Comparative analysis by gas chromatography-mass spectrometry of the essential oils from bark and leaves of Cedrelopsis grevei Baill, an aromatic and medicinal plant from Madagascar

The essential oils from bark and leaves of Cedrelopsis grevei Baill (Ptaeroxylaceae), an aromatic and medicinal plant from Madagascar, are widely used in folk medicine. These two commercially available oils have been examined separately by means of GC-MS. The oil constituents were identified according to their mass spectra and their relative retention indices determined on both polar and non-polar stationary phase capillary columns. A total of 55 compounds have been identified constituting 76.7% (bark) and 91.6% (leaves) of the volatile constituents. Both oils were found to have a similar composition; however the relative percentages of some compounds notably differed. The bark essential oil contained beta-pinene (17.1%), cis-sesquisabinene hydrate (12.8%) and caryophyllene oxide (7.0%) as the main components whereas the leaf essential oil was largely dominated by trans-beta-farnesene (35.6%); beta-pinene (12.8%), cis-sesquisabinene hydrate (9.8%) and ar-curcumene (8.6%) were also present as major components. As far as we know, this is the first report on the Cedrelopsis grevei bark and leaf essential oils which therapeutic properties may be attractive for aromatherapy.     

Additives for the stabilization of double-stranded DNA in UV-MALDI MS

Molecular complexes such as double-stranded oligonucleotides contain non-covalent bonds that are difficult to maintain in the MALDI experiment. Quantifiers are introduced in order to evaluate, summarize, and compare spectra from experiments in which additives are used to stabilize duplex oligonucleotides. Compounds known to complex with and stabilize duplex molecules can be useful as additives in MALDI. Spermine and methylene blue, present at concentrations similar to the matrix, are detected, bound to the duplex. When peptides are used as additives, the duplex is stabilized when the peptide is present at an amount less than that of the duplex.     

Study of the fragmentation of small sulphur clusters

The fragmentation of sulphur clusters caused by electron impact ionization was studied. For this purpose, a beam ofS _n -clusters withn≦8 was generated in a gas aggregation source and ionized by electrons of variable energy. Special care was taken to maintain constant nucleation conditions so that the neutral cluster composition remained unchanged. It was found that the cluster ion mass spectra drastically depend on the electron energy. Even near threshold fragmentation processes contribute significantly to the dependence of the ion intensities on the electron energy.     

Ozonation of pyrene and benzo[a]pyrene in silica and soil –14C-mass balances and chemical analysis of oxidation products as a first step to ecotoxicological evaluation

Ozonation of polycyclic aromatic hydrocarbons (PAHs) in soil is a process that can be used for in-situ soil remediation or in combination with bioremediation techniques. First steps to a comprehensive ecotoxicological evaluation of this method is done by ozonation of radioactively labeled (¹⁴C) pyrene and benzo[a]pyrene in a silty soil (LUFA 2.2) under mass-balancing conditions and GC-MS analysis of aromatic ozonation products. ¹⁴C-Mass-balances for pyrene and benzo[a]pyrene (b[a]p) in soil showed that, apart from ¹⁴CO₂ formation, considerable percentages of both PAHs are oxidized to water soluble substances (20–30%) or to non-extractable or bound residues (10% for pyrene, 30% for b[a]p). TLC and GC-MS analysis of ozonation products extractable from artificially contaminated silica and soil by organic solvents revealed a large number of aromatic substances. PAH-quinones and ten ring fission products with formyl- and carboxy-groups of both pyrene and b[a]p could be identified.     

Palladium-catalyzed, stereoselective rearrangement of a tetracyclic allyl cyclopropane under arylation

The first example of a pi,sigma domino-Heck reaction under concomitant rearrangement of the tetracyclic allylcyclopropane endo,exo-bishomobarrelene (5) is reported; the stereoselective reaction proceeds via an intramolecular insertion of a primarily-formed carbopalladation intermediate into a strained cyclopropane C-C sigma-bond, giving 9.     

Simultaneous measurement of glucose and glutamine in aqueous solutions by near infrared spectroscopy

A method is described for measuring the concentrations of both glucose and glutamine in binary mixtures from near infrared (NIR) absorption spectra. Spectra are collected over the range from 5000–4000/cm (2.0–2.5μm) with a 1-mm optical path length. Glucose absorbance features at 4710, 4400, and 4300/cm and glutamine features at 4700, 4580, and 4390/cm provide the analytical information required for the measurement. Multivariate calibration models are generated by using partial least squares (PLS) regression alone and PLS regression combined with a preprocessing digital Fourier filtering step. The ideal number of PLS factors and spectral range are identified separately for each analyte. In addition, the optimum Fourier filter parameters are established for both compounds. The best overall analytical performance is obtained by combining Fourier filtering and PLS regression. Glucose measurements are established over the concentration range from 1.66–59.91 mM, with a standard error of prediction (SEP) of 0.32 mM and a mean percent error of 1.84%. Glutamine can be measured over the concentration range from 1.10–30.65 mM with a SEP of 0.75 mM and a mean percent error of 6.67%. These results demonstrate the analytical utility of NIR spectroscopy for monitoring glucose and glutamine levels in mammalian and insect cell cultures.     

Studies on the distribution and concentration of thiamine in blood and urine

Studies are reported resulting in a reliable procedure for estimating the thiamine content in human blood and urine. For the determination in blood, heparinized blood is hemolyzed with 0.3 N hydrochloric acid at 100 °C. Cocarboxylase is then converted to free thiamine by means of wheat germ acid phosphatase at pH 5.0 in an acetate buffer. The liberated thiamine is adsorbed to a CG-50 (Rohm & Haas) carboxylic acid ion exchange acrylic resin column and then eluted with 1 N H₂SO₄. The thiamine is then oxidized to thiochrome and extracted with n-butyl alcohol, at pH 9.8–10.0, in the presence of disodium phosphate. Readout is by fluorometry at an excitation wavelength of 371 nm and an emission wavelength of 425 nm. The range found for thiamine in whole blood by this procedure on 18 normal adults was 1.9–3.9 μg/100 ml, with a mean value of 2.77 μg/100 ml of whole blood. The mean recovery of 12 recovery experiments was 94.1%. The same procedure is applicable to the determination of thiamine in urine. Conversion of cocarboxylase to free thiamine is not necessary since it was determined that practically all of the thiamine found in urine is not phosphorylated. Urine values were variable, the range for 11 healthy adults being 5.6–77.9 μg/100 ml with a mean value of 19.2 μg/100 ml. This corresponds to a value of 346 μg of thiamine/24 hours.     

Characterisation and proposed origin of mass spectrometric ions observed 30 Th above the ionised molecules of per-O-methylated carbohydrates

Derivatisation of carbohydrates by permethylation significantly improves the mass spectrometric intensity of carbohydrate-derived ions and allows more readily interpretable fragmentation; in addition, samples are conveniently separated from salts, and larger oligosaccharides are more readily ionised. It has previously been recognised that, in the mass spectra of permethylated carbohydrates, a series of ions indicating species 30 Da larger than the fully methylated carbohydrate molecules are also observed. These species have not been characterised in the literature despite their apparently ubiquitous occurrence in the mass spectra of permethylated carbohydrates. Tandem mass spectrometry (MS/MS) experiments were performed on permethylated carbohydrates and reduced permethylated carbohydrates that exhibit the artefact, demonstrating that the artefact is not reducing terminal specific, and that the artefact can be introduced at any hydroxyl residue. It was further demonstrated through the use of different alkylation reagents that the origin of this artefact group is the alkylating reagent itself. It is proposed that side reactions that occur between the permethylation reagents allow the production of small amounts of iodomethyl methyl ether. This reagent can then compete with methyl iodide for reaction with the carbohydrate -OH groups. The result is partial incorporation of a methoxymethyl moiety instead of a methyl group, detected as '+30' artefact ions.     

Insight into the reactivity of olefins in the Pauson-Khand reaction

The reactivity of different Co(2)(CO)(6)-acetylene complexes in the Pauson-Khand reaction is strongly dependent on the nature of the olefin. Theoretical calculations at both the DFT and ONIOM levels are concordant with experimental observations and suggest how the olefin-cobalt interactions in the complex could have a major effect on the relative reactivity of the olefins. This study rationalizes for the first time the experimentally observed reactivity differences of cyclohexene, cyclopentene, and norbornene.     

A multitechnique surface analytical study of a segmented block copolymer poly(ether-urethane) modified through an H2O radio frequency glow discharge

Recent work in our laboratories has fully characterized the surface region of a segmented poly(ether-urethane) (PEU) extending from the air/polymer interfacial region through bulk depths in the micron range. This characterization utilized energy and angle dependent Electron Spectroscopy for Chemical Analysis (ESCA), Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR–FTIR), and Comprehensive Wettability Profiling (contact angle using a homologous series of liquids) as defined by Zisman. In this study this same multi-analytical-technique approach is used to elucidate changes in these PEU surfaces induced through an H₂O Radio Frequency Glow Discharge (RFGD) plasma. This investigation reports both qualitative and quantitative changes due to the modification treatments as well as the permanency of the changes effected on these surfaces through the plasma treatment. From our analyses, the amount of surface residing polyurethane (hard segment) is observed to increase due to a proposed plasma etching mechanism. Further, the addition of oxygen containing functionality is detected at the modified surfaces unique with respect to the unmodified PEU. These surface modifications which show large increases in wettability, are finally observed to be semi-permanent over a time period of 6 months.