Unknown Metabolites (unknown + metabolite)

Distribution by Scientific Domains

Selected Abstracts

Important roles of the hyphenated HPLC-DAD-MS-SPE-NMR technique in metabonomics

Huiru Tang
Abstract Metabolite identification is a key step for metabonomics study. A fully automated hyphenation of HPLC-diode-array detector (DAD) mass spectrometry (MS) solid phase extraction (SPE),NMR spectroscopy (HPLC-DAD-MS-SPE-NMR) is one of the most efficient methods to determine the structure of a given unknown metabolite in a complex mixture (metabonome) and hence represents one of the most important analytical techniques for the further development of metabonomics. In this review, some recent applications of this technique in identifying novel and trace metabolites in plant extracts and drug metabolism have been discussed. Modification of this hyphenated technique, enabling multiple trappings of strong polar metabolites for biofluids, needs further development. Copyright 2009 John Wiley & Sons, Ltd. [source]

Determination of bupivacaine and metabolites in rat urine using capillary electrophoresis with mass spectrometric detection

Ryan M. Krisko
Abstract A method using capillary electrophoresis-mass spectrometry (CE-MS) was developed for the structural elucidation of bupivacaine and metabolites in rat urine. Prior to CE-MS analysis, solid-phase extraction (SPE) was used for sample cleanup and preconcentration purposes. Exact mass and tandem mass spectrometric (MS/MS) experiments were performed to obtain structural information about the unknown metabolites. Two instruments with different mass analyzers were used for mass spectrometric detection. A quadrupole time-of-flight (Q-TOF) and a magnetic sector hybrid instrument were coupled to CE and used for the analysis of urine extracts. Hydroxybupivacaine as well as five other isomerically different metabolites were detected including methoxylated bupivacaine. [source]

Distribution and metabolism of D/L -, L - and D -glufosinate in transgenic, glufosinate-tolerant crops of maize (Zea mays L ssp mays) and oilseed rape (Brassica napus L var napus),

Monika Ruhland
Abstract The aim of the present study was to determine whether post-emergence application of glufosinate to transgenic crops could lead to an increase in residues or to the formation of new, hitherto unknown metabolites. Transgenic oilseed rape and maize plants were treated separately with L -glufosinate, D -glufosinate or the racemic mixture. Whereas about 90% of the applied D -glufosinate was washed off by rain and only 5,6% was metabolised, 13,35% of the applied L -glufosinate remained in the form of metabolites and unchanged herbicide in both transgenic maize and oilseed rape. The main metabolite was N -acetyl- L -glufosinate with total residues of 91% in oilseed rape and 67% in maize, together with small amounts, of 5% in oilseed rape and 28% in maize, of different methylphosphinyl fatty acids. These metabolites were probably formed from L -glufosinate by deamination and subsequent decarboxylation. The residues were distributed in all fractions of the plants, with the highest contents in treated leaves and the lowest in the grains (0.07,0.3% in maize and 0.4,0.6% in oilseed rape). There was no indication of an accumulation of total residues or of residue levels above the official tolerances for glufosinate. Copyright 2004 Society of Chemical Industry [source]

Metabolism of dimethylarsinic acid in rats: production of unidentified metabolites in vivo

Kaoru Yoshida
Abstract Our previous study revealed that two unidentified metabolites, M-1 and M-2, were excreted in urine after long-term oral administration of dimethylarsinic acid (DMA), the main metabolite of inorganic arsenic. In the present study, we attempted to clarify the mechanism of production of these unknown metabolites. Male F344/DuCrj rats were administered a single dose of DMA (50,mg kg,1) orally or intraperitoneally with or without pretreatment with L -buthionine-SR-sulfoximine (BSO), which inhibits glutathione (GSH) synthesis. Urine was collected by forced urination at various time points after administration of DMA. Arsenic metabolites in urine were analyzed by ion chromatography with inductively coupled plasma mass spectrometry (IC,ICP-MS). The unidentified metabolites M-1 and M-2 were excreted later than elimination of DMA and trimethylarsine oxide (TMAO). GSH depletion decreased in TMAO elimination, suggesting that GSH plays important roles in the methylation of DMA to TMAO in rats. There was no difference in the amount of production of either M-1 or M-2 between BSO-pretreated rats and controls, suggesting that M-1 and M-2 cannot be formed during methylation in the liver. The amounts of elimination of M-1 and M-2 were less after intraperitoneal administration than after oral administration. Male F344/DuCrj rats were given 100,mg As l,1 DMA via drinking water for 20 weeks. Urine and feces were collected forcibly and were analyzed by IC,ICP-MS. A new unidentified metabolite, M-3, was detected only in feces as a metabolite of DMA after 20 weeks exposure to DMA, although M-1 and M-2 were found in both urine and feces. The unidentified metabolites M-1, M-2, and M-3 were excreted mainly as fecal metabolites along with unmetabolized DMA. This finding also suggests that M-1, M-2, and M-3 might be produced in the intestinal tract. Copyright 2001 John Wiley & Sons, Ltd. [source]

Structure and Biosynthesis of Myxochromides S1,3 in Stigmatella aurantiaca: Evidence for an Iterative Bacterial Type I Polyketide Synthase and for Module Skipping in Nonribosomal Peptide Biosynthesis,

CHEMBIOCHEM, Issue 2 2005
Silke C. Wenzel Dipl.-Chem.
Abstract The myxobacterium Stigmatella aurantiaca DW4/3,1 harbours an astonishing variety of secondary metabolic gene clusters, at least two of which were found by gene inactivation experiments to be connected to the biosynthesis of previously unknown metabolites. In this study, we elucidate the structures of myxochromides S1,3, novel cyclic pentapeptide natural products possessing unsaturated polyketide side chains, and identify the corresponding biosynthetic gene locus, made up of six nonribosomal peptide synthetase modules. By analyzing the deduced substrate specificities of the adenylation domains, it is shown that module 4 is most probably skipped during the biosynthetic process. The polyketide synthase MchA harbours only one module and is presumably responsible for the formation of the variable complete polyketide side chains. These data indicate that MchA is responsible for an unusual iterative polyketide chain assembly. [source]