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At least 649 records · Page 36Linked to original sources
PubMed2005

Novel bioactive maloyl glucans from aloe vera gel: isolation, structure elucidation and in vitro bioassays.

In this study, three novel maloyl glucans were isolated at temperatures below 15 degrees C from aloe vera gel (Aloe barbadensis Miller). These compounds were characterized using NMR spectroscopy, ESIMS, MALDITOF-MS and capillary electrophoresis. The compounds were characterized as 6-O-(1-L-maloyl)-alpha-,beta-D-Glcp (veracylglucan A), alpha-D-Glcp-(1-->4)-6-O-(1-L-maloyl)-alpha,-beta,-D-Glcp (veracylglucan B) and alpha-D-Glcp-(1-->4)-tetra-[6-O-(1-L-maloyl)-alpha-D-Glcp-(1-->4)]-6-O-(1-L-maloyl)-alpha,-beta-D-Glcp (veracylglucan C). These unusual malic acid acylated carbohydrates were then tested in vitro for effects on cell proliferation and gene expression of proinflammatory cytokines, IL-6, IL-8 and ICAM-1, using RT-PCR. Veracylglucan B demonstrated potent anti-inflammatory and anti-proliferative effects, while Veracylglucan C, on the other hand, exhibited significant cell proliferative and anti-inflammatory activities. Veracylglucan A could only be isolated in smaller quantities, and it proved to be very unstable. Thus no biological effects could be observed in this respect. The in vitro bioassays also indicated that Veracylglucan B and C are antagonistic and competitive in their effects on cell proliferation. The results of this work represent a major step forward in the research on aloe vera gel. This is the first time that two fully chemically characterized compounds are shown to be responsible for known biological activities of aloe vera gel.

Acylation↗
PubMed2006

Synthesis of 1-homoaustraline.

The 1,3-dipolar cycloaddition of a five-membered cyclic nitrone derived from malic acid and unsaturated D-threo-hexonolactone leads to a single adduct, which was transformed into 1-homoaustraline via a reaction sequence involving rearrangement of the six-membered lactone ring into the five-membered one, removal of the terminal carbon atom from the sugar chain, reduction of the lactone fragment into triol, protection of primary hydroxy groups, mesylation of the secondary one, cleavage of the N-O bond, and the intramolecular alkylation of the nitrogen atom.

Carbohydrates↗
PubMed2006

Computer aided boar semen motility analysis for cereulide detection in different food matrices.

Computer Aided Semen Analysis (CASA) study of the boar semen motility has been demonstrated to be an appropriate assay for detection of cereulide (Bacillus cereus emetic toxin). Application of the boar semen bio-assay to detect cereulide directly in foods requires investigation of potential interference of food components, preservatives and other microbial and chemical food contaminants with the bio-assay. Current study provides evidence that none of included Staphylococcus aureus enterotoxins A, B, C and D nor B. cereus Hemolysin BL (HBL) and non-hemolytic enterotoxin (NHE) and three mycotoxins (Sterigmatocystin, Fumonisin B1 and Patulin) exhibited a toxic impact on semen progressive motility. Aflatoxin M1, M3 and zearalenone impaired semen motility only at concentrations (0.004 mg ml(-1), 0.1 mg ml(-1) and 10 mg ml(-1), respectively) much higher than those found in foods and those permitted by legislation, in comparison to cereulide which induces motility cease at concentrations lower than 20 ng ml(-1). Ten commonly used preservatives, namely potassium sorbate, sodium benzoate, (DL) malic acid, citric acid, (L+) tartaric acid, acetic acid, (DL) lactic acid, (L+) ascorbic acid, sodium chloride and sucrose induced no cease in spermatozoa motility even at preservative concentrations higher than permitted by legislation. Dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), and acrylamide had no acute effect on spermatozoa motility at concentrations of 500 and 10,000 mg ml(-1), respectively. Robustness of computer aided boar semen motility analysis, tested with 14 different foods inoculated with cereulide producing B. cereus, showed distinct cereulide production in seven samples (although B. cereus growth to counts higher than 8 log CFU g(-1) was noted in 11 samples), in amounts close to those reported in foodborne outbreaks. Test evaluation in 33 samples suspected to hold cereulide showed actual cereulide presence in ten samples and no interference of food matrix with the assay.

Animals↗
PubMed2006

Preparation of insulin nanoparticles and their encapsulation with biodegradable polyelectrolytes via the layer-by-layer adsorption.

To develop a new polypeptide delivery system, insulin nano-aggregates with sizes of 100-230nm were prepared by the salting out method with NaCl and encapsulated via the layer-by-layer (LbL) adsorption to provide the insulin nanoparticles shelled with two oppositely charged polyelectrolytes. Poly(alpha,beta-l-malic acid) (PMA) and water-soluble chitosan (WSC) as the weak polyelectrolytes with good biodegradability and biocompatibility in vivo were chosen to be the encapsulating materials of the LbL adsorption. In the preparation of the insulin nano-aggregates, the NaCl concentration and pH in the medium obviously affected yield and particle size of the insulin nano-aggregates. After eight adsorption cycles of the polyelectrolytes on the insulin nano-aggregates, the insulin-polyelectrolyte nanoparticles with the sizes of 100-250nm were obtained with about 20% insulin loss. The insulin release from the nanoparticles was mostly pH-dependent owing to sensitivity of the weak polyelectrolytes to pH. Insulin was hardly released from the nanoparticles in a medium at pH 4-5 while it could be released at pH 7.4, corresponding to the pH of the human blood and the body fluid. A burst effect was also observed although it could be reduced via increasing the polyelectrolyte layers of PMA and WSC assembled on insulin nano-aggregates.

Adsorption↗
PubMed2003

Anodic oxidation with doped diamond electrodes: a new advanced oxidation process.

Boron-doped diamond anodes allow to directly produce OH* radicals from water electrolysis with very high current efficiencies. This has been explained by the very high overvoltage for oxygen production and many other anodic electrode processes on diamond anodes. Additionally, the boron-doped diamond electrodes exhibit a high mechanical and chemical stability. Anodic oxidation with diamond anodes is a new advanced oxidation process (AOP) with many advantages compared to other known chemical and photochemical AOPs. The present work reports on the use of diamond anodes for the chemical oxygen demand (COD) removal from several industrial wastewaters and from two synthetic wastewaters with malic acid and ethylenediaminetetraacetic (EDTA) acid. Current efficiencies for the COD removal between 85 and 100% have been found. The formation and subsequent removal of by-products of the COD oxidation has been investigated for the first time. Economical considerations of this new AOP are included.

Boron↗
PubMed2004

Chemical forms of aluminum in xylem sap of tea plants (Camellia sinensis L.).

To identify the chemical forms of aluminum (Al) transported from roots to shoots of tea plants (C. sinensis L.), 27Al-nuclear magnetic resonance and 19F NMR spectroscopy were used to analyze xylem sap. The concentration of Al in collected xylem sap was 0.29 mM, twice as high as that of F. Catechins were not detected in xylem sap. The concentration of malic acid in xylem sap was higher than that of citric acid, whereas the concentration of oxalic acid was negligible. There were two signals in the 27Al NMR spectra of xylem sap, a larger signal at 11 ppm and a smaller one at -1.5 ppm. The former signal was consistent with the peak for an Al-citrate model solution, suggesting that an Al-citrate complex was present in xylem sap. Although the latter signal at -1.5 ppm was thought to indicate the presence of an Al-F complex (at 1.7 ppm) in xylem sap, there was only one signal at -122 ppm in the 19F NMR spectrum of xylem sap, indicating that the main F complex in xylem sap was F-. These results indicate that Al might be translocated as a complex with citrate, while Al-malate, Al-oxalate and Al-F complexes are not major Al complexes in xylem sap of tea plants.

Aluminum Compounds↗
PubMed2003

Metabolomic analysis of the consequences of cadmium exposure in Silene cucubalus cell cultures via 1H NMR spectroscopy and chemometrics.

Several essential and non-essential metals (typically those from periods 4, 5 and 6 in groups 11-15 in the periodic table) are commonly detoxified in higher plants by complexation with phytochelatin. The genetic and gross metabolic basis of metal tolerance in plants is, however, poorly understood. Here, we have analyzed plant cell extracts using 1H NMR spectroscopy combined with multivariate statistical analysis of the data to investigate the biochemical consequences of Cd(2+) exposure in Silene cucubalus cell cultures. Principal components analysis of 1H NMR spectra showed clear discrimination between control and Cd(2+) dosed groups, demonstrating the metabolic effects of Cd(2+) and thus allowing the identification of increases in malic acid and acetate, and decreases in glutamine and branched chain amino acids as consequences of Cd(2+) exposure. This work shows the value of NMR-based metabolomic approaches to the determination of biochemical effects of pollutants in naturally selected populations.

Cadmium↗
PubMed2001

UV-C irradiation reduces microbial populations and deterioration in Cucurbita pepo fruit tissue.

Tissue slices of zucchini squash (Cucurbita pepo L., cv. Tigress) fruit were exposed to ultraviolet-C (UV-C) radiation from germicidal lamps for 1, 10 or 20 min; however, only 10 and 20 min UV-C exposure significantly reduced microbial activity and deterioration during subsequent storage at 5 or 10 degrees C. UV-C treated slices had higher respiration rates than controls; however, the ethylene production of the slices was not affected by UV-C treatments. Slight UV-C irradiation damage (reddish brown discoloration) was detected on the surface of 10 and 20 min-treated slices after 12 days of storage at 10 degrees C. Slices stored at 5 degrees C did not show UV-C damage. Chilling injury was not observed until after 20 days of storage at 5 degrees C. The symptoms of chilling injury appeared as dried sunken brown spots on the surface of cortex tissue. UV-C treatments did not affect the degree of chilling injury during storage at 5 degrees C. UV-C treatment also had no consistent effect on sugar or malic acid concentrations. The most pronounced effect of UV-C irradiation was to retard microbial growth thereby providing a basis for the frequently observed delay in senescence and subsequent deterioration in fruit tissues.

Journal Article↗
PubMed2003

Transport of glutamate in Oenococcus oeni 8403.

The transport of L-glutamate in Oenococcus oeni 8403 is energy dependent. It could be activated either by carbohydrate or arginine metabolism, and it was shown to be stimulated by L-malic acid at low pH values. Transport was optimal at pH 7.0. The apparent affinity constants for transport (KT) was 0.98 microM at pH 7.0. L-glutamate uptake was inhibited by glutamine, asparagine and L-aspartate.

Amino Acids↗
PubMed1997

Processing and storage of lye-treated carrots fermented by a mixed starter culture.

A mixed culture of Lactobacillus plantarum and Saccharomyces cerevisiae was compared with a single culture of L. plantarum as starter for the fermentation of lye-treated carrots. Using the mixed culture, more than 95% of glucose, fructose and malic acid was consumed after 7 days of fermentation in a brine containing 2.5% w/v NaCl and 0.7% acetic acid, but only 54% of sucrose was degraded. The fermentation products quantified were lactic acid, ethanol and acetic acid and carbon recovery was 88%. Using the single culture of L. plantarum, substrate consumption was lower, and carbon recovery almost 100%. In uninoculated lye-treated carrots, heterofermentative bacteria grew, with the production of considerable amounts of mannitol. In all cases, the stability, sensorial characteristics and carotenoid content of the packed product were studied during 9 months of storage at 30 degrees C, and two different preservation systems were compared: addition of preservatives, approximately 500 and 1000 mg/kg of sorbic and benzoic acid, respectively, and pasteurization at 80 degrees C for 10 min. The pasteurized samples were microbiologically stable during the storage period, while lactic acid bacteria grew in the samples with preservatives. Storage time significantly (P < 0.05) affected the texture and colour parameters (L*, a*, b*) of the carrots, but not the amounts of alpha- and beta-carotene. The type of fermentation had no significant effect on texture, colour parameters or carotenoid content. The preservation method had no significant effect on texture or carotenoid content, but did affect colour (parameter a*). The flavour of carrots fermented by the mixed culture was significantly (P < 0.05) preferred to that of those fermented with a single culture of L. plantarum.

Daucus carota↗
PubMed2001

Ecophysiological responses of Empetrum nigrum to heavy metal pollution.

Chlorophyll, organic (citric and malic acids) and abscisic acid (ABA) contents and stem water potential were measured to indicate possible physiological effects of heavy metal deposition on Empetrum nigrum L. (crowberry). The leaves and stems of E. nigrum were collected at distances of 0.5 and 8 km from the Cu-Ni smelter at Harjavalta, south-west Finland. All the investigated parameters were clearly affected by heavy metal emissions. Chlorophyll contents in the leaves and organic acid contents in the leaves and stems were lower close to the emission source. Generally found increase in organic acid contents with increasing Ni concentrations was not found, which might be due to the lower production of organic acids measured by decreased photosynthesis near the smelter. In contrast, ABA contents in stems and leaves in general, were higher in plants growing 0.5 km from the pollution source. Close to the smelter the stem water potential of E. nigrum was less negative during the day but more negative during the night. These results suggest that smelter emissions have a negative effect on the ecophysiology of E. nigrum even though it is considered to be a tolerant species to heavy metals.

Chlorophyll↗
PubMed1998

Physical and genetic maps of the Leptospira interrogans serovar icterohaemorrhagiae strain Ictero no.1 chromosome and sequencing of a 19-kb region of the genome containing the 5S rRNA gene.

We report the construction of physical and genetic maps of the chromosome of Leptospira interrogans serovar icterohaemorrhagiae strain Ictero No.1 using pulsed-field gel electrophoresis of DNA fragments generated by digestion with enzymes SrfI, AscI, FseI, and NotI and using reciprocal hybridization. We also sequenced the 19-kilobase (kb) DNA segment including the one gene for 5S rRNA (rrf) of pathogenic Leptospira. The size of the chromosome of the strain Ictero No.1 was estimated to be 4673kb and was found to be similar to those of the chromosomes of the leptospira strains Verdun (serovar icterohaemorrhagiae) and RZ11 (serovar pomona). The strains Verdun and RZ11 carry a small 350-kb replicon (minichromosome), and the strain Ictero No.1 also contained the same kind of molecule together with the chromosome. The physical maps of the strains Ictero No.1 and Verdun were almost identical, as were the locations of the selected genes, except for the location of one of the 16S rRNA genes. Overall, the genetic organization appeared to be conserved within the serovar icterohaemorrhagiae strains. In the sequenced region, we identified 10 putative ORFs and one rrf sequence, and the transcription orientations were all the same. A homology search for the products deduced from the sequenced data revealed that the orf H exhibited high similarity to malic acid enzyme of Haemophilus influenzae and fumarate hydratase of Escherichia coli (orf J). The rest of the putative products encoded by ORFs in the sequenced region showed little similarity with the proteins contained in the databases and were considered to be unknown proteins.

Bacterial Proteins↗
PubMed2001

Development and characterization of cross-linked poly(malate) microspheres with dipyridamole.

Biodegradable cross-linked microspheres containing up to 63 wt.% of the active substance were obtained in a polycondensation process between D,L-malic acid and the tetrahydroxy compound dipyridamole. The in vitro release mechanism from biodegradable cross-linked microspheres has been studied. It was found that dipyridamole was released due to two-step hydrolysis of the ester bonds of the network. Initially, the only product of the hydrolytic degradation was found to be an oligomeric ester fraction with M(w)=1000 Da. The release of the free drug started after 8 days due to a further hydrolysis of the oligomers in solution. It was found that blood plasma enzymes in rats did not affect the hydrolytic processes. Biodegradable poly(malate) microspheres containing an anti-aggregating agent dipyridamole can be considered as a novel drug delivery system for a prolonged period of time implying a future parenteral application.

Animals↗
PubMed2002

Isolation and pharmacological activity of phenylpropanoid esters from Marrubium vulgare.

The isolation and identification of major phenylpropanoid esters from Marrubium vulgare: (+) (E)-caffeoyl-L-malic acid 1, acteoside 2, forsythoside B 3, arenarioside 4, ballotetroside 5, as well as their anti-inflammatory activity are reported for the first time. We evaluated the inhibitory effects of these five compounds on cyclooxygenase (Cox) catalysed prostaglandin biosynthesis activity. Only the glycosidic phenylpropanoid esters showed an inhibitory activity towards the Cox-2 enzyme and three of them: acteoside 2, forsythoside B 3, arenarioside 4, exhibited higher inhibitory potencies on Cox-2 than on Cox-1. These results are of interest, as Cox-2 is mainly associated with inflammation and the Cox-1 inhibition with adverse side effects often observed with non-steroidal anti-inflammatory drugs. The occurrence of these phenylpropanoid esters could also explain some other pharmacological properties of M. vulgare.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

Isolation and antibacterial activity of phenylpropanoid derivatives from Ballota nigra.

In addition to the previously isolated phenylpropanoid glycosides verbascoside 1, forsythoside B 2, arenarioside 3 and ballotetroside 4, another four compounds were isolated from generative aerial parts of Ballota nigra: three phenylpropanoid glycosides, alyssonoside 5, lavandulifolioside 6 and angoroside A 7 and a non-glycosidic derivative (+)-(E)-caffeoyl-L-malic acid 8. The antibacterial activity of the five major compounds (1-4 and 8) was tested against gram-positive and gram-negative bacteria. Three of them (1-3) exhibited a moderate antimicrobial activity against Proteus mirabilis and Staphylococcus aureus including one methicillin-resistant strain.

Anti-Bacterial Agents↗
PubMed1998

Metabolite-derived artificial polymers designed for drug targeting, cell penetration and bioresorption.

The use of poly(beta-malic acid) and poly(l-lysine citramide) carriers to transport doxorubicin (Dox) within K562 myeloblastic cells was studied by taking advantage of laser microspectrofluorometry (L-MSF). This technique provided a means to monitor and to quantify the penetration of Dox molecules in the cytoplasm and in the nucleus of Dox-sensitive and Dox-resistant cells. Comparison was made between polymer-drug conjugates more or less hydrophobised by C2, C7 and C12 aliphatic substituents and by the Dox attached to the polymer backbone as pendent chains. Furthermore, a method was proposed to introduce a cleavable non-peptidic spacer of the lactyllactyl-type between the poly(L-lysine citramide) backbone and the drug. It is shown that: Dox was released from the conjugates by a non-enzymatic route in the absence of cells, the Dox-uptake by cells was slower for the conjugates than for the free drug, and the hydrophobisation promoted the penetration of the released drug within the nucleus, even in the case of Dox-resistant cells. However, no reversion of the resistance was observed.

Cell Nucleus↗
PubMed2002

Novel morpholinone-based D-Phe-Pro-Arg mimics as potential thrombin inhibitors: design, synthesis, and X-ray crystal structure of an enzyme inhibitor complex.

A morpholinone structural motif derived from D(+)- and L(-)-malic acid has been used as a mimic of D-Phe-Pro in the thrombin inhibiting tripeptide D-Phe-Pro-Arg. In place of Arg the more rigid P1 truncated p-amidinobenzylamine (Pab) or 2-amino-5-aminomethyl-3-methyl-pyridine have been utilized. The synthetic strategy developed readily delivers these novel thrombin inhibitors used to probe the alpha-thrombin inhibitor binding site. The best candidate in this series of thrombin inhibitors exhibits an in vitro IC(50) of 720 nM. The X-ray crystal structure of this candidate co-crystallized with alpha-thrombin is discussed.

Crystallography, X-Ray↗
PubMed2003

Physiological behaviour of Hanseniaspora guilliermondii in aerobic glucose-limited continuous cultures.

The physiology of Hanseniaspora guilliermondii was studied under aerobic glucose-limited conditions using the accelerostat procedure (continuous acceleration of dilution rate) and classical chemostat cultures. By both cultivation techniques this yeast was found to be Crabtree-positive. Up to a dilution rate of 0.25 h(-1), glucose was completely metabolised into biomass, glycerol and carbon dioxide. Above this value, an increase in the dilution rate was accompanied by the production of other metabolites like ethanol, acetic and malic acids. Biomass yield during the purely oxidative growth was 0.49 g g(-1) and decreased to 0.26 g g(-1) for D=0.34 h(-1). A maximal specific ethanol production rate of 1.36 mmol g(-1) h(-1) and a maximal ethanol yield of 0.05 g g(-1) were achieved at D=0.34 h(-1).

Aerobiosis↗