酿酒葡萄皮渣中多酚物质的提取及其对羟基自由基的清除研究

本文以酿酒葡萄皮渣为研究对象,通过单因素试验以及正交试验研究了超声波辅助提取对葡萄皮渣多酚得率的影响,并对工艺条件进行优化,确定了提取葡萄皮渣多酚的最佳工艺参数为:超声时间30 min,温度60℃,料液比1:20(g/mL),超声功率200 W,在该条件下葡萄皮渣多酚得率为6.72 mg/g。并研究了葡萄皮渣多酚粗提物对羟基自由基的清除能力,结果表明:在实验浓度范围内,当添加的葡萄皮渣多酚的质量浓度为0.79 mg/mL时,对羟自由基的清除率可达78.64%。     

木质素结构对其纳米化的影响及木质素纳米颗粒的功能性应用

木质素纳米颗粒结构和形态多样、绿色环保且可生物降解,其功能性开发和利用受到了广泛关注。受原料及生产工艺的影响,木质素结构差异较大,相应地影响了其纳米颗粒形态、尺寸、稳定性和化学性质等。本文综述了近年来木质素纳米颗粒的制备方法及其性能和应用的研究进展,重点介绍了木质素的结构特征对木质素纳米颗粒形态与功能性的影响,探讨了木质素纳米颗粒在增强纳米复合材料、紫外屏蔽材料、生物医学材料及食品包装等方面的应用,为其在高附加值生物基材料方面的开发提供一定参考。     

乳酸菌发酵对茶花粉营养成分及生物活性的影响

为研究茶花粉乳酸菌发酵前后基本营养成分以及生物活性的影响。以茶花粉为原料在嗜热链球菌和植物乳杆菌的共同作用下进行发酵处理后分析测定发酵前后基本营养成分,α-葡萄糖苷酶抑制活性以及清除羟自由基能力的变化。结果表明,乳酸菌发酵茶花粉发酵终点为72 h,发酵茶花粉与未发酵茶花粉相比,还原糖、脂肪含量有所降低,灰分、蛋白质、多酚、黄酮含量分别有不同程度的提高,对α-葡萄糖苷酶的半抑制浓度(IC₅₀)由49.09 mg/mL降低到38.79 mg/mL,并且清除羟自由基能力的半抑制浓度(EC₅₀)由4.49 mg/mL提高到5.78 mg/mL。该研究为茶花粉乳酸菌发酵产物的开发利用提供了实验参考。     

Some observations on the role of oxygen in lubricated wear

The role of oxygen in lubricated wear is discussed. Previous studies have shown that at low concentrations, oxygen can reduce wear, but at higher concentrations, it can increase wear. The situation is complicated by ZDTP antioxidants. The present paper reports experimental work aimed at elucidating the role of hydroperoxides - whether they participate in the formation of wear-resistant oxide films, if they (or peroxy radicals) are the main source of oxygen, and whether ZDTP-hydroperoxide interactions in the wear zone are important in controlling wear.     

Yield of OH radicals in water under heavy ion irradiation. Dependence on mass, specific energy, and elapsed time

Dependence of yields of OH （hydroxyl） radicals on the mass and specific energy of heavy ions and elapsed time after irradiation was investigated, to understand chemical reactions of aqueous solutions. The yields of irradiation products of phenol, super-linearly increased with the incident energy of He, C, and Ne ions ranging from 2 to 18 MeV/u. The yields of the OH radicals were estimated by analyzing the yields of the irradiation products of phenol. The yields of the OH radicals increased with the specific energy for each ion, but decreased both with the mass of each ion at the same specific energy and elapsed time after irradiation.     

Electrochemical production of alkoxy-substituted phenols

The electrochemical oxidation of hydroquinone and substituted hydroquinones has been studied over graphite and platinum electrodes in different alcohol media. The results have shown that good yields of the corresponding alkoxy-substituted phenols can be obtained with high selectivities towards the hydroquinone monoalkyl ether. A mechanism is put forward to explain the formation of the alkoxyphenol through the creation of a quinhydrone complex, formed between the hydroquinone and benzoquinone, which is then attacked by the alcohol acting as a nucleophile.In this study, the effect of sulfuric acid as supporting electrolyte and acid catalyst was compared with that of methanesulfonic acid. It was found that sulfuric acid gave the best yield for different alkoxyphenols. The alcohols under investigation were C₁-C₈, and it was found that the longer the chain length of the alcohol, the slower the tendency to produce alkoxyphenols. Branched alcohols such as secondary and tertiary alcohols showed no reactivity towards the quinhydrone complex. Some of the yields obtained are as follows: 4-methoxyphenol (97%), 4-ethoxyphenol (71.4%) and 4-propoxyphenol (81.1%).     

Antioxidant effects of reduced water produced by electrolysis of sodium chloride solutions

Antioxidant vitamins and enzymes such as superoxide dismutase, catalase and glutathione peroxidase are considered to function as scavengers against reactive oxygen species and to provide protection against reactive oxygen species, including free radicals. Although antioxidants such as L-ascorbic acid, d-catechin and quercetin dehydrate show superoxide dismutation activity, using reduced water produced in the cathode side by electrolysis as a solvent instead of 2 mM NaC1 solution of the same pH level as the reduced water increased the superoxide dismutation activity of these antioxidants. Moreover, neither the reduced water nor its electrolyte solution showed any superoxide dismutation activity by itself. On the other hand, the reduced water was able to decrease hydrogen peroxide levels. It has been found that the behaviour of H₂ in reduced water, which was activated by a platinum electrode, differed from that of H₂ introduced by bubbling of hydrogen gas. The former decreased H₂O₂, whereas the latter did not. These results suggest strongly that the increase in superoxide dismutation activity, with a proton donor such as L-ascorbic acid, is due to an increase in the dissociation activity of water while the scavenging activity for H₂O₂ is due to activated dissolved H₂ in the reduced water.     

Hydroxyl Group Separation Distances in Anti-Freeze Compounds and Their Effects on Ice Nucleation

Since the discovery of biological antifreeze glycoproteins (AFGPs), which can inhibit ice nucleation, there has been considerable interest in understanding their mechanisms and mimicking them in synthetic polymers. In this study, we used molecular dynamics simulations of modified polyvinyl alcohol (PVA) compounds to show that the hydroxyl (OH) group distance is a key factor in whether certain compounds promote or inhibit ice nucleation. A hydroxyl distance smaller than ~2.8 Å but greater than ~7.1 Å in modified PVA (MPVA) compounds was associated with the promotion of ice nucleation, while a hydroxyl group separation distance of approximately ~5.0 Å was correlated with a delay in ice nucleation, owing to changes in the energy of the system. Thus, these results may help explain some of the mechanisms of current known anti-freeze compounds and may have implications for designing new anti-freeze compounds in the future.