Many in vitro studies demonstrated significant biological effects of trans-resveratrol. Thus, understanding the rate of intestinal absorption and metabolization in vivo of trans-resveratrol is the prerequisite to evaluate its potential health impact. Bioavailability studies mainly in animals or in humans using the pure compound at very high doses were performed. In this work, trans-resveratrol bioavailability from a moderate consumption of red wine in 25 healthy humans has been studied by three different experiments. The wine ingestion was associated to three different dietary approaches: fasting, a standard meal, a meal with high and low amount of lipids. Trans-resveratrol 3- and 4'-glucuronides were synthesized, purified, and characterized as pure standards. Bioavailability data were obtained by measuring the concentration of free, 3-glucuronide and 4'-glucuronide trans-resveratrol by high-performance liquid chromatography (HPLC), both with ultraviolet (UV) and mass spectrometry (MS) detection, in serum samples taken at different times after red wine administration. Free trans-resveratrol was found, in trace amounts, only in some serum samples collected 30 min after red wine ingestion while after longer times resveratrol glucuronides predominated. Trans-resveratrol bioavailability was shown to be independent from the meal or its lipid content. The finding in human serum of trans-resveratrol glucuronides, rather than the free form of the compound, with a high interindividual variability, raises some doubts about the health effects of dietary resveratrol consumption and suggests that the benefits associated to red wine consumption could be probably due to the whole antioxidant pool present in red wine.

Peptide nucleic acids (PNAs) are oligonucleotide analogues in which the sugar-phosphate backbone has been replaced by a pseudopeptide skeleton. They bind DNA and RNA with high specificity and selectivity, leading to PNA-RNA and PNA-DNA hybrids more stable than the corresponding nucleic acid complexes. The binding affinity and selectivity of PNAs for nucleic acids can be modified by the introduction of stereogenic centers (such as D-Lys-based units) into the PNA backbone. To investigate the structural features of chiral PNAs, the structure of a PNA decamer containing three D-Lys-based monomers (namely H-GpnTpnApnGpnAdlTdlCdlApnCpnTpn-NH2, in which pn represents a pseudopeptide link and dl represents a D-Lys analogue) hybridized with its complementary antiparallel DNA has been solved at a 1.66-Å resolution by means of a single-wavelength anomalous diffraction experiment on a brominated derivative. The D-Lys-based chiral PNA-DNA (LPD) heteroduplex adopts the so-called P-helix conformation. From the substantial similarity between the PNA conformation in LPD and the conformations observed in other PNA structures, it can be concluded that PNAs possess intrinsic conformational preferences for the P-helix, and that their flexibility is rather restricted. The conformational rigidity of PNAs is enhanced by the presence of the chiral centers, limiting the ability of PNA strands to adopt other conformations and, ultimately, increasing the selectivity in molecular recognition. P eptide nucleic acids (PNAs) are oligonucleotide mimics in which the sugar-phosphate backbone has been replaced by a pseudopeptide skeleton, composed of N-(2-aminoethyl)glycine units (1) (Fig. 1). Nucleobases are linked to this skeleton through a two-atom carboxymethyl spacer.PNAs bind DNA and RNA with high specificity and selectivity, forming Watson-Crick base pairs and leading to PNA-RNA and PNA-DNA hybrids that are more stable than the corresponding nucleic acid complexes (2). Because of their high thermal stability and resistance to proteases and nucleases, PNAs are ideal candidates as antisense or antigene therapeutic agents (3-6) and are currently used as powerful tools in molecular biology and in diagnostics (7).Three-dimensional structures have been determined for the major families of PNA complexes by different techniques. A PNA-RNA duplex (8) and a PNA-DNA duplex (9) were characterized by NMR in solution, whereas a (PNA) 2 -DNA triplex (10) and three PNA-PNA duplexes (11-13) were solved by x-ray crystallography. The structural analysis in solution of the PNA-DNA (9) and PNA-RNA duplexes (8) showed that PNA, when hybridized to RNA, adopts an A-like helix, whereas, when hybridized to a complementary DNA strand, it adopts a conformation that is different from both the A and the B forms. The crystal structure of the (PNA) 2 -DNA triplex (10) also showed helical parameters significantly different from those of canonical DNA or RNA helical forms, defining a type of helix, named the P-helix, characterized by a small twist angle, a large x-displacem...

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Mycotoxins are fungal toxins produced by molds, which occur universally in food and feed derivatives, and are produced under certain environmental conditions in the field before harvest, post‐harvest, during storage, processing, and feeding. Mycotoxin contamination is one of the most relevant and worrisome problem concerning food and feed safety because it can cause a variety of toxic acute and chronic effects in human and animals. In this review we report the use of mass spectrometry in connection with chromatographic techniques for mycotoxin determination by considering separately the most diffuse class of mycotoxins: patulin, aflatoxins, ochratoxin A, zearalenone, trichothecenes, and fumonisins. Although the selectivity of mass spectrometry is unchallenged if compared to common GC and LC detection methods, accuracy, precision, and sensitivity may be extremely variable concerning the different mycotoxins, matrices, and instruments. The sensitivity issue may be a real problem in the case of LC/MS, where the response can be very different for the different ionization techniques (ESI, APCI, APPI). Therefore, when other detection methods (such as fluorescence or UV absorbance) can be used for the quantitative determination, LC/MS appears to be only an outstanding confirmatory technique. In contrast, when the toxins are not volatile and do not bear suitable chromophores or fluorophores, LC/MS appears to be the unique method to perform quantitative and qualitative analyses without requiring any derivatization procedure. The problem of exact quantitative determination in GC/MS and LC/MS methods is particularly important for mycotoxin determination in food, given the high variability of the matrices, and can be solved only by the use of isotopically labeled internal standards or by the use of ionization interfaces able to lower matrix effects and ion suppressions. When the problems linked to inconstant ionization and matrix effects will be solved, only MS detectors will allow to simplify more and more the sample preparation procedures and to avoid clean‐up procedures, making feasible low‐cost, high‐throughput determination of mycotoxins in many different food matrices. © 2005 Wiley Periodicals, Inc.