Natural toxins: risks,regulations and the analytical situation in Europe

Natural toxins in food and feed are considered important food safety issues of growing concern, in particular mycotoxins, phycotoxins and plant toxins. Most scientific developments have occurred in the past few decades in the area of mycotoxins. Formal health risk assessments have been carried out by the Joint Expert Committee on Food Additives of the World Health Organization and the Food and Agriculture Organization. Limits and regulations for mycotoxins in food and feed have been established in many countries, including practically all European countries. An array of (formally validated) analytical methods and (certified) reference materials have become available. Several European research projects, funded by the European Commission and supported by the European Standardization Committee, have significantly contributed to this development. Quantitative methods of analysis for mycotoxins often make use of immunoaffinity cleanup with liquid chromatographic or gas chromatographic separation techniques in combination with various types of detectors, including mass spectroscopy. For screening purposes (bio)sensor-based techniques are among the promising newcomers. For the phycotoxins the situation is less advanced. Formal risk assessments by authoritative international bodies have not been carried out. Methods of analysis, formally validated according to internationally harmonized protocols, are scarce and animal testing still plays a key role in official methodology. The development of the analytical methodology is partly hampered by the limited availability of certain reliable calibrants and reference materials, although this situation is gradually improving. New regulations in the European Union have increased the pressure to develop and validate chemical methods of analysis. Joint efforts in the European context are now directed towards significantly improving this situation, and techniques such as liquid chromatography–mass spectroscopy offer promise in this respect. Both the working group on biotoxins of the European Standardization Committee and the network of National Reference Laboratories for Marine Biotoxins have taken up responsibilities here. The plant toxins are a category of natural toxins, where the situation is the least developed with respect to regulations, validated methods of analysis and reference materials. Yet, their occurrence in a wide range of consumable plant species demands the attention of the analytical community.     

Preparation of natural isovaleraldehyde by the Maillard reaction

Isovaleraldehyde possesses malty,fruity,cocoa-like odor and is widely used in fruit,chocolate,coffee flavors.The preparation of natural isovaleraldehyde by the Maillard model reaction was studied in this paper.The effects of the ratio of D-glucose/L-leucine, reaction temperature and pH value on the yield of isovaleraldehyde were explored.The optimum conditions were as follows: n(D-glucose):n(L-leucine)=4,temperature 150℃,reaction time 3 h,pH 5.The highest yield of isovaleraldehyde obtained was about 32%.     

Coupling NMR to NOM

This work itemizes and critically assesses several 1D and multi-dimensional nuclear magnetic resonance (NMR) techniques, in both the liquid (solvent suppression, APT, DEPT, INEPT, COSY, TOCSY, HSQC, HMQC, HMBC, NOESY, ROESY and others) and solid states (DP, SACP, RAMP-CP, CP-TOSS, MQ-DEPT, 2D ¹H–¹³C HETCOR and others), which are relevant to the characterization of natural organic matter (NOM). The pros and cons of many of the discussed techniques are compared in an effort to provide guidance to the most beneficial utilization of these NMR instrumental techniques for researchers interested in gaining insight into various aspects of NOM.Abbreviations 1D One dimensional - 2D Two dimensional - APT Attached proton test - BIRD Bilinear rotation decoupling - CP Cross polarization - COSY Correlation spectroscopy - CSA Chemical shift anisotropy - DEPT Distortionless enhancement by polarization transfer - DMSO Dimethyl sulfoxide - DOSY Diffusion ordered spectroscopy - DP Direct polarization - DQ Double quantum - FID Free induced decay - FT Fourier transform - FT-ICR-MS Fourier transform-ion cyclotron resonance-mass spectroscopy - HETCOR Heteronuclear correlation - HH Hartmann–Hahn - HMBC Heteronuclear multiple bond correlation - HMQC Heteronuclear multiple quantum coherence - HSQC Heteronuclear single quantum coherence - INEPT Insensitive nuclei enhanced by polarization transfer - LR-COSY Long-range COSY - MAS Magic-angle spinning - MQ Multiple quantum - MS Mass spectroscopy - NMR Nuclear magnetic resonance - NOE Nuclear Overhauser enhancement - NOESY Nuclear Overhauser enhanced spectroscopy - NOM Natural organic matter - PASS Phase adjustment of spinning sidebands - RAMP Ramped amplitude - RESTORE Restoration of spectra via T _CH and T one rho (T _1H) editing - r.f. Radio frequency - ROESY Rotating frame Overhauser enhancement spectroscopy - SACP Single amplitude cross polarization - SOM Soil organic matter - SS Spinning sideband - TMS Tetramethylsilane - TOCSY Total correlation spectroscopy - TOSS Total suppression of sidebands - TPPM Two-pulse phase modulation - VCT Variable contact time - VSL Variable spin lock - WATERGATE Water suppression by gradient tailored excitation     

Natural Product Chemistry: From Plants to Human

Conventionally, natural product chemistry deals with the isolation, characterization, and synthesis of compounds from plants. It a broad sense, natural product chemistry may include all fields of biochemistry. Two projects are presented to illustrate the expanded definition of natural product chemistry. One deals with phosphatidylinositol (PI) and the key enzyme involved in its metabolism, PI-specific phospholipase C. The other project is on the structure-function relationship of human tumor suppressor p16.     

Supported liquid membrane work-up in combination with liquid chromatography and electrochemical detection for the determination of chlorinated phenols in natural water samples

Summary A sample preparation method has been developed for the determination of chlorinated phenols in water. The method is based on a supported liquid membrane extraction system connected on-line to liquid chromatography with electrochemical detection. The supported liquid membrane technique utilizes a porous PTFE membrane. The membrane is impregnated with an organic solvent which forms a barrier between two aqueous phases and enables selective extraction. The technique can easily be coupled in a flow system. In this investigation five chlorinated phenols (1–5 chlorine atoms) were extracted from natural water samples. Extraction for 30 minutes resulted in detection limits of approximately 25 ng L^–1.     

New C21 Δ pregnanes, inhibitors of mitochondrial respiratory chain, from Indopacific octocoral Carijoa sp.

Two new compounds, pregnanes 1 and 2, the known pregnane 3 and a series of known chlorinated prostanoids (4-9) have been isolated from the Indian octocoral Carijoa sp. Their structures have been elucidated by spectroscopic methods, mainly by 1D and 2D NMR. The new compounds were potent inhibitors of the mitochondrial respiratory chain.     

Na~＋，K~＋‖Cl~－，B_4O_7~（－2）－H_2O四元体系25℃时相平衡研究

Ｎａ~＋，Ｋ~＋‖Ｃｌ~－，Ｂ_４Ｏ_７~（－２）－Ｈ_２Ｏ四元体系２５℃时相平衡研究阎树旺，唐明林，邓天龙（成都理工学院液态矿产综合利用研究室成都，６１００５９）关键词四硼酸钠，四硼酸钾，相平衡，卤水近年来，在四川盆地成都凹陷平落坝地区发现了富硼、钾、低?..     

Biosynthesis of Lichen Substances,Products of a Symbiotic Association

Lichens are composed of algae and fungi living together in symbiotic association and forming characteristic, often polycyclic lichen substances that are rarely encountered in other organisms. While the cultures of the unassociated individual constituents of the lichens can live for an unlimited time some doubt surrounds their viability in nature; their biosynthetic powers are not additive in the lichens. The results concerning the biosynthesis of the lichens that are discussed in the present article were obtained mainly with ¹⁴C-labeled compounds.     

A new approach for the synthesis of 2-substituted indole derivatives via Michael type adducts

4,7-Dihydroindole undergoes regioselective alkylation at the 2-position of the indole nucleus through conjugate addition with α,β-unsaturated carbonyl compounds. The oxidation of the Michael adducts affords the corresponding 2-substituted indole derivatives which were characterized by spectroscopic methods.     

Analysis of C10-C20 hydrocarbons in natural gas by solid phase extraction and CGC

A method is described for the determination of C10-C20 hydrocarbons in natural gas. Enrichment by solid phase extraction on ODS followed by liquid desorption was found to give better results than adsorption on Tenax or charcoal followed by liquid or thermal desorption.