PubMed Health⌕ Search

Biomedical subjects

J Vercauteren

Publications and source records attributed to J Vercauteren.

At least 19 recordsLinked to original sources
PubMed2002

Dietary antioxidants, peroxidation and cardiovascular risks.

Most of the many epidemiological studies in the field strongly suggest that an equilibrated diet such as the so-called "mediterranean diet", is associated with protective effects against major diseases, and particularly, against cardiovascular risks. Since many reports also consider reactive oxygen species or free radical oxidations to be responsible for the accompanying disorders of most pathologies as well as for ageing, it is conceivable that natural plant metabolites such as polyphenols, are likely to play an important role in insuring this protection. Indeed, not only their presence, in particularly high amounts and varieties in foods of such a diet, but also, inter alia, their very potent antioxidant or radical scavenging properties, make polyphenols best accounting for the parodoxical part of the french paradox . Therefore, many efforts have been made to assess the mechanisms for such a cardiovascular disease protection. Whatever convincing were the polyphenols properties demonstrated by many in vitro experiments to support those theories, quite a great number of the results appeared somewhat contradictory when transposed to humans, in the in vivo situation. Some people totally refute this explanation, thinking that health benefits, as far as alcoholic beverages are concerned, originate from ethanol but also, with no doubt, some polyphenols even revealing to be pro-oxidants .

Aged↗
PubMed2001

Stir bar sorptive extraction for the determination of ppq-level traces of organotin compounds in environmental samples with thermal desorption-capillary gas chromatography--ICP mass spectrometry.

The extraction and preconcentration capabilities of a new extraction technique, stir bar sorptive extraction, were combined with the separation power of capillary gas chromatography (CGC) and the low limits of detection (LODs) of inductively coupled plasma mass spectrometry (ICPMS) for the determination of the organotin compounds tributyltin (TBuT) and triphenyltin (TPhT) in aqueous standard solutions, harbor water, and mussels (after digestion with tetramethylammonium hydroxide). Throughout, tripropyltin for TBuT and tricyclohexyltin for TPhT were used as internal standards to correct for variations in the derivatization and extraction efficiency. Calibration was accomplished by means of single standard addition. Derivatization to transform the trisubstituted compounds into sufficiently volatile compounds was carried out with sodium tetraethylborate. The compounds were extracted from their aqueous matrix using a stir bar of 1-cm length, coated with 55 microL of poly(dimethylsiloxane) (PDMS). After 15 min of extraction, the stir bar was desorbed in a thermal desorption unit at 290 degrees C for 15 min, during which the compounds were cold-trapped on a precolumn at -40 degrees C. Flash heating was used to rapidly transfer the compounds to the GC where they were separated on a capillary column with a PDMS coating. After separation, the compounds were transported to the ICP by means of a homemade heated (270 degrees C) transfer line. Monitoring of the 120Sn+ signal by ICPMS during the run of the GC provided extremely low LODs for TPhT in water: 0.1 pg L(-1) (procedure) and 10 fg L(-1) (instrumental) and a repeatability of 12% RSD (n = 10). In harbor water, concentrations of 200 pg L(-1) for TBuT and 22 pg L(-1) for TPhT were found. In fresh mussels, a concentration of 7.2 ng g(-1) (dry weight) TPhT was found. The accuracy of the method was checked by the determination of TPhT in CRM477 (mussel tissue) and comparison of the result to that of an analysis of the same material with a classical liquid/liquid extraction with isooctane.

Animals↗
PubMed2001

Occurrence of anthocyanin-derived pigments in red wines.

Several anthocyanin-derived pigments that showed UV-visible spectra different from those of the original grape anthocyanins were detected by HPLC-DAD analysis in 1-year-old bottled Port wines from the Douro region. Among these, three malvidin 3-glucoside derived pigments were detected in large amounts, representing approximately 60% of the total anthocyanidin monoglucosides content. These pigments were isolated, purified, and identified by LSI-MS and NMR ((1)H, DQF-COSY, ROESY, HSQC, and HMBC) techniques. The major pigment is malvidin 3-glucoside pyruvic adduct, previously characterized, and the other two corresponded to its respective acetyl and coumaroyl glucoside derivatives. The latter is reported for the first time in red wines.

Anthocyanins↗
PubMed2001

Polyphenols newly extracted in red wine from southwestern France by centrifugal partition chromatography.

Polyphenols from the ethyl acetate extracts of red wine were successfully fractionated using a four-step process (solvent extraction, ion-exchange column chromatography, centrifugal partition chromatography, and semipreparative HPLC), which resulted in the isolation of 22 compounds belonging to different classes of polyphenols (stilbenes, cinnamic acids, flavonoids). Five of them are red wine constituents reported for the first time. The newly isolated compounds include resveratrol dimers, dihydroflavonols, and a cinnamic derivative.

Chromatography↗
PubMed2001

NMR and simulated annealing investigations of bradykinin in presence of polyphenols.

Epidemiological studies have shown that the incidence of some cardiovascular degenerative diseases appears to be lower in populations with regular but moderate drinking of red wine rich in polyphenols. One of the most important properties of polyphenols is to form complexes with proteins. The linear nonapeptide hormone bradykinin (H-Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9-OH) is involved in a variety of physiological processes such as the cardiovascular processes. Thus, the goal of this work was to study the effects of tannins on the peptide structure by NMR investigations and molecular modeling. The results of these investigations show that in the presence of catechin, the peptide conformation is not affected and is in a random coil structure. On the contrary, the peptide structure is modified by the addition of dimeric proanthocyanidin B3 (catechin 4alpha-->8 catechin). The dimer leads to the formation of a large flexible turn between the 6-9 residues. Thus, the biological activities of bradykinin in the presence of polyphenols could be affected.

Anthocyanins↗
PubMed2000

DNA triplex stabilization property of natural anthocyanins.

The DNA triplex stabilization property of seven natural anthocyanins (five monoglucosides and two diglucosides) has been measured by the mean of triplex thermal denaturation experiments. We have noticed a difference between the diglucosides that do not modify this melting temperature and the monoglucosides (namely 3-O-beta-D-glucopyranoside of malvidin, peonidin, delphinidin, petunidin and cyanidin) which present a weak but significant stabilizing effect. It appears clearly that the difference between the two series could be due to the supplementary sugar moiety at the 5 position for the diglucosylated compounds, that would make them too crowded to allow interaction with the triplex. Among the monoglucoside series, the most active compounds are the only ones to embody a catechol B-ring in their structure that could be important for such an interaction. The need to have pure and fully characterized compounds to run these measurements, made it possible for us to unambiguously assign the 1H and 13C NMR spectra with the help of 2D NMR experiments. Thus, missing data of compounds not totally described earlier, are provided herein.

Anthocyanins↗
PubMed1999

Production of 13C-labelled anthocyanins by Vitis vinifera cell suspension cultures.

The use of plant cell cultures for producing isotopically (13C) labelled phenolic substances is reported. Vitis vinifera cells synthesize high levels of anthocyanins when they are cultured in a polyphenol synthesis-inducing medium. Three major anthocyanin monoglucosides found in red wine were identified in grape cells: cyanidin-3-O-beta-glucoside, peonidin-3-O-beta-glucoside, and malvidin-3-O-beta-glucoside. Kinetic study of the intracellular level of phenylalanine and its metabolites showed that it is preferable to add this precursor to grape cell suspensions after the 5th day of culture, i.e. at the beginning of the exponential growth phase. After adding phenylalanine to the culture medium, its uptake was complete and the accumulation of anthocyanins in grape cells was stimulated. Incorporation of [1-13C]-phenylalanine into anthocyanins was measured by means of 13C satellites in the proton NMR spectrum. The maximal rate of 13C enrichment anthocyanins obtained with this technique reached 65%. The production of 13C labelled phenolic compounds was undertaken in order to investigate their absorption and metabolism in humans.

Anthocyanins↗
PubMed1999

Determination of stilbenes (trans-astringin, cis- and trans-piceid, and cis- and trans-resveratrol) in Portuguese wines.

Stilbenes have been shown to have cancer chemopreventive activity and to protect lipoproteins from oxidative damage. A method is described for their direct determination in different types of wine using high-performance liquid chromatography with ultraviolet detection. In a survey of 120 commercial wines from Portugal and France, the highest concentrations of stilbenes were found in red wines. The glucosides of resveratrol were present in higher concentrations than the free isomers. Isolation from wine and characterization of trans-astringin in a large quantity are described for the first time.

Chromatography, High Pressure Liquid↗
PubMed1998

Determination of the uptake of [Pt(NH3)4](NO3)2 by grass cultivated on a sandy loam soil and by cucumber plants, grown hydroponically.

Two cultivation experiments were carried out in order to answer the question to what extent platinum can enter the food chain by accumulation in plants, when the platinum is present in a bio-available form: (i) cucumber plants (Cucumis sativus) were grown hydroponically in nutrient solutions containing [Pt(NH3)4](NO3)2 (from 0.5 to 50 micrograms Pt/l solution); and (ii) a water-soluble platinum compound--[Pt(NH3)4](NO3)2--was added in increasing amounts to a sandy loam soil (from 0.5 to 50 mg Pt/kg soil) and rye grass (Lolium perenne) was grown on it. The roots on the one hand and the green plant fractions in the other hand of the cucumber plants and the rye grass were digested using a high-pressure asher. The platinum concentration was determined by means of a quadrupole-based (VG PQ I) or a double focusing sector field ICP-mass spectrometer (Finnigan MAT, Element), depending on the platinum concentration in the sample solution. The detection limit for platinum obtained with the VG PQ I was observed to be 6 ng/1, while with the 'Element' the detection limit could be improved to 0.5 ng/1 Pt. Accumulation factors were calculated as the ratio of the platinum concentration in the plant to that in the soil or the nutrient solution. The grass grown on spiked soil accumulated platinum only to a slight degree (accumulation factors between 0.008 and 0.032). The hydroponically grown cucumber plants, however, strongly accumulated it (accumulation factors of 11-42 in the shoot and 1700-2100 in the roots). There are three possible causes for the large differences in the accumulation factors: (i) Cucumber plants are dicotyledons; grass, however, is a monocotyledon. Other cultivation experiments already showed that dicotyledons accumulate metals to a higher extent than monocotyledons. (ii) In the grass cultivation experiment, the platinum compound was only added once to the sandy loam soil, namely 2 days before grass was cultivated on it. The nutrient solutions of the cucumber plants were changed twice a week. Consequently, the total amount of platinum that the plants were exposed to during the cultivation of the cucumber plants was higher than during the cultivation of the grass. (iii) Immobilization of the platinum compound in the soil most likely occurred.

Biological Availability↗
PubMed1998

Isolation, identification, and antioxidant activity of three stilbene glucosides newly extracted from vitis vinifera cell cultures

Suspension cultures of Vitis vinifera L. (Vitaceae) produce many hydroxylated stilbene glucosides found in red wine. From these cells, we isolated and characterized glycosylated stilbenes, (Z)-piceatannol (3,5,3',4'-tetrahydroxystilbene) -3-O-beta-d-glucopyranoside (6) and (E)- and (Z)-resveratrol (3,5, 4'-trihydroxystilbene)-4'-O-beta-d-glucopyranoside (2 and 7, respectively), which have not previously reported to be constituents of Vitis vinifera or wine. The ability of these compounds to act as radical scavengers was investigated using 1,1 diphenyl-2-picryl-hydrazyl, a stable free radical. Antioxidant activities were assessed by their capacity to prevent Cu2+-induced lipid peroxidation in human low-density lipoprotein.

Journal Article↗
PubMed1996

Quinazoline-2,4(1H,3H)-dione as a substitute for thymine in triple-helix forming oligonucleotides: a reassessment.

A major limitation in triple-helix formation arises from the weak energy of interaction between the third strand and the double-stranded target. We tried to increase the stacking interaction contribution within the third strand by extending the aromatic domain of thymine. We report here the use of 2,4-quinazolinedione as a substitute for thymine in the canonical TA*T triplet. The synthesis and the characterization of the quinazoline beta nucleoside Q and of its phosphoramidite derivative is described. Triple-helix- forming oligonucleotides incorporating Q have been prepared and their ability to form triplexes has been evaluated by UV-monitored thermal denaturation measurements. The introduction of one or multiple Q residues, either contiguous or remote from each other, slightly destabilized triple-stranded structures, whatever the nucleic acid base composition (pyrimidine or GT) of the third strand.

Drug Stability↗
PubMed1995

Structural analysis of the mannan region of lipoarabinomannan from Mycobacterium bovis BCG. Heterogeneity in phosphorylation state.

Lipoarabinomannan (LAM) is a major antigen of mycobacterial cell walls, involved in host-Mycobacterium interactions. In a previous work, LAM from the vaccine strain, Mycobacterium bovis BCG, was found to exhibit mannooligosaccharides at its arabinan nonreducing ends (ManLAM). The present report concerns the mannan core structure of this ManLAM. After partial hydrolysis of ManLAM, two populations of mannans (Ma1 and Ma2) were obtained by gel filtration chromatography. Their structural features were defined by means of two-dimensional homo- and heteronuclear (1H-13C) NMR sequences and methylation analysis. They were both found to be composed of an alpha-(1-->6)-linked mannan backbone with alpha-(1-->2)-Manp-linked side chains. They are highly branched, and Ma2 presents a higher frequency of branching than Ma1. Moreover, chemical analysis indicates that only Ma1 is phosphorylated. By a two-dimensional heteronuclear 1H-31P total correlation experiment, the phosphate was found to be involved in a phosphodiester bond between inositol C-1 and glycerol C-3. Then, the molecular mass of mannan was established by mass spectrometry, which revealed a molecular mass of 3517 Da for the major molecular species of Ma1. Likewise, analysis of unfractionated mannans showed the occurrence of other, quantitatively minor molecular species, endowed with two phosphates. This study clearly indicates that the mannan region of M. bovis BCG ManLAM exists as a heterogeneous population of molecules whose structures differ in their degree of glycosylation, level of branching, and phosphorylation state. The hypothesis that the relative abundance of these different molecules modulates the biological functions of LAM is discussed.

Antigens, Bacterial↗
PubMed1995

Platelet antiaggregant methoxyphenylthienyl ketoxime ethers: synthesis and structure-activity relationships.

Some new oximinoalkanoic (n = 2,3,4) esters and acids derived from methoxyphenylthienyl ketones have been synthesized and evaluated in vitro for their inhibitory effects on arachidonic acid-induced human platelet aggregation. Of the eighteen oximinoethers tested the most active derivatives, which were four times more active as aspirin, belonged to the para methoxy series with Z configuration and n = 2 or 3.

Ethers↗
PubMed1994

Lipo-oligosaccharidic antigen from Mycobacterium gastri. Complete structure of a novel C4-branched 3,6-dideoxy-alpha-xylo-hexopyranose.

The following incomplete structure, alpha-X-(1-->3)-[beta-L-Xylp-(1-->4)]6-3-O-Me-alpha-Rhap-(1- ->3)- beta-D-Galp-(1-->3)-beta-D-Glcp-(1-->4)-2-O-acyl-alpha-D-Glcp-(1<-->1)-4 ,6-di-O-acyl-alpha-D-Glcp, was previously established for the antigenic lipo-oligosaccharide typifying Mycobacterium gastri, namely, LOS-III. The partial structure of the distal monosaccharide (X) was assigned as 3,6-dideoxy-4-C-(1,3-di-O-methylpropyl)-alpha-hexopyranose, which corresponds to a new-found monosaccharide in nature [Gilleron M., Vercauteren J., & Puzo G. (1993) J. Biol. Chem. 268, 3168-3179]. This article reports the complete structure of X, which was determined from the FAB-MS and 2D NMR analysis of the peracetylated LOS-III. The comparative analyses of the native and per-O-acetylated LOS-III FAB-MS spectra revealed, for the monosaccharide X, a molecular mass of 370 Da and five hydroxyl groups that could be acetylated. Additionally, the 1D 1H NMR spectrum of the per-O-acetylated LOS-III showed a dramatically increased dispersion of the protons, which resonated between 3 and 4 ppm in the spectrum of the underivatized LOS-III. Thus, thanks to 2D NMR sequences (COSY, HOHAHA, HMQC, HMQC-HOHAHA, and HMBC), the complete assignment of the 1H and 13C signals was achieved. Starting from the quaternary C4 resonance, the spin system of the C-alkyl chain was assigned, allowing us to propose the following structure, 3,6-dideoxy-4-C-(1,3-dimethoxy-4,5,6,7-tetrahydroxyheptyl)-alpha-x ylo- hexopyranose. The xylo configuration was established from the ROESY spectrum.

Acetylation↗
PubMed1993

Stereochemistry of the reaction catalysed by 2-aminoethylphosphonate aminotransferase. A 1H-NMR study.

(R)- and (S)-2-amino[2-D1]ethylphosphonic acids ([2-D1]AEP) were synthesised to investigate the stereochemistry of the reaction catalysed by 2-aminoethlphosphonate aminotransferase from Pseudomonas aeruginosa. This enzyme catalyses the transfer of the amino group of AEP to pyruvate to produce 2-phosphonoacetaldehyde and alanine. The enzymic reaction proceeding through the abstraction of a proton from the Schiff-base complex formed between the enzyme-bound pyridoxal 5'-phosphate, and the substrate, was carried out in an aqueous buffer at pH 8.5; it was followed by high-field 1H-NMR measurements (500 MHz, H2O) on an AMX 500 Bruker spectrometer. The spectra, recorded with chiral (R)- or (S)-[2-D1]AEP, both showed the methylenic signal (3.0 ppm), whereas (S)-[2-D1]AEP gave the additional aldehydic signal (CHO, 9.6 ppm). These data clearly show that AEP-aminotransferase catalyses the abstraction of the pro-S hydrogen atom at the prochiral C2 carbon of AEP. Furthermore, careful timing of NMR measurements over a 2-hour period allows us to show the occurrence of an isotopic effect.

Catalysis↗
PubMed1993

Structure of a novel glycopeptidolipid antigen containing a O-methylated serine isolated from Mycobacterium xenopi. Complete 1H-NMR and 13C-NMR assignment.

GPL X-1, a novel glycopeptidolipid (GPL) isolated from Mycobacterium xenopi (CIPT 140 35004), has recently been found to typify a new class of mycobacterial glycopeptidolipids devoid of C-mycoside core structure, the so-called serine-containing glycopeptidolipid [Rivière, M. & Puzo, G. (1991) J. Biol. Chem. 266, 9057-9063]. Here we report the purification and characterization of a novel serine-containing GPL termed GPL X-IIb, isolated from the M. xenopi strain NCTC 10042. On thin-layer chromatography, this GPL was found to be present in some other M. xenopi strains isolated from patients with pulmonary infections. The sugar and amino-acid compositions of this GPL were elucidated from the native form using a combination of two-dimensional homonuclear and heteronuclear scalar coupling NMR. The peptide and sugar sequences, as well as the methoxyl group locations on the C-3 of the 6-deoxy-alpha-L-talopyranoside (6dTalp) and on a Ser, were unambiguously determined by heteronuclear multiple-bond correlation experiments. GPL X-IIb was found to be composed of a lipotetrapeptide of the following structure C12-Ser-OMe-Ser-Phe-aThr-OMe (aThr = allothreonine). The sugar part is made up of 3OMe-alpha-L-6dTalp and the following disaccharide: alpha-L-Rhap-(1-->3)-2-O-Lau-alpha-L-Rhap (Rhap = rhanmopyranose). Unlike GPL X-I, the sugar attachment sites on the tetrapeptide were successfully determined from heteronuclear three-bond coupling correlation observed in the heteronuclear multiple bond correlation spectrum between the anomeric carbon resonances and the beta protons of aThr-OMe and Ser. It was established that the 3OMe-6dTalp glycosylates the Ser while the disaccharide is linked to the aThr-OMe. Thus both GPL X-I and GPL X-IIb share a common lipotetrapeptide core [with the exception of Ser(OMe)] but drastically differ in their oligosaccharide appendage. Thus, by analogy with the M. avium complex, the present report suggests that M. xenopi species can be divided in various serovars characterized by the unique structure of their C-mycoside GPL oligosaccharide appendage, enhancing the interest for this new type of serine-containing glycopeptidolipid.

Amino Acid Sequence↗
PubMed1993

Lipooligosaccharidic antigen containing a novel C4-branched 3,6-dideoxy-alpha-hexopyranose typifies Mycobacterium gastri.

Lipooligosaccharides (LOSs) have recently been proposed as markers of mycobacterial avirulence. They have been characterized in Mycobacterium kansasii cell wall and were investigated in Mycobacterium gastri since the distinction between the two mycobacterial species remains in some question. A set of unknown LOSs was isolated from M. gastri W471. The highly antigenic lipooligosaccharide, LOS-III, was purified and appeared in all the M. gastri strains investigated regardless of their morphology. Moreover, by enzyme-linked immunosorbent assay and chromatographic approaches, it was found that LOS-III unambiguously distinguished M. gastri from the opportunistic pathogen M. kansasii. The LOS-III structure was established from its native form using NMR spectroscopy. This strategy revealed the presence of a supplementary monosaccharide (X) which was not characterized by routine carbohydrate analysis. Its core structure, 3,6-dideoxy-alpha-hexopyranose, was established from the complete assignment of the 1H and 13C spectra by two-dimensional homonuclear (COSY, HOHAHA) and heteronuclear 1H-13C heteronuclear multiple quantum correlation spectroscopy (HMQC) and HMQC-HOHAHA spectroscopy. Due to the absence of a proton at C4, the key data of the C4 side chain structure came from the heteronuclear multiple bond correlation spectroscopy (HMBC) spectrum. It was revealed to be a C-alkyl chain of partial structure 1,3-dimethoxypropyl. From the HMBC spectrum, this novel C-branched monosaccharide was located at the nonreducing end of the LOS, while the putative reducing end was found to consist of a 2',4,6-triacylated alpha-alpha-trehalose. The following structure, based on the evidence presented in this paper, is proposed for LOS-III: Xp alpha(1-->3)[L-Xylp beta(1-->4)](6)3-O-Me-Rhap alpha(1-->3)D- Galp beta(1-->3)-D-Glcp beta(1-->4)2-O-acyl-D-Glcp-alpha(1<==>1)alpha 4,6-di-O- acyl-D-Glcp.

Antigens, Bacterial↗