Studies on the determination of chlorotestosterone and its metabolites in bovine urine.

Chlorotestosterone and its metabolites were determined in urine samples from bovine animals treated with chlorotestosterone acetate by oral and intramuscular routes. Sample preparation, involving enzymatic deconjugation and solid-phase extraction, was optimised. The effect of different enzyme preparations, pH, and time of incubation were studied. An extraction/clean-up procedure based on solid-phase extraction (C18 cartridge) and liquid-liquid clean-up was developed. Determination of chlorotestosterone and its metabolites was by enzyme immunoassay and GC-MS. Metabolites were converted into their TMS-enol-TMS-ether and TMS-oxime-TMS-ether forms before GC-MS (EI) analysis.     

Screening for benfluorex and its major urinary metabolites in routine doping controls

Benfluorex [1-(m-trifluoromethylphenyl)-2-(β-benzoyloxyethyl)aminopropane] has been widely used for the treatment of atherogenic metabolic disorders and impaired carbohydrate metabolism (particularly in obese type-II diabetic patients) as well as an anorectic drug. Due to its potentially performance-enhancing properties, benfluorex has been added to the list of prohibited compounds and methods of doping by the World Anti-Doping Agency (WADA) in 2010, necessitating the implementation of the drug as well as its major metabolites into routine doping control procedures. In the present study, human urinary metabolites of benfluorex were characterized by gas chromatography–electron ionization–mass spectrometry (GC-EI-MS) as well as liquid chromatography–electrospray ionization–high resolution/high accuracy tandem mass spectrometry (LC-ESI-MS/MS). Commonly employed sports drug testing approaches consisting of liquid–liquid extraction followed by GC-MS or urine dilution and immediate LC-MS/MS analysis were expanded and validated with regard to specificity, recovery (48–54%, GC-MS only), intra- and interday precision (<25%), limits of detection (5–8 ng/mL for LC-MS/MS and 80 ng/mL for GC-MS), and ion suppression (for LC-ESI-MS/MS only) to allow the detection of benfluorex metabolites 1-(m-trifluoromethylphenyl)-2-(2-hydroxyethyl)aminopropane (M1), 1-(m-trifluoromethylphenyl)-2-(2-carboxymethyl)aminopropane (M2), and 1-(m-trifluoromethylphenyl)-2-aminopropane (M3) as well as the glucuronic acid conjugate of M1.     

Combined thin-layer chromatography-photography-densitometry for the quantitation of cyclophosphamide and its four principal urinary metabolites

A novel method for the quantitative determination of the anti-cancer drug cyclophosphamide and its principal urinary metabolites 4-oxocyclophosphamide, carboxyphosphamide, phosphoramide mustard and bis(2-chloroethyl)amine has been devised. The assay combines adsorption of drug-related material onto Amberlite XAD-2 and thin-layer chromatography with spot visualization using 4-(4-nitrobenzyl)pyridine, rapid photography and densitometry. The intra-assay coefficient of variation for each compound was less than 6%. The limit of detection of the assay was 1 microgram ml-1 for cyclophosphamide, phosphoramide mustard and bis(2-chloroethyl)amine and 0.5 microgram ml-1 for 4-oxocyclophosphamide and carboxyphosphamide. The method was validated for cyclophosphamide and 4-oxocyclophosphamide using gas chromatography. It is concluded that the method provides the first means of determining the full metabolic spectrum for cyclophosphamide in patients without recourse to the administration of radioisotopically labelled drug.     

Detection of 19-nortestosterone and its urinary metabolites in miniature pigs by gas chromatography-mass spectrometry

The metabolism of 19-nortestosterone was investigated in a miniature non-castrated male pig (boar), in a castrated pig (barrow) and in a female pig (sow). Urine samples were taken before and at regular intervals after the injection of 100 mg of Laurabolin (nortestosterone laurate). The sample clean-up consists in preliminary solid-phase extraction, followed by high-performance liquid chromatographic purification and fractionation. Finally, gas chromatography-mass spectrometry is used to identify the 19-nortestosterone metabolites.     

Studies on the metabolism of gomisin A (TJN-101). II. Structure determination of biliary and urinary metabolites in rat

After oral administration of gomisin A (1) to rats, the bile and urine were collected and treated with beta-glucuronidase and arylsulfatase. Seven metabolites, met B (2), met A-III (3), met E (4), met D (5), met F (6), met G (7), and met H (8) were isolated from the bile treated with the enzymes. Eight metabolites 2-8, and met A-II (9) were isolated from the urine treated with the enzymes. A major metabolite 2, and two minor metabolites 3 and 9 were identified as met B, met A-III, and met A-II, respectively, which are oxidative products of 1 formed by rat liver S9 mix. The structures of five new metabolites 4-7, and 8 were determined on the basis of chemical and spectral studies.     

Paramagnetic species on the surface of chemically activated silica

Active centers of SiO₂ formed during thermolysis of methoxylated silica surface has been studied by ESR. Several types of coordinatively unsaturated silicon atoms, which differ in location and number but show similar reactivity toward various adsorbates, have been found.

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, . - , , , H₂, CO, O₂.

     

Understanding the nature of vanadium species supported on activated carbon and its catalytic properties in the aerobic oxidation of aromatic alcohols

Vanadium oxide catalysts supported on activated carbon (V/AC) with V loadings ranging from 1 to 20 wt.% were prepared by a wet-impregnation method. Various physicochemical characterization techniques, including nitrogen physisorption, X-ray diffraction (XRD), Raman spectroscopy, X-ray absorption (XANES and EXAFS), X-ray photoelectron spectroscopy (XPS), and electron spin resonance (ESR), were employed to understand the nature of vanadium species on activated carbon. The results revealed that vanadium oxide mainly existed in a highly dispersed state for 10 wt.% or less vanadium loadings; a large amount of vanadium resulted in aggregated microcrystalline phase. Vanadium species on activated carbon surface showed a similar local coordination structure to that of NH₄VO₃ with a distorted tetrahedral symmetry at low vanadium loadings, whereas octahedral coordination was dominant at high vanadium loadings (>10 wt.%). All V/AC samples showed V⁵⁺ as the major oxidation state. Nevertheless, V⁴⁺ centered in a distorted tetrahedral symmetry could be detected at a vanadium loading greater than 4 wt.%. The catalytic activity for the benzyl alcohol oxidation largely depended on the dispersion, oxidation state, and local coordination of vanadium oxides on activated carbon. Highly dispersed vanadium (5+) species with a distorted tetrahedral coordination were postulated to account for the excellent catalytic performances of V/AC catalysts (TOF = 39.1 h^?1).     

Studies on fungal metabolites—XXXII: A renewed investigation on (−) flavoskyrin and its analogues

1-Oxo-1,2,3,4-tetrahydroanthraquinone (4a), and its 8-hydroxy-(4b) and 8-hydroxy-6- methyl (4c) derivatives were dimerized to the compounds formulated as (6a), (6b) and (6e), respectively. The structure of 6a was confirmed by X-ray crystallographic analysis.By the analogy with these dimers and NMR spectral analysis, a revised structure (7) was proposed for (?) flavoskyrin, a yellow metabolite of Penicillium islandicum NRRL 1175. A biosynthetic scheme involving Diels-Alder type cyclo-addition (π4s + π2s) was proposed for (?) flavoskyrin.     

Copper hydroperoxo species activated by hydrogen-bonding interaction with its distal oxygen

A novel copper(II)[bond]OOH complex with functional ligand that can form a hydrogen bond with the distal oxygen of hydroperoxide has been designed and prepared as a structural/functional model of dopamine beta-hydroxylases, whose spectroscopic characterization and decomposition rates have indicated that the hydroperoxide is activated through the hydrogen-bonding interaction with the distal oxygen.