Laccase-initiated reaction between phenolic acids and chitosan

Phenolic acids are known to possess antioxidant activities whilst chitosan is a biocompatible polymer with antibacterial activity against a broad spectrum of bacteria. Merging both types of molecules could therefore provide several potential applications. In this work, antioxidant properties of phenolic acid–functionalized-chitosan were investigated after being prepared from structurally-different phenolic acids (caffeic and gallic acids) and chitosan using the laccase from Trametes versicolor as the reaction initiator. A laccase-mediated oxidation kinetic of phenolic acids was monitored by UV–vis spectroscopy and cyclic voltammetry, as well as spin-trapping electron paramagnetic resonance spectroscopy (ST-EPR). The pH was shown to have a significant effect on the degree of phenolic acid self-polymerization, indicating the involvement of phenolate anions within the formations of coupled polyphenol products, and their functionalities, i.e. antioxidant activity. All the phenolic acid-functionalized-chitosans displayed greatly improved ABTS radical cation scavenging capacities, compared with the untreated chitosan.     

Organofluorine Hydrazone Derivatives as Multifunctional Anti-Alzheimer's Agents with CK2 Inhibitory and Antioxidant Features

A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH₃)₂ residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC₅₀ values in the kinase assays.     

Antioxidant Capacities and Total Phenolic Contents Enhancement with Acute Gamma Irradiation in Curcuma alismatifolia (Zingiberaceae) Leaves

The present study was conducted in order to assess the effect of various doses of acute gamma irradiation (0, 10, 15, and 20 Gy) on the improvement of bioactive compounds and their antioxidant properties of Curcuma alismatifolia var. Sweet pink. The high performance liquid chromatography (HPLC) and gas chromatography (GC) analysis uncovered that various types of phenolic, flavonoid compounds, and fatty acids gradually altered in response to radiation doses. On the other hand, antioxidant activities determined by 1,1-Diphenyl-2-picryl-hydrazyl (DPPH), ferric reduction, antioxidant power (FRAP), and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging assay showed a higher irradiation level significantly increased the antioxidant properties. This study revealed an efficient effect of varying levels of gamma radiation, based on the pharmaceutical demand to enhance the accumulation and distribution of bioactive compounds such as phenolic and flavonoid compounds, fatty acids, as well as their antioxidant activities in the leaves of C. alismatifolia var. Sweet pink.     

氯代硝基苯类废水臭氧化动力学和机理

采用半连续臭氧化工艺处理氯代硝基苯类废水,对氯代硝基苯（ClNBs）臭氧化过程反应动力学、臭氧分子与自由基氧化反应的贡献、过程降解机理等方面进行了研究。结果表明,ClNBs降解遵循准一级反应动力学,降解速率顺序为o-CNB相似文献   

Optimization of extraction parameters of bioactive components from defatted marigold (Tagetes erecta L.) residue using response surface methodology

Response surface methodology (RSM) was used to estimate the optimum extraction parameters, in which the antioxidant activity (AA) of the extract from the defatted marigold residue was the strongest. The AA of marigold extracts was investigated by the radical scavenging activity assays ((2,2-azinobis-(3-ethylbenzothiazolin-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH)). Results demonstrated that AA was significantly affected by the content of total phenolics (TP) and total flavonoids (TFA) (p < 0.0001). The optimal extraction parameters of marigold extracts for the highest AA by ABTS method were ethanol concentration of 79.7%, extraction temperature of 74.2 °C and time of 8.1 h, and by DPPH assay with 89.3% of ethanol concentration at 81.5 °C for 11.1 h, AA values were 2.42 and 1.86 mmol TE/g, respectively.     

Direct Electrochemical Generation of Catalytically Competent Oxyferryl Species of Classes I and P Dye Decolorizing Peroxidases

This work introduces a novel way to obtain catalytically competent oxyferryl species for two different dye-decolorizing peroxidases (DyPs) in the absence of H₂O₂ or any other peroxide by simply applying a reductive electrochemical potential under aerobic conditions. UV-vis and resonance Raman spectroscopies show that this method yields long-lived compounds II and I for the DyPs from Bacillus subtilis (BsDyP; Class I) and Pseudomonas putida (PpDyP; Class P), respectively. Both electrochemically generated high valent intermediates are able to oxidize ABTS at both acidic and alkaline pH. Interestingly, the electrocatalytic efficiencies obtained at pH 7.6 are very similar to the values recorded for regular catalytic ABTS/H₂O₂ assays at the optimal pH of the enzymes, ca. 3.7. These findings pave the way for the design of DyP-based electrocatalytic reactors operable in an extended pH range without the need of harmful reagents such as H₂O₂.     

Reduction electrochimique de composes organiques en presence de tensio-actifs—IV. Etudes polarographique et spectroscopique des nitroanilines

In order to elucidate the location of substrates in micelles we studied the polarographic and spectroscopic (ESR) behaviour of nitroanilines isomers as a function of pH in the presence of a neutral surfactant (BRIJ 35). In basic or neutral media, two polarogaphic waves are observed and the spectra of anion radicals can be recorded during “in situ” electrochemical reductions. In acidic aqueous solutions and without surfactant, o and p-nitroanilines give a six-electron wave whereas a four-electron wave is observed for m-nitroaniline. If BRIJ is added, the three isomers lead to four electron processes. Presence of surfactant causes a decreasing of the rate of the intermediate chemical step for the ECE mechanism. When the surfactant concentration reaches 0.1 M, electrolysis “in situ” (pH = 3.5) gives no ESR signal for o- and m-nitroaniline. Under the same conditions, the p-nitroaniline solution exhibits a well resolved spectrum of p-phenyl-enediamine cation radical. Formation of such a cationic intermediate during the reduction process is discussed and its stabilization is conceivable by means of a solvent “cage effect”.     

Synthesis of macroporous polymers with radical scavenging properties by immobilization of polyphenolic compounds

Solid phase radical scavengers have been prepared by the immobilization of antioxidant (AOX) compounds on macroporous polymers. Poly(glycidylmethacrylate-co-trimethylolpropane trimethacrylate) [poly(GMA–TRIM)] and poly(N-acryloyl-tris(hydroxymethyl)aminomethane-co-glycidylmethacrylate-co-N,N′-methylenebisacrylamide) [poly(NAT–GMA–BIS)] were prepared by free radical polymerization using a mixture of dimethylsulfoxide (DMSO)-poly(ethyleneglycol) 6000 (PEG 6000) as a porogenic solvent. The polymers were aminated with ethylenediamine (EDA) and the linkage of the polyphenolic compounds (gallic and caffeic acids) was carried out by two different approaches: through N,N′-dicyclohexylcarbodiimide/4-dimethylaminepyridine (DCC/DMAP) system (one-step method) or through the previous formation of the acyl chloride of the polyphenolic compounds and subsequent amidation reaction (two-step method). The available phenolic groups on the macroporous polymers were determined using the Folin–Ciocalteu method; the radical scavenging properties of the materials prepared were evaluated using the radical species 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) and 2,2′-azino-bis-[3-ethylbenzothiazoline-6-sulfonic acid] radical cation (ABTS⁺). From the results, higher antiradical capacities were obtained with the polymers in which the immobilization of the antioxidant molecules was performed through the two-step method. The polymeric networks prepared in this work yielded up to 13.2 μmol AOX/g of dry polymer, which allowed a quantitative removal of the radicals tested in less than 30 min.     

Effect of Accelerated Storage on Microencapsulated Kenaf Seed Oil

In order to improve the quality and protect against degradation, kenaf (Hibiscus cannabinus L.) seed oil was microencapsulated by using spray drying. The microencapsulated kenaf seed oil (MKSO) was then stored at 65 °C for 24 days, the changes of fatty acids and bioactive compounds were examined every six days. Bulk (unencapsulated) kenaf seed oil was used as a control and was compared to the MKSO. The fatty acids and phytosterols compositions were determined by using gas chromatography, while tocopherols and phenolic acids of microencapsulated kenaf seed oil were determined by using high performance liquid chromatography. The results showed that there was a significant decrease (p < 0.05) in bioactive compounds in kenaf seed oil while the bioactive compounds in MKSO were maintained in a stable condition upon accelerated storage. Microencapsulation was shown to protect kenaf seed oil against oxidation, as well as preventing the degradation and/or loss of bioactive compounds in kenaf seed oil.     

Preparation,characterization, and adsorption performance of p‐hydroxybenzoic acid imprinted polymer and selective catalysis of toluene to para‐chlorotoluene

A p‐hydroxybenzoic acid surface molecularly imprinted polymer (p‐HB– S MIP) with si lica microspheres as a supporting matrix was prepared by the adoption of the surface molecular imprinting technique with acrylamide ( AM) as a functional monomer, ethylene glycol dimethacrylate as a crosslinker, and azoisobutyronitrile as an initiator. The p‐HB–SMIP was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetry. Interactions between the functional monomer and template were observed with UV–visible spectroscopy of the solutions of these components as well. The results indicate that a 1:2 molecular complex was formed between p‐hydroxybenzoic acid (p‐HB) and AM. A kinetic binding study showed that p‐HB–SMIP reached saturation adsorption after about 1 h, and the pseudo‐second‐order model fitted the adsorption kinetics data. Static adsorption experiments revealed that the Freundlich equation fitted the adsorption isotherm data. The thermodynamics parameters (with positive values of enthalpy and entropy and negative values of Gibbs free energy) indicated that the binding system for p‐HB–SMIP was endothermic and entropy was gained and was spontaneous. Selective experiments showed that p‐HB–SMIP had a high affinity and excellent recognition selectivity for the template p‐HB. p‐HB–SMIP was further investigated by the catalysis of toluene to para‐chlorotoluene. The catalytic reaction results showed that the conversion of toluene was 85.5% and the molar ratio of para‐chlorotoluene to o‐chorotoluene was 1.38; this was higher than that of traditional catalysts. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40118.     

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.     

Comparative Assessment of Phenolic Content and in Vitro Antioxidant Capacity in the Pulp and Peel of Mango Cultivars

Mango (Mangifera indica L.), also called “the king of fruits”, is one of the most popular fruits in tropical regions. Pulp and peel samples of mango cultivars were analyzed to estimate total phenolic, total flavonoid and total anthocyanin contents. Phenolic acids, hydrophilic peroxyl radical scavenging capacity (hydro-PSC) and oxygen radical scavenging capacity (ORAC) in vitro were also determined. Total phenolics and flavonoid contents were found maximum in the peel of Xiao Tainang and Da Tainang cultivars, respectively, whereas Xiao Tainang also exhibited significant antioxidant capacity. Noteworthy, concentrations of gallic acid, protocatechuic acid, ferulic acid, chlorogenic acid and caffeic acids at 79.15, 64.33, 33.75, 27.19 and 13.62 mg/100 g fresh weight (FW) were quantified for Da Tainang, Xiao Tainang and of Jidan cultivars, respectively. Comparatively, a higher level of phenolics and significant antioxidant capacity in mango peel indicated that it might be useful as a functional food and value-added ingredient to promote human health.     

Simulated Gastrointestinal pH Condition Improves Antioxidant Properties of Wheat and Rice Flours

The present study was conducted to evaluate the antioxidant properties of wheat and rice flours under simulated gastrointestinal pH condition. After subjecting the wheat and rice flour slurries to simulated gastrointestinal pH condition, both slurries were centrifuged to obtain the crude phenolic extracts for further analyses. Extraction yield, total contents of phenolic and flavonoids were determined as such (untreated) and under simulated gastrointestinal pH condition (treated). 1,1-diphenyl-2-picrylhydrazyl radical (DPPH^•) scavenging activity, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) radical cation (ABTS^•+) scavenging activity, ferric reducing antioxidant power (FRAP), beta-carotene bleaching (BCB) and iron chelating activity assays were employed for the determination of antioxidant activity of the tested samples. In almost all of the assays performed, significant improvements in antioxidant properties (p < 0.05) were observed in both flours after treatment, suggesting that wheat and rice flours contain considerably heavy amounts of bound phenolics, and that their antioxidant properties might be improved under gastrointestinal digestive conditions.     

Gelatin hydrolysate powder from the scales of spotted golden goatfish: Effect of drying conditions and juice fortification

Effects of different spray drying temperatures (inlet temperatures of 160, 180, and 200°C) on characteristics, bioactivity, and sensory properties of gelatin hydrolysate from spotted golden goatfish scales using maltodextrin as a carrier agent were investigated. The yield of gelatin hydrolysate powder was higher, when inlet temperature increased (p?p?p?p?相似文献   

Etude electrochimique de radicaux libres—III etude des radicaux derives des naphthyridines −1.5, −1.6, −1.7, −1.8, −2.6 et −2.7 et du bipyridyl-4,4′

In acid medium 1.7, 2.6 and 2.7 naphthyridines gives two 1 F polarographic waves. For certain pH values, the first reduction stage leads to a cation radical B relatively stable for the 1.7 and 2.6 derivatives; in the case of 2.7 naphthyridine, its half life is on the contrary shorter than a few msec. The 1.7 and 2.6 cation radicals disappear by a first order acid and based catalysed reaction leading to a dimer. The mechanism, which is valid for other heterocycles with two nitrogen, is the following: the cation radical B which is formed initially is symmetrical and stable. A hydrogen shift from a nitrogen to a carbon atom leads to a radical C, which is unstable and reacts with B to yield a dimer.     

Correlation of increased antioxidation with the phenolic compound and amino acids contents of Camellia sinensis leaf extracts following ultra high pressure extraction

Antioxidants are indispensable for protecting skin cell membranes against oxidative injury caused by reactive oxygen species and other free radicals. Likewise, phenolic compounds are also important barriers to such oxidative injury. In this study, we examined the correlation between increased antioxidation and the contents of phenolic compounds and amino acids in Camellia sinensis leaf extracts obtained by ultra-high pressure extraction. Compared with extracts obtained by leaching and ultrasonic extraction, to evaluate whether this method can improve the pharmacologic effects of C. sinensis leaves. The ultra-high pressure (50 and 100 MPa) extracts had tremendous enhancement of their extraction yield, 1,1-diphenyl-2-picrylhydrazyl (free radical)-scavenging activity and superoxide anion radical scavenging activity, as well as the total phenolic, amino acid, and caffeine contents. The antioxidative effects were promoted not only by the phenolic compounds contents but also by other factors such as the amino acids content in the C. sinensis leaf extracts. These effects showed pressure-dependent increase with the enhanced phenolic compound and amino acid contents of the ultra high pressure extracts. Taken together, ultra high pressure extraction is a potentially useful method for the pharmaceutical, cosmetic, and food industries, because it improves the antioxidative effects of C. sinensis leaves.     

Microwave Assistant Synthesis,Antifungal Activity and DFT Theoretical Study of Some Novel 1,2,4-Triazole Derivatives Containing Pyridine Moiety

In order to investigate the biological activity of novel 1,2,4-triazole compounds, seventeen novel 1,2,4-triazole derivatives containing pyridine moiety were synthesized under microwave assistant condition by multi-step reactions. The structures were characterized by ¹H NMR, MS and elemental analyses. The target compounds were evaluated for their fungicidal activities against Stemphylium lycopersici (Enjoji) Yamamoto, Fusarium oxysporum. sp. cucumebrium, and Botrytis cinerea in vivo, and the results indicated that some of the title compounds displayed excellent fungicidal activities. Theoretical calculation of the title compound was carried out with B3LYP/6-31G (d,p). The full geometry optimization was carried out using 6-31G (d,p) basis set, and the frontier orbital energy, atomic net charges were discussed, and the structure-activity relationship was also studied.     

筛选和表征抗氧化剂的方法——ABTS法

从植物中筛选抗氧化剂、表征抗氧化活性是近年来的研究热点之一,使用自由基阳离子ABTS·＋进行筛选和表征是目前常用的方法之一,本文对ABTS法的原理、分类及应用进行了总结,并讨论了影响TEAC值的因素和ABTS法的优缺点。     

Kinetics and Antioxidative Sites of Capsaicin in Homogeneous Solution

Reliable quantitative kinetic data on the antioxidant activity of capsaicin (CAP) is lacking, and the antioxidative mechanism of CAP is still unclear. Therefore, an investigation aimed at elucidating the antioxidative sites of CAP that react with chain-propagating peroxyl radicals was undertaken. First, the reaction of CAP with 2,2-diphenyl-1-picrylhydrazyl (DPPH) was investigated, and it was found that the stoichiometric factor of CAP is 2. Then, the rate constant for the reaction of CAP with peroxyl radicals derived from cumene was measured. CAP reacted with peroxyl radicals at a constant rate of k _inh = 5.6 × 10³ M⁻¹ s⁻¹. Furthermore, the inhibitory effects of various related compounds against cumene oxidation were measured, showing that the phenolic OH group is the active portion of the molecule. In addition, the kinetic solvent effects of DPPH/CAP reactions were measured in methanol, acetonitrile, acetone and tetrahydrofuran. In particular, an enhancement in the reaction rate was observed in alkaline methanol, indicating that these results are due to the partial ionization of the phenol of CAP and very fast electron transfers from the phenolate anion to DPPH. We interpreted these results as indicating that the phenolic OH group of CAP is mainly associated with peroxyl radical scavenging.