茶叶中核糖核酸的分析检测

通过对几种茶叶中核糖核酸（ＲＮＡ）的分离与定性鉴定、电泳分离鉴定及紫外分光光度计定量测定，表明茶叶中确实存在ＲＮＡ，其含量随产地不同而有一定差异，其中滇红、滇绿含量较高，可达１％水平。     

Antioxidant activity of green teas in different lipid systems

Different commercial green teas from Japan, China, and India, were compared in different lipid systems. Green teas were active antioxidants in bulk corn oil oxidized at 50°C but were prooxidant in the corresponding oil-in-water emulsions. Green teas also were active antioxidants in soybean lecithin liposomes oxidized at 37°C in the presence of cupric acetate as catalyst. At 50°C, however, three of the samples of green tea were active antioxidants in the absence of copper catalyst, and two samples showed prooxidant activity in the presence of copper catalyst. The marked variation in activity among green tea samples may be due partly to differences in their relative partition between phases in different lipid systems. The improved antioxidant activity observed for green teas in lecithin liposomes compared to corn oil emulsions can be explained by the greater affinity of the polar tea catechin gallates for the polar surface of the lecithin bilayers, thus affording better protection against oxidation. Liposomes may thus be appropriate lipid models to evaluate antioxidants for foods containing phospholipids.     

Selected Tea and Tea Pomace Extracts Inhibit Intestinal α-Glucosidase Activity in Vitro and Postprandial Hyperglycemia in Vivo

Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by postprandial hyperglycemia, which is an early defect of T2DM and thus a primary target for anti-diabetic drugs. A therapeutic approach is to inhibit intestinal α-glucosidase, the key enzyme for dietary carbohydrate digestion, resulting in delayed rate of glucose absorption. Although tea extracts have been reported to have anti-diabetic effects, the potential bioactivity of tea pomace, the main bio waste of tea beverage processing, is largely unknown. We evaluated the anti-diabetic effects of three selected tea water extracts (TWE) and tea pomace extracts (TPE) by determining the relative potency of extracts on rat intestinal α-glucosidase activity in vitro as well as hypoglycemic effects in vivo. Green, oolong, and black tea bags were extracted in hot water and the remaining tea pomace were dried and further extracted in 70% ethanol. The extracts were determined for intestinal rat α-glucosidases activity, radical scavenging activity, and total phenolic content. The postprandial glucose-lowering effects of TWE and TPE of green and black tea were assessed in male Sprague-Dawley (SD) rats and compared to acarbose, a known pharmacological α-glucosidase inhibitor. The IC₅₀ values of all three tea extracts against mammalian α-glucosidase were lower or similar in TPE groups than those of TWE groups. TWE and TPE of green tea exhibited the highest inhibitory effects against α-glucosidase activity with the IC₅₀ of 2.04 ± 0.31 and 1.95 ± 0.37 mg/mL respectively. Among the specific enzymes tested, the IC₅₀ values for TWE (0.16 ± 0.01 mg/mL) and TPE (0.13 ± 0.01 mg/mL) of green tea against sucrase activity were the lowest compared to those on maltase and glucoamylase activities. In the animal study, the blood glucose level at 30 min after oral intake (0.5 g/kg body wt) of TPE and TWE of both green and black tea was significantly reduced compared to the control in sucrose-loaded SD rats. The TPE of all three teas had significantly higher phenolic content than those of the TWE groups, which correlated strongly with the DPPH radical scavenging activity. This is the first report of tea pomace extract significantly inhibits intestinal α-glucosidase, resulting in delayed glucose absorption and thereby suppressed postprandial hyperglycemia. Our data suggest that tea pomace-derived bioactives may have great potential for further development as nutraceutical products and the reuse of otherwise biowaste as valuable bioresources for the industry.     

铜仁市四种绿茶茶多酚提取率的比较分析

为对铜仁市茶叶品质成分提供科学依据,用酒石酸亚铁比色法对铜仁市的印江梵净山绿茶、松桃生态绿茶、石阡苔茶、沿河云雾绿茶四县同一季节同一等级茶叶中茶多酚提取率进行比较研究,同时对松桃生态绿茶同一产地不同采收时节茶叶中茶多酚的提取率进行比较研究。结果表明:茶多酚的提取率含量较高的是石阡苔茶,其次是松桃生态绿茶、沿河云雾绿茶、印江梵净山绿茶;松桃县云雾绿茶不同采收时节的茶叶中茶多酚提取率含量较高的是清明茶,其次是清明前茶、谷雨茶、清明后茶。     

Polycyclic Aromatic Hydrocarbons (PAHs) Occurrence and Toxicity in Camellia sinensis and Herbal Tea

ABSTRACT

This study describes a survey of polycyclic aromatic hydrocarbon (PAH) concentrations in 23 green, herbal, and black tea brands widely consumed in Nigeria by determining the levels of benzo[a]pyrene, chrysene (PAH2), benzo[a]pyrene, chrysene, benz[a]anthracene, benzo[b]fluoranthene (PAH4), benzo[a]pyrene, benz[a]anthracene, benzo[k]fluoranthene, chrysene, benzo[b]fluoranthene, dibenz[ah]anthracene, benzo[ghi]per-ylene and indeno[1,2,3-cd]pyrene (PA-H8). Toxic equivalence factor and mutagenic equivalence factor were applied to evaluate the toxic equivalence and mutagenic equivalence quotients relative to benzo[a]pyrene. The concentrations of PAHs indicate that Regulation 835/2011/EC was not fulfilled by benzo[a]anthracene, B[a]A, benzo[a]pyrene, B[a]P, benzo[b]fluoranthene, B[b]F, and chrysene, CHR. The PAH4 levels ranged from 1.28 to 44.57, 4.34 to 11.20, and 0.76 to 34.82 µg/kg in green, black, and herbal tea products, respectively. On the other hand, the PAH8 concentration varied between 1.63 and 65.73, 5.02 and 68.83, and 12.43 and 24.92 µg/kg in green, herbal, and black tea samples. The PAH4 and PAH8 provide more reliable indicators for determination of PAH contamination and risk characterization in food than PAH2.     

Determination of Polycyclic Aromatic Hydrocarbons in Water- and Gin-Based Tea Infusions of Selected Tea Brands in Nigeria

The concentrations of the 16 priority polycyclic aromatic hydrocarbons (PAHs) in tea infusions made of water and local gin (alcohol) were investigated with a view to providing information on the profiles and health hazards associated with these two common Nigerian methods for tea consumption. The water-based tea infusion was prepared by submerging 4 g of tea in boiling water and allowing it to stand for 15 min, while the gin-based infusion was simply prepared by submerging 4 g of tea in gin at room temperature and allowing it to stand for 15 min. The concentrations of the ∑16 PAHs in the infusions were measured by using gas chromatography equipped with a flame ionization detector (GC-FID) after ultrasound-assisted extraction and clean-up. The concentrations of the ∑16 PAHs ranged from 24.9–623.4 μg kg^?1 with a mean value of 177 μg kg^?1 and 36.8–438.3 μg kg^?1 with a mean of 189 μg kg^?1 for water- and local gin-based infusions, respectively. The concentration of the ∑16 PAHs in the water- and local gin-based infusions of these teas were high when compared with levels reported in the literature for tea infusions. The local gin-based infusions had a higher mean level of the ∑16 PAHs than the water-based infusions. Four- and five-ring PAH compounds were dominant in these tea infusions.     

Antioxidant activity of tea extracts in lipids and correlation with polyphenol content

The present study examined the antioxidative activity of water and ethanol extracts of green and black tea leaves against the oxidation of heated sunflower oil and lard. Oxidation was conducted at 110 °C in the Rancimat test. Total polyphenols and catechin contents in tea extracts were measured. The research showed that the total polyphenol content in green and black tea leaves was 205.2 and 148.7 mg/g, respectively. In tea leaves extracts, it ranged between 245.9 mg/g and 837.7 mg/g and depended on the extraction solvent and the kind of tea used (p <0.001). The highest polyphenol content was observed in samples extracted with 95% ethanol, lower contents were found with the use of water. Results showed that the highest antioxidant activity, measured as an induction period, with 1000 ppm green tea ethanol extract, was comparable to á‐tocopherol activity in sunflower oil. In lard, the longest induction period was measured with 500 and 1000 ppm of green tea ethanol extract. Other tea extract concentrations were significantly less active. Statistical analysis of the tea extract antioxidant activity in lipids in the Rancimat test showed an essential influence of the catechin contents. Further statistical analysis also showed an influence of (?)‐epicatechin gallate (ECG), (?)‐epicatechin (EC), and (+)‐catechin (C) contents in the tea extracts on the antioxidant activity in lipids. It was stated that the antioxidant activity was higher in tea extracts containing high levels of ECG, EC, and C.     

Natural extracts as potential source of antioxidants to stabilize polyolefins

Several natural matrices were investigated as potential sources of antioxidants to be used as plastic additives. Extracts of four matrices obtained under the same experimental conditions were initially considered: green tea, black tea, Lippia citriodora and Hypericum androsaemum. Both, the antioxidant activity of the extracts and their content in flavanols and quercetin, were compared. The antioxidant activity was determined by DPPH analysis and the phenolic composition by high performance liquid chromatography (HPLC) using ultraviolet (UV) diode array and fluorescence (FL) detectors. Concentration of the flavanols reduced in the same way as their antioxidant activity starting with green tea, through black tea, Hypericum androsaemum, and Lippia citriodora. The performance of polypropylene samples stabilized with green tea extract, or its individual components catechin and epicatechin, was compared with samples stabilized with a mixture of the synthetic antioxidants Irganox 1076 and Irgafos 168. Each sample was extruded and consecutively reextruded up to four times. The melt flow index (MFI) and the oxidation induction time (OIT) of the samples were measured after each step. The obtained results showed the interest of this natural matrix as a potential source of antioxidants for plastics. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Antioxidant activity of various teas against free radicals and LDL oxidation

Tea is a widely consumed beverage throughout the world. We assessed the antioxidant activity of six teas, including the aqueous extracts of green tea and oolong tea (Camellia sinensis), tochu (Eucommia ulmoides), Gymnema sylvestre, Japanese mugwort (Artemisia princeps), and barley (Hordeum vulgare), against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and LDL oxidation, and examined the association of LDL oxidizability with the plasma catechin levels in 10 healthy volunteers with a single dose of 5 g green tea powder. In vitro, the inhibitory effects of DPPH radicals and LDL oxidation were found to be strongest in the extract of green tea and weakest in that of barley. After the ingestion of green tea powder, the lag time increased from basal 52.2±4.1 to 60.3±4.2 min at 1 h and 59.5±4.1 min at 2 h, and then returned to the baseline lag time (51.9±1.4 at 4 h and 52.1±4.7 min at 6 h). Regarding the plasma catechin levels, epigallocatechingallate and epicatechingallate significantly increased from basal 3.7±1.3 and 0.8±0.8 ng/mL to 65.7±11.6 and 54.6±12.6 ng/mL at 1 h, and 74.4±18.6 and 49.4±7.1 ng/mL at 2 h, respectively. Green tea therefore showed the strongest antioxidant activity among the six different teas, and the inhibitory effects of green tea on LDL oxidation depended on the plasma catechin levels.     

茶叶中稀土污染调查研究

探讨深圳市茶叶稀土污染状况,并尝试寻找此类污染的主要原因及解决办法。2009～2010年,笔者在市售产品中抽取绿茶,花茶,红茶,黑茶和乌龙茶共324批次,采用ICP-MS测定样本中稀土含量（以稀土氧化物计）,并按GB2762-2003食品中污染物限量标准评价。绿茶,花茶,红茶,黑茶和乌龙茶的合格率分别为65.8%、54.3%、33.3%、27.7%、14.5%。建议从规范施肥方式、定期监测土壤污染情况、探索治理方法等方面寻找解决办法,同时建立更科学合理的安全评价方法。建议相关部门对取消茶叶稀土限量要求慎重考虑。     

Antioxidative effect of ethanol tea extracts on oxidation of canola oil

There is an increasing interest in the biological effects of natural antioxidants present in teas on formation ofin vivo free radicals, carcinogenesis, and atherogenesis. Teas are traditionally classified into six major groups, namely, green, yellow, white, black, dark-green, and oolong teas. The present study examined the antioxidative activity of ethanol extracts from these six major groups of teas against oxidation of heated canola oil. The oxidation was conducted at 100°C by monitoring oxygen consumption and changes in linoleic and linolenic acids in canola oil. The ethanol extracts of green, yellow, and white teas strongly inhibited oxidation of canola oil compared to butylated hydroxytoluene, probably due to the presence of natural polyphenols. In contrast, oolong teas examined exhibited only moderate antioxidative activity because of the partial destruction of natural polyphenols by semifermentation. The ethanol extracts of black, dark-green, and ginseng teas studied showed little or no protection to canola oil from lipid oxidation, probably due to the complete destruction of natural polyphenols by fermentation during manufacturing processes.     

The effect of hue on the perception of blackness using munsell samples

Although black is an important color, the perception of black objects has not been systematically examined. The purpose of this work was to determine the influence of hue on the perception of preferred blackness. A set of 20 glossy low chroma Munsell sheets were purchased comprising a complete hue circle with a value and chroma of two and one, respectively (L* = 19.3–20.75, and C* = 3.66–6.58). The Munsell samples were divided into two interleaved groups: (5R, 5YR, 5Y, 5GY, 5G, 5BG, 5B, 5PB, 5P, and 5RP) and (10R, 10YR, 10Y, 10GY, 10G, 10BG, 10B, 10PB, 10P, and 10RP). Fifty color‐normal observers force‐ranked the two sets of 10 samples from “most like black” to “least like black.” Observers then assessed a set of six samples that represented the three samples from each set of 10 that the observer chose to be “most like black.” The 50 observers were found to have fairly good autoconcordance and concordance values. In repeat experiments observers agreed with themselves in 81% of the pairwise decisions, and they agreed with the grand mean rank 76% of the time. The blue–green samples (with Munsell hue notations 10G, 5BG, and 10BG) were most selected (and were considered blackest), followed by green, blue, and purple–blue. The samples selected the fewest times by any observer as being most black were the red samples. The grand mean rankings demonstrate that greenish to bluish blacks are perceived by the observers as “blacker” than yellowish and reddish blacks. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 423–428, 2013     

Changes of constituents and activity to apoptosis and cell cycle during fermentation of tea

Tea is believed to be beneficial for health, and the effects of the fermentation process on its contributions to apoptosis and cell cycle arrest of gastric cancer cells have not been completely investigated. In this study, the chemical components in green tea, black tea and pu-erh tea aqueous extracts were analyzed and compared. The polysaccharide and caffeine levels were substantially higher in the fermented black tea and pu-erh tea, while the polyphenol level was higher in the unfermented green tea. Hence, a treatment of tea aqueous extract and the components, which are emerging as promising anticancer agents, were pursued to determine whether this treatment could lead to enhance apoptosis and cell cycle arrest. In the human gastric cancer cell line SGC-7901, the cell viability and flow cytometry analysis for apoptotic cells indicated effects in a dose-dependent inhibition manner for the three tea treatment groups. The apoptosis rates were found to be elevated after 48 h of treatment with 31.2, 125, and 500 μg/mL of green tea extract, the higher catechins content may be involved in the mechanism. Cell cycle was arrested in S phase in the fermented black tea and pu-erh tea, and the populations were significantly decreased in G2/M phases, possibly due to the oxidation of tea polyphenols, which causes an increase of theabrownins. CCC-HEL-1 normal cells were not sensitive to tea extract. These findings suggest that the fermentation process causes changes of the compounds which might be involved in the changes of cell proliferation inhibition, apoptosis induction and cell cycle arrest.     

铜仁地区四种茶叶微量元素含量的研究

采用原子吸收分光光度法对铜仁地区的印江梵净山绿茶、沿河谯家茗茶、石阡苔茶、松桃梵净山生态清明茶中Ca、Mn、Fe、Zn、Cu五种微量元素含量进行了测定。结果表明四种茶叶中都含有丰富的以上五种微量元素,含量大小排序都为Ca〉Mn〉Fe〉Zn〉Cu,但不同种类的茶叶中所含微量元素的量有一定的差异。     

红茶、绿茶提取物联合应用的护肤功效研究

以红茶提取物、绿茶提取物为考察对象,考察了红茶提取物和绿茶提取物的单独及联合应用的防晒、保湿、抗氧化、美白、抗衰老等功能,测试了二者在以上功能联合应用是否具有协同增效作用。结果表明,红茶、绿茶提取物在保湿、抗氧化、美白、抗衰老等功能上,联合应用比二者单独应用效果更强,其中2 g/L红、绿茶提取物混合物在抑制酪氨酸酶、弹性蛋白酶方面的联合指数CI仅为0.29和0.054,协同增效效果显著。     

HPLC法测定茶饮料中的咖啡因含量

建立利用高效液相色谱(HPLC)测定绿茶和红茶中的咖啡因的检测方法。流动相为甲醇∶水=20∶80(v/v),检测波长为273 nm,流速为1 mL/min。结果表明,在咖啡因浓度为5～100μg/mL范围内,线性关系良好。两种饮料中测得的咖啡因的相对标准偏差(RSD)均小于1%,加样回收率在100%～105%之间。该方法简便、快捷、准确、重现性好,可用于饮料中咖啡因的测定。     

红茶氨基酸、茶多酚、咖啡因的低强度多频超声浸取特性

用DPS系统建立了包括温度、茶水质量比、时间、超声强度和超声频率(28 kHz和40 kHz)等因素的均匀设计实验方案,探索水为溶剂,低强度(低于0.6 W.cm-2)单频、双频复合和双频交变超声浸取红茶氨基酸、茶多酚、咖啡因的浸取特性;以质量浓度、浸取率为指标,用偏最小二乘法处理实验数据,以标准化回归系数评价各因素的影响程度。结果表明,与单频超声场相比,双频超声场降低了超声作用强度54%~67%,提高了温度、茶水质量比等其他单因素作用强度34%~143%;双频交变超声场的这种作用最强。双频交变超声场降低了除温度-茶水质量比之外所有双因素的作用强度12%~75%;而双频复合超声场提高了与超声强度有关的双因素作用强度19%~1 350%,降低了与超声场无关的双因素作用强度47%~75%。90℃0.3 W.cm-23种超声场浸取5 m in,红茶3种成分浸取特性有明显差异,双频复合超声浸取氨基酸的质量浓度和浸取率最高(分别为369.4mg.L-1和55.0%);双频交变浸取茶多酚、咖啡因最好,质量浓度分别为11.4、2 749.52 mg.L-1,浸取率为39.8%、49.8%,单频超声浸取效果最差。     

The green tea, a good choice for cardiovascular disease prevention?

Tea (Camellia sinensis) has been used for centuries as a medical drink. Around two-thirds of the world's population drink tea. It is originated from southern China and entensive cultivated in Asia and in central African countries. Tea can be grouped into three main types, black, oolong, and green tea. Green tea is not fermented and is a major beverage consumed in Asian countries. Green tea is produced from freshly harvest leaves of the tea plant and they contain water, proteins, carbohydrates, minerals, vitamins and polyphenols of the flavonoid type. The major flavonoids in green tea are catechins which constitute about one third of its total dry weight. The major catechin present is epigallocatechin gallate (>50%). New data have increased the interest in green tea or its catechins and its role in treatment of cardiovascular disease (CHD) risk factors. The aim of the present paper is to review some studies that have found a relationship between green tea and CHD risk factors. From some of them it can be summarized that of green tea and its catechins consumptions (i) decrease body weight by interfering within the sympathoadrenal system and fatty acid synthesis, (ii) decrease cholesterol absorption and plasma levels, (iii) have strong free radical-scavenging activity inhibiting LDL oxidation, (iv) reduce the adhesion molecule expression, (v) have antitrombotic activities by inhibiting platelet aggregation and (vi) decrease systolic and diastolic blood pressures. The positive effects found suggest that a daily intake of 7 cups of green tea (3.5 g catechins) is a good choose for CHD prevention; however, it is still necessary more studies to check the action of the green tea and its catechins in humans in order to recommended its use in the general population or only in target subjects.     

中草药凉茶中苯甲酸、山梨酸、对羟基苯甲酸酯类同时测定的方法研究

目的：建立一种应用高效液相色谱法同时测定中草药凉茶中五种防腐剂含量的新监测方法。方法：样品经ODS-C18层析柱固相萃取净化、分离,20 mmoL乙酸铵与乙腈为流动相,进行梯度洗脱。结果：可将五种防腐剂完全分离,在8～200μg/mL线性范围内（r均大于0.9999）,回收率在88.9%～110.8%之间,RSD在1.18%～6.82%之间（n=6）。最低检出限分别为：2.66×10-4、3.36×10-4、7.36×10-4、3.88×10-4、3.12×10-4 mg/kg;最低定量限分别为：1.33×10-3、1.68×10-3、3.68×10-3、1.94×10-3、1.56×10-3 mg/kg。结论：通过对样品前处理条件的选择和优化,能较好地除去大部分杂质的干扰。本方法能满足中草药凉茶中苯甲酸、山梨酸、对羟基苯甲酸甲酯、对羟基苯甲酸乙酯、对羟基苯甲酸丙酯同时测定的要求,具有较好的推广意义;亦可作为监测儿童中药合剂和凉茶饮料防腐剂含量限制的参考。