Catechin antioxidant action at various pH studied by cyclic voltammetry and PM3 semi-empirical calculations

The mechanism of catechin electro-oxidation at various pH was studied using cyclic voltammetry (CV) on the glassy carbon (GC) electrode and PM3 semi-empirical calculations. The influence of activation of the surface of the GC electrode on CV results has been discussed. Mixed adsorption–diffusion control has been observed by applying mechanistic criteria of CV to the results obtained at the activated electrode. The calculated catechin diffusion coefficient D = 2.78 × 10^?6 cm² s^?1. A linear increase of the current peak has been observed with the increase of substrate concentration up to 40 μmol dm^?3 (surface coverage Γ ～ 10^?11 mol cm^?2). In the whole investigated pH range, the dE/dpH value is very close to the anticipated Nernstian dependence of ?59 mV/pH indicating that the slope is not affected by the different sequences of e^? and H⁺ transfer. Molecular modeling results show a decrease of ≈5 kcal mol^?1 in ΔHoF (between radical and parent molecule) and a decrease of ≈6 eV in IP (of the parent molecule) when the parent molecule is changed from neutral to monoanionic form of catechin showing that both processes – hydrogen and electron abstraction are facilitated by deprotonation. Electrochemical oxidation of catechin is known to proceed as a two step one-electron oxidation of the B-ring of o-phenolic groups. Upon an increase in the pH, the mechanistic pathway of catechin electro-oxidation in both oxidation steps changes from an eH to the He process. In the reaction with a free radical, this may induce the change from hydrogen to electron donation.     

儿茶止泻霜质量标准研究

目的:建立儿茶止泻霜的质量标准。方法:采用薄层色谱法对方中各味药进行定性鉴别;采用高效液相色谱法对方中君药儿茶中主要有效成分儿茶素进行含量测定,并对其进行稳定性测试。结果:薄层鉴别效果较好;儿茶素进样量在0.364～1.82μg范围内呈良好的线性关系。平均回收率为98.94%(RSD=1.28%,n=5)。结论:所建标准可作为该制剂的质量控制标准。     

Cytotoxic and apoptogenic effect of Swietenia mahagoni (L.) Jacq. leaf extract in human leukemic cell lines U937, K562 and HL-60

The apoptogenic activity of Swietenia mahagoni leaf extract (SMLE) was investigated against three human leukemic cell lines – U937, K562 and HL-60. SMLE inhibited cell growth and metabolic activity of the leukemic cells and showed characteristic features of apoptosis. Flow-cytometric analysis showed that SMLE arrested U937 and K562 cell populations in the G2-M phase and the HL-60 cell population in the G1 phase of cell cycle. SMLE induced apoptosis was found to be mediated through mitochondrial intrinsic pathway involving the release of cytochrome c into the cytosol and activation of caspase-9 and caspase-3. Two flavonoids, catechin and quercetin-3-O-glucoside, isolated from SMLE, were found to inhibit the growth and metabolic activity of U937, K562 and HL-60 cells at much lower concentrations thus indicating that these two flavonoids might be the active ingredients responsible for the anti-leukemic activity of SMLE.     

鸡血藤活性化合物儿茶素结构修饰及抗辐射作用研究

目的 对儿茶素进行结构修饰,制备系列衍生物,观察其抗辐射效果.方法 通过乙酸酐,丙酸酐,苯甲酰氯在碱性溶剂下与儿茶素反应,合成产物再利用硅胶层析进行分离纯化,得到纯化合物后进行结构鉴定;60Coγ射线(剂量为6Gy)照射小鼠造成辐射模型,照后给予3,5,7,3',4'-O-五乙酰基儿茶素和儿茶素灌胃;并于照前、后1、3、7、10、14、21 d取鼠尾静脉血,测外周血白细胞(WBC)、红细胞(RBC)、血红蛋白(HGB)、血小板数值(PLT).结果 合成并鉴定得到3种化合物,分别为3,5,7,3',4'-O-五乙酰基儿茶素;5,7,3',4'-O-四苯甲酰基儿茶素;3,5,7,3',4'-O-五丙酰基儿茶素;全乙酰化儿茶素对于辐射小鼠WBC,HGB,RBC,PLT的升高均有一定作用,但作用强度均不及儿茶素.结论 经过结构改造后的3,5,7,3',4'-O-五乙酰基儿茶素有一定的抗辐射作用,但作用效果较儿茶素弱.     

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.     

翻白草中化学成分研究

目的分离、鉴定翻白草中各化学成分。方法采用硅胶柱层析,以氯仿:丙酮,氯仿:甲醇为流动相进行梯度洗脱。结果从翻白草中分离出熊果酸(Ⅰ、Ⅱ)、没食子酸(Ⅲ)、原儿茶酸(Ⅳ)、儿茶素(Ⅴ)和槲皮素(Ⅵ)等单体。结论翻白草中化学成分丰富,该中药具有较大开发价值。     

Anti-pandemic influenza A (H1N1) virus potential of catechin and gallic acid

Background

The pandemic influenza A (H1N1) virus has spread worldwide and infected a large proportion of the human population. Discovery of new and effective drugs for the treatment of influenza is a crucial issue for the global medical community. According to our previous study, TSL-1, a fraction of the aqueous extract from the tender leaf of Toonasinensis, has demonstrated antiviral activities against pandemic influenza A (H1N1) through the down-regulation of adhesion molecules and chemokine to prevent viral attachment.

儿茶素和漆黄素对铁超载模型大鼠血脂的影响

目的:分别从中药苞蔷薇根、叶醇提物中分离得到( )-儿茶素[( )-Catechin,CAT]、漆黄素(Fisetin,FIS),通过铁超载模型来观察CAT和FIS对铁中毒大鼠血脂的影响.方法:定期饲养大鼠含羰基铁的饲料造成大鼠体内铁超载,给药组在造模的同时给予CAT、FIS或去铁胺(desferrioxamine methane sulphonate,DFO).给药3个月后,检测血清中的低密度脂蛋白胆固醇(LDL-CHO)、高密度脂蛋白胆固醇(HDL-CHO)、总胆固醇(T-CHO)、甘油三脂(TG)的含量以及血清铁水平.结果:CAT、FIS能非常显著地抑制铁超载大鼠的体重下降,降低血清中铁的含量,抑制血脂中LDL、T-CHO水平的升高,CAT还可以抑制TG水平的升高.结论:CAT和FIS对铁超载引起的血脂异常有保护作用.