茶叶中锗元素分析

采用高频电感耦合等离子体发射光谱法及催化极谱法，测定了广西部分地区的白毫茶、石龙茶、金花茶、山绿茶、苦丁茶及绞股蓝茶等六种茶叶中铜、锌、铁、锰、钙、镁、钴、铬、锶、钼、硒及锗等１２种无机元素含量，并着重讨论了茶叶中微量元素锗，硒特征，为合理饮茶，增进健康预防疾病提供了参考。     

非土壤因素对茶叶铅污染的影响

通过对18个茶叶生产厂家的分析调查发现,精制茶的生产工艺对茶叶的铅含量在总体上有降低作用,而粗制茶的加工工艺却有增加的趋势,因此茶叶生产工艺对茶叶的铅含量影响很大。通过用水清洗鲜叶发现,茶叶表面有相当一部分的铅可以洗脱下来,这说明在茶叶的种植过程中,大气中粉尘沉降对茶叶也有铅污染的作用。据此提出了一些建议和改进措施。     

原子吸收光谱法测定比较5种不同品牌茶叶中微量元素含量

对市售茶叶崂山绿茶、茯茶、安溪铁观音、乌龙茶、茉莉茶王中微量元素Ca、Mg、Fe、Cu、Zn的含量进行考察.采用V(高氯酸)∶V(硝酸)=1∶4混酸消解的方法将样品在低温下消解,火焰原子吸收光谱法定量.实验测得5种茶叶中均含丰富的Ca、Mg,其中茯茶含Fe最多;崂山绿茶含Cu最多;安溪铁观音和崂山绿茶含Zn多.各元素工作曲线相关系数r0.9948,加标回收率94.38%～105.00%,相对标准偏差在2.26%以下.实验方法快速、定量准确,测得各品牌茶叶中微量元素含量可为消费者提供参考.     

Identification and Quantification of Anthocyanin and Catechin Compounds in Purple Tea Leaves and Flakes

Tea is the first most popular beverage worldwide and is available in several selections such as black (fully oxidized), Oolong (partially oxidized) and green (non-oxidized), in addition to purple tea, an emerging variety derived from the same tea plant (Camellia sinensis). This study investigated purple tea leaves (non-oxidized) and flakes (water extractable) to thoroughly identify their composition of anthocyanins and catechins and to study the effect of a water extraction process on their compositional properties in comparison with green tea. Anthocyanin and catechin compounds were separated and quantified using UPLC, and their identity was confirmed using LC-MS/MS in positive and negative ionization modes. Delphinidin was the principal anthocyaninidin in purple tea, while cyanidin came in second. The major anthocyanin pigments in purple tea were delphinidin-coumaroyl-hexoside followed by delphinidin-3-galactoside and cyanidin-coumaroyl-hexoside. The water extraction process resulted in substantial reductions in anthocyanins in purple tea flakes. There were no anthocyanin compounds detected in green tea samples. Both purple and green tea types were rich in catechins, with green tea containing higher concentrations than purple tea. The main catechin in purple or green tea was epigallocatechin gallate (EGCG) followed by either epicatechin gallate (ECG) or epigallocatechin (EGC), subject to tea type. The extraction process increased the concentration of catechins in both purple and green tea flakes. The results suggest that purple tea holds promise in making healthy brews, natural colorants and antioxidants and/or functional ingredients for beverages, cosmetics and healthcare industries due to its high content of anthocyanins and catechins.     

Study on 1HNMR Fingerprint Spectra of Tea by Common and Variation Peak Ratio Dual-Index Sequence Analysis Method

Abstract

This paper describes the application of the common and variation peak ratio dual-index sequence analysis methods to evaluate the quality of several tea samples obtained from different species and different areas based on ¹HNMR fingerprint spectra (FPS). The method is able to determine the most similar sample groups and identify accurately the varieties and qualities of Blank tea, Longjing tea, and other green tea samples. Longjing tea is a famous brand of local green tea and has its own distinct characteristics. There were obvious differences between Uji tea from Japanese and Chinese green tea. The results showed that the dual index sequent analytical method provides a good approach to accurately describe the resemblance and differences among tea samples. It also can reflect tea's integrity and individual difference, and is an effective method to evaluate the quality of tea samples.     

Enzymatic Oxidation of Tea Catechins and Its Mechanism

Tea (Camellia sinensis, Theaceae) is one of the most widely consumed beverages in the world. The three major types of tea, green tea, oolong tea, and black tea, differ in terms of the manufacture and chemical composition. Catechins, theaflavins, and thearubigins have been identified as the major components in tea. Other minor oligomers have also been found in tea. Different kinds of ring fission and formation elucidate the major transformed pathways of tea catechins to their dimers and polymers. The present review summarizes the data concerning the enzymatic oxidation of catechins, their dimers, and thearubigins in tea.     

Tea and fluorosis

Tea trees (Camellia sinensis), abundant in fluoride, selectively absorb F from the soil and air in the surrounding, and accumulate mainly in the tea leaves in the form of Al and F complex. Long-term consumption of high fluoride tea could result in chronic fluoride intoxication. This review summarized those data of the fluoride content in various tea commodities, and estimated the risk of fluorosis caused by high fluoride tea commodities. We also introduced fluorosis caused by tea from case reports, epidemiology observations and animal models. Fluorosis was easily misdiagnosed and over-looked and people made little acquaintance in the high fluoride in some tea commodities. So it is the time to pay more attentions on the over-looked safety problem of tea and tea products and some measures should be taken to the fluorosis caused by tea. Large-scale epidemiological investigations and further studies on tea-type fluorosis are in need for those tea-drinking areas. In addition, it is urgent that governmental and international agencies adopt safe standards of fluoride content in tea commodities.     

茶皂素―金属复合抗菌剂的制备及抗菌性能研究

通过抑菌环法探讨了茶皂素、金属离子、茶皂素―金属复合抗菌剂对大肠杆菌和金黄色葡萄球菌的抗菌活性,考察了茶皂素纯度、浓度、金属离子种类等因素对抗菌剂抗菌活性的影响。结果表明,茶皂素的抗菌活性与单一的金属离子的抗菌活性相当,茶皂素对大肠杆菌的最低抑制浓度为5 mg/mL,对金黄色葡萄球菌的最低抑制浓度是10 mg/mL;茶皂素与金属离子复配抗菌活性具有协同效应,尤其茶皂素―锌复合抗菌剂对大肠杆菌的抑制效果大大加强。     

Profiling of In Vitro Bioaccessibility and Intestinal Uptake of Flavonoids after Consumption of Commonly Available Green Tea Types

The aim of this study was to profile the bioaccessibility and intestinal absorption of epicatechins and flavonols in different forms of green tea and its formulation: loose leaf tea, powdered tea, 35% catechins containing GTE, and GTE formulated with green tea-derived polysaccharide and flavonols (CATEPLUS™). The bioaccessibillity and intestinal absorption of epicatechins and flavonols was investigated by using an in vitro digestion model system with Caco-2 cells. The bioaccessibility of total epicatechins in loose leaf tea, powdered tea, GTE, and CATEPLUS™ was 1.27%, 2.30%, 22.05%, and 18.72%, respectively, showing that GTE and CATEPLUS™ had significantly higher bioaccessibility than powdered tea and loose leaf tea. None of the flavonols were detected in powdered tea and loose leaf tea, but the bioaccessibility of the total flavonols in GTE and CATEPLUS™ was 85.74% and 66.98%, respectively. The highest intestinal absorption of epicatechins was found in CATEPLUS™ (171.39 ± 5.39 ng/mg protein) followed by GTE (57.38 ± 9.31), powdered tea (3.60 ± 0.67), and loose leaf tea (2.94 ± 1.03). The results from the study suggest that formulating green tea extracts rich in catechins with second components obtained from green tea processing could enhance the bioavailability of epicatechins.     

Green Tea and Its Relation to Human Gut Microbiome

Green tea can influence the gut microbiota by either stimulating the growth of specific species or by hindering the development of detrimental ones. At the same time, gut bacteria can metabolize green tea compounds and produce smaller bioactive molecules. Accordingly, green tea benefits could be due to beneficial bacteria or to microbial bioactive metabolites. Therefore, the gut microbiota is likely to act as middle man for, at least, some of the green tea benefits on health. Many health promoting effects of green tea seems to be related to the inter-relation between green tea and gut microbiota. Green tea has proven to be able to correct the microbial dysbiosis that appears during several conditions such as obesity or cancer. On the other hand, tea compounds influence the growth of bacterial species involved in inflammatory processes such as the release of LPS or the modulation of IL production; thus, influencing the development of different chronic diseases. There are many studies trying to link either green tea or green tea phenolic compounds to health benefits via gut microbiota. In this review, we tried to summarize the most recent research in the area.     

Study on essential and toxic elements intake from drinking of Chinese tea

Twenty different brands of Chinese tea were analyzed for multiple trace elements, including some essential and toxic elements, by neutron activation analysis (NAA). A comparison among tea brands from China, India, US and other countries was made for the ranges and averages of concentrations for Na, K, Mn, Cu, and Br. It has been observed that the trace element contents in tea leaves are largely dependent upon the soil and the environment where the tea grows. Chinese tea is rich in Mn and Cu comparing with those of other counties surveyed, but is indigent in Na. The transference ratio for each element determined (i.e., the fraction of an element in tea leave transferred into solution when tea is leached by percolation) is also reported. Adult daily intakes of some essential and toxic elements from tea drinking were also estimated.     

绿茶的色谱指纹谱分类模式初探

以绿茶的数字化色谱指纹谱为基础,探讨用指纹谱来分类绿茶的新模式。各批次绿茶样品间的两两重叠率可作为筛选构建特征指纹谱样品的依据,14个绿茶样品按照特征指纹检出率和总差异率的不同初步划分为3个级别。本法从内在组成上为绿茶的分类提供了一个客观量化的界定标准,有别于过去凭借外形口感的经验评估,可为茶叶乃至自然界其它植物的化学分类提供新的视角。     

Chromatographic Determination of the Mycotoxin Patulin in 219 Chinese Tea Samples and Implications for Human Health

Patulin (PAT) is a mycotoxin, with several acute, chronic, and cellular level toxic effects, produced by various fungi. A limit for PAT in food of has been set by authorities to guarantee food safety. Research on PAT in tea has been very limited although tea is the second largest beverage in the world. In this paper, HPLC−DAD and GC−MS methods for analysis of PAT in different tea products, such as non-fermented (green tea), partially fermented (oolong tea, white tea, yellow tea), completely fermented (black tea), and post-fermented (dark tea and Pu-erh tea) teas were developed. The methods showed good selectivity with regard to tea pigments and 5-hydroxymethylfurfural (5-HMF) and a recovery of 90–102% for PAT at a 10–100 ppb spiking level. Limit of detection (LOD) and limit of quantification (LOQ) in tea were 1.5 ng/g and 5.0 ng/g for HPLC−UV, and 0.25 ng/g and 0.83 ng/g for GC−MS. HPLC was simpler and more robust, while GC−MS showed higher sensitivity and selectivity. GC−MS was used to validate the HPLC−UV method and prove its accuracy. The PAT content of 219 Chinese tea samples was investigated. Most tea samples contained less than 10 ng/g, ten more than 10 ng/g and two more than 50 ng/g. The results imply that tea products in China are safe with regard to their PAT content. Even an extreme daily consumption of 25 g of the tea with the highest PAT content (124 ng/g), translates to an intake of only 3 μg/person/day, which is still an order of magnitude below the maximum allowed daily intake of 30 µg for an adult.     

浅论绿茶与乌龙茶氟含量对人体健康的影响

分别用重蒸水和自来水，通过蒸煮法和浸泡法制出不同浓度的绿茶液和乌龙茶液，对比测定研究茶液中氟含量，结果表明，茶液中的氟含量随茶叶浓度增加而增加，且乌龙茶高于绿茶，当茶叶浓度超过１０．０ｇ／Ｌ时，茶液中的氟含量即超过国家饮水卫生标准，提示人们饮用水茶液浓度在５．０ｇ／Ｌ左右为宜。     

Green Tea (Camellia sinensis): A Review of Its Phytochemistry,Pharmacology, and Toxicology

Objectives Green tea (Camellia sinensis) is a kind of unfermented tea that retains the natural substance in fresh leaves to a great extent. It is regarded as the second most popular drink in the world besides water. In this paper, the phytochemistry, pharmacology, and toxicology of green tea are reviewed systematically and comprehensively. Key findings Green tea has been demonstrated to be good for human health. Nowadays, multiple pharmacologically active components have been isolated and identified from green tea, including tea polyphenols, alkaloids, amino acids, polysaccharides, and volatile components. Recent studies have demonstrated that green tea shows versatile pharmacological activities, such as antioxidant, anticancer, hypoglycemic, antibacterial, antiviral, and neuroprotective. Studies on the toxic effects of green tea extract and its main ingredients have also raised concerns including hepatotoxicity and DNA damage. Summary Green tea can be used to assist the treatment of diabetes, Alzheimer’s disease, oral cancer, and dermatitis. Consequently, green tea has shown promising practical prospects in health care and disease prevention.     

原子吸收光谱法测定茶叶中铅和镉时消解方法的优化

采用多种方法对同一种茶叶进行消解,用原子吸收光谱法测定不同方法消解的茶叶中有害微量元素铅和镉的含量并进行对比,探索了茶叶中微量元素铅和镉低损耗的最佳消解条件.实验结果表明,不同的消解方式对茶叶中微量元素的测定结果影响很大.测定茶叶中铅和镉元素时,采用硝酸-高氯酸加盖浸泡过夜方法较为理想.     

茶中茶多酚的高效液相色谱法分离分析

用改进的Ａｇａｒｗａｌ方法萃取不同种类茶叶和茶饮料中的茶多酚,建立了用高效液相色谱（ＨＰＬＣ）法对茶多酚进行分离分析方法。ＨＰＬＣ可有效分离ＧＴＰｓ主要组成成分ＥＣ、ＥＧＣ、ＥＣＧ和ＥＧＣＧ并精确定量,相对标准偏差小于５％。茶叶加工过程对ＧＴＰｓ含量有很大影响,绿茶总ＧＴＰｓ含量在６￣１５ｇ／１００ｇ干茶叶、乌龙茶总ＧＴＰｓ含量在５￣７ｇ／１００ｇ干茶叶,红茶总ＧＴＰｓ含量低于２ｇ／１００ｇ干茶叶     

Optimizing conditions for the extraction of catechins from green tea using hot water

Six different factors involved in the extraction of catechins from green tea using water were examined for their impact on the yield of catechins and on the efficiency of water use. The best temperature and time combination for catechin extraction was at 80°C for 30 min. The yield of catechins was also optimal with a tea particle size of 1 mm, a brewing solution pH <6 and a tea‐to‐water ratio at 50:1 (mL/g). In terms of efficient use of water in a single extraction, a water‐to‐tea ratio of 20:1 (mL/g) gave the best results; 2.5 times less water was used per gram of green tea. At the water‐to‐tea ratio of 20:1 mL/g, the highest yield of catechins per gram of green tea was achieved by extracting the same sample of green tea twice. However, for the most efficient use of water, the best extraction was found to be once at a water‐to‐tea ratio of 12:1 (mL/g) and once at a water‐to‐tea ratio of 8:1 (mL/g). Therefore, all six of the factors investigated had an impact on the yield of catechins extracted from green tea using water and two had an impact on the efficiency of water use.     

Multielement determination and speciation of major-to-trace elements in black tea leaves by ICP-AES and ICP-MS with the aid of size exclusion chromatography.

A multielement determination of major-to-trace elements in black tea leaves and their tea infusions was carried out by ICP-AES (inductively coupled plasma atomic emission spectrometry) and ICP-MS (inductively coupled plasma mass spectrometry). Tea infusions were prepared as usual tea beverage by brewing black tea leaves in boiling water for 5 min. About 40 elements in tea leaves and tea infusions could be determined over the wide concentration range in 8 orders of magnitude. The extraction efficiency of each element was estimated as the ratio of its concentration in tea infusions to that in tea leaves. From the experimental results for the extraction efficiencies, the elements in black tea leaves were classified into three characteristic groups: (i) highly-extractable elements (>55%): Na, K, Co, Ni, Rb, Cs and Tl, (ii) moderately-extractable elements (20-55%): Mg, Al, P, Mn and Zn, and (iii) poorly-extractable elements (<20%): Ca, Fe, Cu, Sr, Y, Zr, Mo, Sn, Ba and lanthanoid elements. Furthermore, speciation of major-to-trace elements in tea infusions was performed by using a combined system of size exclusion chromatography (SEC) and ICP-MS (or ICP-AES). As a result, many diverse elements were found to be present as complexes associated with large organic molecules in tea infusions.     

Voltammetric evaluation of the antioxidant capacity of tea on electrodes modified with multi-walled carbon nanotubes

The characteristics of the voltammograms of tea polyphenols on a glassy carbon electrode modified with multi-walled carbon nanotubes (MCNT-GCE) were evaluated. With the use of atomic force microscopy, it was found that MCNTs are oriented as rows 0.8–1.0 μm wide with alternating hills to 586 nm in height. Polyphenols other than of tannin are reversibly oxidized at the first step. Corresponding electrode reaction schemes are proposed. A voltammetric procedure for the estimation of the antioxidant capacity (AOC) of tea based on the oxidation of its polyphenol compounds was developed. The voltammograms of tea exhibited clearly defined peaks and oxidation steps whose potentials depend on the type of tea. The area of oxidation peaks was chosen as the parameter that characterizes antioxidant properties. The AOC of tea was expressed in terms of catechin equivalents per 100 mL of a beverage. 27 tea samples were analyzed. It was found that the AOC of green tea is 79% higher than that of black tea (290 ± 40 and 54 ± 22 mg/100 mL, respectively, P < 0.05). The AOC of oolong tea (70 ± 5 mg/100 mL) is considerably lower than that of green tea and statistically insignificantly higher than that of black tea. The AOC of white tea is comparable with the AOC of green tea (255 ± 11 and 290 ± 40 mg/100 mL, respectively, P > 0.05).