Attenuation of senescence-induced oxidative exacerbations in aged rat brain by (−)-epigallocatechin-3-gallate

Aging is a complex biological phenomenon which involves free radicals and oxidative stress. Brain is more susceptible and vulnerable to oxidative damage due to its high-polyunsaturated fatty acid content and high rate of aerobic metabolism. Since the antioxidant defense system is diminished during aging, antioxidant supplementation might be a protective strategy against age-associated oxidative damage. The present study evaluates the antioxidant potential of (-)-epigallocatechin-3-gallate (EGCG), a major polyphenol present in green tea against age-associated oxidative damage in rat brain. Male albino rats of Wistar strain were used in the study. Group I (young) and Group II (aged) rats received saline alone orally for 30 days. Group III (young) and Group IV (aged) rats received EGCG (2mg/kg body weight/day) orally for 30 days. Antioxidant status and oxidative damage were assessed. EGCG brought about an augmentation in the activities of enzymic antioxidants like superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase and improved the non-enzymic antioxidants like tocopherol, ascorbic acid and glutathione. EGCG ameliorated the malondialdehyde and protein carbonyl levels. Thus, EGCG has emerged out as a good antioxidant neutraceutical and a neuroprotective agent in alleviating the age-associated oxidative damage in aged rat brain.     

儿茶素拮抗过氧化氢诱导的大鼠内皮祖细胞凋亡

目的：观察过氧化氢（H2O2）对大鼠骨髓来源内皮祖细胞（EPCs）增殖及凋亡的影响及儿茶素对H2O2诱导细胞凋亡的的拮抗作用。方法：免疫荧光法检测EPCs表面标志CD34,CD133和血管内皮生长因子受体-2（VEGFR-2）的表达;将第2代EPCs分为空白对照组、H2O2组和儿茶素-H2O2组,干预后常规提取DNA琼脂糖电泳观察细胞凋亡梯带的形成;MTT法检测细胞增殖率的变化。结果：①骨髓单个核细胞培养10 d后均表达CD34,VEGFR-2和CD133抗原;②干预1 d后,3组细胞均未出现明显的DNA凋亡梯带;2 d后,H2O2组出现明显细胞凋亡DNA梯带;3 d后,H2O2组和儿茶素- H2O2组均出现明显的细胞凋亡DNA梯带,H2O2组凋亡DNA梯带数量、灰度强于儿茶素-H2O2干预组;③与对照组相比,H2O2组、H2O2-儿茶素组EPCs增殖活性明显下降（P<0.01）;在H2O2组和H2O2-儿茶素组组内EPCs增殖活性第1天和第3天细胞增殖活性明显高于第2天细胞增殖活性（均P<0.05）;H2O2组-儿茶素组细胞增殖活性在3个不同时间点显著高于同一时间点H2O2组细胞增殖活性。结论：H2O2可以降低EPCs增殖活性,诱导其凋亡;儿茶素可以增强EPCs对H2O2 的抵抗力,减少细胞凋亡。［中国当代儿科杂志,2009,11（1）：61-64］     

超高效液相色谱-串联质谱法同时测定茶叶中儿茶素和茶黄素

目的 建立绿茶、红茶和乌龙茶中8种儿茶素（没食子儿茶素、儿茶素没食子酸酯、儿茶素、表儿茶素、表没食子儿茶素没食子酸酯、没食子儿茶素没食子酸酯、表儿茶素没食子酸酯、儿茶素没食子酸酯）和4种茶黄素（茶黄素、茶黄素 - 3 - 没食子酸酯、茶黄素 - 3,3’ - 没食子酸酯、茶黄素 - 3’ - 没食子酸酯）的超高效液相色谱 - 串联质谱（UPLC - MS/MS）测定方法。方法 样品采用70%甲醇水在70℃水浴提取过滤后,经Eclipse Plus C18色谱柱（100 mm×2.1 mm,1.8 μm）分离,以0.1%甲酸 - 0.1%甲酸乙腈溶液为流动相,梯度洗脱,柱温40℃,流速为0.3 ml/min,采用电喷雾离子源正离子模式,多反应监测（MRM）模式检测。结果 8种儿茶素和4种茶黄素在优化的色谱质谱条件下,分离度良好,且分别在浓度0.60～16.7 μg/ml和1.0～16.7 μg/ml范围内线性关系良好。对3种不同茶叶2个加标水平下的平均加标回收率范围为 71.5%～118.3%,相对标准偏差（RSD）为2.0%～5.9%,检出限范围为0.10～16.10 ng/g。结论 该法操作简便、灵敏度高,适用于茶叶中8种儿茶素和4种茶黄素的日常测定。     

儿茶素类抗乙型肝炎病毒的效果观察

目的观察儿茶素类抗乙肝病毒和保肝降酶作用.方法用1日龄北京雏鸭制备鸭乙型肝炎病毒(DHBV)模型,设儿茶素类给药组(60、120和240 mg/kg)、阳性药物对照组(Are-AMP)、模型组和阴性对照组.取血清用斑点杂交法(dig标记探针)测DHBV*DNA,用单抗夹心ELISA法测定DHBsAg;检测丙氨酸转氨酶(ALT)、天冬氨酸转氨酶(AST)活性观察肝功能变化,并作肝组织病理切片观察形态学改变.结果儿茶素类各给药组鸭血清DHBV*DNA和DHBsAg含量均有降低,与给药前和模型组相比差异有显著性;给药25 d及停药后14 d,鸭血清ALT与AST活性均降低;给药后的肝组织病理变化有明显改善. 结论儿茶素类有抗乙肝病毒、降低转氨酶活性、减轻肝脏病理损伤作用.     

局部应用没食子儿茶素-3-没食子酸抑制移植静脉内膜增生

目的探讨局部应用没食子儿茶素-3-没食子酸对移植静脉内膜增生的抑制作用及其发生机制。方法应用异硫氰酸荧光素荧光标记技术和高效液相色谱法体外定性和定量测定血管对没食子儿茶素-3-没食子酸的吸收情况。日本大耳白兔20只,随机分为没食子儿茶素-3-没食子酸处理组和对照组(n=10)。建立兔颈外静脉与颈内动脉间置移植模型,移植前没食子儿茶素-3-没食子酸处理组血管在0.1 g/L没食子儿茶素-3-没食子酸中常温保存1 h,而对照组血管保存在生理盐水中。组织学方法测定移植三周后移植静脉血管新生内膜厚度、内膜中膜厚度比,原位DNA断裂位点的3′-羟基末端标记、Ki67免疫组织化学染色测定新生内膜阳性细胞百分比。结果0.1g/L没食子儿茶素-3-没食子酸中保存1 h2、h4、h,静脉血管的吸收量分别为2.9±0.9 mg/g、5.8±2.1 mg/g和8.0±2.3 mg/g,分布在血管壁全层。两组移植血管术后3周的通畅率均为90%(9/10)。移植术后3周没食子儿茶素-3-没食子酸处理组较对照组内膜厚度(41.1±13.6μm比89.9±48.3μm,P<0.01)及内膜/中膜厚度比(0.40±0.18比0.77±0.31,P<0.05)均显著降低,新生内膜Ki67阳性染色平滑肌细胞百分比也显著下降(22.4%±8.6%比8.8%±2.4%,P<0.05),而凋亡细胞百分比(0.40%±0.55%比0.60%±0.89%,P>0.05)无明显变化。结论局部应用没食子儿茶素-3-没食子酸能够抑制移植静脉内膜增生,可能与其抑制内膜平滑肌细胞增殖有关。     

薄层色谱法鉴别儿茶中儿茶素和表儿茶素

采用薄层色谱法,对儿茶中儿茶素及表儿茶素进行了鉴别。     

Antioxidant evaluation of O-methylated metabolites of catechin, epicatechin and quercetin

Catechins and quercetin are major polyphenols in many plant foods that have been related to health promotion. In the human organism they are largely metabolized to different metabolites, which are further found in plasma and should contribute to the biological effects associated to the intake of the parent compounds. An important step in quercetin and catechins metabolism is the O-methylation of the catechol group, which can be expected to have an effect on their antioxidant and scavenging properties. In the present work, the 3′- and 4′-methylethers of catechin and epicatechin have been prepared and characterised and their antioxidant activity evaluated and compared to that of the corresponding quercetin derivatives. The antioxidant activity was assessed using the ferric reducing power (FRAP) assay and two methods based on the ability to scavenge the ABTS⁺ radical cation at different pH values. In these assays the three flavonoids behave as better radical scavengers and reducing compounds than usually recognised antioxidants like α-tocopherol. The O-methylation of the hydroxyls of the catechol B-ring resulted in a decrease of the antioxidant activity with regard to the parent compounds. However, the methylated metabolites still retain significant radical scavenging activity at pH 7.4, suggesting that they could act as potential antioxidants in physiological conditions. Quercetin and its methylated metabolites showed, in general, greater activity than (epi)catechin and their O-methyl derivatives, although a relatively high antioxidant activity was found in the case of 3′-O-methyl catechin at pH 7.4, comparable to those of its parent compound and the quercetin metabolites. It was confirmed that the antioxidant activity of the flavonoids assayed was strongly dependent on the pH of the medium, showing higher activity at greater pH values. The results obtained are expected to contribute to the understanding of the mechanisms involved in the biological effects attributed to the intake of flavonoid-rich diets.     

A population-based, case–control study of green tea consumption and leukemia risk in southwestern Taiwan

Objective  This study investigated the association between green tea consumption and leukemia. Methods  A total of 252 cases (90.3% response) and 637 controls (53.4% response) were enrolled. Controls were matched for cases on age and gender. Information was collected on participants’ living habits, including tea consumption. Green tea was used as a standard to estimate the total amount of individual catechin consumption. We stratified individual consumption of catechins into four levels. Conditional logistic regression models were fit to subjects aged 0–15 and 16–29 years to evaluate separate associations between leukemia and catechin consumption. Results  A significant inverse association between green tea consumption and leukemia risk was found in individuals aged 16–29 years, whereas no significant association was found in the younger age groups. For the older group with higher amounts of tea consumption (>550 units of catechins), the adjusted odds ratio (OR) compared with the group without tea consumption was 0.47 [95% confidence interval (CI) = 0.23–0.97]. After we adjusted for smoking status and medical irradiation exposure, the overall OR for all participants was 0.49 (95% CI = 0.27–0.91), indicating an inverse relation between large amounts of catechins and leukemia. Conclusion  Drinking sufficient amounts of tea, especially green tea, which contains more catechins than oolong tea and black tea, may reduce the risk of leukemia.     

The effect of green tea on prostate specific antigen (PSA): A systematic review and meta-analysis of randomized controlled trials

BackgroundProstate cancer is a major malignancy, affecting men, worldwide. The protective effect of green tea consumption on prostate cancer has been reported in several studies; however, the findings are equivocal.ObjectiveThe aim of this study was to evaluate the effects of green tea on PSA level, by conducting a systematic review and meta-analysis of randomized controlled trials.MethodsWe searched online databases, including PubMed, Scopus, and Web of Science, up to 11 Aug 2020, to obtain relevant publications. The publication search was not limited by language or date.ResultsA total of 2488 records were identified in the systematic search; from these, seven were included in the meta-analysis. The overall analysis showed no significant changes in PSA levels in subjects treated with green tea, (WMD: ‒0.60 ng/mL; 95 % CI: ‒1.32, 0.12 ng/mL; P = 0.104, I² = 93.80 %, P heterogeneity<0.001). Subgroup analysis based on geographical location showed that green tea significantly reduced PSA level in the USA population (WMD: ‒1.02 pg/mL, 95 % CI: ‒1.30, ‒0.73, P < 0.001) compared to non-USA populations (WMD: ‒0.22 pg/mL, 95 % CI: ‒0.95, 0.50, P = 0.539) (P < 0.001).ConclusionThe results of this review show that green tea has no significant effect on PSA level. However, due to the heterogeneity among studies more consistent clinical trials, with larger sample sizes are required.     

Catechin induced longevity in C. elegans: From key regulator genes to disposable soma

The flavanol catechin is a ubiquitous metabolite within the plant kingdom. Several health benefits have previously been reported, however, to date, most attention has been devoted to gallated forms of catechin. This study utilized the nematode Caenorhabditis elegans to assess potential life expanding effects of non-gallated catechin. Longevity was observed at three different catechin concentrations, an effect that was neither linked to a specific temperature nor to the viability of the feeding bacteria. Taken all tests into account, hormesis, calorie restriction, as well as the presence of simple antioxidative or antibacterial effects could be excluded. Likewise, the insulin/IGF-1 like signaling pathway and the calmodulin kinase II pathway were not considered to play a major mechanic role. Moreover, stress resistance was enhanced without a marked alteration in reproductive behavior. In addition, lifespan tests with various stress and lifespan relevant mutant strains revealed that the life span extending phenotype was absent in mev-1, daf-2, akt-2 and nhr-8. Finally, catechin elicited a significant reduction in body length, a finding that is in line with the “Disposable Soma Theory”. It is proposed that catechin modulates an energy-intensive stress response and repair system that results in reduced body length and an enhanced lifespan.