Hop as an interesting source of resveratrol for brewers: optimization of the extraction and quantitative study by liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry.

Nowadays, hop is used almost exclusively by brewers for bitterness and flavor. Although hop polyphenols have been widely studied in the past decade for their antioxidant activity in the boiling kettle, very little is known about their real impact on health. The discovery of resveratrol in hop pellets highlights the potential health-promoting effect of moderate beer consumption. Here, we have optimized a quantitative extraction procedure for resveratrol in hop pellets. Preliminary removal of hydrophobic bitter compounds with toluene and cyclohexane at room temperature allows 99% trans-resveratrol recovery by ethanol:water (75:25, v/v) solid/liquid extraction at 60 degrees C. Reverse phase liquid chromatography proves an excellent means of separating isomers. In addition, we have compared two mass spectrometry ionization methods-atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI)-in both the positive and the negative modes. On the basis of standard additions applied with the optimized extraction procedure and reverse phase high-performance liquid chromatography-APCI(+)-tandem mass spectrometry, it appears that Tomahawk hop pellets (T90, harvest 2002) contain 0.5 ppm trans-resveratrol, 2 ppm trans-piceid, no cis-resveratrol, and 0.9 ppm cis-piceid

Desorption chemical ionization tandem mass spectrometry of polyprenyl and dolichyl phosphates

Negative-ion desorption chemical ionization (DCI) tandem mass spectrometry was applied to the analysis of nanomole quantities of semisynthetic polyisoprenyl phosphates, the chain length of which ranged from 7 to 20 isoprene units. The DCI spectrum of all the compounds tested show the presence of independently generated ions [M - HPO3 - H](-), [M - H3PO2 - H](-) and [M - H3PO4 - H](-) resulting from the loss of a part of or the entire phosphate group of a polyisoprenyl-P. In tandem mass spectrometry, the [M - H3PO4 - H](-) fragment produces series of ions 68 mass units apart, indicative of the polyisoprenoid nature of a compound. Studies with deuterated and alpha-saturated polyisoprenyl phosphates demonstrated that fragmentations of the [M - H3PO4 - H](-) ion proceed from both ends (alpha and omega) of a polyisoprenoid chain and may occur at either allylic (A) or vinylic (V) sites. Fragments of masses equal to [n x 68 - 1] and [n x 68 - 13] (where n is the number of isoprene units and 3 I n is less than the total number of isoprene residues within a polyisoprenoid chain) comprise the alpha A and omega V series, respectively, and represent the most abundant ions in tandem mass spectra of the [M - H3PO4 - H](-) fragment of polyprenyl phosphates. alpha-Saturated dolichyl phosphates can be distinguished easily from corresponding polyprenyl phosphates not only on the basis of a 2-u shift of the [M - H3PO4 - H](-) ion and the alpha series of fragments, but also because of the presence of an additional (A + 14) series of ions 14 u heavier than fragments resulting from the allylic cleavages of an alpha-saturated polyisoprenoid chain. Possible mechanisms of the collision-induced dissociation reactions of polyprenyl phosphates are discussed

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 Standardization's 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 OTA l(-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

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 beta-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 beta-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 beta-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

Toxic peptides in populations of two pergid sawflies, potential biocontrol agents of Brazilian peppertree

etermination of the safety of agents prior to release is one of the most important research goals in biological control. In addition to concerns for the safety of non-target plants, determination of the potential toxic properties of new agents needs to be assessed. Numerous phytophagous insects are defended by chemicals against the attack of natural enemies. Some of these defensive compounds could pose an environmental risk if an agent is released. Here, larval populations of two pergid sawflies, Heteroperreyia hubrichi and H. jorgenseni, were analyzed by LC-MS/MS to investigate whether they contain alleged toxic peptides. The first species is a potential candidate for biological control of the invasive weed Brazilian peppertree in Florida and Hawaii. The chemical analyses revealed the presence of the peptides pergidin (Perg), 4-valinepergidin (VPerg), dephosphorylated pergidin (dpPerg), lophyrotomin (LGln and LGlu). The effect of sawfly population for each species was significantly influencing peptide concentration. All peptides occurred at lower concentrations compared with purportedly toxic species of this sawfly family. However, the concentrations of the peptides are of concern for the welfare of wildlife and livestock that would be exposed to these species. These results demonstrate that release of this biological control agent in the invaded range may pose an environmental threat

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

Escherichia coli grew aerobically with 2,4,6-trinitrotoluene (TNT) as sole nitrogen source and caused TNT's 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-(15)N-labeled TNT