Synthesis of copolymer beads with various phenolic derivatives attached via different linkages and their antioxidation activity

Macroporous copolymer beads with various phenolic derivatives introduced via three types of linkages—amide, methylene, and ether—were prepared from chloromethyl styrene/tetra(ethylene glycol) dimethacrylate copolymer beads. The antioxidation activity of these phenolic copolymer beads was investigated by the measurement of the inhibition activity against the hydroperoxidation of 1,4-dioxane. The phenolic copolymer beads with the dihydroxybenzene moiety exhibited the highest antioxidation activity, and the antioxidation activity of methylene- or ether-linked phenolic copolymer beads was higher than that of amide-linked copolymer beads. Thus, the antioxidation activity of the phenolic copolymer beads was affected by not only the kinds of phenolic moieties attached but also the type of linkage group. In addition, the swelling of the copolymer beads in an organic solvent was greatly affected by the linkage type of the phenolic copolymer beads. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis of chloromethylstyrene‐tetraethyleneglycol dimethacrylate copolymer beads having various phenolic derivatives immobilized via amide bond and their antioxidation activity

Resins having phenolic derivatives were prepared by treating a resin (RAS‐4G), having benzylamino groups, with benzoic acids containing phenolic hydroxyl groups. The RAS‐4G was prepared by treating macroreticular chloromethylstyrene‐tetraethyleneglycol dimethacrylate (4G) copolymer beads with potassium phthalimide in N,N‐dimethylformamide, followed by reflux in an ethanol/hydrazine monohydrate mixture. 4‐Hydroxy benzoic acid, (2,4‐, 3,4‐, and 3,5‐)dihydroxy benzoic acids, 3,4,5‐trihydroxy benzoic acid, etc., were used as benzoic acids with phenolic hydroxyl groups. The antioxidation ability of the resins having phenolic derivatives was investigated against the generation of 1,4‐dioxane hydroperoxide. The resins showed high inhibition ability against the generation of hydroperoxide. In particular, the resin (RAS‐4G‐3,4‐DHBA) having two phenolic hydroxyl groups had the highest inhibition ability. The resins were found to act as radical scavengers during the generation of 1,4‐dioxane hydroperoxide by UV irradiation in the presence of oxygen. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2097–2104, 2005     

Synthesis of thermosensitive copolymer beads containing pyridinium groups and their antibacterial activity

Thermosensitive 4VP‐NIPAAm‐4G copolymer beads containing pyridyl groups were first prepared by suspension copolymerization of 4‐vinylpyridine (4VP), N‐isopropylacrylamide(NIPAAm), and tetraethylene glycol dimethacrylate (4G; crosslinking reagent) in a saturated Na₂SO₄ aqueous solution in the presence of surfactant and MgCO₃ as dispersants. Then the copolymer beads containing pyridinium groups were obtained by the quaternization of the copolymer beads with various alkyl iodides (CH₃I, C₄H₉I, C₈H₁₇I) in N,N‐dimethylformamide. The 4VP‐NIPAAm‐4G (15 : 97 : 3) copolymer bead and the 4VP‐NIPAAm‐4G copolymer beads quaternized with butyl iodide exhibited high thermosensitivity in water, although the 4VP‐NIPAAm‐4G copolymer beads quaternized with methyl iodide or octyl iodide hardly exhibited thermosensitivity. All the quaternized copolymer beads exhibited antibacterial activity against Escherichia coli (E. coli), although the 4VP‐NIPAAm‐4G copolymer bead did not. In particular, the copolymer bead quaternized with butyl iodide exhibited the highest antibacterial activity against E. coli at 30°C. It was also found that the antibacterial activity of the quaternized 4VP‐NIPAAm‐4G copolymer beads was greatly affected by not only chain length of alkyl groups in alkyl iodides, with which the 4VP‐NIPAAm‐4G copolymer beads were quaternized, but also by temperature of the solutions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation of resins containing phenol derivatives from chloromethylstyrene-tetraethyleneglycol dimethacrylate copolymer beads and antibacterial activity of resins

Copolymer beads (RCCS-4G) with many chloromethyl groups were prepared by treating macroreticular chloromethylstyrene-tetraethyleneglycol dimethacrylate (4G) copolymer beads with chloromethylether. Copolymer beads (RAAS-4G) with benzylamino groups were prepared by treating RCCS-4G with potassium phthalimide. Then the copolymer beads containing phenol derivatives were prepared by treating RAAS-4G with p-hydroxybenzoic acid (pHBA), 2,4-dihydroxybenzoic acid (DHBA), and 3,4,5-trihydroxybenzoic acid (gallic acid, GA) in N,N-dimethylformamide. The antibacterial activity of the obtained resins was examined against Escherichia coli and Staphylococcus aureus. Resins containing phenolic hydroxy groups of 2.3–7.7 mequiv/g were obtained. Antibacterial activity of the resins containing various phenol derivatives against E. coli or S. aureus increased in the order of RAAS-4G-GA > RAAS-4G-DHBA > RAAS-4G-pHBA. The resins containing phenol derivatives exhibited higher antibacterial activity against E. coli than against S. aureus and high activity even against bacteria in NaCl solution. Scanning electron micrographs showed that high antibacterial activity was brought about by the phenolic hydroxyl groups in the resin. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1621–1630, 1997     

7种茶氨酸类似物的合成及清除自由基活性

以L-谷氨酸为起始原料,经邻苯二甲酸酐保护、酰化开环、肼解脱保护等反应合成了7种茶氨酸类似物,结构经EA、IR、1HNMR、13CNMR和MS进行了确认,并测定了其清除DPPH自由基和羟自由基活性。结果表明:2-氨基-5-氧代-5-[(4-羟基苯基)氨基]戊酸清除自由基活性最强,0.002 mol/L时清除DPPH自由基率为90%,0.004 mol/L时清除羟自由基率达95%;2-氨基-5-氧代-5-[(4-氨基苯基)氨基]戊酸次之。由此可见,茶氨酸类似物中5位连有苯基或所连苯基对位有供电子基团时,可提高其清除DPPH自由基和羟自由基活性,且随对位所连基团供电性的提高,清除活性增强。     

多乙烯多胺桥联受阻酚类抗氧剂的合成及其清除DPPH·性能

以二乙烯三胺和三乙烯四胺为桥联基，β-(3,5-二叔丁基-4-羟基苯基)丙酰氯为抗氧化功能基团，通过酰胺化缩合反应合成了两类具有不同对位桥联基团的受阻酚类抗氧剂。采用傅里叶红外光谱和核磁共振氢谱证实了合成的多乙烯多胺桥联受阻酚类抗氧剂的化学结构。DPPH法研究了多乙烯多胺桥联受阻酚类抗氧剂清除自由基的性能，并探索了酚羟基个数和对位桥联基结构对受阻酚类抗氧剂清除自由基性能的影响。结果表明，多乙烯多胺桥联受阻酚类抗氧剂具有良好的清除DPPH·能力，且随着抗氧剂分子中酚羟基个数的增加，清除DPPH·的活性增加，分子中含有4个酚羟基的三乙烯四胺受阻酚类抗氧剂的抗氧化效率（AE）达到2.65×10^-2 L/(mol·s)。对位桥联基结构对受阻酚类抗氧剂清除DPPH·能力有较大影响，季戊四醇为桥联基的受阻酚类抗氧剂1010清除DPPH·能力最强，其抗氧化效率（AE）为3.08×10^-2L/(mol·s)；乙二胺为核的1.0代树枝状受阻酚类抗氧剂清除DPPH·能力最弱，其抗氧化效率（AE）为2.60×10^-2 L/(mol·s)。     

Radical Scavenging Activity of Lipophilized Products from Lipase-Catalyzed Transesterification of Triolein with Cinnamic and Ferulic Acids

Lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids using an immobilized lipase from Candida antarctica (E.C. 3.1.1.3) was conducted to evaluate the antioxidant activity of the lipophilized products as model systems for enhanced protection of unsaturated oil. The lipophilized products were identified using ESI-MS. Free radical scavenging activity was determined using the DPPH radical method. The polarity of the solvents proved important in determining the radical scavenging activity of the substrates. Ferulic acid showed much higher radical scavenging activity than cinnamic acid, which has limited activity. The esterification of cinnamic acid and ferulic acid with triolein resulted in significant increase and decrease in the radical scavenging activity, respectively. These opposite effects were due to the effect of addition of electron-donating alkyl groups on the predominant mechanism of reaction (hydrogen atom transfer or electron transfer) of a species with DPPH. The effect of esterification of cinnamic acid was confirmed using ethyl cinnamate which greatly enhances the radical scavenging activity. Although, compared to the lipophilized cinnamic acid product, the activity was lower. The radical scavenging activity of the main component isolated from lipophilized cinnamic acid product using solid phase extraction, monocinnamoyl dioleoyl glycerol, was as good as the unseparated mixture of lipophilized product. Based on the ratio of a substrate to DPPH concentration, lipophilized ferulic acid was a much more efficient radical scavenger than lipophilized cinnamic acid.     

Antioxidant activities of hot water extracts from various spices

Recently, the natural spices and herbs such as rosemary, oregano, and caraway have been used for the processing of meat products. This study investigates the antioxidant activity of 13 spices commonly used in meat processing plants. The hot water extracts were then used for evaluation of total phenolic content, total flavonoids content and antioxidant activities. Our results show that the hot water extract of oregano gave the highest extraction yield (41.33%) whereas mace (7.64%) gave the lowest. The DPPH radical scavenging ability of the spice extracts can be ranked against ascorbic acid in the order ascorbic acid > clove > thyme > rosemary > savory > oregano. The values for superoxide anion radical scavenging activities were in the order of marjoram > rosemary > oregano > cumin > savory > basil > thyme > fennel > coriander > ascorbic acid. When compared to ascorbic acid (48.72%), the hydroxyl radical scavenging activities of turmeric and mace were found to be higher (p < 0.001). Clove had the highest total phenolic content (108.28 μg catechin equivalent (CE)/g). The total flavonoid content of the spices varied from 324.08 μg quercetin equivalent (QE)/g for thyme to 3.38 μg QE/g for coriander. Our results indicate that hot water extract of several spices had a high antioxidant activity which is partly due to the phenolic and flavonoid compounds. This provides basic data, having implications for further development of processed food products.     

Phenolic antioxidants – radical‐scavenging and chain‐breaking activity: A comparative study

Fifty phenolic antioxidants (AH) (42 individual compounds and 8 binary mixtures of two antioxidants) were chosen for a comparative analysis of their radical‐scavenging (H‐donating) and chain‐breaking (antioxidant) activity. Correlations between experimental (antiradical and antioxidant) and predictable (theoretical) activities of 15 flavonoids, 15 hydroxy cinnamic acid derivatives, 5 hydroxy chalcones, 4 dihydroxy coumarins and 3 standard antioxidants (butylated hydroxytoluene, hydroquinone, DL ‐α‐tocopherol) were summarized and discussed. The following models were applied to explain the structure‐activity relationships of phenolic antioxidants of natural origin: (a) model 1, a DPPH assay used for the determination of the radical‐scavenging capacity (AH + DPPH? → A? + DPPH‐H); (b) model 2, chemiluminescence of a model substrate RH (cumene or diphenylmethane) used for the determination of the rate constant of a reaction with model peroxyl radicals (AH + RO₂? → ROOH + A?); (c) model 3, lipid autoxidation used for the determination of the chain‐breaking antioxidant efficiency and reactivity (AH + LO₂? → LOOH + A?; A? + LH (+O₂) → AH + LO₂?); and (d) model 4, theoretical methods used for predicting the activity (predictable activity). The highest lipid oxidation stability was found for antioxidants with a catecholic structure and for their binary mixtures with DL ‐α‐tocopherol, as a result of synergism between them.     

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。     

Antimicrobial and Antioxidative Activity of Newly Synthesized Peptides Absorbed into Bacterial Cellulose Carrier against Acne vulgaris

The ongoing search for effective treatment of Acne vulgaris is concentrated, i.a., on natural peptides with antimicrobial properties. The aim of this work was the development of new amino acid derivatives with potential activity on dermal infections against selected microorganisms, including the facultative anaerobe C. acne. The peptides P1–P6 were synthesized via Fmoc solid phase peptide synthesis using Rink amide AM resin, analyzed by RP-HPLC-MS, FTIR, DPPH radical scavenging activity, and evaluated against C. acne and S. aureus, both deposited and non-deposited in BC. Peptides P1–P6 presented a lack of cytotoxicity, antimicrobial activity, or antioxidative properties correlated with selected structural properties. P2 and P4–P6 sorption in BC resulted in variable data, i.a., confirming the prospective topical application of these peptides in a BC carrier.     

Thermal and gas permeation properties of copolymers derived from 3‐methacryloxypropyltris(trimethylsiloxy)silane and adamantyl group‐containing methacrylate derivatives

Novel copolymer membranes derived from three types of adamantyl group‐containing methacrylate derivatives and 3‐methacryloxypropyltris(trimethylsiloxy)silane (SiMA) were synthesized via free radical polymerization. The thermal and permeation properties of these copolymer membranes were investigated. Copolymer membranes with less than 11.9 mol % adamantane content exhibited good membrane forming abilities that are suitable for permeation measurement. The decomposition temperature of all copolymers increased up to approximately 40–80°C with increasing adamantane content compared with poly(SiMA). Moreover, the glass transition temperature (T_g) of all copolymers increased up to approximately 46–60°C with increasing adamantane content compared with the theoretical value, which was estimated from Fox equation. 1‐Adamantyl methacrylate copolymer had the highest fractional free volume among the three types of adamantly group‐containing methacrylate derivatives. The gas permeability coefficient of this copolymer increased by 22–45% with increasing adamantane content compared with that of poly(SiMA). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43129.     

Effect of freeze‐thaw pretreatment on thermal drying process and physicochemical properties of chitosan

The effect of freeze‐thaw pretreatment on the thermal drying process and physicochemical properties of chitosan was investigated in this study. Results showed that the freeze‐thaw treatment changed the form of chitosan paste and reduced 75.6–77.7% of the water content. The freeze‐thaw treatment decreased the drying time of chitosan from 16–19 h to 2.75–4 h and the dried product was loosely packed powder. After freeze‐thaw treatment, the molecular weight of chitosan was unchanged during the thermal drying. The heat‐induced browning effect of chitosan during drying was greatly alleviated by the pretreatment. Furthermore, the pretreatment increased the 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical‐scavenging activity of dried product by 40.4–59.8%. The molecular weight, color, and DPPH radical‐scavenging activity of the pretreated dried chitosan product were close to those of freeze‐dried product. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41017.     

Polyphenolic Contents and Antioxidant Potential of Stem Bark Extracts from Jatropha curcas (Linn)

We assessed the polyphenolic contents and antioxidant potential of the aqueous, ethanol and methanol stem bark extracts of Jatropha curcas. The total phenol, flavonoids, flavonols and proanthocyanidin contents of the extracts were evaluated to determine their effect on the antioxidant property of this plant, using standard phytochemical methods. The antioxidant and free radical scavenging activity of ethanol, methanol and aqueous extracts of the plant were also assessed against 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), ferric reducing, nitric oxide (NO), superoxide anion, (O(2) (-)) and hydrogen peroxide (H(2)O(2)) using spectroscopic methods and results were compared with that of butylated hydroxyl toluene (BHT) and ascorbic acid as standards. The concentrations of different classes of phenolic compounds were higher in methanol and ethanol extracts compared to aqueous extracts. There was correlation between total phenol, total flavonoids, total flavonol and total proanthocyanidins (r = 0.996, 0.978, 0.908, and 0.985) respectively. There was correlations between the amount of phenolic compounds and percentage inhibition of DPPH radicals scavenging activity of the extract (r = 0.98). Findings from the present study indicated that J. curcas is a potential source of natural antioxidants and may be a good candidate for pharmaceutical plant based products.     

野生中草药的抗氧化活性研究

考察了田基黄和马蹄菜提取物对DPPH自由基和羟自由基活性的清除能力,并且与多种抗氧化剂进行对照。结果显示,田基黄提取物清除DPPH自由基活性的能力大于香草酸和对香豆酸。马蹄菜提取物清除DPPH自由基活性的能力大于对香豆酸。田基黄、马蹄菜提取物和4种抗氧化剂清除羟自由基活性顺序为槲皮素>田基黄提取物>马蹄菜提取物>山奈酚>咖啡酸>芦丁。结果表明,田基黄和马蹄菜提取物是两种良好的天然抗氧化剂。     

Effect of maltodextrin concentration and inlet temperature during spray drying on physicochemical and antioxidant properties of amla (Emblica officinalis) juice powder

The effects of inlet temperatures of 125, 150, 175 and 200 °C and maltodextrin levels at 3, 5, 7 and 9% on the physicochemical properties, total phenolic content (TPC) and 2,2-diphenyl picryl hydrazile (DPPH) scavenging activity of spray dried amla juice powder were studied. Moisture content and hygroscopicity of powder were significantly affected by inlet temperature and maltodextrin level. However, an increase in the level of maltodextrin did not significantly affect the bulk density and water solubility index (WSI). An increase in drying temperature and maltodextrin concentration decreased the free radical scavenging activity of the powder. Morphological study revealed that at higher inlet temperatures the spray dried powder had small sized particles that were densely packed. Spray dried amla juice powder made with 7% maltodextrin and processed at 175 °C inlet temperature had less hygroscopicity, acceptable color and potent free radical scavenging activity.     

木犀草素-锌（Ⅱ）配合物的制备及清除自由基活性研究

为增强木犀草素的生物活性将其制成锌（Ⅱ）配合物,采用了紫外、红外、元素分析及核磁共振1H谱的方法对配合物进行了结构表征,并测定了该配合物的稳定常数。抗氧化性试验采用了DPPH·法和水杨酸法分别测定了木犀草素-锌（Ⅱ）配合物对（DPPH·）自由基和羟自由基（·OH）的清除作用。结果表明：木犀草素的5OH～4C=O和一个锌离子发生配位形成木犀草素-锌（Ⅱ）配合物;该配合物比较稳定,稳定常数为：βn=4.03×10^7;木犀草素锌（Ⅱ）配合物能有效清除DPPH·和·OH自由基,其清除能力均强于木犀草素,对DPPH·自由基的清除作用略高于Vc,对·OH自由基的清除作用与Vc相接近,最大清除率分别为89.37%和85.10%,说明木犀草素-锌（Ⅱ）配合物是一种较强的自由基清除剂。     

Radical annihilation of γ‐ray‐irradiated contact lens blanks made of a 2‐hydroxyethyl methacrylate copolymer at elevated temperatures

The annihilation of the radicals in irradiated 2‐hydroxyethyl methacrylate copolymer was analyzed by the use of electron paramagnetic resonance (EPR) spectroscopy. The EPR spectra were deconvoluted into three radicals: a quartet (Ra), a triplet (Rb), and a broad singlet (Rc). Radical Ra was attributed to coupling with a methyl radical and/or a doublet or triplet with about the same hyperfine coupling due to a methylene radical. Radical Rb was due to a methylene radical produced by main‐chain scission. Radical Rc was attributed to various free radicals without coupling to protons. By comparing the EPR spectra of radicals Ra, Rb, and Rc with the spectrum of a 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) standard with a known spin number, we calculated the spin numbers of the radicals, which decreased with time in the temperature range 25–45°C, regardless of the irradiation dose. The annealing of Ra and Rb and the annealing of Rc at longer times followed second‐order kinetics; these were different from the kinetics for the color formation and defect‐controlled hardening of polymers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

开封产3种白色菊花提取物的抗氧化活性

采用清除二苯代苦味肼基(DPPH)自由基、清除[2,2′-连氨-(3-乙基苯并噻唑啉-6-磺酸)二氨盐](ABTS)自由基及铁离子还原/抗氧化能力(FRAP)测定法,对开封产的3种白色菊花(兼六香白、国华万胜及白玉带)不同溶剂提取物的体外抗氧化活性进行了评价,将所测定结果与水溶性维生素E(6-hydroxy-2,5,7,8-tetramethyl-chroman-2-carboxylic acid,Trolox)及阳性对照二丁基羟基甲苯(BHT)进行了比较。结果表明,3种菊花的不同溶剂提取物抗氧化活性不同。同一种菊花的甲醇提取物具有很好清除DPPH自由基和还原铁离子的能力,而石油醚提取物几乎无活性。菊花的3个品种中,兼六香白和国华万胜的抗氧化活性较好,其活性远远超过白玉带的抗氧化活性。9个提取物中,兼六香白的甲醇提取物总的抗氧化活性最好。它对DPPH自由基的清除能力(IC50值为20.49 mg/L)比BHT(IC50值为18.92 mg/L)作用略低;其还原Fe3+的能力(FRAP值为731.73±1.77μmol TE/g)比BHT(1 581.68±97.41μmol TE/g)作用低1/2。3种方法测定结果基本一致,其中以DPPH法和FRAP法相关性最好(R=0.982 0)。     

3, 4‐Dihydroxymandelic acid amides of alkylamines as antioxidants for lipids

The antioxidative and radical scavenging activity of the 3, 4‐dihydroxymandelic acid (DHMA) amides of hexylamine, 2‐ethylhexylamine, octylamine, and cyclohexylamine was determined by several physicochemical test systems. The amides were synthesized by protecting group‐free coupling of in situ prepared N‐hydroxysuccinimidylester of DHMA and the amines. The radical scavenging activity was determined using the DPPH (2, 2‐diphenyl‐1‐picrylhydrazyl) method and by quenching superoxide anions generated using a horse radish peroxidase/H₂O₂ system. In the DPPH assay, all amides show higher radical scavenging activity (EC₅₀ 0.09‐0.12 mol/mol_DPPH) compared to the standard antioxidants ascorbic acid (EC₅₀ 0.27 mol/mol_DPPH) and tocopherol (EC₅₀ 0.25 mol/mol_DPPH). The amides are also more potent superoxide radical scavengers (IC₅₀ < 600 nm) than standard ascorbic acid (IC₅₀ 700 nm). Activity against lipid peroxidation was determined by accelerated autoxidation of highly unsaturated oils and squalene using the Rancimat. Again, the antioxidative potentials of the DHMA amides against lipid oxidation as determined by the Rancimat, are at least equal or higher compared to the standard lipid antioxidants tocopherol, BHT, BHA, and ascorbylpalmitate (concentration in soybean oil 0.05%, all other oils 0.025%, squalene 0.005%). In squalene, an equi‐amount mixture of DHMA octylamide and α‐tocopherol shows a synergistic effect. Last but not least, the amides are able to protect an emulsion of linoleic acid/β‐carotene against oxidation initiated by N, N‐azodiisobutyramidine dihydrochloride (IC₅₀ 0.19‐0.77 mmol/l, ascorbic acid > 0.9, tocopherol 0.08). The DHMA octylamide in combination with ascorbic acid shows a synergistic antioxidative effect in the emulsion model. In conclusion, the new alkylamides of DHMA are easy to synthesize, potent radical scavengers and protect lipids, in particular the highly unsaturated, both in bulk and in emulsions against autoxidation.