迷迭香单体的抗氧化活性

采用柱层析方法对迷迭香抗氧化剂(Rao)进行分离,分离出8个含量较高的单体.用光度法、ESR法、滴定法测定了迷迭香的8个单体、单体组合及Rao的抗氧化活性,并分析了抗氧化活性与其结构的关系.结果表明,在单体中,对超氧阴离子自由基及羟基自由基清除率最高的是槲皮素,分别为82.6%和87.1%.对香烟烟气自由基平均清除率最高的是迷迭香二酚,清除率为48.17%.单体活性最强的槲皮素和迷迭香二酚组合后,其抗氧化活性高于单体.活性强的抗氧化剂对油脂过氧化的抑制效果好,但作用时间较短.     

超声波辅助提取茶叶总黄酮及抗氧化活性分析

采用超声波辅助法探讨了铁观音茶叶中总黄酮的最佳提取工艺条件,并测定了铁观音茶叶总黄酮清除羟基自由基的能力.结果表明,超声波功率400 W,料液比1∶30 g·mL~(-1),浸提时间30 min,乙醇浓度50%为超声波辅助提取铁观音茶叶总黄酮的最佳工艺条件,总黄酮提取率为4.74%;抗氧化实验表明随着铁观音茶叶总黄酮浓度的增大,其对羟基自由基的清除能力增大,当浓度达到0.80 g/L,清除率为65.14%,与BHT相比具有较强的抗氧化能力.     

硒多糖的抗氧化活性及与过氧化氢酶协同作用的研究

对自行培养的富硒蛹虫草中提取的有机硒多糖进行抗氧化活性研究.采用循环伏安法(CV),在铂电极表面构筑支撑磷脂双层膜 (Supported bilayer lipid membrane, s-BLM),以0.1 mol/L KCl-1.0 mmol/L K3Fe(CN)6-1.0 mmol/L K4Fe(CN)6为探针溶液,利用Fenton体系中Fe2+和H2O2反应产生的羟自由基对模拟生物膜的损伤程度考察有机硒多糖的生物活性.结果表明:羟自由基使s-BLM的通透性增强,造成膜体损伤;而在硒多糖存在下,可使羟自由基对膜的这种损伤受到抑制,硒多糖能够清除自由基保护生物膜;采用紫外-可见(UV-Vis)吸收光谱法比较研究不同浓度的过氧化氢酶与硒多糖对羟自由基的清除率.结果表明:硒多糖对羟自由基的清除效果好于过氧化氢酶,且当体系中硒多糖和过氧化氢酶共存时,二者对羟自由基的清除效果具有协同作用.进一步讨论了硒多糖抗氧化活性的可能机理,为有机硒多糖在保护生物膜、抗氧化活性方面的开发与利用提供科学的理论依据.     

基于毛细管电泳的黄芪抗氧化生物指纹图谱研究

根据评价抗氧化剂清除自由基能力的间接化学发光法,结合具有高效分离能力的毛细管电泳技术,建立了能表征中药抗氧化活性的生物指纹图谱。选取中药黄芪为研究对象,以黄芪甲苷为参照物峰,确定了6个共有峰,并首次测得黄芪甲苷对羟自由基的清除率。各共有峰相对迁移时间的RSD<1.5%,相对自由基清除率的RSD<8.4%,表明方法的精密度和重复性较好。7个产地的黄芪药材与道地药材具有良好的抗氧化活性相似度,相似度>96.5%。抗氧化生物指纹图谱对天然产物的质量控制与临床研究具有指导意义。     

褪色光度法测定Fenton反应产生的羟自由基及其应用

建立检测Fenton反应产生羟自由基的新方法。Fenton反应产生的羟自由基与苋菜红反应，颜色发生变化，用分光光度计测定其△A510值的变化，可间接测定羟自由基的生成量。通过对测定条件的研究，确定了体系最佳实验条件。抗氧化药物甘露醇、硫脲与羟自由基清除率具有明显的量效关系。测定了阿魏酸、芦丁等几种中药活性成分清除羟自由基的功能，此法可用于羟自由基清除剂的筛选及抗羟自由基机理研究。     

利用Fenton体系对西藏灵菇酸奶的抗氧化活性的评价

本文采用Fenton体系对市售酸牛奶、自制西藏灵菇酸牛奶进行了抗氧化活性研究.绘制了酸牛奶清除羟自由基清除率曲线,结果表明它们清除羟基自由基能力的大小顺序为:君乐宝酸牛奶＞蒙牛酸牛奶＞西藏灵菇酸牛奶,抗坏血酸的Ec_(50).为0.113mg/mL,约600～700g酸牛奶相当于1g抗坏血酸的抗氧化性活性.同时对反应体...     

洗参水美白与抗氧化活性及其皂苷类成分分析

对洗参水冻干粉样品美白、抗氧化活性及其皂苷成分进行分析。通过采用生化酶学法测定酪氨酸酶抑制率探究洗参水冻干粉样品的美白活性,采用水杨酸法测定羟自由基(Hydroxyl radical,·OH)清除率和1,1-二苯基-2-三硝基苯肼自由基(DPPH自由基)清除率探究洗参水冻干粉样品抗氧化活性,同时利用高分离度快速液相色谱串联四极杆-飞行时间质谱(RRLC-Q-TOF MS/MS)法对洗参水冻干粉样品中的皂苷类成分进行分析,共鉴别出16种人参皂苷。结果表明,洗参水冻干粉样品中总皂苷含量为1.64 g/100 g;该样品对酪氨酸酶活性具有抑制作用,当质量浓度为57.82 mg/mL时,样品对酪氨酸酶抑制率为50.50%;同时具有一定的抗氧化活性,当样品质量浓度为38.03 mg/mL时,对·OH的抑制率达到50.30%;当样品质量浓度为52.04 mg/mL时,对DPPH自由基的清除率为50.10%。综上,洗参水作为人参初加工被废弃的副产物,存量较大,是值得再利用开发的美白、抗氧化、防衰老类产品的原料。     

鸡足山耳蕨总黄酮的提取及抗氧化性研究

研究鸡足山耳蕨中总黄酮的提取及其抗氧化性.采用70％乙醇提取鸡足山耳蕨中总黄酮,用NaNO2Al(NO3)3-NaOH分光光度法测定黄酮含量,将提取液采用Fenton体系、普鲁士蓝法进行体外抗氧化活性研究,用硫代巴比妥酸(TBA)分光光度法研究其对羟自由基·OH引发DNA氧化损伤的抑制作用.结果表明样品中总黄酮含量为4.98％,回收率99.78％( RSD=1.06％,n=5).总黄酮浓度为90μg/mL时,对·OH的清除率可达36.2％;浓度为87.5μg/mL时,对羟自由基引发DNA损伤的抑制率可达93.0％.说明鸡足山蕨中总黄酮对羟自由基有较好的清除能力,对DNA氧化损伤有显著抑制作用.     

抗氧化剂的毛细管电泳-间接化学发光联用在线评价方法研究

根据碱性条件下羟自由基与luminol反应会产生化学发光而抗氧化剂能够清除羟自由基从而抑制发光的原理, 结合毛细管电泳技术, 建立了一种针对多组分共存体系中抗氧化组分的在线评价的新方法. 对这种毛细管电泳-间接化学发光检测技术, 优化化学发光的各种条件, 考察了抗氧化剂硫脲和麻黄碱的抗氧化活性, 采用曲线拟合求出它们对羟自由基的半数清除浓度(IC₅₀), 得出抗氧化活性大小为麻黄碱＞硫脲, 这与荧光分光光度法的结果一致. 该方法初步应用于评价中药槐米提取物化学组分的抗氧化活性.     

蒙药漏芦花多糖提取工艺及其抗氧化抗菌活性研究

本文优化了蒙药漏芦花多糖的提取工艺,并评价其抗氧化和抗菌活性。以超声功率、超声温度、超声时间和浸泡时间为影响因素,多糖提取率为评价指标,在单因素实验的基础上利用正交试验优化提取工艺,测定漏芦花多糖对DPPH自由基、羟基自由基清除效果,检测其抗氧化活性,涂布平板法测定多糖抗菌活性。超声波辅助法提取蒙药漏芦花多糖的最佳工艺条件为超声功率180W,超声温度70℃,超声时间30min,浸泡时间40min,在此条件下多糖得率为1.125%。抗氧化实验表明,漏芦花多糖浓度在0.5～2.5mg·mL~(-1)范围内,随着漏芦花多糖浓度增加,总还原能力不断增强;其体外清除DPPH自由基能力也随浓度增大而增强,清除率最高达72.98%;当多糖浓度为1.5mg·mL~(-1)时,漏芦花多糖体外清除羟基自由基能力最强,为7.24%。漏芦花多糖浓度为12.8mg·mL~(-1)时,对沙门氏菌的抑菌圈直径为9.72mm。超声法提取蒙药漏芦花多糖操作简便、准确、灵敏、重现性好,漏芦花多糖抗氧化能力良好,且对沙门氏菌有一定的抑菌效果。     

不同方法提取菟丝子微量元素Fe，Mn和Mg的比较研究

为比较不同提取方法对菟丝子中微量元素含量的影响,采用酸式提取法、碱式提取法、沸水提取法及超声提取法对中药菟丝子中的微量元素进行提取,用原子吸收分光光度法测定了提取液中微量元素铁、锰和镁的含量并进行了比较。结果表明,4种提取方法对微量元素的溶出率由高到低顺序为：铁-酸提,超提,碱提,沸提;锰-酸提,超提,沸提,碱提。镁酸提,沸提,超提,碱提。     

Influence of Tea Brewing Parameters on the Antioxidant Potential of Infusions and Extracts Depending on the Degree of Processing of the Leaves of Camellia sinensis

The polyphenol content of tea depends on the growing region, harvest date, the production process used, and the brewing parameters. In this study, research was undertaken that included an analysis of the influence of the brewing process parameters on the content of total polyphenols (Folin-Ciocalteu), epigallocatechin gallate (HPLC), and antioxidant activity (against DPPH radicals) of fresh tea shrub leaves grown from Taiwan and of teas obtained from them (oolong, green in bags, and green loose from the spring and autumn harvest). The antioxidant potential was determined in the methanol and aqueous extracts, as well as in infusions that were obtained by using water at 65 or 100 °C and infusing the tea for 5 or 10 min. The highest content of total polyphenols and epigallocatechin gallate was found in green tea extracts from the spring harvest. However, in the case of infusions, the highest content of these compounds was found in green tea in bags. Steaming at 100 °C for 10 min, turned out to be the most favourable condition for the extraction. Oolong tea, brewed at 100 °C for 5 min was characterised by the highest antioxidant activity against stable DPPH radicals.     

Response surface optimized ultrasonic-assisted extraction of flavonoids from Sparganii rhizoma and evaluation of their in vitro antioxidant activities

An efficient ultrasound-assisted extraction technique was employed to extract total flavonoids from Sparganii rhizoma. The optimum extraction conditions for the highest yield of total flavonoids were ethanol concentration 53.62%, ultrasonication time 29.41 min and ultrasound power 300 W, which were determined using response surface methodology. The extraction yields of the optimal ultrasound-assisted extraction were higher than using conventional extraction. The crude extract was then purified on a polyamide resin, whereby the flavonoids content in the purified extract increased to 94.62%. The antioxidant activities of the purified flavonoids including DPPH radical scavenging activity, ABTS+ radical scavenging activity, reducing power, hydroxyl radical scavenging activity and superoxide anion scavenging activity, were evaluated in vitro, which suggested that the flavonoids showed significant antioxidant activities. Rutin, kaempferol and formononetin were identified in the extract by comparing relative retention times and UV-Vis spectra with those of reference standards.     

Comparison of various techniques for the extraction and determination of antioxidants in plants

The following extraction techniques have been used for extracting antioxidants (apigenin, coumarin, esculetin, umbelliferone, bergapten, quercetin, rutin, scopoletin and xanthotoxin) from plant material: supercritical fluid extraction, pressurized liquid extraction, extraction by means of Soxhlet apparatus, ultrasonic extraction in ultrasonic bath, and by means of ultrasonic probe. The analytical method based on HPLC?UV detection for the determination of selected antioxidants was developed. For all extracts the antioxidant capacity based on the reduction of free 2,2‐diphenyl‐1 ‐picrylhydrazyl radical was also determined. Comparing all results the ultrasonic probe method using 0.75 g of sample extracted by 50 mL of acetonitrile in water (30%, v/v) for 25 min at room temperature and with amplitude at 60% (equal to 90 W) without pulsation was evaluated as the best tool. The most significant indicator demonstrating this statement is the antioxidant capacity expressed as gallic acid equivalent where the ultrasonic probe method showed the best results in 10 of 16 samples. Also the operability of ultrasonic probe extraction method compared to other tested methods is more favorable.     

Optimum Ultrasound Assisted Extraction Conditions of Some Flavonoids from Green Tea Leaves. Control Quality of Green Tea Product by TLC Fingerprinting

The optimization of the green tea flavonoid extraction conditions was investigated. The experiments were carried out with two extraction methods: ultrasound assisted extraction (UAE) and reflux extraction (RE). The parameters that were varied in this study were: the extraction solvent system composition, the type of organic modifier of the extraction mixture, temperature, and time. The highest efficiency was obtained with an extraction mixture of ethanol: water, 80:20, v/v. An extraction performed at temperature of 45°C in 50–60 minutes led to optimum results. Moreover, a new fingerprinting procedure based on thin layer chromatography (TLC) image analysis was employed in order to compare the chemical composition of green tea in comparison with white and black tea.     

Dietary burden of phenolics per serving of "Mountain tea" (Sideritis) from Macedonia and correlation to antioxidant activity

This work was afforded from 2 points of view, phytochemical evaluation and relation to antioxidant activity and dietary burden of phenolics of a cup of "Mountain tea", a drink obtained by domestic infusion of Sideritis. Phytochemically, two extraction protocols using water and methanol as solvent were used for comparison. Methanol and boiling water extracts (by domestic infusion procedure) showed that extracts were rich in bound forms of phenolics such as hydroxycinnamic acids, phenylethanoid glycosides and flavonoid glycosides. The total phenolic content for Sideritis species ranged around 190 mg per serving (2 g infusion bag) for methanol extracts and around 72 mg per serving in water extracts. Among the two different Macedonian Sideritis species, Sideritis raeseri (wild growing) showed the highest phenolics content in both extracts (212 mg and 89 mg per serving, respectively). Concerning the phenolic content in the different aerial parts, leaf was the richest plant organ in phenolics followed by flower and stem with the lowest amount. The methanol extract from Sideritis raeseri (wild growing) showed the highest antioxidant capacity as shown by DPPH, ABTS and FRAP assays. The antioxidant capacity was linearly correlated with phenolic content. Nutritionally, the dietary burden of phenolics of a "Mountain tea" bag for domestic infusion (serving size) was established at 89 mg for an homogeneous and equal distribution of the different aerial parts (leaf, flower and stem). However, and according to our results a rate of 60% leaf and 40% flower would increase the content of bioavailable phenolics and also the total phenolics content of a serving bag of "Mountain tea".     

Colorimetric determination of radical scavenging activity of antioxidants using Fe3O4 magnetic nanoparticles

We report the first use of iron oxide magnetic nanoparticles (Fe₃O₄ MNPs) as a novel, alternative, simple and reliable agents for colorimetric measurement of radical scavenging activity of the antioxidants. In the presence of H₂O₂ and the peroxidase colorimetric substrate, Fe₃O₄ MNPs catalyzed the oxidation of colorless peroxidase substrate to form colorimetric products via the generation of hydroxyl radicals. After adding antioxidants, the catalytic activity of Fe₃O₄ MNPs was inhibited due to scavenging of hydroxyl radicals by the antioxidants, producing less colorimetric products resulting in the reduction of color intensity. Two model antioxidant standards including gallic acid (GA) and epigallocatechin gallate (EGCG) were successfully evaluated for their hydroxyl radical scavenging activity using the developed assay. The performance of the developed method was validated against traditional antioxidant assays for 9 tea samples. Using the Spearman rank correlation coefficient method, the antioxidant activity of tea samples obtained from the Fe₃O₄ MNP assay correlated well with the traditional assays at the 95% confidence level. Furthermore, the developed assay was successfully carried out on a paper-based device to provide for high throughput analysis with low amounts of reagents and sample consumption and low analysis cost for screening of radical scavenging activity of the antioxidants. The results from the analysis of antioxidant activity in tea samples obtained from the Fe₃O₄ MNP paper-based assay were not significantly different to those obtained from the developed Fe₃O₄ MNP spectrophotometric assay indicating that the developed assay was also applicable in a low-cost analysis platform.     

亚临界水萃取及气相色谱-串联质谱法检测红茶中多种农药残留

建立了亚临界水萃取及气相色谱-串联质谱(GC-MS/MS)检测红茶中21种有机氯和拟除虫菊酯农药残留的方法。在萃取压力为5 MPa条件下,样品经150 ℃的亚临界水提取15 min后,将目标物转移至丙酮-正己烷(1:1, v/v)中,经ENVI-Carb固相萃取净化小柱净化,DB-5毛细管气相色谱柱分离,在多反应监测(MRM)模式下进行MS/MS检测,基质匹配溶液内标法定量。各目标物在5.0～320.0 μg/L范围内线性关系良好,相关系数均大于0.99,其定量限(信噪比(S/N)＞10)为50 ng/g,检出限(S/N＞3)为10 ng/g。茶叶基质中添加50、100和200 ng/g的标准品时,21种农药的回收率为70.18%～119.98%,相对标准偏差(RSD)为5.01%～11.76%。该方法的灵敏度、准确度和精密度均符合农药残留测定的技术要求,适用于红茶中有机氯和拟除虫菊酯农药残留的检测。     

Effect of extraction conditions on measured total polyphenol contents and antioxidant and antibacterial activities of black tea

Black tea was extracted for 2, 8 and 18 h with absolute acetone, N,N-dimethyl-formamide (DMF), ethanol and methanol and their 50% aqueous solutions. The extracts were screened for total polyphenol contents, antioxidant and antibacterial activities. The polyphenol content of the extracts was found to be in the range of 0.44-114.01 mg gallic acid equivalents (GAE)/g dry weight tea, depending on the solvent used and the length of the extraction process. In general, aqueous acetone or DMF extracts displayed the highest polyphenol contents and antioxidant activity, while absolute acetone was the least efficient solvent. Antioxidant activities of tea extracts tested using the reducing power and 2,2-diphenyl-1-picryhydrazyl (DPPH) radical methods ranged from 0.09 to 1.18 and from 2.60 to 95.42 %, respectively, depending on the extraction conditions and the antioxidant activities correlated well with the polyphenol concentrations. Aqueous solvent black tea extracts also possessed antibacterial activity, depending on the solvent used and bacterial species tested. Staphylococcus aureus was found to be the most sensitive to all tea extracts, except for the methanol extract. Tea extracts were not effective against Y. enterocolitica, L. monocytogenes and E. coli O157:H7.     

基于香气成分气相色谱-质谱指纹图谱的判别分析和相似度评价用于绿茶等级差异研究

该文以研究指纹图谱在绿茶等级判别方面应用的可行性为目的。以信阳毛尖茶为研究对象，以茶汤香气成分为研究目标，采用顶空固相微萃取与气相色谱-质谱联用技术，筛选其香气特征成分，建立不同等级信阳毛尖茶香气成分GC-MS指纹图谱。发现运用判别分析法可以对2个系列7个等级41个信阳毛尖茶样进行很好的等级区分；通过不同等级色谱指纹图谱的相似度计算发现，相似度与茶样等级之间具有较好的相关性，尤其是对于品质较好的茶样，这种相关性更好。表明运用判别分析法和相似度计算方法能够反映绿茶等级之间的差异性，且基于相似度评价的方法具有客观量化的特征。