THE GENOTOXICITY OF BENZANTHRACENES - A QUANTITATIVE STRUCTURE-ACTIVITY STUDY

Molecular orbital (MO) evaluations of a series of 14 methyl-substituted benz[a]anthracenes, calculated by the complete neglect of differential overlap (CNDO/2) method, are reported. By quantitative structure-activity relationship (QSAR) analysis, the carcinogenic and mutagenic potencies of these compounds have been shown to be correlated with their electronic structures, namely, with the magnitude of the energy of the lowest unoccupied molecular orbital (LUMO). The log mutagenicity potencies for the series of 14 benz[a]anthracenes are negatively dependent on E(LUMO), with a correlation coefficient of 0.82, which is increased to 0.90 by inclusion in the QSAR of a second variable, namely Q(3)H, the electronic density in the highest occupied molecular orbital, E(HOMO), of carbon-3. E(LUMO) is also negatively correlated with mouse carcinogenicity of the benzanthracenes, with a correlation coefficient of 0.88 for tumour incidence, and of 0.83 for log carcinogenicity index. The carcinogenicity and mutagenicity of the individual members of this series of polycyclic aromatic hydrocarbons are discussed in terms of the relationships between molecular structure, electron density, metabolic activation and covalent binding of reactive intermediates.