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  • 1
    Electronic Resource
    Electronic Resource
    In vivo metabolism of retrorsine and retrorsine-N-oxide (1993)
    Springer
    Archives of toxicology 67 (1993), S. 39-43 
    Details
    ISSN: 1432-0738
    Keywords: Pyrrolizidine alkaloids ; Retrorsine, retrorsine-N-oxide ; Metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The in vivo metabolism and excretion of the urinary metabolites from the pyrrolizidine alkaloids (PAs), retrorsine (RET) and retrorsine-N-oxide (RET-NO) have been studied in rats. Isatinecic acid (INA), pyrrolic metabolites, N-oxides and retronecine accounted for 31.0, 10.3, 10.8 and 0.39% of the administered RET. Predosing rats with triorthocresyl phosphate (TOCP), had no effect on the excretion of pyrrolic metabolites and INA. Phenobarbital (PB) increased the excretion of both pyrrolic metabolites and INA with a corresponding decrease in the excretion of RET and N-oxides; the retronecine levels remained unaltered. When RET-NO was administered i.p., the urinary levels of pyrrolic metabolites, INA and RET were decreased relative to those treated with RET. The p.o. administration of RET-NO produced significantly higher levels of pyrrolic metabolites, INA and RET. These results suggest that esterase hydrolysis plays a minor role in the formation of INA and that a common metabolic pathway may exist between pyrrolic metabolites and INA formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02072033
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  • 2
    Electronic Resource
    Electronic Resource
    Reaction of methyl mercury with plasmalogens suggests a mechanism for neurotoxicity of metal-alkyls (1974)
    [s.l.] : Nature Publishing Group
    Nature 248 (1974), S. 456-458 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] FIG. 1 a, 220 MHz NMR spectrum of plasmalogen. b, 220 MHz NMR spectrum of the products formed when plasmalogen is incubated with methyl mercury chloride and water. Post mortem examinations of victims of the Minamata disaster, who suffered neurological disease after eating fish contaminated with ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/248456a0
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrolysis rates of Pyrrolizidine alkaloids derived from Senecio jacobaea (1995)
    Springer
    Archives of toxicology 69 (1995), S. 725-728 
    Details
    ISSN: 1432-0738
    Keywords: Key words Pyrrolizidine alkaloid ; Seneciphylline ; Jacozine ; Senecio jacobaea ; Carboxylesterase ; Guinea pig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Many of the commonly studied pyrrolizidine alkaloids (PAs) are built upon the subgroup retronecine (RET), which is released from the parent molecule by either base catalyzed or enzymatic hydrolysis of the ester linkages. The rate of appearance of RET in a hydrolytic study would thus reflect the rate of hydrolysis for the PA being tested. We have developed a gas chromatographic (GC) method to measure the release of RET from incubations of PAs with the guinea pig carboxylesterase, GPH1. The PAs tested were the following: jacobine (JAB), jacozine (JAZ), retrorsine (RES), and seneciphylline (SNP). The Kms for SNP and JAZ were determined to be 64.9 and 349.2 μM, respectively. In addition, a qualitative assessment of hydrolytic activity toward a radiolabelled mixture of retrorsine/riddelliine (RES/RIL) was performed with HPLC and radiometric detection.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002040050240
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  • 4
    Electronic Resource
    Electronic Resource
    Pyrrolizidine alkaloids in overwintering monarch butterflies (Danaus plexippus) from mexico (1987)
    Springer
    Cellular and molecular life sciences 43 (1987), S. 943-946 
    Details
    ISSN: 1420-9071
    Keywords: Pyrrolizidine alkaloids ; macrocyclic diesters ; monoesters ; dihydropyrrolizines ; Lepidoptera ; Danaus plexippus ; monarch butterflies ; overwintering ; asteraceae ; Boraginaceae ; ecological chemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary North American populations of the monarch butterfly,Danaus plexippus, have been found to contain pyrrolizidine alkaloids and their N-oxides. Analytical methods (TLC, GC, and GC/MS) have been developed to isolate, quantitate, and structurally elucidate the alkaloids. Examples of at least two classes of pyrrolizidine alkaloids have been identified, the macrocyclic diesters, senecionine, integerrimine, and seneciphylline, and the monoesters, echinatine, intermedine, and lycopsamine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01951680
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  • 5
    Electronic Resource
    Electronic Resource
    Lipid peroxidation and cellular damage caused by the pyrrolizidine alkaloid senecionine, the alkenal trans-4-hydroxy-2-hexenal, and related alkenals (1987)
    Springer
    Cell biology and toxicology 3 (1987), S. 379-390 
    Details
    ISSN: 1573-6822
    Keywords: cytoxicity ; isolated rat hepatocytes ; lactate dehydrogenase release ; lipid peroxidation ; macrocyclic pyrrolizidine alkaloids ; thiobarbituric acid reactive products ; trans-4-OH-2-hexenal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Lipid peroxidation was examined as a possible mechanism for cell injury by trans-4OH-2-hexenal, the macrocyclic pyrrolizidine alkaloid senecionine and related alkenals in isolated rat hepatocytes. Each compound elicited a positive dose response for peroxidation of cellular lipids as measured by the formation of thiobarbituric acid-reactive products. The addition of the anti-oxidant N, N'-diphenyl-p-phenylenediamine to the hepatocyte suspensions inhibited the production of thiobarbituric acid-reactants. However, the presence of the anti-oxidant had no protective effects on the cell membrane integrity as evidence by the leakage of lactate dehydrogenase from the cells into the sorrounding media. These results suggest that lipid peroxidationwhich occurs in the presence of senicone, trans-4-OH-2-hexenal or related alkenals is not entirely responsible for the cellular damage is isolated rat hepatocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00119911
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of pyrrolizidine alkaloid metabolites from mouse liver microsomes using tandem mass spectrometry and gas chromatography/mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 15 (1988), S. 265-273 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rapid and sensitive identification and quantification of important pyrrolizidine alkaloid metabolites using tandem mass spectrometry (MS/MS) and gas chromatography/mass spectrometry (GC/MS) is described. Identifications of N-oxide and hydrolytic metabolites of the pyrrolizidine alkaloids senecionine and monocrotaline in extracts of mouse hepatic microsomal incubations were accomplished by comparing collisionally activated decomposition/mass-analyzed ion kinetic energy spectra of specific ions from microsomal extracts with spectra obtained from synthetic standards of suspected metabolites. Trace amounts of the toxic metabolite dihydropyrrolizine (DHP) were observed by GC/MS of trimethylsilyl (TMS) derivatives, but the amounts present in hepatic microsomal extracts were below the MS/MS limit of detection. Quantitative determinations of senecionine N-oxide were performed by fast atom bombardment MS/MS. Suppression of N-oxide ionization by other substances in the extracts was judged to be minimal. The TMS derivatives of the metabolites senecic acid, monocrotalic acid and DHP were quantified using capillary GC/MS. Results from the study demonstrate that the relative contributions of the three major pathways of pyrrolizidine alkaloid metabolism (N-oxidation, hydrolysis and oxidation to pyrrolic compounds) can be assessed using a single analytical instrument and minimal sample preparation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200150506
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of mercapturic acid conjugates of xenobiotic compounds using negative ionization and tandem mass spectrometryPresented in part at the 36th Annual Conference on Mass Spectrometry and Allied Topics, San Francisco, 1988. (1993)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1993), S. 68-76 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mass spectra of mercapturic acid conjugates of two xenobiotic products of lipid peroxidation (trans-4-hydroxy-2-hexenal and trans-4-hydroxy-2-nonenal) as well as conjugates of 1,3-dichloropropene, styrene oxide, 1,2-naphthalene oxide and α-chlorotoluene were obtained using fast atom bombardment or negative chemical ionization. Fragmentation pathways were investigated using linked scan and mass-analyzed ion kinetic energy spectrometric techniques. Characteristics of the spectra obtained using different ionization and sample introduction techniques are compared. Deprotonated molecular ions of mercapturic acids gave simple daughter ion spectra, with the dominant mode of decomposition involving cleavage of C—S bonds giving a characteristic neutral loss of 129 Da Screening for mercapturates in urine samples was performed using neutral loss scanning and yielded limits of detection in the low nanogram per milliliter range. Quantitative analysis of the S-benzyl mercapturic acid at 1 p.p.b. in urine has been demonstrated using combined gas chromatography/electron capture mass spectrometry with d3-S-benzyl mercapturic acid as internal standard.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200220109
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