Effect of synthetic antioxidants on hydrogen peroxide formation, oxyferro cytochrome P-450 concentration and oxygen consumption in liver microsomes

Synthetic antioxidants lead in vitro to increased H2O2 formation in rat liver and lung microsomes and in guinea pig and hamster liver microsomes. Butylated hydroxyanisole and ethoxyquin are more potent than propyl-, octyl-, and dodecyl gallate; butylated hydroxytoluene is only weakly active. Extra production of H2O2 is maximal at antioxidant concentrations between 50 and 500 microM and is dependent on the concentration of NADPH. It is paralleled by increased microsomal oxygen consumption and decreased concentration of oxycytochrome P-450 and is enhanced by pretreatment of the animals with phenobarbital. Both the endogenous and the antioxidant-stimulated H2O2 production are inhibited by metyrapone. In vivo administration of ethoxyquin and butylated hydroxyanisole in the diet leads to decreased oxycytochrome P-450 concentrations but not to increased H2O2 formation in liver microsomes. No extra production of H2O2 was observed in a glucose oxidase or xanthine oxidase system; rather, inhibition occurred in the latter system. Our data suggest that antioxidants enhance the oxidase function of cytochrome P-450. This effect is discussed in view of the known toxicity of these food additives.     

Propyl gallate-induced DNA fragmentation in isolated rat hepatocytes

Incubation of isolated rat hepatocytes with propyl gallate (PG) at concentrations of ≥1 mM induced cell killing, whereas PG at ≤0.5 mM did not cause cell death during a 3-h incubation. PG at ≥0.5 mM elicited the ladder formation of soluble low-molecular weight DNA fragments with integer multiples of approximately 180 bp and specific nuclear DNA cleavages detected cytopathologically by labeling of a digoxigenin-nucleotide complex to new 3′-OH ends. Both of these PG-induced changes observed in hepatocytes are characteristic features of apoptosis. In contrast, the pretreatment of N-acetylcysteine (4 mM), a precursor of intracellular glutathione (GSH) and antioxidant, prevented PG (0.5 mM)-induced formation of soluble DNA fragments and loss of cellular GSH, ATP, and formation of blebbing. These results suggest that when the concentration of PG is decreased, the effects of PG on hepatocytes change from acute necrotic to apoptotic mode, and that the onset of DNA fragmentation is associated with GSH depletion. Received: 23 June 1997 / Accepted: 18 August 1997     

表没食子儿茶素没食子酸酯增强阿糖胞苷对HL-60细胞的抗肿瘤活性

目的 :研究表没食子儿茶素没食子酸酯 (EGCG)增强阿糖胞苷 (AraC)对人白血病HL 6 0细胞的抗肿瘤活性。方法 :采用生长曲线法、MTT法测定AraC合并应用EGCG前后对HL 6 0细胞的增殖抑制作用 ;以对消实验研究EGCG能否逆转脱氧胞苷 (dCdR)的补救作用 ;以流式细胞光度仪分析联合用药前后对细胞周期和细胞凋亡的影响。结果 :合并EGCG能增强AraC对HL 6 0细胞的增殖抑制作用 ,倍增时间从 4 8h延长到 70h ,生长饱和密度从 5 .78减少到对 5 .5 4 ;MTT法表明合并EGCG后 ,AraC对HL 6 0细胞的IC50 从 (0 .0 8± 0 .0 7) μg·ml-1减少到 0 .0 2 4± 0 .0 2 6 μg·ml-1(P <0 .0 5 ) ;对消实验表明单用AraC的IC50 为 6 .2 5ng·ml-1,加上dCdR后IC50 为 5 .2 4 μg·ml-1,而在给予EGCG后IC50 减少到 1.17μg·ml-1。细胞周期研究结果表明AraC可使HL 6 0细胞阻滞于G1期 ,S期细胞减少 ,低浓度的EGCG对细胞周期几无影响 ,但增强了AraC的细胞周期阻滞作用及细胞凋亡。结论 :AraC合并应用EGCG可增强对人白血病HL 6 0细胞的抗肿瘤活性。     

Possible Reduction of Cardiac Risk after Supplementation with Epigallocatechin Gallate and Increase of Ketone Bodies in the Blood in Patients with Multiple Sclerosis. A Pilot Study

Multiple sclerosis (MS) is a neurodegenerative disease that causes anthropometric changes characterised by functional disability, increase in fat mass, and decrease in lean mass. All these variables are related to a greater cardiac risk. The polyphenol epigallocatechin gallate (EGCG) and an increase in ketone bodies in the blood have been shown to have beneficial effects on anthropometric and biochemical variables related to cardiovascular activity. The aim of this study was to analyse the impact of the intervention with EGCG and ketone bodies on cardiac risk in MS patients. A population of 51 MS patients were randomly assigned to a control group and an intervention group (daily dose of 800 mg of EGCG and 60 mL of coconut oil). Both groups followed an isocaloric diet for 4 months. Levels of beta-hydroxybutyrate (BHB), albumin, paraoxonase 1 (PON1) and C-reactive protein (CRP) were measured in serum before and after the intervention, as well as determining functional ability, waist circumference, waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), fat percentage and muscle percentage. After 4 months, in the intervention group there was a significant increase in BHB, PON1 and albumin, while CRP did not vary; a significant decrease in cardiac risk associated with a significant decline in WHR; as well as a significant increase in muscle percentage. By contrast, these changes were not observed in the control group. Finally, results from analysis of variance (ANOVA) revealed a significant time–condition interaction effect, observing that WHtR and fat mass decreased in the intervention group, while they increased in the control group.     

Phytochemicals based chemopreventive and chemotherapeutic strategies and modern technologies to overcome limitations for better clinical applications

Naturally occurring phytochemicals or plant derivatives are now being explored extensively for their health's benefits and medicinal uses. The therapeutic effect of phytochemicals has been reported in several pathophysiological settings such as inflammatory disorders, metabolic disorders, liver dysfunction, neurodegenerative disorders, and nephropathies. However, the most warranted therapeutic effects of phytochemicals were mapped to their anticancerous and chemopreventive action. Moreover, combining phytochemicals with standard chemotherapy has shown promising results in cancer therapy with minimal side effects and better efficacy. Many phytochemicals, like curcumin, resveratrol, and epigallocatechin‐3‐gallate, have been extensively investigated for their chemopreventive as well as chemotherapeutic effects. However, poor bioavailability, low solubility, hydrophobicity, and obscure target specificity restrict their therapeutic applications in the clinic. There has been a continually increasing interest to formulate nanoformulations of phytochemicals by using various nanocarriers, such as liposomes, micelles, nanoemulsions, and nanoparticles, to improve their bioavailability and target specificity, thereby maximizing the therapeutic potential. In the present review, we have summarized chemopreventive as well as chemotherapeutic action of some common phytochemicals and their major limitations in clinical application. Also, we have given an overview of strategies that can improve the efficacy of phytochemicals for their chemotherapeutic value in clinical settings.     

表没食子儿茶素没食子酸酯通过抑制角蛋白17诱导角质形成细胞凋亡

【摘要】 目的 探讨表没食子儿茶素没食子酸酯（EGCG）对角蛋白17（K17）介导的人角质形成细胞的凋亡的影响。方法 不同浓度EGCG处理人乳头瘤病毒（HPV）11型基因组的HaCaT细胞（HPV11．HaCaT）12 h,qRT PCR与Western blot检测角蛋白17表达;流式细胞术Annexin V FITC和碘化丙锭（PI）双染检测50 mg/L EGCG处理下KC、HaCaT及HPV11．HaCaT细胞凋亡率。免疫组化法与Western blot检测银屑病和尖锐湿疣患者病理切片中K17以及Caspase3的表达,构建K17过表达（pcDNA31（+）/K17）载体并转染KC与HaCaT细胞48 h继续用EGCG（50 mg/L）处理12 h;检测K17的水平及细胞凋亡。结果 EGCG可在12 h抑制KC、HaCaT 和HPV11．HaCaT细胞中K17表达(P＜005),呈浓度依赖趋势;银屑病和尖锐湿疣病理切片中K17表达范围增多但Caspase3的染色范围减少,K17表达上调,但Cleaved Caspase3显著下调（P＜005）。使用高浓度50 mg/L的EGCG 作用下,KC、HaCaT 和HPV11．HaCaT细胞凋亡率均上调（P＜001）。pcDNA31（+）/K17对KC、HaCaT细胞凋亡率的抑制作用被EGCG显著逆转（P＜001）。结论 EGCG通过抑制K17促进角质形成细胞凋亡,为银屑病和尖锐湿疣基础研究与临床治疗提供前期研究基础。     

三种食品添加剂抗植物油氧化作用效果观察

目的：观察三种食品添加剂对植物油的抗氧化作用。方法：采用菜油及芝麻油为样品，空白对照组不加任何添加剂；实验组按国家标准最大使用量加入没食子酸丙酯、茶多酚、双乙酸钠。于３７℃恒温３０天，以酸价及过氧化值判断其抗氧化作用。结果与结论：没食子酸丙酯、茶多酚、茶多酚、双乙酸钠均有防止植物油过氧化值升高的作用。没食子酸丙酯、茶多酚有防止植物油酸价过高的作用。双乙酸钠有防止菜油酸价升高的作用，但降低芝麻油酸价