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Ionization potentials and metabolic activations of carbazole and acridine derivatives
W Xue1, D Zapien, D Warshawsky
1Department of Environmental Health, University of Cincinnati Medical Center, Cincinnati, Ohio 45267-0056, USA.
Abstract:
7H-Dibenzo[c,g]carbazole (DBC) and dibenz[a,j]acridine (DBA) representing environmental nitrogen-heterocyclic aromatic (NHA) genotoxicants undergo differing metabolism and exhibit differing DNA binding patterns and carcinogenic activities. Two chemical oxidation-related parameters, anodic peak potentials (E(pa)) and maximum absorption energies (E(CT)) of the charge-transfer complexes, were measured for a series of 18 derivatives of carbazole and acridine. On the basis of the E(pa) and E(CT) values and the ionization potential (IP) data of the parent carbazole and acridine that are available in the literature, with linear regression analyses, IP values of the 18 carbazoles and acridines were reported for the first time. The two sets of IP values determined from either E(pa) or E(CT) agreed with one another for most of the compounds. Carbazoles possessed IP values (ranging from 7.2 to 7.6 eV) that are lower than those of acridines (i.e., 7.8-8.1 eV). These data are consistent with the potential activation of carbazole and/or acridine derivatives. For DBC having an IP of approximately 7.3 eV, both one-electron oxidation and monooxygenation pathways are involved in the metabolic activation. In contrast, DBA with a high IP of approximately 8.0 eV is activated through the monooxygenation pathway only. Therefore, just as it is known for carcinogenic PAHs, IP appears to be an important parameter in predicting the metabolic activation for genotoxic NHA in the environment.
Insights
Ionization potential (IP) predicts how environmental genotoxic nitrogen-heterocyclic aromatics (NHAs) like carbazole and acridine derivatives metabolically activate. Lower IP values correlate with different activation pathways, impacting carcinogenicity.
Area of Science:
- Environmental Chemistry
- Toxicology
- Organic Chemistry
Background:
- Environmental nitrogen-heterocyclic aromatics (NHAs), such as 7H-Dibenzo[c,g]carbazole (DBC) and dibenz[a,j]acridine (DBA), are genotoxicants with varying metabolic activation and carcinogenic potential.
- Understanding the metabolic pathways of these compounds is crucial for assessing their environmental risk.
Purpose of the Study:
- To determine the ionization potential (IP) values for 18 carbazole and acridine derivatives.
- To investigate the relationship between IP and the metabolic activation pathways of genotoxic NHAs.
- To establish IP as a predictive parameter for NHA genotoxicity.
Main Methods:
- Measured anodic peak potentials (E(pa)) and charge-transfer complex maximum absorption energies (E(CT)) for carbazole and acridine derivatives.
- Utilized linear regression analysis with literature IP data for parent compounds.
- Calculated IP values for the 18 derivatives, reporting them for the first time.
Main Results:
- IP values were successfully determined for 18 carbazole and acridine derivatives using E(pa) and E(CT) measurements, showing good agreement.
- Carbazoles exhibited lower IP values (7.2–7.6 eV) compared to acridines (7.8–8.1 eV).
- DBC (IP ~7.3 eV) activates via one-electron oxidation and monooxygenation, while DBA (IP ~8.0 eV) activates solely through monooxygenation.
Conclusions:
- Ionization potential (IP) is a significant parameter for predicting the metabolic activation pathways of genotoxic NHAs.
- Lower IP values in carbazole derivatives suggest susceptibility to multiple activation routes, contrasting with acridine derivatives.
- This research provides a foundation for predicting the environmental genotoxicity of NHAs based on their chemical properties.