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  • 1
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 24-29 
    ISSN: 0899-0042
    Schlagwort(e): CHO cells ; HeLa cells ; lipid peroxidation ; catalase ; D-amino acids ; L-amino acids ; toxicity ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: While the L-configuration of amino acids predominates in all known living systems, D-enantiomers of amino acids have been detected with highly sensitive chromatographic techniques in human physiological fluids. In the present study, the survival of Chinese hamster ovary cells (CHO) and HeLa cells was inhibited by exposure to high concentrations of some D- or L-amino acids. Inhibition of colony formation, though, was not necessarily observed to be chiral-dependent. Some L-amino acids (LAAS) were found to be toxic while other D-amino acids (DAAS) were innocuous in both cultures. This is contradictory to the previous observations that DAAS were generally considered to be harmful. Frequently it was implied, although not experimentally proven, that the LAAS were not toxic. One of the metabolites produced by oxidative deamination of D- or LAAS is hydrogen peroxide (H2O2), a reactive oxygen species (ROS) that is decomposed by catalase. Increased intracellular H2O2 can result in peroxidation of lipids. We measured catalase activity and the lipid peroxide levels (LPO) after incubating cells in either D- or LAAS. The amino acids (AAS) that were found to inhibit colony formation were found to be associated with higher levels of catalase activity and LPO. Therefore, we hypothesize that enhanced ROS generation may be, in part, responsible for the observed toxicity of some amino acids. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 587-591 
    ISSN: 0899-0042
    Schlagwort(e): snuff ; chewing tobacco ; Turkish tobacco ; Burley tobacco ; Virginia tobacco ; transdermal patches ; gum ; nasal spray ; Chemistry ; Organic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The enantiomeric composition of nicotine in 18 smokeless tobaccos, 3 strains of tobacco leaf, 8 pharmaceutical products, and 4 commercial reagents was determined. The relative amount of the minor enantiomeric component, (R)-(+)-nicotine, ranged from ∼0.1% to ∼1.2% of the total nicotine in all samples. In some cases it appears that (R)-(+)-nicotine may be considered one of the five most common alkaloids in tobacco products. The highest level of (R)-(+)-nicotine was found in a commercial transdermal patch. The extraction and purification processes used in obtaining commercial (S)-(-)-nicotine supplies from tobacco do not appear to decrease the amount of (R)-(+)-nicotine present. Chirality 10:587-591, 1998. © 1998 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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