The phenolic profiles and antioxidant activity in different types of tea

Phenolics are suggested to be the major bioactive compounds responsible for the health benefits of tea. Seven types of tea were extracted using boiling water. The extraction kinetics was investigated. To more fully characterise the antioxidant profiles and possible associated health benefits of these tea types, the total water‐soluble solid content, phenolics, flavonoids, and antioxidant and antiproliferative activities were quantified. Green tea leaves (GTL) were found to have the highest phenolic content (128.7 ± 1.7 mg g^?1, P < 0.05), followed by teas of decaffeinated green tea bag (dGTB), green tea bag (GTB), black tea bag (BTB), decaffeinated BTB, black tea leaves and oolong tea leaves (OTL). Among the three leaf teas, GT displayed the greatest antioxidant activity (4850.2 ± 60.7 μmol g^?1, P < 0.05), followed by black tea (BT) and oolong tea (OT). As for the four bag teas, decaffeinated GT possessed the strongest antioxidant activity (4431.1 ± 335.0 μmol g^?1, P < 0.05), followed by GT, BT and decaffeinated BT. The results display that phenolic/flavonoid content well correlated with antioxidant activity. Proliferation of three human cancer cells was significantly inhibited in a dose‐dependent manner after exposure to some tea extracts. This may influence consumers in selecting the type of tea and tea brewing times, exhibiting greater health benefits.     

Determination of catechins and flavonol glycosides in Chinese tea varieties

A standardised profiling method based on high performance liquid chromatography combined with ultraviolet (UV) and mass spectrometric detection (MS) was established to analyse the phenolic compounds of selected tea varieties used for manufacturing of green, black and oolong teas. The composition and content of 24 tea constituents were analysed, including catechins, flavonol and flavones glycosides, phenolic acids and purine alkaloids. Each tea variety had a unique chemical profile. The compositions of catechins were lower in the tea varieties for green tea manufacturing, while the content of myricetin glycosides was the lowest in the tea variety for oolong tea manufacturing. The content of individual phenolic compounds in the selected tea varieties is highly variable. However, the content of total catechins is proposed to be helpful to classify tea according to the future application as non fermented green and fermented oolong or black tea.     

An investigation into low‐temperature nitrogen plasma environment effect on the content of polyphenols during withering in made Kenyan tea

Low‐temperature nitrogen plasma (LTNP) was used to wither green tea leaf to study its effect on the polyphenol content. Using a dielectric barrier discharge chamber to provide the LTNP environment, green tea leaf was withered at various withering times. Made tea samples indicated that LTNP had an effect on polyphenol content. The highest polyphenol content of 78.56 mg g^?1 in made tea was attained in 1 h after which it showed a decreasing trend with increasing retention time. For comparison purposes, green tea leaf was also withered in nonplasma environments. Highest polyphenol content of 133.4 mg g^?1 in made tea was attained in a sample withered anaerobically in nitrogen gas at room temperature and atmospheric pressure for 18 h. In another sample, green tea leaf was directly macerated and dried without withering and fermenting and had polyphenol content of 101.91 mg g^?1 in made tea. These contents were compared with green tea 4, purple tea and oolong tea that are currently manufactured in Kenya.     

An integrated sustainable approach for the development of Kyoho skin functional tea

Kyoho (Vitis labruscana) skin is one of the valuable and eco-friendly agricultural waste and a potential source of phenolic compounds. Therefore, we attempted to develop Kyoho skin functional tea and evaluated its nutritional-functional properties as affected by drying temperatures (30, 40, 50 and 60 °C). Kyoho skin functional tea reported negligible protein (0.02 mg g⁻¹), fat (0.04–0.19%) and calories (0.36–0.70 cal g⁻¹). Total phenolic and flavonoid contents ranged from 0.25 to 0.56 mg GAE mL⁻¹ and 0.03 to 0.19 mg QE mL⁻¹, respectively. Kyoho skin functional tea showed functional properties including antioxidant activity (63.33–79.78%) and anthocyanins (0.25–0.34 mg per 100 mL). The sensory evaluation of Kyoho skin functional tea (dried at 40 °C) rated as acceptable (>6) with attractive colour (>6). Overall, these findings recommended the possibility of using Kyoho skin to develop functional teas, which may strengthen the global beverage industries.     

Effect of consecutive steeping on antioxidant potential of green,oolong and black tea

After water, tea is considered to be one of the most consumed drinks worldwide. To get the maximum benefit from the whole‐leaf teas, the manufacturers provide instruction that these teas can be steeped 2–3 times over 6–8 h. In this study, the effect of consecutive steeping on radical‐scavenging ability of whole leaf green tea (unfermented), oolong tea (partially fermented) and black tea (fully fermented) was determined. Green tea showed the highest level of antioxidant activity, total phenolic and flavonoid content followed by oolong tea and black tea irrespective of the number of steeping done. The result also demonstrated that re‐steeping reduced the antioxidant potential of teas. Moreover, it was revealed that green tea is the best candidate for re‐steeping followed by oolong and then black tea.     

Effects of baking and aging on the changes of phenolic and volatile compounds in the preparation of old Tieguanyin oolong teas

A series of old oolong teas was prepared by baking fresh Tieguanyin oolong teas at 120–140 °C for 72 h, followed by a long-term storage of 5, 10 and 20 years. To monitor the chemical changes of the tea preparation, phenolic and volatile compounds in a fresh or its newly baked tea were analyzed and compared with those in the three aged teas. The contents of phenolic compounds in the teas were apparently altered by the baking, but remained relatively stable thereafter in the aging process. The contents of major catechin derivatives and flavonol glycosides presumably responsible for astringency and bitterness of teas were reduced while those of gallic acid and gallocatechin gallate, putatively originated from the decomposition and isomerization of (−)-epigallocatechin gallate, were elevated after baking. In contrast, linear and branched hydrocarbons, the abundant volatile compounds in the fresh tea, were relatively stable in the baking process, but nearly diminished during the long-term storage. Relatively minor contents of substituted benzaldehydes and pyrrole derivatives probably rendering the unique flavor of old oolong teas were generated after the baking and aging processes.     

Comparison of catechins and volatile compounds among different types of tea using high performance liquid chromatograph and gas chromatograph mass spectrometer

As tea is one of the most popular beverages consumed worldwide, it is important for customers and business investigators to develop an easy and reliable method to discriminate between different types of teas from each other. A total of eighty‐seven types of various white, green, oolong, black and Puer teas were collected from the major tea estates in China, and their catechin contents and volatile compounds were compared by high performance liquid chromatograph and gas chromatograph mass spectrometer. It was found green tea contained the highest concentrations of total catechins, (?)‐epicatechin gallate (ECG) and (?)‐epigallocatechin gallate (EGCG), while oolong teas contained the highest concentrations of (?)‐epigallocatechin (EGC) among these five types of teas. The aroma composition and their quantities in different types of teas varied quite widely. The concentration of ECG, EGCG, pentanal, hexanal, methyl jasmonate, indole, (E,E)‐2,4‐hexadienal and 1,2,3‐trimethoxybenzene was shown to be different and could be used to discriminate white, green, oolong, black and Puer teas. The result showed that different types of teas could be partially classified by cluster analysis using index of individual catechins and volatile components.     

The analysis by HPLC of green,black and Pu'er teas produced in Yunnan

Samples of tea (Quingmao, steamed, black and Pu'er) produced in Yunnan Province, People's Republic of China, from the locally characteristic large-leaved Camellia sinensis, have been brewed and the brews analysed for their contents of flavonol glycosides, flavan-3-ols and their oxidation products. Several samples of Pu'er tea manufactured in the 1920s, 1930s and 1940s were also examined. The brews prepared from Quingmao tea and steamed green tea leaf were very similar containing primarily flavan-3-ols accompanied by flavonol glycosides, theogallin and gallic acid. The profile of flavanols was unusual, being dominated by (?)-epicatechingallate (rather than (?)-epigallocatechingallate) and by an unusually large (+)-catechin content. The brew of the equivalent black tea retained significant amounts of residual flavanols (particularly (?)-epicatechingallate and (+)-catechin), and contained significant amounts of thearubigins, theaflavic acids and theaflavins (including the less common analogues probably derived from the oxidation of (+)-catechin). The brews prepared from the Puer teas were distinguishable from the black tea brew by the absence of theaflavins and theaflavic acids, and by much smaller residues of flavanois and flavonol glycosides. The contents of thearubigins varied considerably whereas those of gallic acid were similar.     

White and green tea polyphenols inhibit pancreatic lipase in vitro

Green, white and black teas were assayed for inhibition of pancreatic lipase activity in vitro. White tea proved to be more effective than green tea with black tea showing little inhibition even at 200 μg GAE/ml. The EC₅₀ values for inhibition were 22 μg/ml for white tea and 35 μg/ml for green tea; both easily achievable from normal infusions of tea. Liquid chromatography-mass spectroscopy analysis showed that white and green teas had essentially equal amounts of flavan-3-ols but green tea had higher levels of flavonols. White tea had higher levels of 5-galloyl quinic acid, digalloyl glucose, trigalloyl glucose and the tannin, strictinin.After chromatography on Sephadex LH-20, the main inhibitory fraction was enriched in strictinin and fractions enriched in other components were ineffective. This suggests that strictinin content may be crucial for inhibition of pancreatic lipase. However, the possibility of synergies between the polyphenols cannot be disregarded.     

Distribution of Catechins, Theaflavins, Caffeine, and Theobromine in 77 Teas Consumed in the United States

ABSTRACT: To help define the composition of commercial teas consumed in the United States, we have developed and validated an high-performance liquid chromatography (HPLC) method to analyze levels of catechins, theaflavins, and alkaloids in 77 commercial black, green, specialty (brown rice, white, oolong), and herbal teas extracted with hot water to simulate home use. The following 13 compounds were separated in a single analysis on an Inertsil ODS-3v column with acetonitrile/potassium dihydrogen phosphate as the mobile phase: (−)-epigallocatechin, (+)-catechin, (−)-epicatechin, (−)-epigallocatechin-3-gallate, (−)-gallocatechin-3-gallate, (−)-epicatechin-3-gallate, (−)-catechin-3-gallate, theaflavin, theaflavin-3-gallate, theaflavin-3'-gallate, theaflavin-3, 3'-digallate, caffeine, and theobromine. The data show that (1) extraction time from 3 min to 20 min did not significantly affect measured levels of tea compounds and (2) there was a wide variation in the composition of the tea compounds both within each tea category and among categories: black teas contained both theaflavins and catechins, green and white teas contained catechins and trace amounts of theaflavins, herbal teas contained very low amounts of all tea compounds. A statistical profile of the distribution of catechins, theaflavins, caffeine, and theobromine in the evaluated teas offers consumers a choice of teas containing high levels of health-promoting compounds.     

红茶、绿茶、乌龙茶活性成分抗氧化性研究

目的与方法：通过醇提得到各种茶多酚提取液,酒石酸亚铁法测定了多酚的含量;水提得到各种茶多糖提取液,用硫酸- 苯酚法测定其中多糖的含量。通过DPPH·法、水杨酸法及邻苯三酚法测定不同茶叶中多酚、多糖含量对自由基的清除作用的影响,对比研究八种茶叶的抗氧化能力。结果：不同茶叶中多糖的含量从2.19%增大到2.89% (半发酵乌龙茶＞红茶＞绿茶),抗氧化能力：红茶＞绿茶＞乌龙茶(DPPH·法);红茶＞绿茶＞乌龙茶(水杨酸法);红茶＞乌龙茶＞绿茶(邻苯三酚法);不同茶叶中多酚的含量从1.71% 增大到9.75% (绿茶＞半发酵乌龙茶＞红茶);结论：茶多糖和多酚是茶叶的主要抗氧化成分。绿茶的抗氧化作用主要来自茶多酚,红茶的抗氧化作用主要来自茶多糖。除乌龙茶多糖提取液外,两种抗氧化成分的抗氧化能力与其含量成量效关系。     

Aluminium in foodstuffs

The aluminium content of a comprehensive food assortment typical of German nutritional habits was determined within the framework of market basket studies. Carried out in 1988 and 1991, a total of 128 items out of 12 groups of foodstuffs were included in this investigation. Aluminium content of the food assortment was low and comparable with literature data. Most investigated foodstuffs contained <5 μg Al g⁻¹ FM. Highest concentrations were determined in cocoa/cocoa products (33 μg g⁻¹), spices (145 μg g⁻¹) and black tea leaves (899 μg g⁻¹). In general, aluminium content of frequently consumed food, increased in the following order: beverages, food of animal origin, food of plant origin. With this low level of aluminium concentration in food, there is no danger of aluminium exposure in healthy persons.     

Comparison of the relative dissipation rates of endosulfan pesticide residues between oolong and green tea

The dissipation behaviour of endosulfan in dry made-tea leaves of oolong and green tea was compared to establish whether there was any difference in dissipation rates between the two teas. The dissipation of endosulfan in oolong and green tea corresponded with a first-order kinetics curve. The average half-life of endosulfan (n = 12) was 1.60 ± 0.44 days in green tea and 2.01 ± 0.55 days in oolong tea, showing a statistically significant difference, and indicating that the dissipation of the pesticide was significantly slower in oolong tea than that in green tea. Although the initial levels of residual endosulfan were lower in oolong tea, due to the slower dissipation rate, the residues 5–7 days after application were higher in oolong than in green tea. It is suggested that the minimum interval between endosulfan application and tea leaf harvesting is 7 days for green tea and 10 days for oolong tea in the case where the maximum residue limit of endosulfan in made-tea is fixed as 10 mg kg^?1.     

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.     

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.     

Evaluation of flavonoid and polyphenol constituents in mulberry leaves using HPLC fingerprint analysis

The mulberry leaf is a promising dietary source of antioxidants due to its high levels of beneficial compounds. To further examine its antioxidant properties, twelve batches of authenticated mulberry leaf, with total flavonoid contents (TFC) ranging from 24.34 mg g⁻¹ DW to 58.42 mg g⁻¹ DW and total polyphenol content (TPC) ranging from 11.49 mg g⁻¹ DW to 30.03 mg g⁻¹ DW, were investigated. According to Spearman’s coefficient, antioxidant activities, including the DPPH radical scavenging assay and the ferric reducing antioxidant power (FRAP), were positively correlated with TFC and TPC. The HPLC-DAD analysis results identified the characteristic fingerprint peaks in mulberry leaves as chlorogenic acid, rutin, quercetin 3-O-glucoside and kaempferol 3-O-glucoside, all of which directly contribute to the antioxidant capacity of mulberry leaves. Notably, young mulberry leaves showed higher antioxidant capacity than those of mature leaves. These promising results help create a compelling case for future development of mulberry leaf products.     

高效液相色谱-二极管阵列法检测四川绿茶、黄茶、黑茶、红茶和青茶中甲基化儿茶素含量

采用高效液相色谱-二极管阵列检测法(HPLC-DAD)对四川省雅安、成都、乐山、宜宾、绵阳23家企业生产的绿茶、黄茶、黑茶、红茶和青茶中48个茶样的(-)-表没食子儿茶素-3-O(3-O-甲基)没食子酸酯(EGCG3″Me)含量进行了比较研究。结果表明:青茶EGCG3″Me含量最高,在3.14~6.08 mg/g之间,平均值为4.40 mg/g;黑茶EGCG3″Me含量在0~1.72 mg/g,平均值为0.35 mg/g;绿茶和黄茶中EGCG3″Me含量较低;绿茶中含量在0~0.39 mg/g之间,平均值为0.10 mg/g;黄茶中含量在0~0.09 mg/g之间,平均值为0.05 mg/g;红茶中未检出。各茶类间EGCG3″Me含量差异显著,主要原因在于加工所用鲜叶原料(品种、采摘标准等)及加工工艺等不同。建议易过敏人群应适当饮用青茶。     

Determination of anthocyanins,flavonoids and phenolic acids in potatoes. I: Coloured cultivars of Solanum tuberosum L

The major anthocyanins, flavonoids and phenolic acids in the tubers (skin and flesh), flowers and leaves of 26 cultivars of Solanum tuberosum L with coloured skins and/or flesh have been identified and quantified using analytical HPLC. Red tubers contained mostly pelagonidin-3-(p-coumaroyl-rutinoside)-5-glucoside (200–2000 μg g⁻¹ FW) plus lesser amounts of peonidin-3-(p-coumaroyl-rutinoside)-5-glucoside (20–400 μg g⁻¹ FW). Light to medium purple tubers contained petunidin-3-(p-coumaroyl-rutinoside)-5-glucoside (1000–2000 μg g⁻¹ FW) plus small amounts of malvidin-3-(p-coumaroyl-rutinoside)-5-glucoside (20–200 μg g⁻¹ FW) whilst dark purple–black tubers contained similar levels of petunidin-3-(p-coumaroyl-rutinoside)-5-glucoside together with much higher concentrations of malvidin-3-(p-coumaroyl-rutinoside)-5-glucoside (2000–5000 μg g⁻¹ FW). Tuber flesh also contained chlorogenic acid (30–900 μg g⁻¹ FW) and other phenolic acids plus low concentrations of flavonoids (0–30 μg g⁻¹ FW). Tuber skins showed much higher levels (1000–4000 μg g⁻¹ FW) of chlorogenic acid. The major anthocyanins in flowers were present as the rutinosides or other glycosides of pelargonidin, petunidin and malvidin whilst glycosides of cyanidin and delphinidin were found in some flowers, together with many of the same phenolic acids as found in tubers. The commonest flavonoids included rutin, kaempferol-3-rutinoside and two quercetin-rhamnose-glucosides. Flowers and leaves contained higher concentrations of flavonoids which fell into two patterns, with some cultivars containing high concentrations of quercetin-3-glycosides, whilst others had much lower concentrations. © 1998 SCI.