Antioxidative activity measurement in lipid peroxidation systems with malonaldehyde and 4-hydroxy nonenal

Antioxidative activities of vitamin E, ethylenediamine tetraacetic acid (EDTA), ferulic acid, and butylated hydroxy toluene (BHT) were monitored with lipid peroxidation systems. Formation of malonaldehyde (MA) and 4-hydroxy nonenal (4-HN) from ethyl linoleate or rat liver microsome oxidized by FeCl₂/H₂O₂ or ADP/FeSO₄ was measured by gas chromatography. Over 90% of MA and 4-HN formation was inhibited by 100 mmol/L of vitamin E. A synthetic antioxidant, BHT, showed the strongest antioxidative activity, followed by that of vitamin E, whereas EDTA accelerated formation of MA and 4-HN in the ethyl linoleate/FeCl₂/H₂O₂ system. Vitamin E did not suppress lipid peroxidation significantly when microsome was oxidized by ADP/FeSO₄. EDTA inhibited oxidation of microsome by ADP/FeSO₄ considerably; in contrast, it did not in the case of oxidation by FeCl₂/H₂O₂.     

Analysis of free malonaldehyde formed in lipid peroxidation systemsvia a pyrimidine derivative

A high-performance liquid chromatographic (HPLC) method for the determination of malonaldehyde (MA) in foods and biological samples was developed. MA was derivatized by reaction with urea under acidic conditions to form 2-hydroxypyrimidine, which was subsequently measured by HPLC. The highest yield (98%) of the product was obtained when 100 nmol of MA was reacted with 60 mmol of urea for 60 min at 100°C. Arachidonic acid, linolenic acid, linoleic acid and oleic acid were oxidized by a FeCl₂/H₂O₂ reagent in aqueous solution. MA formed was determined as 2-hydroxypyrimidine by HPLC. Arachidonic acid produced the highest level of MA (60 nmol/mg fatty acid), whereas oleic acid did not produce any. The formation levels of MA in microsomes upon enzymatic and nonenzymatic oxidation were 34 nmol/mL and 45 nmol/mL, respectively. Antioxidative activity of α-tocopherol was also monitored successfully by this HPLC method.     

Inhibition of malonaldehyde formation by antioxidants from ω3 polyunsaturated fatty acids

The inhibitory effect of α-tocopherol, β-carotene, 2″-O-glycosyl isovitexin (2″-O-GIV), and butylated hydroxytoluene (BHT) on malonaldehyde (MA) formation from ω3 polyunsaturated fatty acids (PUFA) was determined by gas chromatography. The levels of MA formed from 1 mg each of octadecatetraenoic acid (ODTA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) upon oxidation with Fenton's reagent were 29.8±1.5, 17.2±1.5, and 22.0±0.7 nmol, respectively. BHT was most effective toward protecting all three ω3 PUFA, whereas β-carotene did not exhibit any inhibitory effect. 2″-O-GIV inhibited MA formation from EPA and DHA by 56 and 43%, respectively, showing the second greatest inhibitory activity after BHT. α-Tocopherol inhibited MA formation from ODTA and DHA by 67 and 28%, respectively, but it did not show any activity toward EPA oxidation. The naturally occurring antioxidant, 2″-O-GIV, may be useful to prevent oxidation of ω3 PUFA.     

Specific determination of malonaldehyde by N-methyl-2-phenylindole or thiobarbituric acid

Reactivity of a commercially available test kit (LPO-586), based on N-methyl-2-phenylindole, toward aldehydes was characterized and compared with that of thiobarbituric acid (TBA). In hydrochloric acid, LPO-586 produced a violet pigment with malonaldehyde (MA) but not with other tested aldehydes. In methane sulfonic acid, LPO-586 produced the violet pigment with MA and 4-hydroxynonenal (HNE), but not with other tested aldehydes. Pigment formation with MA was not inhibited by other aldehydes, but that with HNE was inhibited by alka-2,4-dienals. TBA produced a red pigment with MA but not with other tested aldehydes in hydrochloric acid or in acetate with ethylenediaminetetraacetic acid (EDTA). Both the LPO-586 test in hydrochloric acid and the TBA test in hydrochloric acid or in acetate with EDTA can be used for specific measurement of MA in oxidized lipid samples.     

Analysis of lipids from cooked beef by thin-layer chromatography with flame-ionization detection

Lipids were extracted from cooked ground beef with methylene chloride/methanol (2:1). The lipids were separated on a silicic acid column, into neutral and polar fractions by elution with methylene chloride, followed by methanol. These fractions were analyzed by Iatroscan thin-layer chromatography with flame-ionization detection instrumentation on Chromarods S-III (silica gelcoated quartz rods). Comparison of cooked beef stored for 0, 4 and 7 d at 4°C indicated that storage caused a decrease in total lipids, an increase in neutral lipids and a decrease in polar lipids, specifically in phosphatidylcholine. These changes in the lipid fraction were associated with meat flavor deterioration and an increase in lipid oxidation.     

Microscale recovery of total lipids from fish tissue by accelerated solvent extraction

A number of techniques are available for the extraction of lipids from a variety of tissues; however, conventional methods are characteristically labor intensive, typically involve large volumes of toxic solvents, and usually require at least 1 g of tissue. With the availability of accelerated solvent extraction (ASE) technology, the opportunity exists to modify classical lipid extraction techniques such that automated high-pressure, high-temperature extractions may be performed with the use of far smaller volumes of costly and harmsul solvents. Moreover, the high extraction efficiency attainable by ASE suggests that significantly less tissue would be required than is routinely used. This paper describes the adaptation of previously developed lipid extraction solvent systems for use with ASE toward the purpose of extracting total lipids from 100 mg of fish tissue. The efficacy of three solvent systems for lipid extraction from representative fish tissues, including a standard reference material, was explored using gravimetry and FA analysis by GC. A TG was used as a surrogate to monitor overall method performance. The findings herein demonstrate that microscale ASE represents an effective and efficient alternative to traditional lipid extraction techniques based on quantity and composition of extracted lipid, surrogate recovery, and precision.     

水蒸气抑制2-甲基戊烷在USHY上催化裂解反应中焦炭生成

The effect of steam dilution on the formation of coke and minor products in 2-methylpenatne cracking on ultra stable HY at 673 K has been studied. The results show that steam dilution suppresses the formation of coke and minor aromatic products, but enhances the H/C atomic ratio of coke and the production of di-olefins. This and other evidences suggest that steam dilution enhances the desorption of coke precursors, diolefinic ions and cyclic ions, by inhibiting the further pathological reactions to produce aromatics and polyaromatics. These insights into the chemistry underlying coke formation in hydrocarbon cracking on solid acid catalysts can potentially be applied to the development of additives which inhibit coke formation and control catalyst deactivation.     

Structural and physicochemical characterization of hemicelluloses isolated by alkaline peroxide from barley straw

Seven hemicellulosic preparations were obtained from barley straw by extraction with 1.5% H₂O₂ at pH 12.0 for 14 h at 45 °C with extractant to straw ratios of 10:1, 13:1, 15:1, 18:1, 20:1, 25:1 and 30:1. The respective yields of dissolved hemicelluloses were 28.4 wt%, 28.8 wt%, 29.7 wt%, 30.1 wt%, 30.6 wt%, 30.8 wt% and 30.8 wt% or dry barley straw, corresponding to release of 78.7%, 79.8%, 82.3%, 83.4%, 84.8%, 85.3% and 85.3% of the original hemicelluloses. The polymers were mainly composed of xylose, arabinose, glucose, galactose and 4-O-methyl-D -glucuronic acid (59.3–62.6%, 19.7–22.0%, 8.8–12.5%, 5.6–6.9% and 5.8–6.7%, respectively) and had weight-average molecular weights of between 38 470 and 41 050 g mol⁻¹.¹³ CNMR spectroscopy confirmed the results obtained by chemical methods, and showed that the hemicellulosic fraction was mostly by L -arabino-(4-O-methyl-D -glucurono)-D -xylan. More importantly, it was found that lignin provides some protection for the hemicelluloses in barley straw against attack by hydrogen peroxide. © 2002 Society of Chemical Industry     

Inhibition of Oxidative Stress by Low-Molecular-Weight Polysaccharides with Various Functional Groups in Skin Fibroblasts

The aim of this study was to evaluate the in cellulo inhibition of hydrogen-peroxide-induced oxidative stress in skin fibroblasts using different low-molecular-weight polysaccharides (LMPS) prepared from agar (LMAG), chitosan (LMCH) and starch (LMST), which contain various different functional groups (i.e., sulfate, amine, and hydroxyl groups). The following parameters were evaluated: cell viability, intracellular oxidant production, lipid peroxidation, and DNA damage. Trolox was used as a positive control in order to allow comparison of the antioxidant efficacies of the various LMPS. The experimentally determined attenuation of oxidative stress by LMPS in skin fibroblasts was: LMCH > LMAG > LMST. The different protection levels of these LMPS may be due to the physic-chemical properties of the LMPS’ functional groups, including electron transfer ability, metal ion chelating capacities, radical stabilizing capacity, and the hydrophobicity of the constituent sugars. The results suggest that LMCH might constitute a novel and potential dermal therapeutic and sun-protective agent.     

Isolation of polyphenols from the extracts of olive leaves (Olea europaea L.) by adsorption on silk fibroin

General objective of the present work was to assess the isolation of polyphenols from olive leaves. The effects of extraction conditions on the total phenol content and antioxidant activity of olive leaf extract (OLE) were investigated. An extract with good antioxidant activity (7.52 mmol of Trolox equivalent antioxidant capacity (TEAC)/g olive leaf extract), and a high content of oleuropein (13.4%) and rutin (0.18%) could be obtained using 70% ethanol as extraction solvent. There was a good correlation between the antioxidant activity and the total phenol content. Furthermore, silk fibroin was used as a novel adsorbent to recover the polyphenols from the olive leaf extracts. The adsorbed amounts of rutin and oleuropein were 15 mg rutin/g silk fibroin and 96 mg oleuropein/g silk fibroin. Fraction consisting of mainly oleuropein and fraction rich in rutin, luteolin-7-glucoside, verbascoside, apigenin-7-glucoside were obtained by using silk fibroin filled column. Silk fibroin was found to be a promising adsorbent for the purification of oleuropein and rutin from olive leaf extracts.     

硫酸铵和尿素抑制飞灰合成二(口恶)英

二(口恶)英(PCDD/Fs)排放制约了当前焚烧技术在垃圾处置和资源化利用领域的应用和推广。研究了硫酸铵和尿素在不同温度下对垃圾焚烧飞灰合成PCDD/Fs的抑制能力。实验结果表明:高温下(650℃)硫酸铵和尿素对PCDD/Fs合成具有更高的抑制效率,但高温下飞灰合成PCDD/Fs量远低于低温下(350℃)的生成量;PCDD/Fs的降低量均主要来自于PCDFs的减少,并且低温下TeCDF减少量最大,而高温下减少最多的同系物为OCDF。由于实际烟道中,高温处投入的抑制剂会进入低温段继续产生抑制作用,所以仍需要更多的研究正确评价抑制剂的抑制效果和最优使用温度。     

On the reaction pathway for the formation of benzene from acetylene catalyzed by palladium

The reaction between gas‐phase acetylene and alumina‐supported palladium saturated with ¹³C‐labelled vinylidene is studied using both one‐pulse, ¹³C magic‐angle spinning, nuclear magnetic resonance (NMR) spectroscopy and by mass spectroscopic analysis of the reaction products to probe the reaction pathway. The presence of vinylidene on alumina‐supported palladium is confirmed by comparing the infrared spectra of the species formed on the supported sample with those found on a Pd(111) single crystal. It is shown using NMR that a high pressure (∼350 Torr) of gas‐phase acetylene reacts with adsorbed vinylidene at the same rate at which benzene is formed catalytically on the same sample. The resulting benzene incorporates two ¹³C atoms. This indicates that benzene is formed by a slow reaction between gas‐phase (¹²C‐labelled) acetylene and adsorbed vinylidene (¹³CH₂=¹³C=) to form a C₄ intermediate which reacts rapidly with further acetylene to yield benzene. There are precedents for such reactions in homogeneous phase. The proposed reaction pathway differs from that elucidated previously from ultrahigh vacuum studies on clean Pd(111), where it was found that benzene synthesis also proceeds via a C₄ intermediate, in this case formed from two adsorbed acetylenes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Crystal Structure of an SSB Protein from Salmonella enterica and Its Inhibition by Flavanonol Taxifolin

Single-stranded DNA (ssDNA)-binding proteins (SSBs) play a central role in cells by participating in DNA metabolism, including replication, repair, recombination, and replication fork restart. SSBs are essential for cell survival and thus an attractive target for potential anti-pathogen chemotherapy. In this study, we determined the crystal structure and examined the size of the ssDNA-binding site of an SSB from Salmonella enterica serovar Typhimurium LT2 (SeSSB), a ubiquitous opportunistic pathogen which is highly resistant to antibiotics. The crystal structure was solved at a resolution of 2.8 Å (PDB ID 7F25), indicating that the SeSSB monomer possesses an oligonucleotide/oligosaccharide-binding (OB) fold domain at its N-terminus and a flexible tail at its C-terminus. The core of the OB-fold in the SeSSB is made of a six-stranded β-barrel capped by an α-helix. The crystal structure of the SeSSB contained two monomers per asymmetric unit, which may indicate the formation of a dimer. However, the gel-filtration chromatography analysis showed that the SeSSB forms a tetramer in solution. Through an electrophoretic mobility shift analysis, we characterized the stoichiometry of the SeSSB complexed with a series of ssDNA dA homopolymers, and the size of the ssDNA-binding site was determined to be around 22 nt. We also found the flavanonol taxifolin, also known as dihydroquercetin, capable of inhibiting the ssDNA-binding activity of the SeSSB. Thus, this result extended the SSB interactome to include taxifolin, a natural product with a wide range of promising pharmacological activities.     

Membrane formation via phase separation induced by penetration of nonsolvent from vapor phase. I. Phase diagram and mass transfer process

The isothermal phase diagram for poly(vinylidene fluoride)/dimethyl formamide/water system was derived. The binodal and spinodal were calculated based on the Flory–Huggins theory and the calculated binodal was approximately in agreement with the experimental data of the cloud points. The isothermal crystallization line was also obtained according to the theory of melting point depression. Mass transfer of the three components during membrane formation by the precipitation from the vapor phase has been analyzed. During this process, phase separation of the polymer solution is induced by the penetration of water vapor in the solution. The calculated result on the changes of the cast film weights indicated the good agreement with the experimental data. The time‐course of the polymer concentration profile in the film was calculated for various cases of different humidity of the vapor phase and different initial polymer concentration. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 159–170, 1999