Theoretical chemistry study on the toxicity of some polychlorobiphenyl (PCB) compounds using molecular descriptors

Abstract

This study was carried out to establish, validate and apply a model that relates the toxicity of some PCBs (2,4-dichlorobiphenyl, 2,4’5-trichlorobiphenyl, 2,2’3,4,4’,5’,6-heptachlorobiphenyl, 2,2’,5,5’-tetrachlorobiphenyl and 2,3,3’4,4’-pentachlorobiphenyl) to molecular descriptors (quantum chemical, physicochemical and topological descriptors) through quantitative structure toxicity relationship. The established model reveal that the total molecular energy, electronic energy, core repulsion energy, energy of the highest occupied molecular orbital, energy of the lowest unoccupied molecular orbital, cosmo area, cosmo volume and dipole moment displayed excellent correlation with LD50 values of the PCBs. Some topological parameters (namely molecular topological index, Weiner index, total connectivity and Balaban index) also exhibited excellent correlation with experimentally determined LD50 data. Two equations suitable for estimating theoretical LD50 values of the studied PCBs were derived using quantum chemical and topological descriptors. These equations gave perfect fitness when experiment and theoretical LD50 values were plotted (i.e. R2 value approximated unity) against each other. Perfect correlation was also obtained between theoretical and experimentally derived LD50 values for 2,2’,3,4’,5’,6-hexaxhlorobiphenyl, 2,2’,4,5,5’-pentachlorobiphenyl, 2,3’,4,4’-tetrachlorobiphenyl and 2,2’,4,4’,5,5’-hexachlorobiphenyl, where were PCBs used for model validation. The model was also used to predict the toxicity of other PCBs that lacks accurate experimental data. The study revealed that the reactivity of PCBs can be influence by the number of substituted chlorine atom and by the position of the reactive aromatic carbon. From the results and findings of the study, it was concluded that the applications of quantitative structure-toxicity relation principles to quantum and topological parameters provide excellent avenue for estimating the degree of toxicity of PCBs.