Raoul Rozenberg

Phytosterol analysis and characterization in spelt (Triticum aestivum ssp spelta L.) and wheat (T aestivum L.) lipids by LC/APCI-MS

Spelt is still a minor cereal crop, mainly grown in Belgium. It is said to have a better nutritive value than winter wheat. Moreover, interesting functional properties have traditionally been attributed to spelt, such as a cholesterol-lowering effect. However, such properties are not substantiated by scientific evidence. Considering their physiological effects, phytosterols could partly account for spelts properties and have never been studied in this cereal. Phytosterols were analysed by LC/APCI-MS in spelt and winter wheat fine bran, a lipid and fibre-rich milling by-product. Sample preparation was suitable for the determination of glycosylated and free sterols, combined to their released counterparts after saponification. Chromatographic retention times, full mass spectra and MS2 spectra of 12 reference sterols allowed the characterization of phytosterols present in cereal samples.

Carbon source-induced modifications in the mycolic acid content and cell wall permeability of Rhodococcus erythropolis E1.

ABSTRACT The influence of the carbon source on cell wall properties was analyzed in an efficient alkane-degrading strain of Rhodococcus erythropolis (strain E1), with particular focus on the mycolic acid content. A clear correlation was observed between the carbon source and the mycolic acid profiles as estimated by high-performance liquid chromatography and mass spectrometry. Two types of mycolic acid patterns were observed after growth either on saturated linear alkanes or on short-chain alkanoates. One type of pattern was characterized by the lack of odd-numbered carbon chains and resulted from growth on linear alkanes with even numbers of carbon atoms. The second type of pattern was characterized by mycolic acids with both even- and odd-numbered carbon chains and resulted from growth on compounds with odd-numbered carbon chains, on branched alkanes, or on mixtures of different compounds. Cellular short-chain fatty acids were twice as abundant during growth on a branched alkane (pristane) as during growth on acetate, while equal amounts of mycolic acids were found under both conditions. More hydrocarbon-like compounds and less polysaccharide were exposed at the cell wall surface during growth on alkanes. Whatever the substrate, the cells had the same affinity for aqueous-nonaqueous solvent interfaces. By contrast, bacteria displayed completely opposite susceptibilities to hydrophilic and hydrophobic antibiotics and were found to be strongly stained by hydrophobic dyes after growth on pristane but not after growth on acetate. Taken together, these data show that the cell wall composition of R. erythropolis E1 is influenced by the nutritional regimen and that the most marked effect is a radical change in cell wall permeability.

Ochratoxin A in domestic and imported beers in Belgium: occurrence and exposure assessment.

Determination of ochratoxin A (OTA) concentration was performed in commercial beer in Belgium using immunoaffinity column (OchraTest™) clean-up and liquid chromatography. The procedure was validated and fulfilled the European Committee for Standardizations criteria. It offered a detection limit of 3 ng l-1 and a quantification limit of 10 ng l-1. Recovery experiments carried out with the spiked samples in the range 50–200 ng OTAl-1 showed an overall average recovery rate of 97% (RSD = 2.8%). The validated method was applied to the analysis of 62 Belgian beers and 20 commercial beers imported from Denmark, France, Germany, Ireland, Mexico, The Netherlands and Scotland. None of these beers exceeded the previously suggested EU limit of 200 ng l-1. However, OTA was detected in 60 Belgian beers and in all imported beers. The average levels of contamination were 33 ng l-1 (RSD = 112%) and 32 ng l-1 (RSD = 81%), respectively. The highest level found was 185 ng l-1. On the basis of the established tolerable daily intake (TDI) of 5 ng kg-1 body weight, accepted by the scientific committee on food of the EU, this study indicates that beer consumption in Belgium is not likely to contribute to more than a few per cent of the TDI based on the average consumption. This study also shows variability of the OTA contamination in beer with time. Thus, there is a potential risk of having highly contaminated batches from time to time. We therefore recommend to control further the OTA contamination in brewery products and to take precautionary measures during harvest, transport and storage of the raw materials to maintain the OTA intake at the lowest achievable level.

On the Presence of Phosphorylated Sphingoid Bases in Rat-tissues - a Mass-spectrometric Approach

A simple and straightforward procedure to analyze phosphorylated sphingoid bases has been developed. After phase separation of lipid extracts under alkaline conditions, the compounds were quantitatively recovered in the aqueous upper phase. Following a clean‐up of the aqueous phase on C18‐solid phase extraction columns, the amino‐group of the bases was derivatized by means of phenylisothiocyanate addition. FAB‐MS of the phenylthiocarbamate derivatives of sphingenine‐ and sphinganine‐phosphate in the negative mode revealed the expected pseudo‐molecular ions (M‐1) at 513 m/z and 515 m/z, respectively. Moreover, a typical fragmentation pattern, characterized by the loss of the phenylthiocarbamate moiety (m/z = 135), was observed. When applied to rat tissues, the presence of sphingenine‐phosphate in brain, kidney and liver could easily be demonstrated. Highest levels, amounting to 5 nmol/g of wet weight, were present in brain.

Analysis of minor flavonoids in Piper hostmannianum var. berbicense using liquid chromatography coupled with atmospheric pressure chemical ionization mass spectrometry.

The fragmentations of hydroxylated flavanones, chalcones and dihydrochalcones were investigated by direct loop injection using an ion trap mass spectrometry equipped with atmospheric pressure chemical ionization (APCI) probe. Some of them have been isolated from the leaves of Piper hostmannianum var. berbicense and standards were used to confirm their fragmentation behaviour. In negative ion mode, fragmentations of these three types of flavonoids revealed specific diagnostic ions which allowed us to identify aglycones in a crude plant extract. The major fragment ion obtained in MS/MS experiment for methoxylated chalcones is the neutral loss of a methyl radical whereas a H(2)O molecule is lost in the case of methoxylated dihydrochalcones. Methoxylated chalcones and flavanones isomers could be differentiated by the relative intensity ratio of [M-H-CH(3)]*(-) and [M-H-C(2)H(2)O](-) ions. Based on UV and MS data, a decision tree that includes UV lambda(max) absorptions and MS/MS diagnostic ions was built in order to obtain structural information of unknown compounds present in the extract. This tree was used to identify flavonoids in the ethyl acetate extract of P. hostmannianum var. berbicense leaves after analysis by high-performance liquid chromatography-diode array detection-atmospheric pressure chemical ionization ion trap multistage mass spectrometry. A total of 11 flavonoids were tentatively characterized based on the MS fragmentations pattern observed in MS(n) experiments.

Aerobic Growth of Escherichia coli with 2,4,6-Trinitrotoluene (TNT) as the Sole Nitrogen Source and Evidence of TNT Denitration by Whole Cells and Cell-Free Extracts

ABSTRACT Escherichia coli grew aerobically with 2,4,6-trinitrotoluene (TNT) as sole nitrogen source and caused TNTs partial denitration. This reaction was enhanced in nongrowing cell suspensions with 0.516 mol nitrite released per mol TNT. Cell extracts denitrated TNT in the presence of NAD(P)H. Isomers of amino-dimethyl-tetranitrobiphenyl were detected and confirmed with U-15N-labeled TNT.

Study of the thermal evolution of the cyclic-oligomer formation in a cyclic-oligomer-free PET

A low percentage of cyclic oligomers can be found in poly(ethylene terephthalate) (PET) from its synthesis onward. In this article, a cyclic-oligomer-fr ee PET (COFP) obtained by solvent extraction was used to study the thermodynamics of the re-formation of cyclics from the melt. The cyclic-oligomer content re-increased into molten COFP, finally reaching an equilibrium. An analysis of the fraction of the re-formed cyclic oligomers showed that a majority of cyclic trimer (60-70%) was found at the equilibrium Before the establishment of the equilibrium, an unusual behavior was observed in the relative proportion of cyclic trimer and tetramer during the first steps of their formation that was probably due to a competition between kinetic and thermodynamic products

Fragmentation of conjugate bases of esters derived from multifunctional alcohols including triacylglycerols

Enolate anions of esters from 1,2 and 1,3 diols undergo an internal nucleophilic substitution reaction that produces a β-ketoester and an alkoxide ion within the molecular species. These intermediate ions undergo two competitive fragmentation pathways. The first pathway corresponds to a second nucleophilic substitution of the ketoester by the alkoxide that yields a neutral cyclic ether and the β-ketoacid carboxylate. The latter then loses carbon dioxide and produces the enolate anion of the corresponding ketone. The second proposed pathway is stepwise: it starts with a proton transfer from the methylene group between the two carbonyls to the alkoxide anion that produces an alcohol and the enolate ion of the β-ketoester inside the molecular species. The latter undergoes cleavage of the ester bond induced by the negative charge to yield an ion-dipole complex composed of a neutral acylketene and an alkoxide ion. The direct dissociation of this ion-dipole complex competes with an internal proton exchange to yield a new complex that consists of an alcohol molecule and the anion of the acylketene, which can also dissociate. The fragmentation pathway that leads to the ketone enolate is sensitive to the relative positions (1,2 or 1,3) of the esters on the molecular backbone. This position-sensitive reaction is useful for the assignment of the primary and secondary positions in triacylglycerols, even in mixtures, as shown by some examples.

Activity of ceftaroline against extracellular (broth) and intracellular (THP-1 monocytes) forms of methicillin-resistant Staphylococcus aureus: comparison with vancomycin, linezolid and daptomycin

BACKGROUND Ceftaroline fosamil is approved for treatment of acute bacterial skin and skin structure infections caused by methicillin-resistant Staphylococcus aureus (MRSA). We examined the activity of its active metabolite (ceftaroline) against intracellular forms of S. aureus in comparison with vancomycin, daptomycin and linezolid. METHODS Two methicillin-susceptible S. aureus (MSSA) and 11 MRSA strains with ceftaroline MICs from 0.125 to 2 mg/L [two strains vancomycin- and one strain linezolid-resistant (EUCAST interpretative criteria); VISA and cfr+] were investigated. The activity was measured in broth and after phagocytosis by THP-1 monocytes in concentration-dependent experiments (24 h of incubation) to determine: (i) relative potencies (EC(50)) and static concentrations (C(s)) (mg/L and × MIC); and (ii) relative activities at human C(max) (E(C)(max)) and maximal relative efficacies (E(max)) (change in log(10) cfu compared with initial inoculum). Ceftaroline stability and cellular accumulation (at 24 h) were measured by mass spectrometry. RESULTS Ceftaroline showed similar activities in broth and in monocytes compared with vancomycin, daptomycin and linezolid, with no impact of resistance mechanisms to vancomycin or linezolid. For all four antibiotics, intracellular E(C)(max) and E(max) were considerably lower than in broth (∼0.5 log(10) versus 4-5 log(10) cfu decrease), but the EC(50) and C(s) showed comparatively little change (all values between ∼0.3 and ∼6× MIC). The mean cellular to extracellular ceftaroline concentration ratios (20 mg/L; 24 h) were 0.66 ± 0.05 and 0.90 ± 0.36 in uninfected and infected cells, respectively. CONCLUSION In vitro, ceftaroline controls the growth of intracellular MRSA to an extent similar to that of vancomycin, linezolid and daptomycin for strains with a ceftaroline MIC ≤ 2 mg/L.

Structure and transformations of the alkaloid sanguilutine

Sodium carbonate treatment of sanguilutine chloride yielded 6-hydroxy-5,6-dihydrosanguilutine. In a non-polar environment, 6-hydroxy-5,6-dihydrosanguilutine spontaneously transforms to bis[6-(5,6-dihydrosanguilutinyl)] ether, whose structure was confirmed by X-ray analysis. Treatment of sanguilutine chloride with aqueous ammonia gave bis[6-(5,6-dihydrosanguilutinyl)]amine. Reaction of sanguilutine chloride with potassium cyanide yielded 6-cyanodihpdrosanguilutine; reaction of bis[6-(5,6-dihydrosanguilutinyl)]amine with ethanol gave 6-ethoxydihydrosanguilutine