儿茶素对超氧阴离子自由基的清除及其自氧化作用研究

采用NBT光还原法证实了儿茶素具有清除O—·2 的作用 ,确定了儿茶素自氧化作用的最佳测定波长 ,并探讨了儿茶素溶液浓度和 pH对其自氧化作用的影响。     

天然抗氧化剂的抗氧化与促氧化作用

近年来研究表明,天然抗氧化剂因其结构、剂量以及存在环境不同可能会发生对人体不利的促氧化作用。本文综述近年来天然抗氧化剂的抗氧化与促氧化用的研究进展,为正确使用天然抗氧化剂和相关产品的开发提供参考。     

茶多酚对β-淀粉样蛋白25-35肽段诱导红细胞溶血的影响

β-淀粉样蛋白在神经组织中聚集被认为与Alzheimer's疾病密切相关,一些天然多酚化合物证实可抑制蛋白质的淀粉样聚集.本文采用β-淀粉样蛋白25-35肽段诱导人红细胞溶血为实验模型,检测几种结构相似的茶多酚化合物对β-淀粉样蛋白诱导细胞损害的影响.结果表明,表没食子儿茶素没食子酸酯(ECCG)可以抑制β-淀粉样肽导致的溶血,而表儿茶素没食子酸酯(ECG)则可以促进溶血.两者在结构上仅在B环上相差一个羟基.这种对溶血作用的差异可能来源于对金属离子螯合能力的差异.一种铁离子的强力螯合剂甲磺酸去铁胺可抑制ECG的促溶血作用,说明体系中的微量铁离子可能是ECG促多肽溶血过程中的一个重要因素,同时也表明β-淀粉样蛋白诱导细胞损害与金属离子介导的氧化还原作用有关.     

儿茶素经PI3K-Akt-eNOS信号通路对冠心病大鼠心肌损伤及抗炎作用分析

摘要 目的：探讨儿茶素经PI3K-Akt-eNOS信号通路对冠心病大鼠心肌损伤及抗炎作用分析。方法：健康成年SPF级SD雄性大鼠,经腹腔注射垂体后叶素构建冠心病模型。采用Western blot法检测大鼠PI3K-Akt-eNOS信号通路相关蛋白的表达情况。采用ELISA法检测大鼠炎症因子和氧化应激指标的表达。观察并记录大鼠心肌损伤情况。结果：与空白组相比,模型组、儿茶素小剂量组、儿茶素中剂量组、儿茶素大剂量组的心肌缺血和心肌梗死面积均明显更高（P＜0.05）;儿茶素大剂量组心肌缺血和心肌梗死面积明显小于模型组、儿茶素小剂量组、儿茶素中剂量组（P＜0.05）;与空白组相比,模型组、儿茶素小剂量组、儿茶素中剂量组、儿茶素大剂量组的PI3K、p-Akt /Akt、p-eNOS /eNOS均明显更高（P＜0.05）;儿茶素大剂量组PI3K、p-Akt /Akt、p-eNOS /eNOS明显高于模型组、儿茶素小剂量组、儿茶素中剂量组（P＜0.05）;与空白组相比,模型组、儿茶素小剂量组、儿茶素中剂量组、儿茶素大剂量组的TNF-α、IL-1β、IL-18均明显更高（P＜0.05）;儿茶素大剂量组TNF-α、IL-1β、IL-18明显低于模型组、儿茶素小剂量组、儿茶素中剂量组（P＜0.05）;与空白组相比,模型组、儿茶素小剂量组、儿茶素中剂量组、儿茶素大剂量组的ROS、GSH-Px、MDA均明显更高（P＜0.05）;儿茶素大剂量组TNF-α、IL-1β、IL-18明显低于模型组、儿茶素小剂量组、儿茶素中剂量组（P＜0.05）。结论：儿茶素可通过PI3K-Akt-eNOS信号通路靶向改善冠心病大鼠心肌炎症和氧化应激状况,进而发挥心肌保护作用。     

苦茶Camellia assamica var.kucha茶多酚的HPLC-DAD/MS分析

苦茶是一种特殊的茶组植物,它以1,3,7,9-四甲基尿酸为主要的嘌呤生物碱。本文采用高效液相色谱-二极管阵列检测/质谱联用(HPLC-DAD/MS)的方法对苦茶水提液中的茶多酚和嘌呤生物碱进行了定性分析,检测到3种嘌呤生物碱、7种儿茶素类化合物和2种非儿茶素类茶多酚(没食子酰奎宁酸酯和咖啡酰奎宁酸酯)。同时与传统绿茶在儿茶素类化合物的组成和含量上进行了比较,结果显示,苦茶中总儿茶素含量(13.82%)远高于传统绿茶(7.37%),但各儿茶素类化合物的相对组成比在两种茶中极其相近,均以酯型儿茶素为主。     

广西不同产地金樱根及炮制品中没食子酸和儿茶素的含量差异分析

为了建立金樱根中没食子酸和儿茶素含量的测定方法,分析广西不同产地金樱根及炮制品中没食子酸和儿茶素含量的变化,该文以没食子酸和儿茶素的含量作为指标成分,采用HPLC法对广西产金樱根生品、炒炙品、酒炙品、盐炙品及醋炙品进行测定,并采用SPSS 23.0软件进行方差分析和聚类分析。结果表明：广西不同产地金樱根及炮制品中没食子酸和儿茶素含量均存在差异,所有样品中儿茶素的含量均比没食子酸高,南部地区(除贵港桂平外)的没食子酸和儿茶素含量整体上比北部地区高,在炮制品中醋炙后没食子酸和儿茶素含量最高。该研究表明HPLC测定方法简单可行,金樱根中没食子酸和儿茶素含量的变化差异主要表现为产地地域及炮制方法的不同,可为今后金樱根资源的合理利用、质量标准制定以及临床用药的研究提供一定科学依据。     

抗坏血酸与铁离子反应的ESR及UV—VIS研究

利用ＥＳＲ－自旋捕捉技术和ＵＶ－ＶＩＳ电子光谱研究了抗坏血酸与铁离子间的反应,证实了１ｍｏｌＡａ可还原４ｍｏｌＦｅ（Ⅲ）,但检测不到自由基信号。由此提出了Ａａ与铁离子反应的可能机理,并探讨了抗坏血酸化促氧化作用机制。     

抗坏血酸与铁离子反应的ESR及UV-VIS研究

利用ＥＳＲ－自旋捕捉技术和ＵＶ－ＶＩＳ电子光谱研究了抗坏血酸（Ａａ）与铁离子间的反应,证实１ｍｏｌＡａ可还原４ｍｏｌＦｅ（Ⅲ）,但检测不到自由基信号。由此提出了Ａａ与铁离子反应的可能机理,并探讨了抗坏血酸的抗氧化与促氧化作用机制。     

一测多评法测定茶多酚中6种儿茶素类含量

采用HPLC法,以表没食子基儿茶素没食子酸酯(EGCG)为对照品,外标法测定其在茶多酚提取物中的量,并分别测定EGCG与表没食子儿茶素(EGC)、儿茶素(C)、表儿茶素(EC)、没食子基儿茶素没食子酸酯(GCG)和没食子酰表儿茶素(ECG)的相对校正因子,用获得的相对校正因子计算后5种成分的量,实现一测多评;同时,用外标法测茶多酚提取物中EGC、C、EC、GCG和ECG的量。向量夹角余弦法分析,表明外标法的测定值与采用相对校正因子的计算值之间无显著性差异,说明一测多评法可以应用于茶多酚提取物及其制剂的多指标质量评价。     

金荞麦果实中有效成分的分析

采用HPLC法对金荞麦果实中的有效成分进行了分析,结果表明:金荞麦果实中含有芦丁、槲皮素和表儿茶素等有效成分,其中主要以芦丁为主,槲皮素、表儿茶素等含量甚微.金荞麦果实中的有效成分主要集中在种子部分,果皮中则不合或含量甚微.     

Fabrication of Surface-Active Antioxidant Food Biopolymers: Conjugation of Catechin Polymers to Egg White Proteins

The oxidation of unsaturated lipids commonly occurs at oil-water interfaces in heterogeneous foods (such as emulsions), and so there is a need for surface-active antioxidants to inhibit lipid oxidation. In this study, catechin was oxidatively polymerized by horseradish peroxidase to obtain catechin polymers (CTP). An amphiphilic antioxidant was then produced by conjugating CTP with egg white proteins (EWP) using a hydrogen peroxide-ascorbic acid pair as a radical initiator system. The covalent attachment of CTP to EWP was confirmed by electrophoresis, liquid chromatography-mass spectrometry, and fluorescence analyses. The antioxidant capacity of CTP-EWP conjugates was evaluated using several in vitro models. The conjugates exhibited strong scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (79% at 1 mg/mL), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (97% at 0.5 mg/mL), and had a high ferric reducing power. Furthermore, CTP-EWP conjugates exhibited an inhibitive effect on lipid peroxidation in linoleic acid oil-in-water emulsions, indicating that the conjugates may have potential applications in food, pharmaceutical and cosmetic industries.     

Catechin content and consumption ratio of the collared lemming

Chemical- plant defences as mechanisms affecting herbivore populations have been debated during the past decade. Several authors have questioned the hypothesis, but the present study shows that collared lemmings ( Dicrostonyx groenlandicus) in northeast Greenland prefer food plants with a lower catechin content. Dicrostonyx species are known to have specialised on shrubs, especially Dryas spp. and Salix spp., rather than graminoids like other related microtines. Bioassays were conducted using food material from Dryas spp., Salix arctica, Vaccinium uliginosum, Kobresia myosuroides and Poa glauca. Enclosures with the first three species mentioned were further treated by clipping to simulate herbivory in order to induce the production of the plant defence compound catechin. Treatment increased the catechin content in Dryas spp., S. arctica (females only) and V. uliginosum significantly compared with the catechin concentration in untreated plants. These elevated catechin concentrations had a significantly negative effect on the consumption rate of Dryas spp. and female S. arctica by collared lemmings.     

儿茶素分光光度法与微量法抗氧化活性研究

为比较微量法和分光光度法的差异,以Trolox为参比物,PG、BHA和BHT为阳性对照品,比较其IC50和TEAC;以儿茶素的抗氧化活性为研究对象,对2种方法的相关性做Paired—samplet t est。发现2种方法所得到的TEAC基本一致,4个标准品和儿茶素的抗氧化活性顺序一致,即：PG〉儿茶素〉BHA〉Trolox〉BHT;2种方法的相关系数r=0．998,显著性P=0．501。研究结果表明,分光光度法操作繁琐费时,用样量大;微量法操作简单快速,用样量小,准确性好,适合对微量天然产物抗氧化活性的评价。     

Catechin inhibition of mutagenesis and alteration of DNA binding of 2-acetyl-aminofluorene in rat hepatocytes

Bioflavonoids are naturally occurring plant products that have demonstrated inhibitory effects on chemically induced carcinogenesis or mutagenesis. The chemoprotective effects are either direct scavenging of reactive molecules or indirect effects, such as enzyme activity alteration. Exposure of cultures of isolated rat hepatocytes to catechin (0.01-1.0 mM), a plant phenolic flavonoid, and subsequent addition of 2-acetylaminofluorene (AAF) resulted in an enhanced binding of AAF metabolites to hepatocellular DNA. Incubations of hepatocytes with catechin and S. typhimurium demonstrated no mutagenicity of catechin. At 1.0 and 5.0 mM concentrations of catechin with AAF and 30-min incubation with hepatocytes prior to plating there was inhibition of AAF-induced mutagenicity. However, at 0.5 mM of catechin there was a significant enhancement in mutagenicity. The increase in DNA binding of AAF in the cultures of hepatocytes is due to the alteration of metabolism by exposure to catechin. Catechin increases both N-hydroxylation and deacetylation pathways in the hepatocytes producing increases in N-hydroxy-AAF and aminofluorene. Both of these metabolites are important in AAF intermediates binding with DNA. The short-term incubation of catechin, AAF, hepatocytes, and S. typhimurium in the mutagenesis assay is not sufficient for induction of metabolic pathways. However, previously reported inhibition of detoxification pathways and/or scavenging of the proximate carcinogen can occur to alter mutagenesis in a dose-dependent manner.     

Catechin and Catechin Fractions as Biochemical Markers to Study the Diversity of Indian Tea (Camellia sinensis (L.) O. Kuntze) Germplasm

The heterogeneous Indian tea germplasm includes ‘China’, ‘Assam’, ‘Cambod’, and their hybrids which were evaluated using biochemical markers viz., total catechin and their fractions, for varietal identification and characterization. Principal component analysis (PCA) of biochemical characters showed that the total catechin and trihydroxylated catechin has higher eigenvalues. The first two principal components (PCs) could differentiate more than 90% of the clones studied. This grouping based on first two principal component matrices differentiated ‘China’, and their hybrids with ‘Assam’ and ‘Cambod’ variety. Morphologically indistinct large‐leaved ‘Cambod’ variety and ‘Assam’ varieties could not be differentiated using biochemical markers, since both varietal types taxonomically belong to a single species. Clones of ‘China’ type showed low total catechin content and catechin ratio which are distinctly grouped. The ‘China–Assam’ and ‘China–Cambod’ hybrids formed intermediate groups between ‘China’ PC group and ‘Cambod’/‘Assam’ PC groups, providing evidence for genetic control of catechin ratio variation. Tea clones which are differentially positioned in the PC group could be explained based on the genetic contribution by other varietal type as parents. This biochemical characterization will be a useful tool in the development of quality‐tea clones with different proportion of total catechin and their fractions.     

Catechin safely improved higher levels of fatness, blood pressure, and cholesterol in children

Objective: The purpose of this study was to evaluate the effects of a catechin‐rich beverage on body fat and cardiovascular disease risk factors in obese children and to verify the safety of its use. Methods and Procedures: Obese or near‐obese Japanese children were recruited for this study. A double‐blind, randomized, controlled study was performed with a 4‐week lead‐in, a 24‐week beverage ingestion period and a 12‐week follow‐up. Subjects ingested green tea containing 576 mg catechins (catechin group) or 75 mg catechins (control group) once per day for 24 weeks. Randomization was stratified by gender, age, and BMI. Subjects were instructed to maintain their usual lifestyles during the study period. Results: Data were analyzed using samples from 40 subjects (catechin group; n = 21, control group; n = 19). There were no significant differences in major outcome variables, such as body fat mass, between the catechin and the control groups. When, however, the analysis was stratified using the median of the week‐0 values, the decrease at week 24 in waist circumference, systolic blood pressure, and low‐density lipoprotein cholesterol in the catechin group was significantly greater than that in the control group for the above‐median category. Ingestion of the catechin‐rich beverage was not associated with any adverse effects. Discussion: These findings suggest that ingestion of a catechin‐rich beverage ameliorates serious obesity and cardiovascular disease risk factors without raising any safety concerns in Japanese children.     

Catechin conjugated with fatty acid inhibits DNA polymerase and angiogenesis

Catechins in green tea have anticancer and antiangiogenesis activities, with epigallocatechin-3-gallate (EGCG) being the most potent antiangiogenic tea catechin. This study examined whether chemical modification of catechin enhanced anticancer and antiangiogenic effects. Catechin, conjugated with fatty acid (acyl-catechin), strongly inhibited DNA polymerase, HL-60 cancer cell growth, and angiogenesis. Catechin conjugated with stearic acid [(2R,3S)-3',4',5,7-tetrahydroxyflavan-3-yl octadecanoate; catechin-C18] was the strongest inhibitor in DNA polymerase alpha and beta and angiogenesis assays. Catechin-C18 also suppressed human endothelial cell (HUVEC) tube formation on the reconstituted basement membrane, suggesting that it affected not only DNA polymerases but also signal transduction pathways in HUVECs. These data indicate that acyl-catechins target both DNA polymerases and angiogenesis as anticancer agents. These results suggest that acylation of catechin is an effective chemical modification to improve the anticancer activity of catechin.     

儿茶素诱导的拟南芥根细胞膜脂变化

儿茶素是一种可以短时间内杀死植物细胞的植物毒素,由于具有强的植物毒性,儿茶素是开发除草剂的理想化合物,它可以诱导植物根系统的死亡。为了研究植物根细胞膜脂对化学胁迫的响应规律,我们运用高通量的脂类组学方法检测了拟南芥根中膜脂分子的组成,比较了儿茶素处理下拟南芥野生型（WS）及磷脂酶Dδ缺失突变体（PLDδ KO）根中膜脂分子的组成情况、膜脂含量、双键指数及碳链长度值。结果发现,儿茶素处理拟南芥根90min后,二半乳糖基二酰甘油（DGDG）、单半乳糖基二酰甘油（MGDG）、磷脂酰甘油（PG）、磷脂酰胆碱（PC）及磷脂酰肌醇（PI）的总含量在WS与PLDδ KO植株根中都显著下降,磷脂酰乙醇胺（PE）和磷脂酰丝氨酸（PS）在WS中下降,在PLDδ KO中上升。儿茶素处理导致PLDδ KO植株的PC/PE比值显著下降,WS植株PS碳链长度显著增加。上述结果说明儿茶素处理后,磷脂酶Dδ缺失突变体膜不稳定性增加,PLDδ KO植株对儿茶素胁迫更加敏感。     

儿茶素诱导的拟南芥根细胞膜脂变化

儿茶素是一种可以短时间内杀死植物细胞的植物毒素,由于具有强的植物毒性,儿茶素是开发除草剂的理想化合物,它可以诱导植物根系统的死亡.为了研究植物根细胞膜脂对化学胁迫的响应规律,我们运用高通量的脂类组学方法检测了拟南芥根中膜脂分子的组成,比较了儿茶素处理下拟南芥野生型(WS)及磷脂酶Dδ缺失突变体( PLDδ-KO)根中膜脂分子的组成情况、膜脂含量、双键指数及碳链长度值.结果发现,儿茶素处理拟南芥根90 min后,二半乳糖基二酰甘油(DGDG)、单半乳糖基二酰甘油(MGDG)、磷脂酰甘油(PG)、磷脂酰胆碱(PC)及磷脂酰肌醇(PI)的总含量在WS与PLDδ-KO植株根中都显著下降,磷脂酰乙醇胺(PE)和磷脂酰丝氨酸(PS)在WS中下降,在PLDδ-KO中上升.儿茶素处理导致PLDδ-KO植株的PC/PE比值显著下降,WS植株PS碳链长度显著增加.上述结果说明儿茶素处理后,磷脂酶Dδ缺失突变体膜不稳定性增加,PLDδ-KO植株对儿茶素胁迫更加敏感.     

Antioxidant Activity and α-Glucosidase Inhibitory Activities of the Polycondensate of Catechin with Glyoxylic Acid

In order to investigate polymeric flavonoids, the polycondensate of catechin with glyoxylic acid (PCG) was prepared and its chemically antioxidant, cellular antioxidant (CAA) and α-glucosidase inhibitory activities were evaluated. The DPPH and ABTS radical scavenging activities and antiproliferative effect of PCG were lower than those of catechin, while PCG had higher CAA activity than catechin. In addition, PCG had very high α-glucosidase inhibitory activities (IC₅₀ value, 2.59 μg/mL) in comparison to catechin (IC₅₀ value, 239.27 μg/mL). Inhibition kinetics suggested that both PCG and catechin demonstrated a mixture of noncompetitive and anticompetitive inhibition. The enhanced CAA and α-glucosidase inhibitor activities of PCG could be due to catechin polymerization enhancing the binding capacity to the cellular membrane and enzymes.