Antioxidants in neoplastic cells: I. Changes in the antioxidative capacity of mouse neuroblastoma cells measured by a single-phase assay

Cultured mouse neuroblastoma cells exhibit a striking increase in antioxidative capacity during the transition from logarithmically dividing cells to nondividing, neurite-bearing cells. Two physically separable phenomena are involved: (a) the membrane pellet of neurite-bearing cells is highly resistant to lipid peroxidation, and (b) the postmicrosomal supernatant of these cells inhibits peroxidation in rat liver mitochondria and other biological membranes. A precise, single-phase assay has been developed for assessing antioxidant levels in lipid extracts. By means of this assay, the increase in membrane resistance to lipid peroxidation has been correlated with a threefold increase in the antioxidant activity of the neuroblastoma neutral lipid fraction. This finding implies that generation of a neutral lipid antioxidant (or antioxidants) is involved in the profound increase in antioxidative capacity which occurs in differentiating neuroblastoma cells.     

Antioxidants in neoplastic cells: IV. Evidence that the phenolic antioxidant A274 is 9-(4-hydroxyphenyl)xanthene,an artifact in tissue culture media

An extensively conjugated phenol (A274), recently shown to be present as a common trace constituent in randomly selected batches of commercial tissue culture media, was diazomethylated; the monomethyl derivative so prepared was shown to exhibit gas chromatographic and mass spectrometric properties identical to those observed for synthetically prepared 9-(4-methoxyphenyl)xanthene, but different from those of several isomeric compounds. The structure 9-(4-hydroxyphenyl)xanthene is thus proposed for A274.     

Egg plant lipoxygenase: Isolation and partial characterization

Egg plant lipoxygenase EC 1.13.1.13 when purified on Ecteola cellulose was resolved into two active fractions with most of the activity in the first fraction (A). This fraction when further purified on Sephadex G200-120 had 20 times the specific activity of the crude material. It proved to be a single substance by electrophoresis and immunological technique. The pH optimum was 6.5. Its activity was specific for thecis,cis-1,4 pentadiene structure. There was no inhibition by cyanide, azide, EDTA or fluoride. Nordihydroguaretic acid, on the other hand, exhibited strong inhibition at 3 × 10⁻³M concentration. The specific antibody caused 50% inhibition.     

Isolation and partial characterization of phenoloxidase from apples (Malus domestica, var. Anna)

This study pursued the isolation and partial characterization of the enzyme polyphenoloxidase from apple (Malus domestica Anna variety), grown in the Hermosillo Coast (State of Sonora, Mexico). The effects of pH and temperature as well as its specificity towards substrates, and its behavior under conditions of hydrophobic chromatography, were studied. The enzyme was isolated from a residual powder obtained from ripe apples homogenized with cold acetone. The extract thus prepared was used to characterize the enzyme, and it showed an optimum pH of 5.36 and an optimum temperature of 35 degrees C. The substrate specificity proved to decrease from 4-methyl catechol, chlorogenic acid, catechol, and caffeic acid, to 3,4-dihydroxiphenyl alanine (DOPA). The enzyme resulted to be more thermostable (temperature range: 35 degrees C to 60 degrees C) than the rest of oxidases of plant origin. When the extract was eluted under conditions of hydrophobic chromatography separation, it appeared as a single peak resulting in a 300 fold purification. The phenolase activity characteristics found in the present study were similar to those observed in other apples from temperate climates; however, this particular polyphenoloxidase is more thermostable under natural conditions. This explains why apples of the Anna variety, at the high harvesting temperature, show a very fast formation of brown spots even when there is a minor damage. The content of compounds with phenolic group was high (1.16 g/100 g fresh weight). Further increase of the velocity of fruit enzymatic browning was due to this reason.     

Isolation and characterization of a nitrile hydratase from a Rhodococcus sp.

A new nitrile hydratase producing strain of Rhodococcus has been found. A method for purification of the nitrile hydratase and a characterization of the enzyme is described. The hydratase is a 52-kdal protein consisting of two subunits of molecular weights, 26 and 23 kdal, respectively. The hydratase exhibits a broad substrate specificity. Aliphatic saturated or unsaturated nitriles, as well as aromatic nitriles, are substrates for the enzyme. Inhibition of the enzyme activity by amides and carboxylic acids was observed. The optimum pH of the hydratase is 7.5. The enzyme is rather unstable, even at room temperature. The enzyme may be applied for the production of acrylamide. For this application of the enzyme, the optimal temperature is about 4°C, where the enzyme exhibits a satisfactory activity and stability.     

Isolation and partial characterization of phytotoxic compounds from lantana (Lantana camara L.)

Phytotoxic compounds obtained from methanol extracts of field-grown lantana (Lantana camara L.) were quantified in terms of their inhibition of ryegrass (Lolium multiflorum Lam.) seed germination and/or seedling growth. Subsequent partition of the aqueous fraction (derived from drying the MeOH extract in vacuo and redissolving in distilled water) at various pHs with solvents of differing polarity indicated the phytotoxic compounds were both polar and slightly acidic. Thin-layer Chromatographic separation of the acidic butanol fraction in a solvent mixture of butanol, acetic acid, water (4∶1∶5, by volume) yielded an active fraction with anR _f value of 0.89–1.0 that was inhibitory to both root and shoot growth of ryegrass. Two other fractions withR _f values of 0.04–0.23 and 0.41–0.57 were inhibitory only to root but not shoot growth.     

野油菜黄单胞菌反枝苋致病菌毒素的分离和结构分析

A phytotoxin from Xanthomonas campestris pv. retroflexus was isolated using a chromatographer and HPLC, and the components were identified to be a mixture of minor molecular compounds including organic acids and cyclo-（proline-phenylalanine）. The greenhouse cultivation test was used to determine the influence of the isolated fractions on the growth of target weed redroot pigweed （Amaranthus retroflexus L）. The experimental results demonstrated that the cyclo-（Pro-Phe） had the weed inhibit activity obviously on dicotyledonous weed and the mixture with six organic acids showed stronger bioactivity. Further, greenhouse and field test were processed, and the test showed that the use of the toxin appeared to have the potential to be developed further as a bioherbicide system to control weedy grasses.     

Antioxidants and the autoxidation of fats IV. Lecithin as an antioxidant

The commercial preparations known as “lecithin” have moderate antixoygenic action on refined cottonseed oil, little effect on lard, and none at all on lard-cod liver oil mixtures. Commercial lecithins contain only small amounts of true lecithin. The antioxygenic agent in these preparations is cephalin. Purified lecithin is not an oxidation inhibitor, but purified cephalin is. There is no quantitative relation between the amount of cephalin used and the prolongation of the induction period. The particular portion of the cephalin molecule responsible for its antioxygenic action is probably the mono-basic phosphoric acid radicle.     

Antagonistic effects ofMyxococcus xanthus on fungi: II. Isolation and characterization of inhibitory lipid factors

The chemical composition of the lipophilic excretion ofMyxococcus xanthus inhibitory to the germination of fungal spores and growth has been investigated. The inhibitory effect was attributed to a mixture of fungistatically acting fatty acids and a component of antibiotic character. The fatty acid mixture has been fully characterized and found to constitute a mixture of saturated (68%) and unsaturated (32%) structures in the C₁₃–C₁₇ range. The major part is methylbranched of theiso-type, with 13-methyltetradecanoic acid being the main component (33% of the total). The fungistatic activity of the fatty acid mixture on spore germination is attributed to the structures withiso-configuration. The presence of unsaturation is of minor importance. Observed morphological changes of the spores and hyphae in the presence ofiso-fatty acids suggest that they act on the plasma membrane.     

Antioxidants from a heated histidine-glucose model system. I: Investigation of the antioxidant role of histidine and isolation of antioxidants by high-performance liquid chromatography

The radical-combining activity of Maillard reaction products [MRP_(aq)], produced by heating d-glucose and l-histidine (3:1) in a 0.1 M phosphate buffer for 10 h at 105°C (final pH 6.53), was estimated directly by means of a diphenylpicrylhydrazyl radical (DPPH^·) method. Additionally, the indirect methods of peroxide values changes (oven test), hexanal formation, and protection factors (Rancimat method) were determined on a lipid model system that consisted of sunflower seed oil/water (1:2), emulsified with 3% (w/w) Tween 40. Results from the DPPH^· method showed a potential antioxidant activity of MRP_(aq), which was confirmed by the indirect methods. Surprisingly, histidine in solution alone (heated or not) exhibited an antioxidant activity greater than or similar to the MRP_(aq) activity in the indirect methods with the lipid model system, in contrast to the results from the DPPH^· method. The suitability of various solvents for extraction of potential antioxidant compounds from freeze-dried MRP_(aq) was examined, and ethanol extracts showed the greatest activity by the DPPH^· method. Consequently, the ethanol extract of freeze-dried MRP_(aq) was separated by means of preparative reverse-phase high-performance liquid chromatography (HPLC) with a 0.05 M phosphate buffer (pH 4.4)/water/acetonitrile gradient system. The antioxidant activity of the eluate was measured through the DPPH^· method, and a fraction (Fraction A) with antiradical activity was further purified by preparative HPLC. Fraction B was collected, and its freeze-dried residue exhibited potent antiradical activity, significantly greater than that of the same level of n-propyl gallate.     

Antioxidants from a heated histidine-glucose model system. Investigation of the copper(II) binding ability

The metal binding ability of Maillard reaction products (MRP) was investigated by spectrophotometric monitoring for complex/chelate formation. In addition, the antioxidant activity of MRP, in the presence of Cu(II), was evaluated on a lipid model system consisting of sunflower seed oil/water (1∶2). Results from the Rancimat test indicated a significant decrease in pro-oxidant ability of Cu(II) in the presence of MRP in contrast to histidine alone, whether heated or not. Results from the diphenylpicrylhydrazyl method showed that, in contrast to histidine (heated or not), the antiradical ability of MRP is reduced in the presence of Cu(II), but depends on the reaction time between MRP and Cu(II).     

Effect of methylmercuric chloride on gangliosides of mouse neuroblastoma cells in culture

The effect of methylmercuric chloride (CH3HgCl) on the levels of gangliosides in mouse neuroblastoma cells (NBP2) in culture was studied. The treatment of NB cells with low concentrations (0.1 microM and 0.2 microM) of CH3HgCl, which did not affect the growth rate or morphology, caused an increase in the level of the GM3 ganglioside without changing the level of other gangliosides. The treatment of NB cells with higher concentrations (0.5 microM and 1 microM) of CH3HgCl, which inhibited the growth of NB cells, caused a decrease in the level of GM3 and an increase in the level of GM2. These results show that alterations in the levels of specific gangliosides can be observed in cells which do not exhibit any detectable change in growth rate or morphology. This change may be associated with subtle changes in brain functions, including behavioral and psychological changes, after exposure to low concentrations of organic mercury.     

Synthesis and characterization of polyethoxylate surfactants derived from phenolic lipids

Polyethoxylates from cardanol and from cardol, the main component phenolic lipids in technical cashew nutshell liquid derived from the replenishable source Anacardium occidentale, were obtained by reaction with ethylene oxide under base-catalyzed conditions. Oligomeric mixtures resulted. In the cardanol series, the first six members of the mixture were independently synthesized for characterization purposes by a variety of reactions. The members in the oligomeric mixture were separated by HPLC, and the composition was determined by ¹H NMR spectroscopy and by chromatography. These studies were preparatory to surfactant and biodegradation studies involving comparison with commercially available polyethoxylates derived from petrochemical nonylphenol.     

Water extraction and degradation of a sterically hindered phenolic antioxidant in polypropylene films

Water extraction of the sterically hindered phenolic antioxidant Irganox 1010 from three polypropylene based polymeric films has been studied in isothermal conditions at 40, 50 and 70 °C. The films made of isotactic polypropylene and two different heterophasic polypropylene/ethylene–propylene monomers copolymers (PP/EPM copolymers) were immersed in closed water baths under nitrogen atmosphere in order to minimise the oxidative process. The amounts of antioxidant that have left the films and are dissolved in the water bath have been monitored over time by HPLC analysis and faster extraction kinetics were observed from the polymers than from the homopolymer. No appreciable amounts of Irganox 1010 were found in the extraction water at any time, whereas its degradation by-products were found by LC/MS analysis in the extraction water.

The experimental extraction kinetics from the three polymers were compared with the theoretical curves based on the Fick's diffusion equations solved both for a semi-infinite (degradation reaction faster than extraction) and a finite system (no degradation reaction) and Irganox 1010 was demonstrated to be extracted by water from polypropylene based material faster than predictable only on the basis of the values of its coefficient of diffusion in the polymers and of partition between water and polymer.     

新型含磷酚醛树脂的合成与性能

通过亚膦酸酯与碳碳双键之间的亲电加成反应,合成了一种新型的含磷马来酰亚胺酚醛树脂。采用红外光谱(FTIR)和元素分析法对聚合物的结构进行了表征。并用此含磷酚醛树脂作为环氧树脂的固化剂制得了一含磷氮的环氧固化物。采用热分析法、极限氧指数法对相应环氧固化物的耐热性能和阻燃性能进行了表征。研究结果表明:以该含磷聚合物作为环氧树脂的固化剂,对稳定固化物骨架碳的结构和交联成炭能力的提高起到了增强作用;环氧固化物具有较高的玻璃化转变温度(145.4℃)和较高的热稳定性(T508℃),极限氧指数显示其具有较好的阻燃性能。     

Evaluation of antioxidant activity: II. application of a heme- Catalyzed system

A study was made of the inhibitory effect of the antioxidants propyl gallate,tert-butylated hydroxyanisol, α-tocopherol and ethoxyquin on the hemoglobin-catalyzed oxygenation of linoleic acid. The concentration of unchanged fatty acid after varying incubation periods and at varying concentrations of antioxidant was measured by gas chromatography. The effect of the antioxidants is compared with results obtained previously from the lipoxygenase-catalyzed oxidation of a linoleic acid emulsion. It is concluded that all 4 antioxidants are good inhibitors of fatty acid oxidation cata-lyzed by hemoglobin.     

Ascorbate and phenolic antioxidant interactions in prevention of liposomal oxidation

Efficient prevention of membrane lipid peroxidation by vitamin E (α-tocopherol) may involve its regeneration by vitamin C (ascorbate). Conceivably, the efficacy of antioxidants designed as therapeutic agents could be enhanced if a similar regeneration were favorable; thus, a model membrane system was developed which allowed assessment of interaction of phenolic antioxidants with ascorbate and ascorbyl-6-palmitate. Ascorbate alone (50–200 μM) potentiated oxidation of soybean phosphatidylcholine liposomes by Fe²⁺/histidine-Fe³⁺, an effect which was temporally related to reduction of Fe³⁺ generated during oxidation. Addition of 200 μM ascorbate to α-tocopherol-containing liposomes (0.1 mol%) resulted in marked, synergistic protection. Accordingly, in the presence but not absence of ascorbate, α-tocopherol levels were maintained relatively constant during Fe²⁺/histidine-Fe³⁺ exposure. Probucol (4,4′-[(1-methylethylidine)bis(thio)]bis[2,6-bis(1,1-dimethylethyl)]phenol), and antioxidant which prevents oxidation of low density lipoproteins, and its analogues MDL 27,968 (4,4′-[(1-methylethylidene)bis(thio)]-bis[2,6-dimethyl]phenol) and MDL 28,881 (2,6-bis(1,1-dimethylethyl)-4-[(3,7,11-trimethyldodecyl)thio]phenol) prevented oxidation but exhibited no synergy with ascorbate. Ascorbyl-6-palmitate itself was an effective antioxidant but did not interact synergistically with any of the phenolic antioxidants. Differential scanning calorimetry revealed significant differences among the antioxidants in their effect on the liquid-crystalline phase transition of dipalmitoyl phosphatidylcholine (DPPC) liposomes. Both α-tocopherol and MDL 27,968 significantly reduced the phase transition temperature and the enthalpy of the transition. MDL 28,881 had no effect while probucol was intermediate. The potential for ascorbate or its analogues to interact with phenolic antioxidants to provide a more effective antioxidant system appears to be dictated by structural features and by the location of the antioxidants in the membrane.