酯型儿茶素均与茶汤抗氧化活性有较强的相关性。结论:白茶与其他茶在成分和抗氧化性上均有显著差异;EGCG与抗氧化活性相关性最强。     

Ethylamine content of fresh tea shoots and made tea determined by high performance liquid chromatography

The ethylamine contents of tea shoots and made teas were derived with o-phthalaldehyde and 2-mercaptoethanol, and quantified by high performance liquid chromatography. The coefficient of variation of this method was 1.97% from eight analyses. The levels of ethylamine in tea shoots declined markedly during growth and senescence after plucking; they also declined in the extracts of fresh tea during the incubation at 37°C, but this decrease was completely inhibited by amine oxidase inhibitors. The content of ethylamine in high grade green teas was higher than in low grade teas, but was almost identical in high and low grade black tea. The mean contents of ethylamine in 22 green teas and 17 black teas were 6.76±3.07 μmol g^?1 and 6.40±1.82 μmol g^?1, respectively.     

Effect of electrolyzed reduced water on chiral theanine and polyphenols in tea

Pure d/l-theanine enantiomers were synthesized separately, and SEM was used for their crystal-structure observation. The novel enantiomeric separating method by HPLC was established using the chiral selector of β-CD in the mobile phase. Green tea, white tea, oolong tea, black tea and Pu-erh tea were tested for theanine enantiomers by different degrees of fermentation. The significantly higher d-enantiomeric proportion of theanine was found in white tea than the others, which was probably due to its specific processing step of withering. The effect of electrolyzed reduced water (ERW) on enantiomeric theanine and polyphenols in tea was explored. There was no change of theanine, but rather a loss of ECG (epicatechin gallate) and an increasing amount of GA (gallic acid). ERW also reduced tea cream, which contains significant amount of polyphenols, indicating its potential application in the tea-beverage industry.     

Determination of Theanine and Catechin in <Emphasis Type="Italic">Camellia sinensis</Emphasis> (Kangra Tea) Leaves by HPTLC and NMR Techniques

Camellia sinensis is used to make special tea and also become a raw material for dietary supplements, health foods, and cosmeceuticals. Theanine (amino acid) and catechins (polyphenol) are most abundantly found in tea leaves. Theanine and catechins are also responsible for taste and flavor of tea products along with therapeutic and nutritional values. Hence, identification and quantification method for theanine and catechin has been developed using high performance thin layer chromatography (HPTLC) and NMR techniques. HPTLC method was validated for selectivity, sensitivity, accuracy, and precision. Theanine and catechin were quantified in three tea samples including randomly plucked tea leaves (HAR), authentically plucked tea leaves (HAN), and processed tea (HAT). Both theanine and catechin were found maximum in HAN as compared to HAR and HAT. The Validated HPTLC method is economical, rapid, and highly suitable for quantification of theanine and catechin. Moreover NMR studies were also used for the qualitative and quantitative estimation of theanine and catechin along with other important metabolites in C. sinensis samples.     

不同光质萎凋对贡眉白茶滋味品质的影响

为筛选改善贡眉白茶滋味的最优萎凋光质,采用LED精量调制光源,通过感官审评法、超高效液相色谱串联三重四级杆质谱、高效液相色谱等方法,研究无光(对照)、日光、蓝光、黄光和红光萎凋,对贡眉白茶的感官品质、主要生化成分、部分代谢物的影响。结果表明,4个光照组感官审评的滋味、香气及总得分,均比无光组高,且红光滋味得分最高。相比无光和其他光质组,红光组的可溶性糖、水浸出物、咖啡碱、没食子儿茶素没食子酸酯、茶氨酸、苏氨酸、谷氨酸、谷氨酰氨、甘氨酸、丙氨酸、γ-氨基丁酸及总氨基酸的含量最高,有益于“醇厚鲜甜”的滋味特征形成。相比无光组,4个光照组显著降低部分黄酮(醇)苷的含量(P<0.05),红光组的茶黄素和茶黄素-3-没食子酸酯的含量显著降低(P<0.05),而黄、蓝、白光组的山奈酚含量显著升高(P<0.05)。综合认为,红光萎凋对白茶滋味提高最有益。     

萎凋时间对丹霞8号主要生化成分和挥发性成分的影响

以丹霞8号为试验材料,比较不同萎凋时间茶叶中生化成分和挥发性成分,探明其变化规律。结果表明:茶多酚含量在0～23h显著增加,23～32h显著降低。0～16h游离氨基酸含量显著增加,茶氨酸则显著降低;16～50h游离氨基酸和茶氨酸均显著降低。0～50h咖啡碱含量显著增加;可可碱显著降低;叶绿素a差异不显著。叶绿素b和类胡萝卜素含量在5～28h显著降低;28～50h显著增加。萜烯是5～32h萎凋叶主体挥发性成分,萜醇是0h和50h萎凋叶主体挥发性成分。主成分分析表明,0～50h萎凋叶的生化成分特征和香气轮廓呈规律变化,生化特征可分为0～16,23～28,32～50h3个阶段;香气轮廓分为0～9,16～23,26～32,50h4个阶段。16h和23h是茶叶萎凋过程中生化成分特征和香气轮廓变化的共有时间点。     

Intestinal transport of pure theanine and theanine in green tea extract: Green tea components inhibit theanine absorption and promote theanine excretion

Theanine, an amino acid contained in green tea, is known to possess many pharmacological functions. In this paper, we investigated the absorption of theanine in the human intestinal epithelium, using a Caco-2 monolayer model. Different concentrations of either pure theanine or green tea extracts were administered to Caco-2 cells. The theanine content in the samples was analysed by high-performance liquid chromatography, coupled with fluorescence detection. Cell permeation was also measured. The data revealed that the transport of pure theanine occurred in a manner consistent with passive diffusion. Surprisingly, pure theanine showed good absorption, whereas theanine in the green tea extract was poorly absorbed in the Caco-2 cell model. Furthermore, the transport of theanine in green tea extract in the basolateral (BL) to apical (AP) direction was much greater than that in the AP–BL direction, suggesting that green tea components profoundly affect the trans-epithelial transport of theanine in this Caco-2 cell model.     

Rheology of Ice Cream Mix Flavored with Black Tea or Herbal Teas and Effect of Flavoring on the Sensory Properties of Ice Cream

Rheological characteristics and physicochemical properties of ice cream mix flavored with black tea or some herbal teas and sensory profile of flavored ice cream was investigated. In this respect, black tea and three different herbal tea samples (sage, chamomile, and linden) were used to produce a new ice cream formulation. Some physicochemical properties and sensory characteristics of samples were determined. Total phenolic content of ice cream samples increased with the use of tea or herbal teas and it was in the range of 123.37–415.20 mg kg^?1. Incorporation of black tea and herbal tea except chamomile decreased the sensory scores of ice cream compared to control sample. The apparent viscosities of samples were measured as a function of shear rate and consistency coefficient and flow behavior index were calculated by using power law model. All ice cream mix samples showed non-Newtonian pseudoplastic behavior. The apparent viscosities of ice cream mixes treated with no tea at the shear rate of 50 s^?1 were 1.13, 0.91, and 0.76 Pa s at 10, 20, and 30 °C, respectively. The activation energy for the viscosity change of the samples ranged between 10.87–20.25 J?mol^?1 at 50 s^?1.     

Factors affecting the levels of catechins and caffeine in tea beverage: estimated daily intakes and antioxidant activity

Increased public awareness of health benefits of green tea is generally based on the high polyphenol content of tea leaves and the resulting beverage. A number of factors, such as species, season, agronomic condition and age of the leaves, are known to affect the composition of commercial teas. In the present study the effects of factors associated with domestic preparation and analytical methods, such as brewing time, concentration, solvent and type of tea product, on levels of catechins and caffeine, antioxidant activity and estimated daily intakes were investigated. There were large variations in the levels of total catechins: 43 and 117 mg g^?1 dry matter (DM) (brewed for 30 s and 5 min respectively); 72 and 161 mg g^?1 DM (extracted in boiling water and 50% acetonitrile respectively); 72 and 117 mg g^?1 DM (a tea bag and tea leaves respectively). The effects on caffeine content were comparatively smaller. These variations consequently led to considerable variations in estimated daily intakes based on three cups (600 ml), ranging between 538 and 2014 mg g^?1 DM of total catechins and between 103 and 466 mg g^?1 DM of caffeine. The antioxidant activity was highest (26 680 µmol g^?1 DM) for tea leaves brewed for 5 min and lowest (10 110 µmol g^?1 DM) for a tea bag product brewed for 1 min. Copyright © 2005 Society of Chemical Industry     

Occurrence of pyrrolizidine alkaloids in animal- and plant-derived food: results of a survey across Europe

Pyrrolizidine alkaloids (PAs) are secondary metabolites of plant families such as Asteraceae or Boraginaceae and are suspected to be genotoxic carcinogens. Recent investigations revealed their frequent occurrence in honey and particularly in tea. To obtain a comprehensive overview of the PA content in animal- and plant-derived food from the European market, and to provide a basis for future risk analysis, a total of 1105 samples were collected in 2014 and 2015. These comprised milk and milk products, eggs, meat and meat products, (herbal) teas, and (herbal) food supplements collected in supermarkets, retail shops, and via the internet. PAs were detected in a large proportion of plant-derived foods: 91% of the (herbal) teas and 60% of the food supplements contained at least one individual PA. All types of (herbal) teas investigated were found to contain PAs, with a mean concentration of 460 µg kg^?1 dry tea (corresponding to 6.13 µg L^?1 in [herbal] tea infusion). The highest mean concentrations were found in rooibos tea (599 µg kg^?1 dry tea, 7.99 µg L^?1 tea infusion) and the lowest in camomile tea (274 µg kg^?1 dry tea, 3.65 µg L^?1 tea infusion). Occurrence of PAs in food supplements was found to be highly variable, but in comparable ranges as for (herbal) tea. The highest concentrations were present in supplements containing plant material from known PA-producing plants. In contrast, only 2% of the animal-derived products, in particular 6% of milk samples and 1% of egg samples, contained PAs. Determined levels in milk were relatively low, ranged between 0.05 and 0.17 µg L^?1 and only trace amounts of 0.10–0.12 µg kg^?1 were found in eggs. No PAs were detected in the other animal-derived products.     

Liver Injury-preventive Effect of Tea Theanine in Rats

This study was conducted to isolate the constituent, which had a preventive effect on D-galactosamine-induced rat liver injury, from the 70% ethanol-soluble fraction of Japanese green tea. Theanine (glutamic acid γ-ethylamide) was identified as the active compound, and the liver injury-preventive effect of theanine was dose-dependent. L-Glutamic acid γ-ethyl ester, but not glutamine, also brought about a significantly preventive effect on liver injury when added to the diet at equimolar levels to that of 1% theanine. The results indicate that theanine is one of the effective constituents of Japanese green tea in preventing D-galactosamine-induced liver injury.     

Determination of alkaloids and phenolic compounds in black tea processed by two different methods in different plucking seasons

The effects of two different rolling methods and three tea plucking seasons on alkaloids and phenolics, mainly flavan‐3‐ols and theaflavins, in black tea were studied using an improved high‐performance liquid chromatographic method. Better separation of all tea compounds analyzed—the most important factor for their identification and quantitation—was achieved only with long elution gradients, which overcame the limitations of previously reported methods. Precision of the assay method was very high since intra‐day and inter‐day variations were within 0.76% and 1.66%, respectively. All analytes exhibited good linearity over the range evaluated with a correlation coefficient of 0.9987–1.000. Among the four solvents evaluated, 80% methanol was the most solvent for extracting individual tea compounds. The extraction method applied exhibited good repeatability (CV: 0.39–3.29%). The content of tea compounds analyzed varied with processing method and plucking season. Teas processed using the Cay‐Kur method contained higher levels of identified phenolic compounds than orthodox teas, but their alkaloid content was similar to each other. The most abundant alkaloid in teas was caffeine, ranging from 17.84 mg g^?1 dry weight in September plucking to 23.79 mg g^?1 dry weight in May plucking. With respect to phenolic compounds, theaflavins were at the highest level, 14.27 mg g^?1 dry weight, in Cay‐Kur tea processed in May. Copyright © 2007 Society of Chemical Industry     

Hastening of leaf senescence in the processing of green tea leaf to black tea

The current system of processing green tea leaf (Camellia sinensis) to produce black tea involves a long period, especially because of the withering process practised in acquiring leaf senescence which is essential to impart fullness to the resulting tea liquors. Hastening leaf senescence by artificial withering at temperatures favourable to enzymic transformations accelerated the process and considerably shortened the manufacture of black teas.