Chemo‐enzymatic synthesis and evaluation of novel structured phenolic lipids as potential lipophilic antioxidants

Chemo‐enzymatic synthesis of structured triacylglycerol bearing ferulic acid as a phenolic acid at sn‐1/3 position is described in the present work. Four compounds of varying chain lengths, namely 3‐(4‐hydroxy‐3‐methoxy‐phenyl)‐acrylic acid‐2,3‐bis‐hexanoyloxy‐propyl ester, 3‐(4‐hydroxy‐3‐methoxy‐phenyl)‐acrylic acid‐2,3‐bis‐octanoyloxy‐propyl ester, 3‐(4‐hydroxy‐3‐methoxy‐phenyl)‐acrylic acid‐2,3‐bis‐dodecanoyloxy‐propyl ester, and 3‐(4‐hydroxy‐3‐methoxy‐phenyl)‐acrylic acid‐2,3‐bis‐9‐octadecenoyloxy‐propyl ester were synthesized, and their structures were confirmed by IR, NMR, and MS. Antioxidant activity of the structured phenolic lipids were evaluated using three different in vitro antioxidant assays such as 2, 2‐diphenyl‐1‐picrylhydrazyl free radical (DPPH^•) scavenging, antioxidant potency in lipid matrix using rancimat, and by the rate of inhibition of autoxidation of linoleic acid in micelles. Ferulic acid and dodecylgallate were used as reference antioxidant compounds. DPPH^• assay did not show any improvement in the antioxidant activity of ferulic acid with lipophilic modification. However, the antioxidant potency of the structured phenolic lipids measured by rancimat method as well as by the rate of inhibition of autoxidation of linoleic acid in micelle showed improvement in antioxidant activity compared to ferulic acid. This is probably due to better solubility of the synthesized phenolic lipids in a hydrophobic medium and appropriate anchorage in Tween 20 micelle. The observed activities of the structured phenolic lipids are comparable to dodecyl gallate in rancimat assay, but superior to dodecyl gallate in Tween 20 micellar system.     

电化学诱发羟基自由基降解水中酚类污染物

DMPO（5,5-dimethyl-1-pyrroline-N-oxide）为自旋捕集剂,采用电子自旋共振技术（electron spin resonance spectroscopy,ESR）直接证实了经氟树脂改性的β PbO₂阳极和不锈钢网阴极构成的电化学体系中产生的羟基自由基（·OH）。通过电化学氧化水中含酚类及其前驱体污染物,发现环状结构化合物受电化学产生的羟基自由基攻击而发生开环反应产生易生物降解的有机酸,如反丁烯二酸和草酸,直至完全矿化为CO₂和水分子,苯醌是酚类污染物开环前产生的共同稳态中间体。该类污染物的电化学降解共性规律为电化学氧化技术的工业化应用和提高其处理工艺的经济性提供了理论依据。     

Effect of lipid unsaturation on the antioxidative activity of some phenolic acids

Antioxidative properties ofp-hydroxybenzoic, vanillic, syringic, 3,4-dihydroxybenzoic,p-coumaric, ferulic, sinapic and caffeic acids were studied in the concentration range 0.02–0.20 wt% during autoxidation at 100°C of lard and sunflower oil methyl esters (MEL and MESO, respectively). In both lipid systems, the derivatives of benzoic acid had weaker inhibiting properties than did the corresponding analogues of cinnamic acid. The effectiveness and strength of the antioxidative action were considerably lower in the lipid system MESO, which was rich in linoleic acid and was more easily oxidized. Thep-hydroxybenzoic, vanillic, syringic andp-coumaric acids in this system exercised no inhibiting effect. We established that the molecules of the investigated phenolic acids initiated the chain radical process of autoxidation, and the formed antioxidant radicals propagated the chains as a result of the reaction with the lipid substrate. These reactions proceeded at a higher rate in MESO than in MEL.     

Studies on the enzymatic synthesis of lipophilic derivatives of natural antioxidants

The esterification of some natural antioxidants such as cinnamic acid derivatives and ascorbic acid in non-aqueous media, catalyzed by immobilized lipases from Candida antarctica and Rhizomucor miehei, was investigated. The alcohol chain length affected the rate of esterification of cinnamic acids by both lipases. Higher reaction rates were observed when the esterification was carried out with medium- or long-chain alcohols. The rate also depended on aromatic acid structure. The reactivity of the carboxylic function of the cinnamic acids was affected by electron-donating substituents in the aromatic ring. Higher yields were observed for the esterification of p-hydroxyphenylacetic acid (97%) catalyzed by C. antarctica lipase and for the esterification of cinnamic acid (59%) catalyzed by R. miehei lipase. Candida antarctica lipase was more suitable for producing ascorbic acid fatty esters, catalyzing with a relatively high yield (up to 65% within 24 h) the regioselective esterification of ascorbic acid with various fatty acids in 2-methyl-2-propanol. The reaction rate and yield depended on the fatty acid chain length and on the molar ratio of reactants. All ascorbic acid fatty esters produced by this procedure exhibited a significant antioxidant activity in a micellar substrate composed of linoleic acid.     

Synthesis of macroreticular copolymer beads having various phenolic derivatives immobilized via different bond and their radical scavenging activity

The macroreticular copolymer beads (RCS‐4G) were prepared by suspension copolymerization of chloromethylstyrene (CS) and tetraethyleneglycol dimethacrylate (4G) in water, using cyclohexane as a diluent. Then, the copolymer beads carrying phenolic derivatives immobilized via amide, methylene, or ether bond were prepared by subsequent reactions of RCS‐4G with various phenolic derivatives. The radical scavenging activity against 2,2‐Diphenypicrylhydrazil (DPPH) of the copolymer beads carrying phenolic derivatives immobilized was investigated in toluene. It was found that the copolymer beads had high radical scavenging activity against DPPH. The order of the radical scavenging activity against DPPH of the copolymer beads carrying phenolic derivatives immobilized did not coincide with the order of inhibition activity against the generation of 1,4‐dioxane hydroperoxide. The radical scavenging activity against DPPH of the copolymer beads having phenolic derivatives immobilized via methylene bond or ether bond was higher than that of the copolymer beads having phenolic derivatives immobilized via amide bond. It was found that the radical scavenging activity of the copolymer beads having phenolic derivatives was affected by not only the kind of phenolic derivatives immobilized and bond groups through which phenolic compounds were immobilized, but also the swelling ratio of the copolymer beads in toluene. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4791–4800, 2006     

Are natural antioxidants better – and safer – than synthetic antioxidants?

Antioxidants are necessary in the Western diet as it is rich in polyenoic fatty acids, which are easily oxidized with formation of free radicals that are harmful if present in higher amounts. Consumers prefer natural antioxidants to synthetic antioxidants, mainly for emotional reasons. The common Western daily diet contains about 1 g natural antioxidants even if no natural antioxidants have been added for lipid stabilization. Their main sources are cereals, fruits, vegetables, and beverages. Only a part of the natural antioxidants is absorbed and used as free‐radical scavengers in vivo. Natural antioxidants should be added to food in larger amounts than synthetic antioxidants as they are less active, but the actual activity depends very much on particular conditions and food composition. Nevertheless, the addition of additional antioxidants is still negligible in comparison with the dietary supply of native antioxidants. The safety limits of natural antioxidants are mostly not known, but they are hardly safer than synthetic antioxidants. The best protection would be to replace high‐polyenoic oils in the diet with high‐oleic oils, and to use alternative methods of food protection against autoxidation.     

三白草提取物对自由基的清除作用研究

考察了三白草乙醇提取物经不同溶剂萃取所得的各部分对1,1-二苯基-2-三硝基苯肼(DPPH)自由基、羟基自由基和超氧自由基的清除能力。以2,6-二叔丁基-4-甲基苯酚(BHT)为参考。结果表明,三白草乙醇提取物经不同溶剂萃取所得的各部分对DPPH自由基、羟基自由基和超氧自由基都具有清除能力,且随着提取物浓度的增加,清除能力逐渐增高;其中乙酸乙酯部分对DPPH自由基、羟基自由基和超氧自由基的清除作用最强。     

交联型特辛基酚醛树脂酚羟基间位的溴化改性

以交联型特辛基酚醛树脂为原料进行改性,得到了一种交联型酚羟基间位溴化特辛基酚醛树脂,采用红外光谱（FTIR）、核磁碳谱（NMR）对树脂的结构进行了表征,结果表明成功地在酚羟基的间位上取代上了溴。采用莫尔法滴定反应测定剩余溴含量,计算得到苯环上的溴化率为84.7%。采用凝胶渗透色谱（GPC）对改性前后的酚醛树脂进行表征,结果表明经过溴化改性的酚醛树脂的数均分子量、重均分子量有所降低,分子量分布变窄。根据交联型特辛基酚醛树脂的交联机理,分别对交联型特辛基酚醛树脂、交联型链端溴化特辛基酚醛树脂树脂和交联型酚羟基间位溴化特辛基酚醛树脂交联橡胶的硫化历程和物理力学性能进行测试,结果表明改性后的酚羟基间位溴化特辛基酚醛树脂交联橡胶的硫化程度、硫化速度、力学性能都有明显提升。     

Stabilisation of edible oils with natural antioxidants

Natural antioxidants have recently gained increased interest because of the belief that natural food ingredients are better and safer than synthetic ones. The review presents the results on stabilisation of the main edible oils with different types of natural antioxidants. Sources of natural antioxidants are spices, herbs, teas, oils, seeds, cereals, cocoa shell, grains, fruits, vegetables, enzymes, proteins. Researchers concentrate on ascorbic acid, tocopherols and carotenoids as well as on plant extracts containing various individual antioxidants such as flavonoids (quercetin, kaemferol, myricetin), catechins or phenols (carnosol, rosmanol, rosamaridiphenol) and phenolic acids (carnosic acid, rosmarinic acid). Ascorbyl palmitate is regarded as a 'natural' antioxidant because it is hydrolysed in the body to ascorbic and palmitic acids. Among the herbs of the Lamiaceae family, rosemary has been more extensively studied and its extracts are the first marketed natural antioxidants. Oregano, which belongs to the same family, has gained the interest of many research groups as a potent antioxidant in lipid systems. The review concerns the following main topics: stabilisation of oil with individual natural antioxidants, interaction of antioxidants with synergists, stabilisation of oil with extracts or dry materials from different plant sources (e.g. herbs and spices), stabilisation at frying temperatures and in emulsions.     

Antioxidant effect of naturally occurring furan fatty acids on oxidation of linoleic acid in aqueous dispersion

Naturally occurring furan fatty acids were synthesized and their antioxidant activity has been studied during the oxidation of linoleic acid in the phosphate buffer, pH 6.9, in the dark. The extent of the oxidation was followed both by the accumulation of conjugated diene and by the measurement of the residual amounts of linoleic acid. The tetra-alkylsubstituted furan fatty acids were found to suppress the oxidation. The trialkylsubstituted compound also showed antioxidant activity, being about 50% as effective as the tetra-alkylsubstituted ones. The di-alkylsubstituted one revealed no significant activity. The antioxidant activity of furan fatty acids depended on the number of substituents on the furan ring. Therefore, a tetra-alkylsubstituted furan ring may be necessary for the antioxidant action of furan fatty acids. The tetra-alkylsubstituted furan fatty acids reduced 1,1-diphenyl-2-picrylhydrazyl, reacted with the peroxyl radical generated from the thermal decomposition of a radical initiator, 2,2′-azobis(2-amidinopropane)hydrochloride (AAPH), and also suppressed the AAPH-induced oxidation of linoleic acid, indicating that, by scavenging, the peroxyl radical furan fatty acids inhibit the oxidation.     

Lipophilic and hydrophilic antioxidants,lipid peroxidation inhibition and radical scavenging activity of two Lamiaceae food plants

Medicinal and aromatic plants are highly prized all over the world. According to local cuisine and pharmacopoeias, they used to be important as dietary supplements, providing bioactive compounds. Herein, we describe lipophilic (fatty acids, tocopherols and carotenoids) and hydrophilic (ascorbic acid, sugars and phenolic compounds) antioxidants, lipid peroxidation inhibition and free radical scavenging activity in aerial parts of two Lamiaceae species (Mentha pulegium and Thymus pulegioides). M. pulegium gave the highest antioxidant properties (EC₅₀<0.56 mg/mL), which is in agreement with its highest content in tocopherols, mainly α‐tocopherol (69.54 mg/100 g), ascorbic acid (7.90 mg/100 g), reducing sugars (7.99 g/100 g) and phenolics. The presence of these lipophilic and hydrophilic antioxidants could explain its use as antiseptic, anti‐inflammatory and as food preservative and special sauce. M. pulegium revealed the highest content of fat, α‐linolenic (ω‐3) and linoleic (ω‐6) fatty acids, while T. pulegioides revealed the highest content of carbohydrates (89.35 g/100 g). This could explain its use to improve the nutrition value of rye flour broth or potato based soups.     

羟自由基化学发光体系测定抗坏血酸

研究发现,铁(Ⅲ)与过氧化氢在酸性条件下生成羟自由基(·OH),羟自由基(·OH)和罗丹明6G(Rh6G)混合可以产生微弱的化学发光,抗坏血酸可以增敏其微弱化学发光,结合流动注射技术,建立了一种新的抗坏血酸化学发光分析法.增敏的化学发光强度与2.0×10-6～8.0×10-4 mg/mL范围内的抗坏血酸呈良好线性,检出限为1×10-6 mg/mL(3σ),对5.0×10-5mg/mL的抗坏血酸平行测定11次,其相对标准偏差为3.1%.文章最后对其反应的可能机理进行了探讨.     

Effects of phenolic antioxidants on ultrahigh molecular weight polyethylene/decalin solution

The degradation of ultrahigh molecular weight polyethylene (UHMW‐PE) during its dissolution into decalin is discussed. The stabilization of the solution by three phenolic antioxidants, octadecyl β‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate (1076), tetrakis[methylene‐β‐(3,5‐di‐tert‐butyl‐4‐hydroxyphenyl)propionate]methane (1010), and 1,1,3‐tris(2‐methyl‐4‐hydroxy‐5‐tert‐butylphenyl)butane (CA), and an auxiliary antioxidant, dilaurylthiodipropionate (DLTP) is also discussed. Among the three phenolic antioxidants, 1076 had the greatest effect. The auxiliary antioxidant was effective in stabilizing the solution when combined with one of the three phenolic antioxidants. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2877–2881, 2000     

电导滴定法测定桉木浆中酚羟基和羧基

两相含水有机介质中电导滴定法测定接木浆中酚羟基和羟基的方法是可行的。较好的滴定条件是：滴定介质为丙酮：吡啶：乙醇：水（40：10：1：1,体积比）;样品浓度为2g/L,滴定剂KOH-异丙醇浓度为0．01mol/L。     

水相电位滴定法测定木质素的酚羟基和羧酸基含量

引言木质素是自然界中仅次于纤维素的第二大可再生资源,是人类未来的主要资源来源[1]。以木质素为原料制备新材料和化工原料,逐步替代化石等日趋枯竭的不可再生资源,正成为一种新的发展趋     

对《茜素紫光度法检测H2O2/Co2+产生的羟自由基》一文中自由基清除率计算公式的刍议

提出对《茜素紫光度法检测H2O2／Co^2 产生的羟自由基》一文中自由基清除率计算公式的修改,并探讨公式适应范围。实验发现该文中的公式有疏忽,按原公式计算结果和其他文献对相同物质维生素C清除羟自由基的结果有差异。故对原公式提出修改,并提出有颜色的抗氧化剂适用公式。     

Evaluation of antioxidant capacity of sesamol and free radical scavengers at different heating temperatures

Sesamol is a natural antioxidant found in sesame oil from roasted sesame seeds. Activation energy and antioxidant capacity of sesamol were determined and compared with other free radical scavengers (FRSs) including tert‐butylated‐hydroxyquinone (TBHQ), butylated‐hydroxyanisol (BHA), or α‐tocopherol in a lard model system treated with different heating temperature. Each FRS was added in lard and heated at 90, 120, 150, and 180°C for 48, 24, 8, or 2 h, respectively and antioxidant capacity was evaluated by conjugated dienoic acid (CDA) value, conjugated diene hydroperoxides, p‐anisidine value (p‐AV), and a modified 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) method. Apparent activation energy of sesamol was determined as 12.98 kcal/mol in a lard model system. Antioxidant capacity of sesamol was as good as that of TBHQ and was higher than those of BHA and α‐tocopherol at 90, 120, and 150°C based on CDA, conjugated diene hydroperoxides, and p‐AV assays. The results of a modified DPPH method showed that each FRS showed different distribution of radical scavenging compounds from oxidized lipids (RSOLs) during oxidation. Sesamol may replace synthetic FRSs like TBHQ and BHA in processed foods treated with high temperature. Practical application: Processed foods are frequently treated with high temperature during oven‐drying, roasting, baking, and deep‐fat frying. This study showed that sesamol, one of natural antioxidants, had stronger antioxidant capacities than other synthetic FRSs at the temperature ranges from 90 to 180°C. The results of this study can be applied in food industries producing deep‐fat fried foods including snacks, chips, and French fries to extend the shelf‐life of final foods with high temperature treatment.     

Simultaneous determination of ascorbyl palmitate and nine phenolic antioxidants in vegetable oils and edible fats by HPLC

This study describes an HPLC method for the simultaneous determination of ascorbyl palmitate (AP) and synthetic phenolic antioxidants (SPA) in vegetable oils and edible fats in a single run. To achieve this, citric acid was used in combination with isoascorbic acid for stabilization of AP in standard and sample solutions and for deactivation of oxidizing agents in the HPLC system. SPA and AP were directly extracted from samples with methanol containing 1 mg/mL each of citric acid and isoascorbic acid. HPLC analytical and guard columns were pretreated with 90% methanol/acetonitrile 1∶1 (vol/vol), containing 4 mg/mL each of citric acid and isoascorbic acid, and 10% water at pH 3, for 30 min. Under these conditions, AP was stable for about 7 h at room temperature. The relative SD of repeatability for AP (0.5–3.6%) was comparable to that for SPA (0.3–2.8%). Average recovery from spiked samples was 100% for AP, 98–103% for SPA, and 85% for BHT (up to 90% using double extraction with methanol).     

多级结构羟基硝酸铜纳米酶的制备及其对酚类污染物的降解

漆酶是一种多铜氧化酶,在空气条件下即可催化氧化多胺、多酚类有机物,被认为是水处理及土壤修复领域的绿色催化剂。纳米酶是一种具有酶催化活性的纳米材料,因其具有多功能性、低成本、高稳定性等优点,近年来引起广泛关注。因此,本文以尿素水解过程中产生的异氰酸根离子为模板剂,与Cu(NO₃)₂溶液反应制备具有漆酶活性的多级结构羟基硝酸铜[H-Cu₂(OH)₃NO₃]纳米酶。其催化活性是传统Cu(NO₃)₂与尿素水解法制备的羟基硝酸铜的1.85倍,其最大反应速率是漆酶的1.27倍。H-Cu₂(OH)₃NO₃纳米酶在不同pH、温度、储存时间和盐浓度条件下体现良好的催化稳定性。在重复利用12次后,保持58%的催化活性,体现出良好的重复利用性。而且H-Cu₂(OH)₃NO₃纳米酶具有降解土壤与地下水中常见的2,4-二氯苯酚、对...     

羟基自由基活性氧用于中水处理

羟基自由基在液相中的氧化电势为2.8 V,能够破坏微生物通透性屏障,破坏病原微生物的蛋白质、酶和核酸,导致病原微生物的死亡.在现场进行的中水灭菌实验中,当药剂质量浓度为38.2 g/L,投加量为O.14 kg/t时,大肠杆菌杀灭率可达到99.9%以上.同时,水体中的COD降低50%、NH3-N降低35%.羟基自由基制备原料为空气、水和电解质溶液,在常温常压条件下进行,无三废排放,兼具安全性和环境友好性.实践证明:它是替代氯气消毒的优选消毒品种.