Oxalate content and calcium binding capacity of tea and herbal teas

Thirty-two commercially available teas consisting of green, oolong and black teas were bought from supermarkets in Christchurch, New Zealand in June 2001. Fifteen herbal teas were also purchased at the same time. The soluble oxalate content of the infusate made from each of the teas was determined using high pressure liquid chromatography. The mean soluble oxalate contents of black tea in tea bags and loose tea leaves were 4.68 and 5.11 mg/g tea, respectively, while green teas and oolong tea had lower oxalate contents, ranging from 0.23 to 1.15 mg/g tea. The soluble oxalate content of the herbal teas ranged from not detected to 3.00 mg/g tea. A regular tea drinker consuming six cups of tea/day would have an intake of between 26.46 and 98.58 mg soluble oxalate/day from loose black tea, 17.88 and 93.66 mg soluble oxalate/day from black tea in tea bags and a maximum of 18.0 mg/day from herbal teas. The oxalate intake from the regular daily consumption of black teas is modest when compared to the amounts of soluble oxalate that can be found in common foods. However, oxalate in black teas has the potential to bind to a significant proportion of calcium in the milk, which is commonly consumed with the black teas.     

Catechin content of 18 teas and a green tea extract supplement correlates with the antioxidant capacity

Our literature review of currently available data in the area of tea and cancer prevention demonstrated that there is more conclusive evidence for the chemopreventive effect of green tea compared with black tea. We suggest that this is due to a large variation of the flavanol content in tea, which is not taken into consideration in most of the epidemiological studies. It was the purpose of this study to determine the flavanol content of various teas and tea products and to correlate it with their radical scavenging activity. A modified oxygen radical absorbance capacity (ORAC) assay at pH 5.5 was utilized. The total flavavol content varied from 21.2 to 103.2 mg/g for regular teas and from 4.6 to 39.0 mg/g for decaffeinated teas. The ORAC value varied from 728 to 1686 trolox equivalents/g tea for regular teas and from 507 to 845 trolox equivalents/g for decaffeinated teas. There was a significant correlation of flavanol content to ORAC value (r = 0.79, P = 0.0001) for the teas and green tea extract. The large variation in flavanol content and ORAC value among various brands and types of tea provides critical information for investigators using tea in studies of nutrition and cancer prevention.     

Polycyclic aromatic hydrocarbons in tea and tea infusions

Tea is the one of most widely consumed beverage in the world. It is generally believed that tea consumption might have health promoting properties. But residues of certain chemical compounds might impose a health threat on tea drinkers. The main contaminants are heavy metals, fluoride, pesticides and even dioxins. Tea lives which possess a high surface area can be contaminated with atmospheric PAHs. The manufacturing processes may also introduce PAHs into tea lives. The aim of his study was to determine the contamination of black, green, red and white teas by PAHs. In this investigation, content of 23 PAH, i.e 16 EPA PAH and 15 EU PAH were determined in 18 brands of tea and its infusions. The analytical procedure was based on ultrasonic extraction for dried tea and liquid-liquid extraction for infusions. All samples were cleaned up by florisil cartridge. The total content of 23 PAH varied between 22.9 microg/kg to 2945.5 microg/kg and 2.7 microg/kg to 63,1 microg/kg microg/kg for BaP. The analysed tea samples showed an increasing presence of PAH in the following order (mean value): black tea < red tea < green tea < white tea. However the highest content of PAH was found in the one brand of black tea bag both in sum of PAH and BaP content. During tea infusion 1.6% of total PAHs contained in tea was released into the beverage. The dominant PAHs in tea infusion were 2, 3 and 4 rings PAH, while the most toxic compounds were found at trace amounts. The concentrations of total 23 PAHs and BaP in tea infusions ranged from 332.5 ng/dm3 to 2245.9 ng/dm3 and 0.35 ng/dm3 to 18.7 ng/dm3 respectively.     

Comparison of the antioxidant activity of roasted tea with green, oolong, and black teas

Although the antioxidant properties of green, oolong, and black teas have been well studied, antioxidant activity has not been examined in roasted tea. Therefore, in the current studies, we investigated the antioxidant activity of roasted tea in comparison with those of green, oolong, and black teas. Using water extracts of the various teas, we examined the total phenolic content as well as the antioxidant activities, including the reducing power, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and the inhibition of hemolysis caused by 2,2'-azo-bis(2-amidinopropane) dihydrochloride (AAPH)-induced lipid oxidation in erythrocyte membranes. The roasted tea contained lower levels of total phenolics than green, oolong, or black tea (green tea > oolong tea > black tea > roasted tea). The relative reducing power and DPPH scavenging activity decreased in the following order: green tea > roasted tea > oolong tea > black tea. Also, green tea was more effective against AAPH-induced erythrocyte hemolysis than other teas (green tea>roasted tea = oolong tea = black tea). These results suggest that roasted tea is beneficial to health, in humans, because of its high antioxidant activity.     

Comparison of the antioxidant activity of roasted tea with green,oolong, and black teas

Although the antioxidant properties of green, oolong, and black teas have been well studied, antioxidant activity has not been examined in roasted tea. Therefore, in the current studies, we investigated the antioxidant activity of roasted tea in comparison with those of green, oolong, and black teas. Using water extracts of the various teas, we examined the total phenolic content as well as the antioxidant activities, including the reducing power, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and the inhibition of hemolysis caused by 2,2’-azo-bis(2-amidinopropane) dihydrochloride (AAPH)-induced lipid oxidation in erythrocyte membranes. The roasted tea contained lower levels of total phenolics than green, oolong, or black tea (green tea>oolong tea>black tea>roasted tea). The relative reducing power and DPPH scavenging activity decreased in the following order: green tea>roasted tea>oolong tea>black tea. Also, green tea was more effective against AAPH-induced erythrocyte hemolysis than other teas (green tea>roasted tea=oolong tea=black tea). These results suggest that roasted tea is beneficial to health, in humans, because of its high antioxidant activity.     

Ethyl acetate extract from black tea prevents neuromuscular blockade by botulinum neurotoxin type A in vitro

Botulinum neurotoxin produced by Clostridium botulinum is the strongest neurotoxin and causes botulism in mammals. The current study aimed to find an inactivator for botulinum neurotoxin in black, oolong, roasted, and green teas. The ability of the four teas to inactivate the neuromuscular blocking action of botulinum neurotoxin was determined. Water extracts from black, oolong, and roasted teas protected against the toxicity of botulinum neurotoxin type A in mouse phrenic nerve-diaphragm preparations. The order of potency of the water extracts was black tea > oolong tea > roasted tea > green tea (no effect). The effects of several organic solvent extracts of black tea water extract were examined, and the order of potency was ethyl acetate extract > butanol extract = remaining extract > chloroform extract (no effect). Ethyl acetate extracts from oolong, roasted, and green tea water extracts also exhibited a stronger protecting effect than chloroform, butanol, and remaining extracts from these teas, but they had weaker protective effect than ethyl acetate extract from black tea water extract. These protective effects occurred only when each extract was pre-mixed with the toxin before the assay, and they were not modified by mixing each extract with bovine serum albumin (BSA) before adding the toxin. These results indicate that ethyl acetate extract from black tea is the best source for searching for tea-derived inactivating substance(s) of botulinum neurotoxin.     

Fluoride and aluminum in teas and tea-based beverages

OBJECTIVE: To evaluate fluoride and aluminum concentration in herbal, black, ready-to-drink, and imported teas available in Brazil considering the risks fluoride and aluminum pose to oral and general health, respectively. METHODS: One-hundred and seventy-seven samples of herbal and black tea, 11 types of imported tea and 21 samples of ready-to-drink tea were divided into four groups: I-herbal tea; II-Brazilian black tea (Camellia sinensis); III-imported tea (Camellia sinensis); IV-ready-to-drink tea-based beverages. Fluoride and aluminum were analyzed using ion-selective electrode and atomic absorption, respectively. RESULTS: Fluoride and aluminum levels in herbal teas were very low, but high amounts were found in black and ready-to-drink teas. Aluminum found in all samples analyzed can be considered safe to general health. However, considering 0.07 mg F/kg/day as the upper limit of fluoride intake with regard to undesirable dental fluorosis, some teas exceed the daily intake limit for children. CONCLUSIONS: Brazilian and imported teas made from Camellia sinensis as well as some tea-based beverages are sources of significant amounts of fluoride, and their intake may increase the risk of developing dental fluorosis.     

Ethyl acetate extract from black tea prevents neuromuscular blockade by botulinum neurotoxin type A in vitro

Botulinum neurotoxin produced by Clostridium botulinum is the strongest neurotoxin and causes botulism in mammals. The current study aimed to find an inactivator for botulinum neurotoxin in black, oolong, roasted, and green teas. The ability of the four teas to inactivate the neuromuscular blocking action of botulinum neurotoxin was determined. Water extracts from black, oolong, and roasted teas protected against the toxicity of botulinum neurotoxin type A in mouse phrenic nerve–diaphragm preparations. The order of potency of the water extracts was black tea?>?oolong tea?>?roasted tea?>?green tea (no effect). The effects of several organic solvent extracts of black tea water extract were examined, and the order of potency was ethyl acetate extract?>?butanol extract?=?remaining extract?>?chloroform extract (no effect). Ethyl acetate extracts from oolong, roasted, and green tea water extracts also exhibited a stronger protecting effect than chloroform, butanol, and remaining extracts from these teas, but they had weaker protective effect than ethyl acetate extract from black tea water extract. These protective effects occurred only when each extract was pre-mixed with the toxin before the assay, and they were not modified by mixing each extract with bovine serum albumin (BSA) before adding the toxin. These results indicate that ethyl acetate extract from black tea is the best source for searching for tea-derived inactivating substance(s) of botulinum neurotoxin.     

绿茶保健作用研究

[目的]探讨绿茶保健作用。[方法]应用722分光光度仪测定绿茶中茶多酚含量,应用原子吸收分光光度仪测定微量元素含量及溶出率。[结果](1)绿茶等级越高其氨基酸、茶多酚的含量越高,锌含量亦越高。不同等级间茶多酚、微量元素锌含量差别甚大,茶多酚含量高者达36.2%,低者仅10.9%。锌含量高者达53.2μg/g,低者仅35.25μg/g。(2)铜、铁含量不高且品种间差别不大。(3)锰、氟、铝含量则随茶叶等级降低而升高,且品种间含量差别甚大。(4)5种绿茶中锌的溶出率均较高,达79.95%～88.26%,铜达70.6%～92.89%,氟达72.75%～95.63%,铁多为35%左右,锰36.08%～44.66%,铝8.81%～51.69%。[结论]高级别绿茶具有保健作用,低级别绿茶无益于健康。     

Effects of oral administration of tea, decaffeinated tea, and caffeine on the formation and growth of tumors in high-risk SKH-1 mice previously treated with ultraviolet B light.

Treatment of SKH-1 mice with ultraviolet B light (UV-B, 30 mJ/cm2) twice a week for 22-23 weeks resulted in tumor-free animals with a high risk of developing malignant and nonmalignant tumors during the next several months in the absence of further UV-B treatment (high-risk mice). In three separate experiments, oral administration of green tea or black tea (4-6 mg tea solids/ml) as the sole source of drinking fluid for 18-23 weeks to these high-risk mice inhibited the formation and decreased the size of nonmalignant squamous cell papillomas and keratoacanthomas as well as the formation and size of malignant squamous cell carcinomas. In one experiment all these inhibitory effects of tea were statistically significant, whereas in the two other experiments many but not all of the inhibitory effects of tea were statistically significant. The decaffeinated teas were inactive or less effective inhibitors of tumor formation than the regular teas, and adding caffeine back to the decaffeinated teas restored biological activity. Oral administration of caffeine alone (0.44 mg/ml) as the sole source of drinking fluid for 18-23 weeks inhibited the formation of nonmalignant and malignant tumors, and this treatment also decreased tumor size in these high-risk mice.     

Green tea and theanine: health benefits

Historically, the medicinal use of green tea dates back to China 4700 years ago and drinking tea continues to be regarded traditionally in Asia as a general healthful practice. Numerous scientific publications now attest to the health benefits of both black and green teas, including clinical and epidemiological studies. Although all tea contains beneficial antioxidants, high-quality green and white teas have them in greater concentrations than black tea. Today, scientists believe that the main active ingredients of green tea include the polyphenols, in particular the catechins and the amino acid, theanine. Studies on the health benefits of drinking tea, particularly green tea, are finding exciting results, particularly in cancer research. Modern studies in both Asia and the West have provided encouraging results indicating that drinking green tea contributes to fighting many different kinds of cancers including stomach, oesophageal, ovarian and colon. Recent studies describing the health benefits of these compounds will be reviewed.     

Phosphorylation of hepatic AMP-activated protein kinase and liver kinase B1 is increased after a single oral dose of green tea extract to mice

We have previously shown that green and black tea extracts increase the phosphorylation of AMP-activated protein kinase (AMPK) and HMG-CoA reductase in rat hepatoma cells in culture, concomitant with a decrease in cholesterol synthesis. In the present study, we evaluated the ability of a single oral dose of green or black tea extract to promote the phosphorylation of AMPK, liver kinase B1 (LKB1, an AMPK-kinase), and HMG-CoA reductase in mouse liver. Green tea extract administered by gavage at 50 and 100 mg/kg caused a 2- to 3-fold increase in hepatic AMPK phosphorylation at 3 and 6 hours after dosing and a 1.5- to 2-fold increase in LKB1 phosphorylation at these same time points. The phosphorylation of HMG-CoA reductase at these and later time points was not significantly increased. Black tea administered by gavage at up to 250 mg/kg was ineffective in increasing hepatic AMPK phosphorylation. Both green and black tea extracts increased LKB1 phosphorylation in hepatoma cells in culture at 15 μg/mL, and black tea also increased the phosphorylation of protein kinase A in hepatoma cells. These results suggest that compounds in both tea extracts activate AMPK by activating its upstream kinase, LKB1, and that black tea may do so by first activating protein kinase A, a known kinase for LKB1. Only green tea, at 50 and 100 mg/kg, was able to activate AMPK and LKB1 in mouse liver after oral dosing, suggesting that the polymerized catechins present in black tea do not reach the liver in sufficient concentration to affect AMPK activity.     

The efficacy of black tea in ameliorating endothelial function is equivalent to that of green tea

Consumption of tea has been shown to improve endothelial function. It is assumed that catechins are the tea components responsible for these beneficial effects. In black tea, catechin concentrations are significantly lower than in green tea. The present study was designed to compare green and black tea with regard to amelioration of endothelial function. Endothelial function in response to both teas was assessed in bovine aortic endothelial cells (BAEC) and rat aortic rings. To elucidate whether these findings are also applicable to humans, flow-mediated dilation (FMD) and nitro-mediated dilation (NMD) were assessed by ultrasound in twenty-one healthy women before and 2 h after consumption of green and black tea (2 h of FMD and NMD), in comparison with water (control). In BAEC, green and black tea significantly increased endothelial NO synthase activity to the same extent. Similarly, both teas induced comparable endothelial-dependent vasodilation in rat aortic rings. In human subjects, ingestion of green and black tea led to significant increases in FMD: from 5.4 (sd 2.3) to 10.2 (sd 3) % (baseline-adjusted difference (BAD) for 2 h of FMD, green tea v. water: 5.0 (95 % CI 3.0, 7.0) %; P < 0.001) and from 5 (sd 2.6) to 9.1 (sd 3.6) % (BAD for 2 h of FMD, black tea v. water: 4.4 (95 % CI 2.3, 6.5) %; P < 0.001), respectively. The increase in FMD was not significantly different between the two tea preparations (BAD for 2 h of FMD, green tea v. black tea: 0.66 (95 % CI - 0.76, 2.09) %; P = 0.36). NMD did not vary between any of the groups. In conclusion, green and black tea are equally effective in improving endothelial function.     

Flavanol database for green and black teas utilising ISO 14502-1 and ISO 14502-2 as analytical tools

A worldwide data collection was undertaken using the validated ISO methods ISO 14502 parts 1 and 2, with 17 laboratories participating worldwide. This is the largest tea database worldwide, containing 295 black- and 358 green-origin teas. We found it quite easy to differentiate most green and black teas by the type of analysis presented in this study. The geographic spread gave a good representation of the vast majority of the producing countries. The production figures of the countries and the proportion of teas in the database are very similar. There are only a few origins which are not easy to differentiate, e.g. Darjeeling samples fall into the area of green teas. Other types of tea, e.g. Oolong or white teas, are currently not in the database. In the future other standardized methods for tea phenolics, such as theaflavins or flavonol glycosides, might become available. Additional data will certainly contribute to an even more robust discrimination between the types of tea.     

Tea as a potential chemopreventive agent in PhIP carcinogenesis: effects of green tea and black tea on PhIP-DNA adduct formation in female F-344 rats

The heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is formed during the cooking of proteinaceous animal foods (meat, chicken, and fish). PhIP is a carcinogen in the Fischer 344 (F-344) rat; it induces mammary tumors in female rats and lymphomas and colon and prostate tumors in male rats. In F-344 rats, PhIP forms DNA adducts in various organs, including the target organs. Inhibition of PhIP-DNA adduct formation is likely to lead to inhibition of PhIP tumorigenicity. We have examined the chemopreventive properties of green tea and black tea in PhIP carcinogenesis by evaluating their effects on PhIP-DNA adduct formation in the female F-344 rat. Young adult animals were maintained on powdered AIN-76A diet while receiving regular drinking water or 2% (wt/vol) infusions of green tea or black tea for a total of six weeks. During Weeks 3, 4, and 5, all animals received PhIP by gavage (1 mg/kg/day). Three rats per group were euthanized on Days 1 and 8 after termination of PhIP exposure. DNA was isolated from a number of organs and analyzed for PhIP-DNA adducts by 32P-postlabeling assays. Compared with animals on regular drinking water, PhIP-DNA adduct formation was inhibited in small intestine, colon, liver, and mammary epithelial cells (MECs) of animals receiving green tea or black tea as the sole source of drinking fluid. Green tea inhibited adduct formation in colon, liver, and MECs (33.3-80.0%) on both days, but only on Day 8 (54.4%) in small intestine. Black tea inhibited adduct formation on both days in liver (71.4-80.0%), on Day 1 in colon (40.0%), and on Day 8 in small intestine (81.8%); it had no effect on MEC adducts. Neither green tea nor black tea had an effect on adduct levels in pancreas, lungs, white blood cells, heart, kidneys, spleen, cecum, or stomach. Similarly, these teas did not affect the rate of adduct removal (percent change from Day 1 to Day 8) in any organ. It is concluded that green tea and black tea are potential chemopreventive agents in PhIP-induced tumorigenesis in the F-344 rat.     

Polycyclic aromatic hydrocarbons (PAHs) in herbs and fruit teas

Polycyclic aromatic hydrocarbons (PAHs) of which benzo[a]pyrene is the most commonly studied and measured, are fused - ring aromatic compounds formed in both natural and man made processes and are found widely distributed throughout the human environment. PAHs occur as contaminants in different food categories and beverages including water, vegetables, fruit, cereals, oils and fats, barbecued and smoked meat. The sources of PAHs in food are predominantly from environmental pollution and food processing. PAHs emissions from automobile traffic and industry activities were show to influence the PAHs levels in vegetables and fruits. The present study was carried out to determine levels of 16 basic PAHs in herbs and fruit teas. The method was based on the hexane extraction and cleaned up by florisil cartridge. The extracts were analysed by GC-MS. The levels of total PAHs varied from 48,27 microg/kg (hibiscus tea) to 1703 microg/kg (green tea). The highest level of BaP was found in lime tea (74,2 microg/kg).     

凝胶渗透色谱和固相萃取净化气相色谱-质谱法检测动物性食品中26种有机氯农药残留

目的:建立一种测定动物性食品中有机氯类多种农药残留的气相色谱质谱分析方法。方法:采用丙酮和正己烷提取肉中多种有机氯类农药,以凝胶渗透色谱(GPC)和固相萃取(SPE)净化、浓缩后,用气相色谱—质谱选择离子监测方式分析检测26种有机氯农药残留。结果:所有26种农药均在20 min内流出,分离良好,农药标准的线性范围在0.01 mg/L～0.5 mg/L相关系数r均在0.99以上,低、高两种浓度加标回收率均在61%～95%之间,相对标准偏差均小于13%,方法最低检出限在0.002 mg/kg～0.005 mg/kg。结论:本方法适合动物性食品中有机氯类农药残留的测定。     

威海市农产品及人乳中有机氯农药残留量的调查

目的 了解有机氯农药的环境污染水平和人体蓄积水平。方法 检测了威海市主要农产品（小麦、玉米、花生、苹果）中的有机氯农药残留量和人乳中有机氯农药蓄积水平。结果 所调查的4种农产品中残留有机氯农药的检出率在0－60.0%,多数属于痕量检出,其最大检出值为国家卫生标准的1／28－1／5。人乳中666总量中位数为2.29mg/kg（以乳脂汁）;DDT总量中位数为2033mg/kg（以乳脂计）。分别降为全国80年代初期水平的1／3和1／5。结论 威海市有机氯农药的环境污染已基本消除,母乳中残留的有机氯农药对下一代健康影响不容忽视。     

绍兴地区市售茶叶及代用茶中有害元素含量调查

目的 测定绍兴地区市售茶叶及代用茶中Pb、Cd、Ni、Cr、Hg、As和Al共7种有害元素的含量,并对污染水平进行分析。 方法 2016-2017年随机采集绍兴地区的商店、农贸市场等地的茶叶样品85份(其中绿茶58份,红茶11份,青茶12份,黑茶4份),代用茶样品158份(其中大麦茶48份,花茶73份,苦丁茶37份),采用微波消解-电感耦合等离子体质谱法测定样品中7种元素的含量,按GB 2762-2017《食品安全国家标准 食品中污染物限量》和NY 659-2003《茶叶中铬、镉、汞、砷及氟化物限量》评价检测结果。 结果 四种茶叶中Pb、Cd、Hg和As的含量差异均无统计学意义(P>0.05);Ni、Cr和Al含量最高的茶叶分别是绿茶、黑茶和青茶,中位数分别为5.59、0.70和1 265 mg/kg;绿茶、红茶和青茶中As的超标率分别为20.69%、18.18%和16.67%。苦丁茶中Cd、Ni和Al均为代用茶中最高,中位数分别为0.93、1.72和158 mg/kg;花茶中Pb和Cr均为代用茶中最高,中位数分别为0.31和0.19 mg/kg;大麦茶、花茶和苦丁茶中砷的超标率分别为2.08%、4.11%和2.70%;大麦茶和苦丁茶中Pb超标率分别为14.60%和2.70%;苦丁茶中Cd超标率为43.24%,最大值23.7 mg/kg。 结论 绍兴地区市售茶叶中As及苦丁茶中Cd污染情况需引起重视,建议继续加强监测力度,寻找污染来源并采取适当的控制措施。     

Breast Milk Excretion Kinetic of β-HCH, pp′DDE and pp′DDT

Breast milk is considered the most important route in the elimination of deposited organochlorine pesticides in a mother’s body. The equilibrium of organochlorine pesticides in the human body considers the elements of internal transport processes, the equilibrium pattern between pesticides and tissue fat contents, and the mobilization of lipids and lipoproteins among body parts. The aim of this study was to determine organochlorine pesticide levels in breast milk samples from the 4th to the 30th day of lactation and the trend in their concentration time so as to forecast the time tendency of residue levels and the pesticide excretion pattern. Milk samples were taken from forty participants and analyzed by GLC-ECD. The organochlorine pesticide residues determined in the breast milk samples during lactation decreased: β-HCH from 0.095 to 0.066 mg/kg, pp′DDE from 1.807 to 1.423 mg/kg and pp′DDT from 0.528 to 0.405 mg/kg, at the characteristic rate for each compound. The obtained results compared with the calculated fits of forecasts were parallel and did not exhibit significant differences. The newborn baby exposed during lactation had organochlorine pesticide residues whose levels decreased permanently. The levels depended not only on the breast milk nutrition, but also on the total environmental exposures which included air pollution as a significant contamination source.