茶多酚微球的制备及其抗氧化性能的研究

采用喷雾干燥法,以生物可降解高分子材料羟丙基甲基纤维素邻苯二甲酸酯(HPMCP)为骨架材料,制备茶多酚微球。制备茶多酚微球的最佳条件为：进风温度100℃,进料速度6．25mL/min,芯壁材比为2：1,总固形物含量为3%。茶多酚微球和未包埋的茶多酚有相似的相变峰,说明在微球制备过程中茶多酚未发生变性。茶多酚微球对食用油有较好的抗氧化效果,且随着添加量的增加效果更加明显。     

Use crude olive leaf juice as a natural antioxidant for the stability of sunflower oil during heating

Olive leaves (Kronakii cultivar) were obtained from the annual pruning of olive trees and pressed to obtain a crude juice. Aliquots from the concentrated crude olive leaf juice, representing 400, 800, 1600 and 2400 ppm as polyphenols, were added to sunflower oil. Samples of sunflower oil mixed with olive leaf juice were heated intermittently at 180 ± 5 °C for 5 h day^?1 and the heating process was repeated for five consecutive days. A control experiment was performed where butylated hydroxyl toluene (BHT) at 200 ppm was added to sunflower oil prior to intermittent heating in order to compare the antioxidant efficiency between the natural polyphenolics of olive leaf juice and synthetic antioxidant BHT. Some physical and chemical constants for the unheated and heated sunflower oil were determined. The data indicate that the addition of olive leaf juice to sunflower oil heated at 180 °C induced remarkable antioxidant activity and at 800 ppm level was superior to that of BHT in increasing sunflower oil stability.     

大孔吸附树脂对葵仁多酚的分离富集

针对酸液浸提葵仁后所得的多酚粗提液(主要含3-O-咖啡酰奎尼酸、4-O-咖啡酰奎尼酸和5-O-咖啡酰奎尼酸),研究大孔吸附树脂对其分离富集的工艺条件。考察9种大孔吸附树脂的吸附解吸性能,筛选出XDA-1树脂用于分离纯化。结果表明:经超滤初步纯化后,粗提液纯度可由4%提高到15%;将此超滤液进一步进行树脂吸附,其优化后的吸附工艺条件为进料液多酚浓度2.0mg/mL、pH 3.0、上样流速2BV/h、上样量30倍床体积(BV);吸附结束后,先采用10%(V/V)的乙醇进行部分去杂,然后用50%(V/V)的乙醇以4BV/h的流速进行洗脱收集。经树脂分离纯化后所得的多酚,其回收率为82.3%,纯度由15%提高到77%。联合超滤和大孔吸附树脂分离是一种从葵花籽提取液中回收CQA的高效经济方法。     

Evaluation of the antiradical and reducing properties of selected Greek white wines: correlation with polyphenolic composition

The total hydroxycinnamate (THC) and total flavanol (TF) contents were determined in 26 selected Greek white wines of ‘Appellation of Origin of High Quality’ using well‐established spectrophotometric methodology. Furthermore, two parameters related to the antioxidant capacity of wines, the antiradical activity (A_AR) and the reducing power (P_R), were also determined using the stable DPPH· radical and a ferric reducing power assay respectively. THC content varied from 64.4 to 197.1 mg l^?1 chlorogenic acid equivalents (CGAE), whereas TF content exhibited larger variation, ranging from 3.3 to 205.3 mg l^?1 catechin equivalents (CTE). A_AR and P_R were found to range from 0.47 to 0.60 mM Trolox equivalents (TRE) and from 0.32 to 2.05 mM quercetin equivalents (QE) respectively. Regression analysis at 95% significance level indicated that reducing effects are likely to be exerted by the flavanol fraction (SF < 0.05), as opposed to antiradical efficiency which is primarily affected by the sum of THC and TF contents (SF < 0.05), suggesting that synergistic phenomena account for the overall antioxidant status of white wines. © 2002 Society of Chemical Industry     

表儿茶素没食子酸酯及表没食子儿茶素没食子酸酯单体的化学氧化研究

试验对两种多酚类物质进行化学氧化，并利用高效液相色谱对其氧化产物进行了分析。同时，试验中还对来自表没食子儿茶素没食子酸酶（EGCG）的氧化产物及存在于红茶中的相应产物进行技层析，所流出的高聚合某红素成分在所用介质中的溶解性相对较差，有别于以前类似的研究报道。在相同的氧化体系中，表儿茶素没食子酸酯（ECG）的表现不同于表没食子儿茶素没食子酸酯，表明其在该试验所选定的化学氧化条件下为相对稳定。表没食子儿茶素没食子酸酷氧化产物的高效液相色谱峰十分明显，在对红茶汤的HPLC分析中，大部分色谱峰都可以找到其对应峰。因此，该试验对类黄酮化学的研究提供了一个简便的实验方法。     

冲泡条件对湘西黄金茶生物活性成分及其抗氧化活性的影响

在不同冲泡温度与时间条件下,通过紫外—可见分光光度计测定了黄金茶茶多酚、游离氨基酸的浸出变化规律,建立浸出动力学模型,并通过DPPH法、ABTS法测定茶汤抗氧化性能。结果显示,冲泡温度为60～90℃时,黄金茶茶汤中茶多酚、游离氨基酸含量及DPPH、ABTS清除率随温度升高而增加;冲泡时间为1～30min时,茶汤中的茶多酚、游离氨基酸浓度及DPPH、ABTS清除率随时间延长而增加,30min后趋于稳定。茶多酚、游离氨基酸的浸出遵循二阶动力学反应,温度与浸出速率常数k有良好的线性关系,茶多酚表观活化能为4.312 6×104 J/mol,游离氨基酸表观活化能为1.238 9×104 J/mol。     

Free‐radical scavenging activity of wormwood (Artemisia absinthium L) extracts

In an effort to discover new antioxidant natural compounds, wormwood (Artemisia absinthium L) an aromatic‐bitter herb, was screened. The sequential extraction was realized with five solvents of different polarities (70% methanol, petroleum ether, chloroform, ethyl acetate, n‐butanol). The antioxidative activity was tested by measuring their ability to scavenge stable 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free radical and reactive hydroxyl radical during the Fenton reaction trapped by 5,5‐dimethyl‐1‐pyrroline‐N‐oxide (DMPO), using electron spin resonance (ESR) spectroscopy. Results demonstrated that the antiradical and antioxidative activity depend on the type and concentration of applied extracts and increased in the order ethyl acetate > methanol > n‐butanol > chloroform > petroleum ether > remaining water extracts. The investigation showed that the antiradical activity increased with increasing concentration of all extracts. The high contents of total phenolic compounds (25.6 mg g^?1) and total flavonoids (13.06 mg g^?1) indicated that these compounds contribute to the antiradical and antioxidative activity. In a model system, the formation of o‐semiquinone radicals from quercetin and chlorogenic acid was obtained to prove the mechanism (hydrogen donating and/or one‐electron reduction) of free‐radical scavenging activity. Copyright © 2004 Society of Chemical Industry     

SYNTHESIS AND CHARACTERISATION OF DIMERS OF CATECHIN AND EPICATECHIN

A method of synthesis of ‘dimers’ of catechin and epicatechin is described which gives 50% yields of the pure substances. The structures of the products are confirmed by nuclear magnetic resonance using ¹H and ¹³C resonances and by mass spectrometry. Mass spectrometry using laser impact with (+) ions allows a rapid distinction to be made between the ‘dimers’ derived from catechin or epicatechin.     

Phytic acid and extractable phosphorus of pearl millet flour as affected by natural lactic acid fermentation

Lactic acid fermentation of pearl millet flour decreased its phytic acid content and increased extractable phosphorus. Fermentation at 40 and 50°C for 72 h or longer eliminated phytic acid almost completely; extractable phosphorus was more than doubled. Lower temperatures (20 and 30°C) were less effective. The changes in concentration of phytic acid and extractable phosphorus may be attributed partly to phytase activity inherent in pearl millet flour.     

啤酒大麦、麦芽中多酚类化合物HPLC指纹图谱分析技术研究

以10个进口和8个国产啤酒大麦品种及其相对应的麦芽为样本,采用高效液相色谱（HPLC）建立大麦和麦芽中14种多酚类物质的指纹图谱,并分别进行相似度分析、聚类分析（CA）和主成分分析（PCA）。结果表明,进口大麦样品的相似度（0.938～0.989）高于国产大麦样品（0.911～0.937）,而进口大麦麦芽的相似度（0.892～0.967）普遍低于国产大麦麦芽的相似度（0.956～0.981）;CA（判别距离＜5）结果和PCA结果一致,8个国产大麦和1个进口大麦样品B2聚为一类,8个国产麦芽和3个进口麦芽样品M2、M3、M4聚为一类,说明通过大麦、麦芽多酚类物质的HPLC指纹图谱技术能基本区分国产和进口大麦品质的差异。