灯盏花乙素及其苷元结构与抗氧化活性关系研究

采用密度泛函理论B3LYP方法对灯盏花乙素及其苷元分子进行几何结构全优化,获得两个化合物的最低能量结构。从分子的几何结构、NBO电荷、酚羟基解离能BDE、绝热电离势IP和前线分子轨道等方面分析了两个化合物的结构与抗氧化活性之间的关系。计算结果表明,C6位的酚羟基为灯盏花乙素及其苷元的最大反应活性位点,灯盏花乙素的抗氧化活性弱于其苷元的抗氧化活性,计算结果与实验结果吻合。天然的糖苷类物质水解为苷元后,其抗氧化活性增强。此外,还考虑了溶剂效应,考察溶剂极性对抗氧化活性的影响。在所有环境中,抽氢反应机制是化合物自由基清除反应的最主要机制。     

异鼠李素和异鼠李素-3-O-葡萄糖苷的抗氧化活性分析

槲皮素类化合物是众多黄酮类中活性最高的化合物之一,在医药方面有很强的药效功效。本研究选取两种槲皮素类黄酮化合物异鼠李素和异鼠李素-3-O-葡萄糖苷作为目标化合物,运用Gaussian 09软件密度泛函(DFT)方法从分子总能量、OH解离焓(BDE)的理论表征、前线分子轨道及其轨道能级、原子的净电荷布居等方面研究异鼠李素和异鼠李素-3-O-葡萄糖苷的抗氧化活性。结果表明,异鼠李素活性大于异鼠李素-3-O-葡萄糖苷,两类分子4'位的酚羟基失去氢之后对抗氧化活性的整体影响是最大的,酚羟基在这个位置上就具有较明显的高活性特征,分子中引入的糖苷不参与前线分子轨道的形成,不具有消除自由基活性的作用,但它对于分子本身的极性有很大的影响,可以改变分子在机体反应时的溶解度和吸收度。这对进一步深入研究槲皮素类黄酮化合物的抗氧化活性以及抗氧化剂的结构改良等提供了重要的科学依据。     

不同产地生漆中漆酚清除自由基及构效关系的初步研究

为更好地开发和利用生漆资源,探寻生漆中主要有效成分漆酚的抗氧化性能,为生漆的深加工提供理论依据和参数。分别应用丙酮提取中国和越南生漆,对得到的漆酚粗提物中的漆酚含量进行测定,建立了阳性对照组Vc和二丁基羟基甲苯(BHT)基础的DPPH、ABTS及O2-.法,对提取物抗氧化性能进行测试;在此基础上,结合紫外光谱分析了中国和越南生漆中漆酚含量及结构差异性,并初步分析其抗氧化的构效关系。结果显示,各地生漆中漆酚提取物具有强的抗氧化活性:中国毛坝生漆提取物抗氧化活性最强,其次是越南红漆和中国小木漆;紫外光谱分析亦表明毛坝生漆中含有丰富的不饱和键可能与其较强的抗氧化性相关。     

茶多酚对氧化脂肪-蛋白质体系的作用研究

目的:研究茶多酚对氧化脂肪-蛋白质体系的作用机理。方法:利用分光光度计和红外光谱检测法对冻藏条件下氧化脂肪-蛋白质模拟体系中肌原纤维蛋白巯基含量、表面疏水性和二级结构进行研究。结果:在冻藏过程中,添加氧化6 h鱼油的肌原纤维蛋白液,巯基含量的减少和表面疏水性的增加最显著,其减少值和增加值分别为28.62%和53.72%;同时β-折叠、α-螺旋的减少和β-转角、无规卷曲的增加也最明显。添加0.05%茶多酚的三个组合与其相应的对照组相比,巯基含量的减少、表面疏水性的增加和二级结构的改变都较为缓慢,其中茶多酚抑制巯基含量减少的效果十分显著。结论:氧化鱼油能加速蛋白质的变性,且氧化程度越大,加速效果越明显;而茶多酚能够通过抑制巯基含量的减少来抑制鱼油氧化而导致的蛋白质变性。     

茶色素及其药理学功能

茶色素是茶叶多酚类及其衍生物的混合物,主要成分为茶黄素类、茶红纱类。茶色素含有大量的活性酚羟基等活性基因、具有极强的清除自由基和抗氧化作用。近代药理学研究表明,花色素具有防癌抗癌、防紫外线照射、抗氧化、抗动脉粥样硬化、抗龋护齿等多种药理功能。花色素产品的开可广泛用于医药、食品工业。     

茶多酚对金黄色葡萄球菌和铜绿假单胞菌的抑菌机理

以革兰氏阳性的金黄色葡萄球菌和革兰氏阴性的铜绿假单胞菌为试验菌,通过测定茶多酚与两种菌作用前后细菌培养液的电导率和可溶性总糖的变化,以及菌体在磷代谢和蛋白质表达方面的变化,初步阐明了茶多酚对这两种菌的抑菌机理。研究结果表明,茶多酚对金黄色葡萄球菌和铜绿假单胞菌均有抑菌活性,但对金黄色葡萄球菌的抑菌活性更强。经茶多酚处理后,细菌培养液的电导率和总糖浓度均增大,表明了茶多酚可破坏细胞膜的结构、导致细胞通透性增加,进而使细胞内容物外泄。另一方面,经茶多酚处理后的两种菌对磷的消耗量降低,以致严重影响了核酸、磷脂等细胞重要成分的合成以及能量代谢;通过SDS-PAGE分析,证实茶多酚可以阻碍细菌蛋白质的正常表达,以致影响其细胞的结构组成以及酶的催化活性,最终导致细菌正常生理功能的丧失。     

不同产区川芎提取物抗氧化及抑菌活性研究

为研究道地产区敖平镇川芎与非道地产区中江县川芎醇提物、石油醚提取物抗氧化活性、抗菌活性的大小,采用自由基清除能力(DPPH自由基和羟基自由基清除能力)和还原能力测定法评价提取物的抗氧化活性,采用滤纸片扩散法测定抑菌圈直径考察川芎提取物的抑菌活性。研究结果表明:两产区川芎醇提物和醚提物在测定浓度范围内均具有抗氧化活性和抑菌活性。但与中江县川芎提取物相比,道地产区敖平镇川芎提取物具有更强的抑菌活性,而对于中江县是否适合大面积推广种植川芎,还需要结合多种环境因素具体分析。     

肾茶多酚提取工艺及其抗氧化活性研究

采用回流提取法,进行单因素试验和L9(34)正交试验,确定肾茶多酚最佳提取工艺;并通过测定1,1-二联苯基-2-苦肼自由基(DPPH·)和羟自由基(·OH)清除率评价其抗氧化活性。得到的肾茶多酚的优化提取工艺为液料比10∶1(m L/g),50%乙醇回流3次,每次提取2 h,肾茶多酚提取率为3.60%,优选的提取工艺稳定可靠,重现性好。体外抗氧化活性实验结果显示:肾茶多酚的抗氧化能力随质量浓度的增大而增强,在1~10μg/m L浓度范围内和100~1250μg/m L浓度范围内,其清除DPPH自由基和羟基自由基的能力略强于抗坏血酸,两者的对DPPH自由基半数抑制浓度分别为5.78和6.31μg/m L;对羟基自由基的半数抑制浓度为851.1和940.1μg/m L。     

粒毛盘菌YM-223胞外黑色素总酚含量及其抗氧化活性

<正>酚类化合物是具有抗氧化活性的天然化合物,在预防人类某些疾病方面有重要作用(Cai et al.2004)。黑色素是一类通过多羟基酚氧化而成的构     

5-氯水杨醛缩2,4-二羟基苯酰肼的抗菌抗氧化活性研究

目的考察5-氯水杨醛缩2,4-二羟基苯酰肼对金黄色葡萄球菌的抗菌活性及体外抗氧化活性。方法采用试管法和平板法测定其对金黄色葡萄球菌最小抑菌浓度(MIC)、最小杀菌浓度(MBC),绘制杀菌曲线,并通过扫描电镜研究其作用机制,采用DPPH法测定抗氧化活性。结果该化合物对金黄色葡萄球菌的MIC为2.5 mg/m L,MBC为5 mg/m L。杀菌曲线结果表明该化合物对金黄色葡萄球菌的杀菌作用表现出明显的浓度依赖性。扫描电镜结果表明该化合物的作用机制可能与破坏菌体细胞壁、改变其通透性有关。同时该化合物具有较强的清除自由基的能力。结论 5-氯水杨醛缩2,4-二羟基苯酰肼具有显著的抗金黄色葡萄球菌作用,同时具有较好的体外抗氧化活性。     

Cancer chemoprevention by tea polyphenols

Tea is one of the most widely consumed beverages, second only to water. Many experimental researches in laboratory animals demonstrated that tea components had an inhibitory effect on carcinogenesis at a number of organ sites. The inhibitory effects of tea against carcinogenesis have been attributed to the biologic activities of the polyphenol fraction in tea. This review summarizes experimental data on chemopreventive effects of tea polyphenols in various tumor bioassay systems. Many laboratory studies have demonstrated the inhibitory effects of green tea polyphenols, especially (-)-epigallocatechin-3-gallate (EGCG), on carcinogenesis in animals models. The majority of these studies have been conducted in mouse skin tumor models, where tea polyphenols were used either as oral feeding in drinking water or in direct local application. Most studies used 12-O-tetradecanoylphorbol-13-acetate (TPA) or ultraviolet (UV) radiation as the tumor promoter and found anticarcinogenic effects caused by green tea polyphenols. Black tea was also found to be effective, although the activity was weaker than that of green tea in some experiments. Other studies showed that black tea polyphenols-theaflavins exhibited stronger anticarcinogenic activity than did EGCG. Caffeine in tea was also important for tea to prevent tumorigenesis. The molecular mechanisms of the cancer chemopreventive effects of tea polyphenols are not completely understood. They are most likely related to the mechanisms of biochemical actions of tea polyphenols, which include antioxidative activities, modulation of xenobiotic metabolite enzymes and inhibition of tumor promotion. In addition, we have also proposed that tea polyphenols function as cancer chemopreventive agents through modulation of mitotic signal transduction. However, the molecular mechanisms involved in this modulation need further investigation.     

Protective effect of tea polyphenols on renal ischemia/reperfusion injury via suppressing the activation of TLR4/NF-κB p65 signal pathway

Tea polyphenols (TP) was investigated in rats for its protective effect on renal ischemia/reperfusion injury (RIRI). Rats were randomized into groups as follows: (I) sham group (n = 10); (II) RIRI group (n = 10); (III) RIRI + TP (100 mg/kg) group (n = 5); (IV) RIRI + TP (200 mg/kg) group (n = 5); (V) RIRI + TP+ Astragalus mongholicus aqueous extract (AMAE) (300 mg/kg + 100 mg/kg) group (n = 5). For the IRI + TP groups, rats were orally given with tea polyphenols (100, 200 and 300 mg/kg body weight) once daily 10 days before induction of ischemia, followed by renal IRI. For the sham group and RIRI group, rats were orally given with equal volume of saline once daily 10 days before induction of ischemia, followed by renal IRI. Results showed that tea polyphenol pretreatment significantly suppressed ROS level and MDA release. On the other hand, in rats subjected to ischemia–reperfusion, the activities of endogenous antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and glutathione peroxidase (GSH-Px) showed recovery, whereas the levels of urea nitrogen and serum creatinine were reduced by administration of tea polyphenols orally for 10 days prior to ischemia–reperfusion. Moreover, tea polyphenol pretreatment significantly decreased TLR4 and NF-κB p65 protein expression levels in RIRI rats. At the same time, tea polyphenol pretreatment attenuated the increased level of serum IL-1β, IL-6, ICAM-1 and TNF-α, and enhanced IL-10 production in RIRI rats. Furthermore, tea polyphenol pretreatment significantly decreased renal epithelial tubular cell apoptosis induced by renal ischemia/reperfusion, alleviating renal ischemia/reperfusion injury. These results cumulatively indicate that tea polyphenol pretreatment could suppress the TLR4/NF-κB p65 signaling pathway, protecting renal tubular epithelial cells against ischemia/reperfusion-induced apoptosis, which implies that antioxidants may be a potential and effective agent for prevention of the ischemic/reperfusion injury through the suppression extrinsic apoptotic signal pathway induced by TLR4/NF-κB p65 signal pathway. Moreover, supplement of AMAE can increased renal protection effect of TP.     

Protective Effect of Green Tea Extract and Tea Polyphenols against the Cytotoxicity of 1,4-Naphthoquinone in Isolated Rat Hepatocytes

The cytoprotective effect of green tea extract and its phenolic compounds against 1,4-naphthoquinone-induced hepatotoxicity was evaluated in primary cultured rat hepatocytes. After exposure to 1,4-naphthoquinone, lactate dehydrogenase (LDH) leakage and cell viability were both improved by the presence of the tea extract and tea polyphenols. This cytoprotective effect was related to the structure of tea polyphenols, the galloyl group of (–)-epigallocatechin-3-gallate and (–)-epicatechin-3-gallate being particularly effective. The production of liquid peroxidation by 1,4-naphthoquinone was not inhibited by the tea extract nor by tea polyphenol addition. After 2h of incubation, the protein thiol concentration was reduced by 1,4-naphthoquinone, but this reduction was prevented by the tea extract and tea polyphenols. The reduction in protein thiol content of the cells closely paralleled the LDH leakage and loss of cell viability. These results suggest that the mechanism of protection by tea polyphenols against 1,4-naphthoquinone-induced toxicity to rat hepatocytes was due to the maintenance of protein thiol levels.     

Polyphenols based on isoflavones as inhibitors of Helicobacter pylori urease

Twenty polyphenols were synthesized and evaluated for their effect on Helicobacter pylori urease. Among these compounds, 4-(p-hydroxyphenethyl)pyrogallol (15) (IC(50)=0.03 mM) and 7,8,4'-trihydroxyisoflavone (19) (IC(50)=0.14 mM) showed potent inhibitory activities, and inhibited Helicobacter pylori urease in a time-dependent manner. The structure-activity relationship of these polyphenols revealed: the two ortho hydroxyl groups were essential for inhibitory activity of polyphenol. When the C-ring of isoflavone was broken, the inhibitory activity markedly decreased. As for deoxybenzoin, the carboxyl group was clearly detrimental.     

Relationship between the methylation status of dietary flavonoids and their growth-inhibitory and apoptosis-inducing activities in human cancer cells

Flavonoids are polyphenolic compounds widely distributed in the plant kingdom. Compelling research indicates that flavonoids have important roles in cancer chemoprevention and chemotherapy possibly due to biological activities that include action through anti-inflammation, free radical scavenging, modulation of survival/proliferation pathways, and inhibition of the ubiquitin-proteasome pathway. Plant polyphenols including the green tea polyphenol (-)-epigallocatechin gallate or (-)-EGCG, and the flavonoids apigenin, luteolin, quercetin, and chrysin have been shown to inhibit proteasome activity and induce apoptosis in human leukemia cells. However, biotransformation reactions to the reactive hydroxyl groups on polyphenols could reduce their biological activities. Although methylated polyphenols have been suggested to be metabolically more stable than unmethylated polyphenols, the practical use of methylated polyphenols as cancer preventative agents warrants further investigation. In the current study, methylated and unmethylated flavonoids were studied for their proteasome-inhibitory and apoptosis-inducing abilities in human leukemia HL60 cells. Methylated flavonoids displayed sustained bioavailability and inhibited cellular proliferation by arresting cells in the G(1) phase. However, they did not act as proteasome inhibitors in either an in vitro system or an in silico model and only weakly induced apoptosis. In contrast, unmethylated flavonoids exhibited inhibition of the proteasomal activity in intact HL60 cells, accumulating proteasome target proteins and inducing caspase activation and poly(ADP-ribose) polymerase cleavage. We conclude that methylated flavonoids lack potent cytotoxicity against human leukemia cells and most likely have limited ability as chemopreventive agents.     

Black Tea Represents a Major Source of Dietary Phenolics Among Regular Tea Drinkers

The phenolic composition and antioxidant activities [TEAC, ORAC, FRAP] of consumer brews (1 tea bag in 230 ml for 1 min) of seven different brands of black tea from the British market were investigated. The main phenolic compounds identified were epigallocatechin gallate, four theaflavins, as well as epicatechin gallate, theogallin (tentative assignment), quercetin-3-rutinoside and 4-caffeoyl quinic acid. Thearubigins represented an estimated 75-82% of the total phenolics. Further, polyphenol fractions were in decreasing order theaflavins, flavan-3-ols, flavonols, gallic acids and hydroxycinnamates. On average, a cup of a consumer brew of black tea is providing polyphenols at the level of 262 mg GAE/serving, of which 65 mg were assigned to individual polyphenols. The antioxidant activity of black tea preparations is higher than that of most reported dietary agents on a daily basis. Correlations were observed between the antioxidant activities and the sum of all quantified polyphenols by HPLC analysis as well as with the total phenolics. Treatment of the black tea brew with simulated gastric juice resulted in a significant increase of the identified theaflavins implying a partial cleavage of thearubigins in the environment of the gastric lumen. Therefore, black tea can be considered to be a rich source of polyphenols and/or antioxidants.     

Black tea represents a major source of dietary phenolics among regular tea drinkers

The phenolic composition and antioxidant activities [TEAC, ORAC, FRAP] of consumer brews (1 tea bag in 230 ml for 1 min) of seven different brands of black tea from the British market were investigated. The main phenolic compounds identified were epigallocatechin gallate, four theaflavins, as well as epicatechin gallate, theogallin (tentative assignment), quercetin-3-rutinoside and 4-caffeoyl quinic acid. Thearubigins represented an estimated 75-82% of the total phenolics. Further, polyphenol fractions were in decreasing order theaflavins, flavan-3-ols, flavonols, gallic acids and hydroxycinnamates. On average, a cup of a consumer brew of black tea is providing polyphenols at the level of 262 mg GAE/serving, of which 65 mg were assigned to individual polyphenols. The antioxidant activity of black tea preparations is higher than that of most reported dietary agents on a daily basis. Correlations were observed between the antioxidant activities and the sum of all quantified polyphenols by HPLC analysis as well as with the total phenolics. Treatment of the black tea brew with simulated gastric juice resulted in a significant increase of the identified theaflavins implying a partial cleavage of thearubigins in the environment of the gastric lumen. Therefore, black tea can be considered to be a rich source of polyphenols and/or antioxidants.     

水麻果多酚的提取纯化及其抗氧化、抗肿瘤活性作用

为提取分离水麻果多酚,探索水麻果多酚的抗氧化及抗肿瘤能力。本研究通过单因素试验和正交试验优化水麻果多酚超声提取工艺,使用大孔树脂纯化水麻果多酚,通过测定水麻果多酚的总还原力以及清除·OH、DPPH·、ABTS·的能力来表征其抗氧化活性,以宫颈癌Hela细胞和肺癌A549细胞为抗肿瘤研究对象,测定水麻果多酚的抗肿瘤作用。在最优超声提取工艺条件下,即乙醇浓度为60%,料液比为1∶30,超声功率200 W,超声温度为70℃,提取时间为40 min,水麻果多酚得率为3. 29%,纯化产物总酚含量为40. 47 mg/100 mg,水麻果多酚的总还原力与维生素C相当,对·OH、DPPH·、ABTS·均具有显著清除作用,可抑制Hela细胞和A549细胞的生长增殖,并导致癌细胞产生大量活性氧,出现凋亡形态特征。该提取工艺简单、高效且多酚得率高,提取物经大孔树脂纯化后总多酚含量显著提高,且具有显著的抗氧化和抗肿瘤活性。     

Analysis of tea polyphenols

Tea is the most highly consumed beverage in the world, other than water. However, unlike water, tea contains substantial amounts of polyphenols that have unique biological activities and may be responsible for many of the health benefits of tea. As a result, it is essential to be able to measure the various tea-associated polyphenols. Total polyphenol content is currently measured by using methodology based on reducing activity. Several HPLC systems with detectors that, collectively, have wide ranges in sensitivity have been developed for analysis of individual flavonoids in tea and biological samples, and for theaflavins in tea. Catechins also have been measured in plasma by solid phase extraction, addition of a chromophore, and colorimetric quantification. Except for theaflavins in tea, routine and robust methods for the measurement of polyphenol condensation products (dimers and thearubigens) in tea and biological samples have not been developed. Although in vitro and animal studies suggest substantial metabolism of flavonoids in the gastrointestinal tract, only a single HPLC procedure has been assembled for monitoring the metabolic products of quercetin in urine of human subjects.     

Polyphenols as potential indicators for drought tolerance in tea (Camellia sinensis L.)

Plant polyphenols have gained prominence in quality of plant products and in human health. An experiment was conducted to determine the association of tea polyphenols with water stress and their suitability as indicators for drought tolerance. The experiment was conducted in a 'rain-out' shelter, and consisted of six tea clones (BBK 35, TRFK 6/8, TRFK 76/1, TRFK 395/2, TRFK 31/30, and TRFK 311/287) and four levels of soil water contents (38, 30, 22, and 14% v/v), which were maintained for a period of 12 weeks. The treatments were arranged in a completely randomized design and replicated three times. Plant growth was monitored over 6 weeks, and a water stress index was calculated to determine water-stress tolerant clones. Total polyphenols in tea shoots was analyzed and a regression analysis done. The results indicate that declining soil water content (SWC) reduced both growth and content of polyphenols in tea. Tolerant clones maintained a high polyphenol content at low SWC, and also showed less fluctuation in phenolics when subjected to changes in SWC. There was significant (P<0.001) correlation of total polyphenol content with shoot growth and WSI of tea, and a linear relationship (r2=0.97) between SWC for tea and both, water stress index and shoot polyphenol content. We report that there is a potential to use polyphenols as indicators for selection of drought-tolerant tea cultivars.