Effect of antioxidant oxidation potential in the oxygen radical absorption capacity (ORAC) assay

The “oxygen radical absorption capacity” (ORAC) assay (Ou, B., Hampsch-Woodill, M., Prior, R.L. (2001). Development and validation of an improved oxygen radical absorbance capacity assay using fluorescein as the fluorescent probe. Journal of Agricultural and Food Chemistry 49, 4619–4626) is widely employed to determine antioxidant content of foods and uses fluorescein as a probe for oxidation by peroxyl radicals. Kinetic modeling of the ORAC assay suggests that the lag phase for loss of fluorescence results from equilibrium between antioxidant and fluorescein radicals and the value of the equilibrium constant determines the shape of the lag phase. For an efficient antioxidant this constitutes a “repair” reaction for fluoresceinyl radicals and produces a well defined lag phase. The lag phase becomes less marked with increasing oxidation potential of the antioxidant. Pulse radiolysis confirms that fluoresceinyl radicals are rapidly (k ∼ 10⁹ dm³ mol⁻¹ s⁻¹) reduced by Trolox C, a water soluble vitamin E analogue. ORAC assays of phenols with varying oxidation potentials suggest that it might be employed to obtain an estimate of the redox potential of antioxidants within food materials.     

Production of functional substances from black rice bran by its treatment in subcritical water

Black rice bran was treated by water and subcritical water at temperatures ranging from 20 to 260 °C for 5 min and at 200 and 260 °C for 5-120 min. The bran extracts were analyzed for their radical scavenging activity, protein and carbohydrate contents, molecular-mass distribution, antioxidation activity, emulsifying activity, and emulsion-stabilizing activity. The radical scavenging activity and the protein content of the extract were higher at higher treatment temperature. The carbohydrate content also increased with increasing temperature up to 200 °C, then steeply decreased at the temperatures higher than 200 °C. The bran extracts treated at 260 °C for 5 min exhibited a suppressive activity toward autoxidation of linoleic acid with the increasing the weight ratio of the bran extract to linoleic acid. The bran extracts prepared at 40-200 °C for 5 min showed the emulsifying- and emulsion-stabilizing activities, while the extracts prepared at 220-260 °C were low in the activities.     

氯代烷烃对气相缩合法合成苯基三氯硅烷的影响(英文)

To enhance the process of phenyltrichlorosilane synthesis using gas phase condensation, a series of chloralkanes were introduced. The influence of temperature and chloralkane amount on the synthesis was studied based on the product distribution from a tubular reactor. The promoting effect of chloralkane addition was mainly caused by the chloralkane radicals generated by the dissociation of C–Cl bond. The promoting effect of the chloromethane with more chlorine atoms was better than those with less chlorine atoms. Intermediates detected from the reactions with isoprene and bromobenzene demonstrated that both trichlorosilyl radical and dichlorosilylene existed in the reaction system in the presence of chloralkanes. A detailed reaction scheme was proposed.     

单、双极电凝在腹腔镜下全子宫切除术中的应用

目的探讨单、双极电凝在腹腔镜下全子宫切除术中的可行性及安全性。方法将128例有腹腔镜全子宫切除术指征的患者按随机数字表法分为2组,单双极电凝组和双极电凝组,每组64例。对2组患者的手术时间、术中出血量、并发症、住院时间以及预后情况进行比较。结果单双极电凝组手术时间为（72.64±6.72）min,双极电凝组为（89.12±10.23）min,2组比较差异有统计学意义（P〈0.05）,单双极电凝组术中出血量为（78.70±26.26）mL,双极电凝组为（98.23±27.89）mL,单双极电凝组的术中出血量明显少于双极凝血组（P〈0.01）;2组术中并发症、住院时间、预后情况等比较差异均无统计学意义（均P〉0.05）。结论联合使用单、双极电凝于腹腔镜全子宫切除术是安全、可行的;只要掌握单、双极电凝的操作技巧,手术时间可明显缩短,出血量减少。     

Computer-Assisted Determination of Reaction Parameters for the Simulation of Micropollutant Abatement in Wastewater Ozonation

For the purpose of the simulation of the kinetics of the reaction of ozone with wastewater in a bubble column, the kinetics can be adequately described by two components and their respective rate constants. Ozone uptake and ozone steady states along a bubble column have been determined. A modeling procedure has been developed that allows us to describe this behavior and to simulate the degradation of micropollutants. For fast (diclofenac) and moderately fast (bezafibrate) reacting micropollutants this model describes their measured elimination well.     

富硒灵芝不同提取物清除自由基活性的ESR研究

以不同提取方法制备的富硒灵芝提取物为试样,采用ESR技术比较了富硒灵芝不同提取物清除羟自由基(·OH)和超氧自由基(O-2·)的抗氧化活性及提取物之间抗氧化活性的相互作用,结果表明:富硒灵芝的水提物、醇提物和酶提物均具有清除·OH和O2-·的能力,呈明显的剂量-效应关系,清除率与提取物浓度之间可用对数曲线拟合。3种提取物对·OH的清除能力由强到弱依次为水提物﹥酶提物﹥醇提物;对O-2·的清除能力则依次为醇提物﹥水提物﹥酶提物。所有提取物对O-2·的清除活性均高于对·OH的清除活性。此外,3种提取物之间不存在清除O2-·的协同作用,但可以彼此增强其清除O2-·的活性。在清除·OH作用方面,醇提物与酶提物之间相互抑制,醇提物与水提物之间彼此增强,水提物与酶提物之间则几近相互协同。     

High pressure treatment of dry-cured Iberian ham. Effect on radical formation,lipid oxidation and colour

The effect of high-pressure treatment (200, 400, 600 and 800 MPa) on radical formation in solid samples of dry-cured Iberian ham and in ham slurries was evaluated using the spin-trapping technique and electron spin resonance (ESR) spectroscopy. In addition, hexanal was, as a secondary lipid oxidation product, assessed by gas chromatography. The effect of pressure treatments on ESR signals determined in the spin-trapping assay following pressure treatment in solid samples of dry-cured Iberian ham was not statistically significant. However, the lowest level of pressure applied initiated radical formation and promoted lipid peroxidation, whereas intermediate to high levels of pressure seemed to promote further reaction and disappearance of free radicals. Pressure significantly affected hexanal content in the same way as seen for formation of free radicals. Regarding the slurries prepared from dry-cured ham, pressure significantly increased the tendency of radical formation as seen from the ESR signals and significantly increased the hexanal content. The different pattern between solid ham and ham slurries points toward an initiation mechanism associated with the membrane phospholipids for oxidation. In addition, surface colour (L*, a* and b* values and percent reflectance values) of non-pressurized and pressurized (200–800 MPa) dry-cured Iberian ham samples was assessed. Non-pressurized samples showed a higher lightness than pressurized samples, and redness significantly decreased with pressure treatment.     

A durable and robust Fe–N–C electrocatalyst for oxygen reduction reactions by introducing Ti3C2–TiO2 as radical scavengers

Modern Fe–N–C electrocatalysts are promising as alternatives to expensive Pt-based catalysts for oxygen reduction reactions (ORR). Although the activity of this type of electrocatalyst have been improved over the years, their durability and longevity need critical enhancements for practical applications in fuel cells. Typically, the incomplete oxygen reduction inevitably generates reactive oxygen species, including ·OH and HO₂· radicals, which will fiercely attack the carbon support and directly damage active sites in Fe–N–C electrocatalysts. Herein, a durable and robust Fe–N–C@Ti₃C₂–TiO₂ electrocatalyst for high-efficiency ORR is synthesized, in which Ti₃C₂–TiO₂ could effectively scavenge ·OH radicals or decompose H₂O₂ molecules, and synergistically work with Fe–N–C catalysts to improve the durability. Consequently, the Fe–N–C@Ti₃C₂–TiO₂ electrocatalyst shows prominent ORR performance in both alkaline and acidic electrolytes, low H₂O₂ yield, and long-term stability. This work provides great prospects for the design of highly stable ORR electrocatalysts by introducing radical scavengers as an active defense to proactively eliminate H₂O₂ and its radicals.     

Ozone/electron beam process for water treatment: Design,limitations and economic considerations

Electron beam irradiation of water is technically the easiest way to generate OH free radicals but the efficiency of the irradiation process as an advanced oxidation process (AOP) is deteriorated by reducing species formed simultaneously with the OH free radicals. Addition of ozone to the water before or during irradiation improves the efficiency by converting the reducing species into OH free radicals and turning the irradiation process into a full AOP. The main reaction pathways of the primary species formed by the action of ionizing radiation on water in a natural groundwater with and without the presence of ozone are reviewed. Based on these data an explanation of both the dose rate effect and the ozone effect is attempted. New data are presented which illustrate the effect of alkalinity on the way in which ozone is introduced into the water, and the impact of both water matrix and chemical structure of the pollutants to the efficacy of the ozone/electron beam process.