THE STRENGTH OF MUTAGENICITY, 13C NMR CHEMICAL SHIFTS,AND ELECTRONIC STATES OF NITROBENZANTHRONES

Mutagenic activities of nitrated benzanthrones (NBAs) vary largely with the position and the number of the nitro group. To investigate the structure-activity correlations for NBAs, we have performed nuclear magnetic resonance (NMR) measurements and molecular orbital calculations for the three nitrobenzanthrones, 2-NBA, 3-NBA, 11-NBA; the three dinitrobenzanthrones, 1,9-DNBA, 3,11-DNBA, 3,9-DNBA; and the trinitrobenzanthrone, 3,9,11-TNBA. It was confirmed that the ¹³ C chemical shifts (δ) of the ortho carbon atoms with respect to the nitro group of the compounds tend to be more upfield with decreasing mutagenic activities. The molecular orbital calculations revealed that the LUMO energies of the compounds decrease with mutagenic activities, and that the HOMO and LUMO densities tend to decrease and increase, respectively, with decreasing mutagenic activities. These results indicate that reduction is very important in the metabolism of nitrobenzanthrones.