Phase I and II metabolites of speciogynine, a diastereomer of the main Kratom alkaloid mitragynine, identified in rat and human urine by liquid chromatography coupled to low- and high-resolution linear ion trap mass spectrometry

Mitragyna speciosa (Kratom in Thai), a Thai medical plant, is misused as herbal drug of abuse. Besides the most abundant alkaloids mitragynine (MG) and paynantheine (PAY), several other alkaloids were isolated from Kratom leaves, among them the third abundant alkaloid is speciogynine (SG), a diastereomer of MG. The aim of this present study was to identify the phase I and II metabolites of SG in rat urine after the administration of a rather high dose of the pure alkaloid and then to confirm these findings using human urine samples after Kratom use. The applied liquid chromatography coupled to low- and high-resolution mass spectrometry (LC-HRMS-MS) provided detailed information on the structure in the MS(n) mode particularly with high resolution. For the analysis of the human samples, the LC separation had to be improved markedly allowing the separation of SG and its metabolites from its diastereomer MG and its metabolites. In analogy to MG, besides SG, nine phase I and eight phase II metabolites could be identified in rat urine, but only three phase I and five phase II metabolites in human urine. These differences may be caused by the lower SG dose applied by the user of Kratom preparations. SG and its metabolites could be differentiated in the human samples from the diastereomeric MG and its metabolites comparing the different retention times determined after application of the single alkaloids to rats. In addition, some differences in MS(2) and/or MS(3) spectra of the corresponding diastereomers were observed.     

Effective Polytropic Indices of Anisotropic Planetary Magnetosheath Plasmas with Magnetoacoustic Waves

Magnetosheath models for the planets Earth, Jupiter and Saturn are developed within the frame of the double‐adiabatic Chew‐Goldberger‐Low approximation. It is shown that in all three magnetosheaths slow and fast magnetoacoustic waves are generated, the dispersions of which considerably differ from that of isotropic systems. If slow magnetoacoustic waves exist in the magnetosheaths, then the effective polytropic coefficient of the plasma may be smaller than unity ‐ that means compression of the plasma is accompanied, in the average, by cooling. Such polytropic coefficients are not obtained when fast magnetoacoustic waves are excited (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Systematic investigation of ion suppression and enhancement effects of fourteen stable‐isotope‐labeled internal standards by their native analogues using atmospheric‐pressure chemical ionization and electrospray ionization and the relevance for multi‐analyte liquid chromatographic/mass spectrometric procedures

In clinical and forensic toxicology, multi‐analyte procedures are very useful to quantify drugs and poisons of different classes in one run. For liquid chromatographic/tandem mass spectrometric (LC/MS/MS) multi‐analyte procedures, often only a limited number of stable‐isotope‐labeled internal standards (SIL‐ISs) are available. If an SIL‐IS is used for quantification of other analytes, it must be excluded that the co‐eluting native analyte influences its ionization. Therefore, the effect of ion suppression and enhancement of fourteen SIL‐ISs caused by their native analogues has been studied. It could be shown that the native analyte concentration influenced the extent of ion suppression and enhancement effects leading to more suppression with increasing analyte concentration especially when electrospray ionization (ESI) was used. Using atmospheric‐pressure chemical ionization (APCI), methanolic solution showed mainly enhancement effects, whereas no ion suppression and enhancement effect, with one exception, occurred when plasma extracts were used under these conditions. Such differences were not observed using ESI. With ESI, eleven SIL‐ISs showed relevant suppression effects, but only one analyte showed suppression effects when APCI was used. The presented study showed that ion suppression and enhancement tests using matrix‐based samples of different sources are essential for the selection of ISs, particularly if used for several analytes to avoid incorrect quantification. In conclusion, only SIL‐ISs should be selected for which no suppression and enhancement effects can be observed. If not enough ISs are free of ionization interferences, a different ionization technique should be considered. Copyright © 2010 John Wiley & Sons, Ltd.     

Thermal expansivity of particulate composites: Interlayer versus molecular model

We continue the comparison of the results of an interlayer model, based on the theory of elastic continua, and a molecular model, derived from a theory of mixtures, previously presented in terms of bulk moduli K. We now derive expressions for the dependence of the thermal expansivity _c on the volume fraction _f of the filler, at low and elevated values of _f . Correspondencies between the characteristic parameters, viz. adhesion and repulsion ratios on the one hand, and interlayer content and thermal properties of matrix, filler, and layer, on the other, are examined. Since in the molecular theory both andK are derived from an equation of state, the identical set of parameters determines both functions and suggests correlations between them.     

Methylenedioxy designer drugs: Mass spectrometric characterization of their glutathione conjugates by means of liquid chromatography-high-resolution mass spectrometry/mass spectrometry and studies on their glutathionyl transferase inhibition potency

Methylenedioxy designer drugs of abuse such as 3,4-methylenedioxymethamphetamine (MDMA) can be selectively toxic to serotonergic neurons and glutathione (GSH) adducts have been implicated in its neurotoxicity. The catecholic demethylenyl metabolites of MDMA, 3,4-dihydroxymethamphetamine and 3,4-dihydroxyamphetamine, are metabolically oxidized to the corresponding ortho-quinones, which are highly reactive intermediates. These intermediates can then be conjugated with GSH preventing cellular damage. Furthermore, glutathionyl transferase (GST) activity was described to be irreversibly inhibited by the catechols dopamine, α-methyldopa and their GSH conjugates. Therefore, the aims of the present work were the detection and characterization of GSH conjugates of ten methylenedioxy drugs of abuse and their phase I metabolites as well as to assess their inhibition potency on GST activity. The substrates were incubated using human placental GST with or without preincubation by cytochrome P450 enzymes preparations. GST inhibition was tested using chlorodinitrobenzene GSH conjugation as marker reaction. GSH conjugates were analyzed and characterized using LC-high-resolution-MS/MS. For confirmation of postulated fragmentation patterns, formation of GSH conjugates of selected deuterated analogs (deuterated analogue approach, DAA) of the investigated drugs was explored. For the methylenedioxy amphetamines the following steps could be identified: conjugation of the parent compounds at position 2, 5, 6, of the demethylenyl metabolites at position 2 and 5, and of the further deaminated demethylenyl metabolites at position 2. For the β-keto-phenylalkylamine and pyrrolidinophenone, conjugation of the demethylenyl metabolites and of the deaminated demethylenyl metabolites at position 2 could be identified. The DAA allowed the differentiation of the 2 and 5/6 isomers by confirmation of the postulated mass spectral fragments. Finally, the tested drugs and phase I metabolites showed no inhibition potency on GST activity.     

Site-selectively functionalizing microelectrode arrays: the use of Cu(I)-catalysts

Site-selective Cu(I)-catalyzed reactions have been developed on microelectrode arrays. The reactions are confined to preselected electrodes on the arrays using oxygen as the confining agent. Conditions initially developed for the Cu(I)-catalyzed click reaction have proven general for the coupling of amine, alcohol, and sulfur nucleophiles to both vinyl and aryl iodides. Differences between reactions run on 1-K arrays and reactions run on 12-K arrays can be attributed to the 1-K array reactions being divided cell electrolyses and the 12-K array reactions being undivided cell electrolyses. Reactions on the 12-K arrays benefit from the use of a non-sugar-derived porous reaction layer for the attachment of substrates to the surface of the electrodes. The reactions are sensitive to the nature of the ligand used for the Cu catalyst.     

Drugs of abuse screening in urine as part of a metabolite-based LC-MS<Superscript>n</Superscript> screening concept

Today, immunoassays and several chromatographic methods are in use for drug screening in clinical and forensic toxicology and in doping control. For further proof of the authors’ new metabolite-based liquid chromatography-mass spectrometry (LC-MSⁿ) screening concept, the detectability of drugs of abuse and their metabolites using this screening approach was studied. As previously reported, the corresponding reference library was built up with MS² and MS³ wideband spectra using a LXQ linear ion trap with electrospray ionization in the positive mode and full scan information-dependent acquisition. In addition to the parent drug spectra recorded in methanolic solution, metabolite spectra were identified after protein precipitation of urine from rats after administration of the corresponding drugs and added to the library. This consists now of data of over 900 parent compounds, including 87 drugs of abuse, and of over 2,300 metabolites and artifacts, among them 436 of drugs of abuse. Recovery, process efficiency, matrix effects, and limits of detection for selected drugs of abuse were determined using spiked human urine, and the resulting data have been acceptable. Using two automatic data evaluation tools (ToxID and SmileMS), the intake of 54 of the studied drugs of abuse could be confirmed in urine samples of drug users after protein precipitation and LC separation. The following drugs classes were covered: stimulants, designer drugs, hallucinogens, (synthetic) cannabinoids, opioids, and selected benzodiazepines. The presented LC-MSⁿ method complements the well-established gas chromatography-mass spectroscopy procedure in the authors’ laboratory.