QSAR study on the joint toxicity of 2,4-dinitrotoluene with aromatic compounds to Vibrio fischeri

The individual and joint toxicities of binary mixtures of 2,4-Dinitrotoluene (2,4-DNT) and 8 nitrobenzenes and anilines to V. fischeri were determined respectively and their mixture toxicity effects were assessed using the Additivity Index (AI). The energy of the lowest unoccupied molecular orbital (E-LUMO) of studied compounds was calculated and was used to develop QSARs. The prediction models for the individual and mixture toxicity data were respectively: log 1/EC50 = 3.213-0.716 E-LUMO, n=9, r=0.830, s=0.545 and log 1/EC50 = 3.672-0.882 E-LUMO, n=8, r=0.925, s=0.406. The joint toxic effects derived from AI values show that the mixture toxicity of 2,4-DNT and the other nitrobenzenes is synergistic (AI > 0), whilst the mixture toxicity of 2,4-DNT and the anilines is antagonistic (AI < 0). These results confirm that the mixture toxicity is mainly related to intracellular oxidation and reduction. -E-LUMO values of nitrobenzenes are higher. The nitrobenzenes when mixed with 2,4-DNT make the mixture systems easily reduced; the mixture toxicity effect is synergism. On the other hand, -ELUMO values of anilines are lower. The anilines when mixed with 2,4-DNT can make the mixture systems less easily reduced, and the mixture toxicity effect is antagonism.