Wilhelm J. Richter

Biotransformation and pharmacokinetics of sulfinpyrazone (Anturan®) in man

SummaryThe absorption, biotransformation and elimination of sulfinpyrazone, 1,2-diphenyl-3,5-dioxo-4-(2′-phenylsufinylethyl)-pyrazolidine, have been studied by administration of single 200 mg oral doses of a14C-labelled preparation to two male volunteers. Absorption from the gastro-intestinal tract was rapid and complete and the plasma concentration of unchanged drug reached maximum values of 22.67 and 13.04 µg/ml, respectively, after 1 – 2 hours. The elimination half-life in the two subjects, calculated from the decline between 3 and 8 hours, was 2.7 and 2.2 hours. The integrated concentration of unchanged sulfinpyrazone in plasma, estimated from the area under the concentration curves (AUC), was almost as high as that of total14C-substances, so the proportion of metabolized drug in plasma was low. In no case did the AUC of the three specifically determined metabolites, i.e. the sulphone G 31 442, the “para-hydroxy”-compound G 32 642 and the “4-hydroxy”-compound GP 52 097, exceed 4% of the sulfinpyrazone value. More than 95% of whole blood radioactivity was confined to plasma. The oral dose was rapidly and completely excreted, since within 4 days more than 95% was recovered, 85% from urine and 10% from faeces. A large proportion of the dose was excreted as unchanged drug in the two volunteers: 51 and 54% of total urinary radioactivity was present as sulfinpyrazone; 8.2 and 8.8% was present as “para-hydroxy”-metabolite, 2.7 and 3.0% as sulphone-metabolite, and 0.6 and 0.8% as “4-hydroxy”-metabolite. About 30% of urinary radioactivity consisted of highly polar metabolites. Spectroscopy of them showed that they were the C-β-glucuronides of sulfinpyrazone (28%) and the corresponding sulfone (2%). In these metabolites the C(4) of the pyrazolidine ring was directly attached to glucuronic acid, and thus they represent a new type of biosynthetic conjugate.

Oviposition stimulants for the cabbage root fly: isolation from cabbage leaves

Abstract Two compounds present on the surface of Brassica oleracea cv. botrytis leaves have been isolated and identified which stimulate very effectively oviposition in the cabbage root fly, Delia radicum and which are perceived by a specific receptor neuron in the tarsal sensillum C5 of the female fly. Activity of extracts and chromatographic fractions were bioassayed, using oviposition experiments and mainly electrophysiological recordings from the C5 tarsal contact chemoreceptor sensillum of female flies. Spectroscopic data indicate that the main compound is 1,2-dihydro-3-thia-4,10,10b-triaza-cyclopenta[.a.]fluorene-1-carboxylic acid, a novel compound related to Brassica phytoalexins like brassicanal C. It is accompanied by its glycine conjugate.

False sugar sequence ions in electrospray tandem mass spectrometry of underivatized sialyl-Lewis-type oligosaccharides

Abstract Formation of “false” sugar sequence ions from branched tetrasaccharides of the sialyl-Lewis-type by migration of fucose towards sialic acid residues is shown to occur in [M + H] + and [M + NH 4 ] + ions produced by electrospray ionization and subjected to low energy collision induced dissociation (CID). For the verification of their composition and sequence, such irregular ions were produced in the orifice region of the ion source, mass selected in Q1, and subjected to a second CID step in Q2 of a triple quadrupole analyser. When produced and analysed in the same “double CID” fashion, the branched B 3 ions still containing all four sugar subunits show such migration to only a minor extent. The analysis of B n fragment ions with high numbers for n may thus have advantages over the analysis of M-like species

A genetic approach to the biosynthesis of the rifamycin-chromophore in Nocardia mediterranei. III. Isolation and identification of an early aromatic ansamycin-precursor containing the seven-carbon amino starter-unit and three initial acetate/propionate-units of the ansa chain.

A number of rifamycin non-producing UV-mutants derived from Nocardia mediterranei strains N813 (rifamycin B producer) and A10 (aro--mutant excreting shikimate derived from strain N813) were found to accumulate an identical complex of aromatic components instead of rifamycin B. The main component of this aromatic complex, product P8/1-OG, was isolated from six of these P--mutant strains and identified spectroscopically as a very early precursor in the biosynthesis of rifamycins.

Parallel flame ionization detection-total ion current recording in capillary gas chromatography-chemical-ionization mass spectrometry

Abstract The need for independent dual detection in the analysis of complex mixtures by gas chromatography-chemical-ionization mass spectrometry is illustrated. Monitoring of the gas chromatographic effluent by means of universal detection and unaltered uniform response by flame ionization detection is a desirable supplement to the customary, highly selective, monitoring of the total ion current, especially in consecutive analyses of the same sample, where the chemical-ionization reagent gas is varied. Since the gas chromatograms obtained by flame ionization detection are unaffected by changes in chemical-ionization conditions, they provide a safer common basis for interrelating spectral data from successive runs than do the total ion current records. For the special case of reconstructed gas chromatograms generated by computers from digitized total ion current values, direct correlations are conveniently achieved by calibrating both the flame ionization detection and total ion current records in spectrum index numbers through the use of an event marker, triggered by the data system.

[33] Tandem mass spectrometry in structural characterization of oligosaccharide residues in glycoconjugates

Publisher Summary This chapter discusses tandem mass spectrometry in structural characterization of oligosaccharide residues in glycoconjugates. In tandem mass spectrometry (MS/MS), two-stage mass analysis is performed. In the first stage (MS-l), a specific ion of interest is selected according to its mass from the set of ions that constitute the conventional mass spectrum. The second stage (MS-2) generates, from this selected precursor ion, a spectrum of product ions that arise from metastable ion (MI) or collision-induced dissociation (CID). The discussion in this chapter is limited to the structural analysis of small carbohydrate subunits (up to 5 sugar units) attached to larger aglycon moieties. At present, MS/MS of sugar ions formed from glycoconjugates appears to fulfill some, but not all, of the basic requirements of structure analysis.

Determination of interglycosidic linkages in disaccharides by high performance tandem mass spectrometry

Abstract High performance tandem mass spectrometry employing a four-sector instrument is used for the characterization of disaccharides. In contrast to low energy collisions, high energy collision induced dissociation (CID) of B2 sequence ions (C(1)-carbenium ions) derived from trideuterioacetylated dihexopyranosides permits immediate differentiation of all four linkage types (1–2, 1–3, 1–4 and 1–6) irrespective of the nature of the monosaccharide subunits. Moreover, high energy collisions produce spectra richer in features in that less energy-demanding processes (loss of peripheral residues such as AcOH-d3, Ac2O-d6 and ketene-d2) are supplemented by characteristic charge-remote fragmentations (radical eliminations, cleavages within the sugar rings). In some cases, assignment of the anomeric configuration (α/β) of the interglycosidic linkages (requiring difficult conditions in low energy CID) is also possible.

Protein C-glycosylation

Publisher Summary Glycosylation of amino acid side chains of proteins is a common and widespread modification. Two types of carbohydrate-protein linkages are known for a long time—that is, the N- and O-glycosidic bonds to Asn, and hydroxy amino acids, respectively. A third type of linkage, the C-glycosidic attachment of an α-mannopyranosyl moiety to the indolic C-2 atom of Trp-7 in human RNase U s is reported in the chapter. The chapter summarizes the evidence for this modification, and describes a number of its properties that may be useful for its detection in other proteins. As C-glycosidic bonds are resistant to acid hydrolysis, and do not yield a sugar ion in mass spectrometry (MS) experiments, the identification of the monosaccharide had to be achieved by nuclear magnetic resonance (NMR). The first indication for the presence of Trp Man in a polypeptide is obtained by Edman degradation and MS. Under certain conditions PTH-Trp Man and PTH-Tyr coeluted. Moreover, the yield of PTH-Trp Man is lower than that of most other amino acids, and varies.

Status of, and developments in, mass spectrometry of peptides and proteins*

Abstract Four mass spectrometric methods — plasma desorption, fast atom bombardment, electrospray and laser desorption — are presently used for peptide and protein analysis. Their strengths and limitations are evaluated relative to the class of compound, the type of analytical information required and the performance parameters. Finally, the prospects for the future role of mass spectrometry in protein chemistry are predicted.

Intramolecular hydrogen—deuterium exchange in isomeric methyl ethyl esters of phenylmaleic, -fumaric, and -succinic acids under chemical ionization: low energy CID study and geometrical requirements of the exchange

Abstract MH + ions of isomeric methyl ethyl phenylmaleates, 2 , and -succinates, 3 , obtained by chemical ionization (CI), exhibit preferential collision induced elimination of alcohol involving the 1-alkoxyl group which is adjacent to the phenyl substituent. MD + ions of 2 and 3 exhibit major elimination of ROD under collisional activation, and little (when generated under CD 4 -CI) or no (under ND 3 -CI) hydrogen—deuterium exchange of the external deuteron with the phenyl hydrogen atoms is observed in this process. The favored collision-induced alcohol elimination from MH + ions of isomeric methyl ethyl phenylfumarates, 4 , involves the 4-alkoxyl group. An extensive hydrogen—deuterium exchange and scrambling of the external deuteron with the five phenyl hydrogen atoms precedes the elimination of each of the two alcohols from MD + ions of 4 independent of the reagent gas (CD 4 or ND 3 ). A practically complete exchange takes place in the course of elimination involving the 4-alkoxyl group. These results are explained in terms of proximity of the 4-alkoxycarbonyl group to the phenyl ring in phenyl fumarates, 4 .