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.     

Column-chromatographic extraction and separation of polyphenols, caffeine and theanine from green tea

A highly efficient column-chromatographic extraction (CCE) followed by sequential adsorption to extract and separate bioactive compounds from green tea was developed. Tea powder was loaded into columns with 4-fold solvents and eluted through a cyclic CCE. High-quality tea extracts with greater than 90% extraction efficiencies of polyphenols, epigallocatechin-3-gallate, caffeine, theanine and polysaccharides were obtained with 4-fold water circulated five times among different columns at 70 °C. Similar results, except for low polysaccharide extraction (35.5%), were obtained with 4-fold 30% ethanol circulated three times at room temperature. The highly concentrated water extraction was directly passed through columns of polyamide, DM130 macroporous and 732 ion exchange resins, resulting in high-purity polyphenols (99%), caffeine (98%) and theanine (98%) after simple purification of the eluates from each column. This method uses simple equipment, minimum solvents and can be used for both quantitative analysis and continuous preparation of high-quality tea extracts and bioactive compounds.     

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.     

我国红茶产业现状及可持续发展对策

为探明祁门红茶、GABA红茶、滇红等三种红茶特征挥发性成分差异,采用顶空固相微萃取（HS-SPME）与气相色谱-质谱联用（GC-MS）方法,结合多元统计分析进行研究。气-质联用结果表明,共定性鉴定出78种已知挥发性成分,包括碳氢化合物、萜烯类、醇类、酯类、酮类、醛类、杂环化合物、酚类。三种红茶总挥发性物质种类数量相近,但其含量差异较大,其共有挥发性成分主要包括芳樟醇、香叶醇、壬醛、水杨酸甲酯、氧化芳樟醇等。多元统计分析结果表明,根据挥发性成分可以区分GABA红茶、滇红、祁门红茶。经偏最小二乘判别分析筛选出12种差异挥发性成分,包括醋酸橙花酯、水杨酸甲酯、异龙脑、芳樟醇、柠檬醛等,其中醋酸橙花酯、柠檬醛在祁门红茶中含量最高,有助于形成祁门红茶的花果香型;异龙脑、芳樟醇在滇红中含量最高;芳樟醇、水杨酸甲酯在GABA红茶中含量较高,有利于形成GABA红茶鲜嫩花果香。本研究结果可为科学客观地评价GABA红茶香气特征,阐明祁门红茶、GABA红茶、滇红香气品质差异及构建不同种类红茶风味品质鉴别图谱奠定理论基础。     

Effects of potassium and magnesium nutrition on the quality components of different types of tea

In field experiments, the effects of potassium and magnesium nutrition on the quality components of different types of tea, including black tea, oolong tea and green tea, were studied. The results show that K and Mg fertilizer application increased the contents of free amino acids and caffeine of the various tea types with the maximum increase found in the treatment including both nutrients. The content of polyphenols in tea leaves was also increased by K application. The effect of Mg on polyphenol content was inconsistent. In general, Mg apparently decreased the content of polyphenols and only in case the soils were depleted of plant available K and Mg, a slight increase could be observed. The contents of theaflavins and thearubigins, important quality components of brewed black tea, were also increased by K application. Flavour compounds in brewed oolong tea were considerably improved by K and Mg application. © 1999 Society of Chemical Industry     

Content of various elements in different parts of the tea plant and in infusions of black tea from Southern India

Contents of various elements in dyferent parts of the tea plant (shoot, mature leaf, small stem, thick wood and root), black tea manufactured by the crush-tear-curl and orthodox processes, and tea brew after 1 and 5 min of infusion were determined by inductively coupled plasma atomic emission spectrometry. From these, the amount of each element assimilated in the production of 1000 kg of marketable tea, as well as the quantity of each element brought into infusion and thus possib f y taken up through drinking tea, were calculated and discussed. Among the various elements assimilated by the tea plant, the shoot jraction (economically important for manufacturing commercial tea) contained high concentrations of N, P, K and Mg while the mature leaf accumulated Al, Bu, Ca, Cd, Mn, Pb and Sr. Of the dgerent elements brought into infusion while brewing black tea, the amount of K was found to be the largest (> 10000 μg g⁻¹ tea) followed by P (700–1200 μg g⁻¹), Mg (300–700 μg g⁻¹), Ca and A1 (each 150–300 μg⁻¹), Mn (60–150 μg g⁻¹), Cu, Na, Si and Z n (each 6–50 μg g⁻¹), B, Ba, Cr, Fe, Ni and Pb (each Id μg g⁻¹), and Sr, Co and Gd (each <1μg g⁻¹). The proportion of the totalamount of an element brought into infusion showed that the elements Ba, Ca, Fe and Sr were less soluble (<10 % of total amount), Al, B, Cd, Co, Cr, Cu, Mg, Mn, P, Pb, Si and Zn were moderately soluble (10–50 %), and K, Nu and Ni were highly soluble (>50%). The overall mean of the extent of solubility of all elements in 1 and 5 min showed that, out of the amount soluble in 5 min, about 68% was dissolved within 1 min.     

吡咯里西啶生物碱及茶叶中的来源分析

吡咯里西啶生物碱(pyrrolizidine alkaloids,PAs)是一类广泛存在自然界中的植物生物碱。其代谢产物对人和动物肝脏有高毒性,能够引起静脉闭塞性疾病,严重时具有致死作用。茶叶本身并不含有PAs,但最近出口欧盟的个别茶样被检测到含有PAs,同时一些花草茶及饮料茶中也检测到吡咯里西啶生物碱的存在。本文从吡咯里西啶生物碱的结构、毒性研究结果出发,分析了PAs植物种类,也对植物样品中PAs的分析方法及组分分析进展进行介绍。结合我国茶园杂草种类的鉴定结果,发现我国茶园的主要杂草中含有PAs植物,如一点红、胜红蓟、千里光、猪屎豆等。茶叶PAs污染风险主要来自于茶园杂草,人工采摘加工的茶叶不存在PAs污染。     

Comparison of Azorean tea theanine to teas from other origins by HPLC/DAD/FD. Effect of fermentation,drying temperature,drying time and shoot maturity

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.     

不同干燥成形方式的白叶红茶品质分析

目的 研究不同干燥成形方式对白叶红茶品质的影响。方法 以白叶1号鲜叶为原料, 采用相同的萎凋、揉捻、初烘程序, 用不同的干燥做形方式制成不同形态的红茶,以感官审评结合理化分析的方法对不同形态的红茶进行了品质分析。结果 通过不同干燥成形方式获得了卷曲形、毛峰型、针形、扁形4种形态的红茶。4种红茶茶黄素、茶红素及氨基酸含量稍有差别,针形红茶茶黄素、类黄酮与氨基酸总量略高, 有利于提高其饮用价值,但4种红茶色、香、味感官品质总体接近。二次干燥(足火)-成形过程促使不同形态白叶红茶香气组成发生一定变化, 进而对红茶香型产生了细微影响,4种红茶以甜香为基本香型,卷曲型红茶香气特征偏于花香,扁形红茶略带果香。结论 毛火过程对白叶红茶品质的形成和固定具有关键意义, 干燥成形方式不改变总的香气特征, 但可使白叶红茶的具体香型发生细微分化。     

云南红茶加工过程中香气成分的变化

为提高云南红茶品质和指导实际生产,采用同时蒸馏萃取法(SDE)提取香气物质并用GC-MS检测香气成分,研究加工过程中云南工夫红茶主要香气成分组成的变化规律。结果表明:云南工夫红茶在发酵结束后挥发油含量达到最高,经过干燥过程后挥发油含量则大幅降低;不同阶段过程样的香气成分组成和含量上有明显差异;红茶在加工过程中,挥发性香气成分中的萜类化合物中的芳樟醇、芳樟醇氧化物、α-松油醇的相对含量大幅减少,而醛类化合物中的苯甲醛、苯乙醛,芳香族醇类化合物中的苯甲醇、苯乙醇的相对含量则大幅增加。萎凋、发酵、干燥工序是影响红茶香气形成的关键工序,对云南红茶香气的形成至关重要。     

普洱大叶种红茶和熟茶中20种挥发性组分对比研究

目的比较分析普洱大叶种红茶和熟茶的挥发性组分。方法采用水蒸气蒸馏法提取普洱大叶种红茶和熟茶的挥发性组分,气相色谱-质谱仪(gas chromatography-mass spectrometry,GC/MS)测定,结合组分香气阈值和气味活度值讨论各组分在茶叶呈香中的贡献。结果 20种挥发性组分中,红茶中呋喃型氧化芳樟醇、芳樟醇、苯乙醇、α-松油醇、香叶醇和棕榈酸甲酯的含量为熟茶的4～72倍,而熟茶中1,2,3-三甲氧基苯、1,2,4-三甲氧基苯、顺式茉莉酮和二氢猕猴桃内酯的含量为红茶的16～610倍。呋喃型氧化芳樟醇两种异构体含量在红茶和熟茶中优势构型表现出一致性,而橙花叔醇2种异构体含量在红茶和熟茶中优势构型表现出不一致性。结论从20种挥发性组分在熟茶和红茶中的气味活度值角度对比,苯甲醛、呋喃型氧化芳樟醇、芳樟醇、β-环柠檬醛、1,2,3-三甲氧基苯、1,2,4-三甲氧基苯、α-紫罗兰酮、β-紫罗兰酮和棕榈酸甲酯9个挥发性组分在红茶和熟茶呈香均有实际的贡献,其中呋喃型氧化芳樟醇、芳樟醇和棕榈酸甲酯在红茶中呈香贡献远高于熟茶,而1,2,3-三甲氧基苯,1,2,4-三甲氧基苯在熟茶中的呈香贡献远高于红茶。     

高效液相色谱法测定汉中茶叶中茶氨酸含量

目的以汉中市不同县区主栽茶叶品种鲜叶为试验材料,系统分析汉中茶区茶叶中茶氨酸的含量,并对其进行分析评价。方法采用高效液相色谱法(high performance liquid chromatography,HPLC),Diamonsil C18(46 mm×250 mm,5μm);以乙酸铵和乙酸铵、甲醇、乙腈的混合溶液(乙酸铵:甲醇:乙腈=1:2:2,V:V:V)作为流动相,流速:1 mL/min;柱温:25℃;检测波长为338 nm;对不同地区不同品种的茶叶中的茶氨酸的含量进行测定。结果方法的精密度高和重复性好。加标回收率在87.85%~96.95%之间,相对标准偏差为2.25%。汉中茶叶茶氨酸含量总体较高,均值可达3.55 g/100 g。宁强县种植的龙井长叶茶氨酸含量最高,为5.3 g/100 g,远高于群体种茶氨酸最高值4.72 g/100 g。结论就茶氨酸而言,不同品种茶树的差异较大,且新引进品种优于群体种。     

壶瓶山茶区19个优异茶树单株理化品质分析

目的 研究壶瓶山茶区茶树单株的品质特征及其适制性.方法 以壶瓶山19个优异茶树单株的夏梢作为研究对象,测定其叶片形态性状及主要生化成分.结果 壶瓶山19个茶树单株夏梢叶形以椭圆形中叶种为主,多数叶面隆起,叶缘多表现为波浪型,叶尖多为渐尖;19个茶样的茶叶生化成分含量存在明显差异.结论 HP-4最适宜制作绿茶,HP-15...     

斯里兰卡红碎茶与滇红碎茶主要香气成分比较分析

目的 比较分析斯里兰卡红碎茶与滇红碎茶香气成分及含量的差异性,探明区分两地红碎茶差异的主要香气成分。方法 采用GC-MS法测定斯里兰卡红碎茶及滇红碎茶样品的香气成分,通过主成分分析法比较斯里兰卡红碎茶与滇红碎茶香气成分特征差异性,根据第一主成分贡献值大小,筛选出决定区分两地红碎茶差异的主要香气成分。结果 两地红碎茶样品共分析到香气化合物40种,以醛类、酮类、酯类、醇类为主,香气成分及含量相近,但略有差异。其中反-2-己烯醛、苯乙醇、香叶醇、壬醛香气成分滇红碎茶明显高于斯里兰卡红碎茶（高出80%以上）,分别高出110.00%、108.73%、93.64%、84.91%,二氢猕猴桃内酯、吲哚香气成分滇红碎茶明显低于斯里兰卡红碎茶（50%以上）,分别低至56.19%、52.38%。其中烯类香气成分滇红碎茶比斯里兰卡红碎茶高出最为明显,高出53.53%,吲哚类香气成分滇红碎茶比斯里兰卡红碎茶低出最为明显,低出52.48%。两类红碎茶中,水杨酸甲酯占比最高,在斯里兰卡红碎茶中最高可达26.60%,在滇红碎茶中最高可达29.79%。斯里兰卡红碎茶和滇红碎茶中,酯类和醇类含量最高,酯类在斯里兰卡红碎茶中最高可达34.38%,在滇红碎茶中最高可达35.69%,醇类在斯里兰卡红碎茶中最高可达32.48%,在滇红碎茶中最高可达34.84%。各香气成分中二氢猕猴桃内酯（C15）、反-戊酸-2-己烯酯（C29）最能代表斯里兰卡红碎茶香气特征,a-萜品醇（C30）、橙花醇（C40）最能代表滇红碎茶香气成分特征。结论 对香气成分进行分析,可明显区分斯里兰卡红碎茶与滇红碎茶特征。     

Valorisation of theanine from decaffeinated tea dust in bakery functional food

Nowadays, consumers appreciate the positive properties of decaffeinated tea for their well‐being. During decaffeination process, a very fine tea dust powder is obtained as by‐product, which contains the same quantity of bioactives as decaffeinated tea: the antioxidant polyphenols and the amino acid theanine. The aim was to add value to theanine gained from black tea powder dust and to develop theanine‐enriched bread. A theanine containing powder was obtained by column separation of decaffeinated tea dust extract and spray‐drying using carrier supports. This powder contains also the very polar compounds from decaffeinated tea such as amino acids, sugars and minerals. Breads with 110, 220 and 330 ppm of theanine, respectively, were prepared with the theanine powder. Physical properties, theanine and total polyphenolic content in bread were analysed. Bread and other bakery food serve as good products to add value to bioactive tea dust ingredients.     

Residues and contaminants in tea and tea infusions: a review

Consumers are very aware of contaminants that could pose potential health hazards. Most people drink tea as an infusion (adding hot water); however, in some countries, including India, China and Egypt, tea is drunk as a decoction (tea and water are boiled together). An infusion usually brings the soluble ingredients into solution, whereas a decoction brings all soluble and non-soluble constituents together. Therefore, a cup of tea may contain various kinds of contaminants. This review focuses on green and black tea because they are most commonly consumed. The target was to examine the transfer rate of contaminants – pesticides, environmental pollutants, mycotoxins, microorganisms, toxic heavy metals, radioactive isotopes (radionuclides) and plant growth regulators – from tea to infusion/brewing, factors contributing to the transfer potential and contaminants degradation, and residues in or on the spent leaves. It is concluded that most contaminants leaching into tea infusion are not detected or are detected at a level lower than the regulatory limits. However, the traditional practice of over-boiling tea leaves should be discouraged as there may be a chance for more transfer of contaminants from the tea to the brew.     

黑茶茶褐素与茶多糖对脂肪酶的抑制作用

为探讨黑茶茶褐素与茶多糖对脂肪酶的抑制作用,选择不同地区相同级别的黑茶为原料,提取茶褐素与茶多糖,采用对硝基苯酚法,分析茶褐素与茶多糖对脂肪酶活性的抑制率,并探讨各黑茶茶褐素与茶多糖对脂肪酶的抑制机理。结果表明:黑茶茶褐素与茶多糖对脂肪酶具有显著的抑制作用,普洱茶茶褐素与茶多糖IC50最小,分别为25.96,47.57mg/mL,抑制效果最好;其次为六堡茶;抑制效果最差的为茯砖茶褐素与茶多糖;康砖茶褐素与茶多糖抑制效果介于六堡茶与茯砖茶之间。各黑茶茶褐素的抑制类型均为可逆竞争性与非竞争性混合型,其中六堡茶接近于竞争性抑制类型;普洱茶、六堡茶与康砖茶多糖的抑制类型为可逆竞争性与非竞争性混合型,茯砖茶多糖抑制类型为可逆竞争性抑制。     

夏秋红茶的再加工与冷泡茶制备研究

目的 探索利用夏秋红茶再加工制作冷泡茶的可行性和最佳工艺条件。方法 利用纤维素酶处理夏秋红茶,通过单因素实验和正交实验筛选最佳酶解条件,测定处理前后红茶中主要化学成分和挥发性风味物质变化,并对其冷泡性能进行评价。结果 优化获得了夏秋红茶再加工的工艺条件为:纤维素酶添加量为1.2 kU/g,料液比为5:8(g:mL),处理时间为24h,处理温度为25℃。纤维素酶加工后茶叶中的主要滋味物质和风味物质含量以及冷泡性能等品质指标均有所提高。冷泡茶汤中的可溶性总糖含量由4.33%升高至9.35%,水浸出物含量由26.64%升高至35.73%。在挥发性风味物质方面,加工后茶叶中苯甲醇(芳香、果香)、苯乙醇(玫瑰花香、蜜香)和水杨酸甲酯(清香、花香)等特征香气物质的相对含量升高。冷泡性能方面,加工后的红茶水浸出物冷泡溶出大幅增加和可溶性总糖则可完全冷泡溶出,产品适于冷泡饮用。结论 本研究通过纤维素酶再加工提升夏秋红茶品质,制备冷泡茶,不仅能实现夏秋茶资源的充分利用,也为冷泡茶的生产提供了稳定的原料供应。     

Determination of essential and non-essential elements in various tea leaves and tea infusions consumed in Turkey

Tea is one of the most popular beverages in the world. Thus, the chemical components in tea are of great interest, especially in relation to health. In this study, 12 tea samples (10 black, 1 white and 1 green) and 5 herbal tea samples were purchased from supermarkets in Izmir, Turkey. Sample preparation has been performed using wet and microwave digestion procedures. The elemental content (Fe, Zn, Cu, Mn, Ni, Na and K) in the digests and infusions has been analysed. Generally, elemental contents in tea leaves were found to be higher than those in tea infusions. The accuracy of the method was checked and confirmed by standard reference material analyses. The comparison of wet and microwave digestion has not shown significantly different results. Therefore, the microwave digestion procedure was preferred because it is less laborious. The elemental intake related to tea consumption has also been studied.