Solid-state NMR study of N labelled polyaniline upon reaction with DPPH

The quantitative investigation of the radical scavenging properties of polyaniline (PANI) upon reaction with excess of the stable DPPH radical (a 4:1 ratio of DPPH to aniline units in the polymer) was carried out using ¹⁵N and ¹³C solid state NMR spectroscopy. During the process the polyaniline was oxidised so that the imine content increased from 45 to 65%. The extent of oxidation measured by NMR was confirmed by N1s XPS analysis. However, within a 30 min reaction time, about 85% of the DPPH radicals were scavenged as monitored by the decay in its EPR signal. This is about 20 times greater than the fraction of DPPH required to oxidize PANI from an imine content of 45-65%. An identification of further redox processes is required to explain the high degree of radical scavenging. At the same time, there was no evidence of significant chemical binding or trapping of DPPH in the PANI structure.     

Radical scavenging activity of canola hull phenolics

Possible use of canola hulls as a source of natural anti-oxidants was explored. Cyclone canola hulls were extracted with methanol (30 to 80%, vol/vol) and acetone (30 to 80%, vol/vol). The free radical-scavenging activity of phenolic extracts so prepared was evaluated using the 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical ion (ABTS^o−), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and chemiluminescence assays. The total content of phenolics in prepared extracts from canola hulls ranged from 15 to 136 mg sinapic acid equivalents per gram of extract. Higher levels of condensed tannins were detected in the acetone extracts than in the corresponding methanolic counterparts. Seventy and 80% (vol/vol) acetone extracts displayed markedly stronger antioxidant activity than any of the other extracts investigated. Statistically significant linear correlations were found between TEAC (Trolox equivalent antioxidant capacity) values (expressed in mM of Trolox equivalents per gram of extract) and total pehnolics, TEAC and total condensed tannins (i.e., determined using the modified vanillin and pronthocyanidin assays), as well as TEAC and protein precipitation activity of phenolic extracts (i.e., measured using the dye-labeled assay). The antioxidant activities of extracts as determined by the ABTS^o− radical ion assay correlated highly with those of the chemiluminescence and DPPH radical assays.     

超声引发聚苯乙烯磺酸钠的降解

用低功率、高频率的超声波对水溶液中的聚苯乙烯磺酸钠进行降解,研究溶液浓度、pH值等对降解反应的影响,用凝胶色谱法测定降解产物的分子量及其分布,用红外光谱法以及紫外分光光度法表征了降解过程中的产物结构变化,用2,2-二苯基-1-苦肼基(DPPH)对降解过程中产生的自由基进行捕捉,证实降解反应经历了自由基历程。     

用二苯代苦味酰基自由基分光光度法测定川芎、红景天和黄芪的抗氧化活性

用乙醇提取川芎、红景天和黄芪三种中药中的抗氧化物质,并采用DPPH法测定各种中药提取液的抗氧化性,并同特丁基对苯二酚(TBHQ)、维生素E进行比较。结果表明,川芎提取液、红景天提取液和黄芪提取液对DPPH·有很好的清除作用,TBHQ、维生素E、川芎提取液、红景天提取液和黄芪提取液的IC50分别为5.2×10-6g/mL、4.5×10-3g/mL、4.5×10-4g/mL、7.8×10-5g/mL和3.1×10-3g/mL,其清除能力的大小依次为:TBHQ>红景天提取液>川芎提取液>黄芪提取液>维生素E。     

不同烹调方法对蔬菜抗氧化活性的影响

为了检测不同烹调方法对蔬菜抗氧化活性的影响,选择扬州市场上的8种蔬菜,分别进行爆炒、炖煮和微波加热处理,用二苯代苦味肼基自由基（DPPH·）法测定它们的抗氧化活性,并与新鲜蔬菜的抗氧化活性进行比较。结果表明：不同烹调方法对蔬菜的抗氧化活性的影响不同,8种蔬菜的抗氧化能力经炖煮处理后全部明显下降,但绝大多数蔬菜经微波或爆炒后有所提高,其中,花菜、韭菜、冬笋、紫甘蓝经微波加热后的抗氧化活性都增加10％左右。     

酶解法制备禾虫多肽液的工艺优化及其脱腥工艺探究

目的 应用单因素和响应面实验优化禾虫的酶解工艺,结合模糊数学法探究一种有效的脱腥方法。方法 以中性蛋白酶为酶解剂,禾虫为主要原料,研究液料比、酶用量、时间、温度、pH对酶解效果的影响。在单因素实验的基础上,以液料比、酶解温度、酶用量为自变量,禾虫多肽液的1,1-二苯基-2-三硝基苯肼（1,1-diphenyl-2-picrylhydrazyl,DPPH）自由基清除率为响应值,通过Box-Behnken响应面法分析不同因素对酶解效果的影响,确定酶解的最优组合,并应用美拉德反应、硅藻土和酵母粉对禾虫多肽液进行脱腥实验,模糊数学法评价3种脱腥处理的效果。结果 根据响应面实验得出禾虫的最佳酶解组合为：液料比1:1 (g/mL)、酶解温度60℃、中性蛋白酶用量2450 U/g,得到酶解液的DPPH自由基清除率47.25%±0.11%;禾虫多肽液脱腥的最佳处理为：酵母粉添加量0.7%,反应温度35℃,反应时间30 min。结论 中性蛋白酶酶解禾虫制备禾虫多肽液并采用酵母粉脱腥效果最佳,为禾虫的精深加工提供借鉴,促进禾虫产业的发展。     

Solvent and Extraction Conditions Control the Assayable Phenolic Content and Antioxidant Activities of Seeds of Black Beans,Canola and Millet

The effects of extraction solvent and conditions on the total phenolic content (TPC) and antioxidant activity of black beans, canola and foxtail millet were investigated. The antioxidant activity was assayed using 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging activity (DRSA) and oxygen radical absorbance capacity (ORAC). Four solvent systems, namely 70 % acetone, 80 % ethanol, 80 % methanol and a mixture of acetone/methanol/water (7:7:6, v/v/v) were used. The extraction methods adopted in this study included refluxing, homogenization, cold extraction and sonication. The TPC as measured using the Folin Ciocalteu's method were 12.35–28.39, 2.43–16.73, and 1.78–5.06 µmol catechin equivalents/g dry matter (dm) for canola, black beans and foxtail millet, respectively. Aqueous acetone afforded the highest TPC for black beans and canola. Within the same solvent system used, the TPC, DRSA and ORAC obtained from different extraction techniques differed for black beans, canola and foxtail millet. The results demonstrated that the solvent system as well as method influenced the extraction of phenolic compounds and their antioxidant activities, depending on the type of matrix in which phenolics were embedded.     

Formation and antioxidant activity of volatile compounds produced by heating glucose with tyrosine/histidine in water-ethanol and water-glycerol media

Volatile compounds prepared by heating glucose-tyrosine and glucose-histidine models in water-ethanol and water-glycerol media were studied under different water contents (0%, 25%, 50%, 75%, 100%, v/v). Aliphatic compounds, cyclopentenones, pyrazines, furans, furanones and pyrones were identified by GC–MS and analysed by factor analysis which showed that the presence of ethanol or glycerol in water could result in the increase of most volatile compounds in the Maillard reaction with the higher amount of volatile compounds formed in water-ethanol media, especially in the 50% ethanol medium. The measurement of antioxidant activity revealed that volatile MRPs prepared in water-ethanol media showed greater DPPH radical scavenging activity than those in water-glycerol media with the maximal DPPH radical scavenging activity observed in 100% ethanol medium for the glucose-tyrosine model and in 75% ethanol medium for the glucose-histidine model. Hence, water-ethanol medium could be used to promote the formation of volatile compounds, especially those with antioxidant activity.     

芸豆蛋白酶解工艺的研究

以芸豆蛋白为原料研究芸豆抗氧化活性肽的酶解工艺。首先以DPPH.清除率和水解度为评价指标筛选最适用酶,并采用单因素及正交实验设计优化酶解工艺。结果表明,Alcalase碱性蛋白酶对芸豆蛋白水解能力最强,酶解产物的抗氧化能力最高;最佳酶解工艺条件为底物浓度4.0%,温度55℃,加酶量2000u.g-1,pH9.0,时间6h,该条件下水解度和DPPH.清除率分别为16.16%和74.10%,比优化前分别提高4.95%和7.63%;芸豆活性肽显示出较强的抗氧化活性。     

黑龙江产芫荽籽精油成分及其清除DPPH自由基能力研究

用水蒸气蒸馏法提取黑龙江产芫荽籽,以0.50%的产率获得精油。用GC-MS联机对精油进行了成分分析,检测出31个成分,解析鉴定了占精油99.726%的29个成分。主要成分芳樟醇占总精油含量的73.614%。该精油对DPPH(1,1-Diphenyl-2-picrylhydrazyl)自由基的清除率为94%。水蒸气蒸馏后残渣的甲醇萃取物对DPPH的最大清除率为91%。