Degradation of Phenolic Compounds in Aqueous Sucrose Solutions by Ozonation

The sugar industry is concerned with color formation due to the oxidation of phenolic compounds in the presence of carbohydrates. In this study, we investigated the ozonation of a mixture of five phenolic compounds in water and aqueous sucrose solution: p-coumaric (p-COU), caffeic (CAF), syringic (SYR), and chlorogenic (CHO) acids, as well as the flavonoid quercetin (QUE). The experiments were carried out in a 3-L glass reactor with magnetic stirring and a diffuser plate at the bottom to feed the ozone-oxygen gas mixture. Initial solution concentrations of 5 mg L?1 of each acid, 15 mg L?1 of quercetin, and 40 g L?1 of sucrose were used. The degradation of phenolic compounds followed apparent first-order kinetics, with rate constants and percent removals decreasing in the presence of sucrose. In water, average consumed ozone dosages of 10.4 and 18.7 mg L?1 were necessary for 50% and 90% removals, respectively, for CHO, CAF, and p-COU; for QUE they were slightly higher (13.9 and 20.5 mg L?1, respectively). At a consumed dosage of 20.8 mg O3 L?1, more than 99% removal was obtained for CHO, CAF, and p-COU, while 96.2% was achieved for SYR. In contrast, QUE revealed to be more recalcitrant during ozonation in the absence of sucrose, with only 70% removal at the highest consumed O3 dosage. The consumed ozone dosages for 50% and 90% removals were higher for CHO, CAF, and p-COU in aqueous sucrose solution, which may impact ozone consumption during real sugarcane juice treatment. Sucrose and t-butanol were the main influential parameters that significantly affected the total amount of phenolic compounds degraded.     

Protein Folding and Aggregation into Amyloid: The Interference by Natural Phenolic Compounds

Amyloid aggregation is a hallmark of several degenerative diseases affecting the brain or peripheral tissues, whose intermediates (oligomers, protofibrils) and final mature fibrils display different toxicity. Consequently, compounds counteracting amyloid aggregation have been investigated for their ability (i) to stabilize toxic amyloid precursors; (ii) to prevent the growth of toxic oligomers or speed that of fibrils; (iii) to inhibit fibril growth and deposition; (iv) to disassemble preformed fibrils; and (v) to favor amyloid clearance. Natural phenols, a wide panel of plant molecules, are one of the most actively investigated categories of potential amyloid inhibitors. They are considered responsible for the beneficial effects of several traditional diets being present in green tea, extra virgin olive oil, red wine, spices, berries and aromatic herbs. Accordingly, it has been proposed that some natural phenols could be exploited to prevent and to treat amyloid diseases, and recent studies have provided significant information on their ability to inhibit peptide/protein aggregation in various ways and to stimulate cell defenses, leading to identify shared or specific mechanisms. In the first part of this review, we will overview the significance and mechanisms of amyloid aggregation and aggregate toxicity; then, we will summarize the recent achievements on protection against amyloid diseases by many natural phenols.     

焦化柴油中酚类化合物的分离分析

采用碱液抽提法对四种不同产地的焦化柴油中的酸性物进行了分析。气相色谱-质谱联用(GC-MS)分析结果表明,酸性物中含有微量的小分子硫醇和硫醚,酚类化合物占90%以上,同时还含有少量的苯硫酚衍生物。对比分析结果表明,延迟焦化原料渣油中硫含量越高,对应的焦化柴油中苯硫酚衍生物含量越高。针对从辽阳石化焦化柴油中提取的酸性物,对其在300℃之前进行常压蒸馏切割成5个不同馏分段,对每一个馏分段逐一进行GC-MS分析,总计鉴定出38种物质,其中小分子硫醇和硫醚7种,苯酚衍生物24种,萘酚衍生物6种。焦化柴油中酚类化合物来源与减压渣油中含氧量以及烷基芳基醚含氧结构有关。     

酚醛模塑料在汽车轻量化中的应用

简要概括了汽车轻量化技术发展状况及其实现方法,介绍了酚醛模塑料及其成型工艺。同时详细讨论了酚醛模塑料在汽车刹车系统和发动机等部件中的应用以及酚醛模塑料在汽车应用中存在的问题。     

Antioxidant Properties of Phenolic Lignin Model Compounds

Antioxidant activities of phenolic lignin model compounds were determined by measurements of inhibition rate constants (k_inh) during inhibited peroxidation of styrene in chlorobenzene initiated by azobisisobutyrylnitrile with known rates of initiation (R_i). The number of peroxyl radicals trapped by each antioxidant, the stoichiometric factors (n), were determined by comparison with pentamethyl-hydroxychroman, PMHC, n = 2. Monomeric lignin models, 4-propylguaiacol (1), eugenol (2), isoeugenol (3), coniferyl alcohol (4), coniferyl aldehyde (5), and 4-allyl-2,6-dimethoxyphenol (6) were all more active antioxidants than the commercial inhibitor 2,6-di-tert-butyl-4-methylphenol (BHT). Two dimer models, bis(2-hydroxy-3-methoxyl-5-allylphenyl)methane (7) and 2,2′-dihydroxy-3,3′-dimethoxy-5,5′-dimethoxymethylbiphenyl (8) and a synthetic tetramer, bis[2-hydroxy-5-(2′-hydroxy-3′-methoxy-5′-methylbenzyl)-3-methoxyphenyl]methane (9) were more active antioxidants. The overall relative activity was tetramer > dimers > monomers > BHT. The stoichiometric factors of 1 to 6 ranged from 1.6 to 1.7 compared to PMHC. The n factors for 7, 8, and 9, showed an additive effect per phenolic hydroxyl. Phenolic groups in lignin may protect lignin-containing pulps and paper against damaging free radical peroxidation.     

Microwave-Assisted Extraction of Phenolic Compounds from Caper

In this study, it was aimed to extract phenolic compounds from caper by using microwave and to compare the results with conventional extraction. For microwave-assisted extraction, power, extraction time, solid to solvent ratio, and solvent type were selected as independent variables. Dependent variables were total phenolic content (TPC), antioxidant activity, and concentration of phenolic compounds. The increase in solvent amount increased TPC. The highest TPC was obtained by using extraction conditions of 5 min at 400 W, solid to solvent ratio of 1:30, and ethanol-water mixture at a ratio of 50:50. There was no significant difference between microwave and conventional extraction on TPC and antioxidant activity (AA). However, microwave-assisted extraction decreased extraction time significantly.     

Perstraction of Phenolic Compounds from Aqueous Solution Using a Nonporous Membrane

Abstract

An exploratory study of nondispersive extraction of various phenolic solutes using a nonporous membrane has been carried out. Sorption and permeation data for these solutes have been obtained using a silicone rubber membrane. The effects of hydrodynamic factors, concentration of phenols, and temperature on the trans-membrane flux are discussed. A film model is used to determine the intrinsic mass transfer characteristics of the membrane. Comparison of sorption of phenolic solutes from the membrane into the organic solvent indicates that methyl isobutyl ketone is a better solvent than butyl acetate.     

Antioxidative and Bactericidal Properties of Phenolic Compounds in Rapeseeds

Antioxidative and bactericidal properties were investigated in isolated and fractionated phenolic compounds of rapeseeds. Among the investigated groups of compounds (phenolic acids, sinapine and the products of its hydrolysis) phenolic acids, and especially sinapic acid, were found to be the most active. Due to valuable properties of these compounds they can be considered to be applied for food and fodder preserving.     

Variation in Phenolic Compounds within a Birch (Betula pendula) Population

In previous studies, the qualitative and quantitative variation found in defense chemistry among birch populations and even among individual clones has been considerable. However, information about variation among adult, naturally regenerated birch trees from natural populations is still lacking. In this study, the phenolic composition of leaves of 30 naturally regenerated 20-year-old birch (Betula pendula) trees was analyzed for two successive years in order to characterize the chemical composition of individual trees, analyze the annual variation, and determine chemical similarities among individual trees within a population. The main phenolic compounds were flavonoid glycosides, myricetin, and quercetin derivatives. Annual variation in concentration among leaves was large. In most trees, concentrations were markedly higher in 1998 than in 1997; for certain compounds, the detected increase was as much as a 50%. However, for some individual trees, there were no differences between years in chemical quantity. Thus, when selection or grouping of trees is based on secondary chemistry, quantitative variation should be considered carefully. With the qualitative UPGMA method of classification, four chemotypes were found. The grouping was similar for both years, and qualitatively the results of an individual tree seem to be independent of sampling year. The stability in chemical profile of individual trees suggests that quality is tightly controlled by genotype, which provides a recognition tool for chemotaxonomy. The high within-population variation found in leaf defense chemistry may provide protection against different types of insects (generalists or specialists) and, thus, have positive effects on population survival.     

A New Method for Nitration of Phenolic Compounds

Phenolic compounds can be nitrated by 65% nitric acid in the presence of catalytic amounts of montmorillonite KSF and bismuth(III) nitrate to give the corresponding nitrated products in good yields in a heterogeneous phase. The co‐catalyst of KSF and Bi(NO₃)₃ can be easily recovered and reused in the next batch of nitration.     

用酚类化合物提高漆酶的稳定性(译文)

包括木素磺酸盐在内的多种酚类化合物，都能够提高漆酶（EC1．10．3．2）的存储稳定性。其中效果最为明显的是间苯三酚和3，5-二羟基安息香酸等酚类化合物。这些具有代表性的漆酶底物因具有相对较高的氧化还原电势而不易被氧化，并且在一定测试时间内不会从溶液中沉淀析出。杀菌也能够提高漆酶的稳定性，但作用效果不如酚类化合物显著。因此，我们可以得出结论：防止微生物降解并不是提高漆酶稳定性的唯一途径。     

化学法降解木质素为酚类化合物的研究进展

木质素是一种具有潜在巨大应用前景的可再生资源,其降解的酚类化合物产物是可替代部分仅依靠石油能源为主要来源的化工原料,故可缓解一定的石油能源压力。主要从化学法降解木质素的方法和防止降解物重聚两个角度综述木质素降解的研究现状,总结木质素降解存在的主要问题及对其未来的发展提出了展望。     

Characterisation of Phenolic Compounds in Oils Produced from Frosted Olives

Frost is one of the most important weather related hazards for the Australian olive industry and it has caused significant economic losses during the last decade. Its impact on oil quality was significant in 2006 with more than 20% of Australian oil of that year being affected to some degree. Early frosts will normally affect the fruit leading to significant changes in the chemical and organoleptic characteristics of the oils. The aim of this work was to study the effect of freeze damage on the phenolic composition and quality parameters of oils from three different varieties: Frantoio, Barnea and Picual. Quality chemical parameters showed significant differences in oils produced from fruit that was frozen for 2 and 4 weeks. Those chemical parameters were not significantly different in the oil produced from fruit immediately after being frosted. Nonetheless, the sensorial profile and the polyphenols showed significant changes even with oils produced within a short time after the freezing event. Those changes became more evident with the oils produced at increasing time from the moment of fruit freezing.     

奶粉中苯酚类污染物残留量检测方法研究

建立气相色谱法检测奶粉中苯酚类污染物残留的分析方法,样品经过酸性水溶液提取,采用正己烷萃取,碳酸钾溶液反萃取,乙酸酐衍生,GC-ECD法同时检测,外标法定量,阳性样品采用GC/MS确证,方法回收率为75.8%~93.5%,RSD为2.61%~4.88%,方法检测限为:0.8~.3.0μg/kg。     

Acrylamides as Phenolic Antioxidants for Acrylqnitrile-Butadiene Rubber Compounds

A number of phenolic antioxidants were prepared using the reaction between acridly chloride and o-, m-, and p-amino phenols. These antioxidants were used in acrylonitrile-butadiene rubber compounds to achieve better products for various sealing applications. Several techniques were used to evaluate the prepared antioxidants and the processed rubber compounds.     

高效液相色谱法测定酚类化合物

高效液相色谱法（HPLC）测定了饮用水和地面水中的酚类污染物。水样前处理用固相萃取法,经过比较,选择了回收率较高的小柱,用紫外分光光度检测器测定了方法的精密度、准确度和检出限。方法具有重现性好、选择性好、灵敏度高、操作简便的优点。