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  • A quantum chemical study of the reactivity of acetaminophen (paracetamol) toxic metabolite N-acetyl-p-benzoquinone imine with deoxyguanosine and glutathione
    Klopčič, Ivana ...
    Acetaminophen (APAP) forms some reactive metabolites that can react with DNA. APAP is a potentially genotoxic drug and is classified as a Group 3 drug according to International Agency for Research ... on Cancer (IARC). One of the possible mechanisms of APAP genotoxicity after long term of use is that its reactive the quinone imine (QI) metabolite of acetaminophen (NAPQI), can chemically react with DNA after glutathione (GSH) depletion. A quantum chemical study of the reactions between the NAPQI and deoxyguanosine (dG) or GSH was performed. Activation energies ([delta]G) for the reactions associated with the 1, 4-Michael addition were calculated on the M062X/6-311++G(d,p) level of theory. We modeled the reaction with dG as a multi-step process. The first step is rate-limiting ([delta]G=26.7 kcal/mol) and consists of formation of a C-N bond between the C3 atom of the QI moiety and the N7 atom of dG. The second step involves proton transfer from the C3 moiety to the nitrogen atom of the QI with [delta]G of 13.8 kcal/mol. The depurination reaction that a [delta]G of 25.7 kcal/mol. The calculated [delta]G for the nucleophilic attack of the deprotonated S atom of GSH on the C3 atom of the NAPQI is 12.9 kcal/mol. Therefore, the QI will react with GSH much faster than with DNA. Our study gives mechanistic insight into the genotoxicity of the APAP metabolite and will be useful for estimating the genotoxic potential of existing drugs with aQI moiety. Our results show that clinical application of APAP is safe, while in the case of severely depleted GSH levels APAP should be administred with caution.
    Source: Chemico-biological interactions. - ISSN 0009-2797 (Vol. 242, Dec. 2015, str. 407-414)
    Type of material - article, component part ; adult, serious
    Publish date - 2015
    Language - english
    COBISS.SI-ID - 3977585