RELATIONSHIPS BETWEEN BIOLOGICAL POTENCY AND ELECTRONIC STATES OF POLYCHLORINATED DIBENZOFURANS AND POLYCHLORINATED-BIPHENYLS

It was found that the differences between the frontier molecular orbital energies (epsilon(homo)-epsilon(lumo) = DELTAepsilon) in polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) have a correlationship with the magnitude of the biological activity which is influenced by both the number and position of chlorine atom substituents on PCDFs and PCBs skeletons. Moreover, it was found that the DELTAepsilon's values of PCBs are classified into two types which coincide with the well-known classification of PCBs to types of 3-methylcholanthrene and phenobarbital according to their biological activities. The relationship between DELTAepsilon and biological activity in these xenobiotics suggests that the congeners having small DELTAepsilon values such as 2,3,4,7,8-pentaCDF, 2,3,4,6,7-pentaCDF, 3,4,5,3',4'-pentaCB, and 3,4,5,3',4',5'-hexaCB form stable molecular complexes with an Ah-receptor, eg. (2,3,4,7,8-PentaCDF-Ah-receptor), while the congeners having large DELTAepsilon values are strongly suggested to be unstable in a complex formation. Thus, this work presents an explanatory method to help understand the structure-activity relationship of the xenobiotics PCDFs and PCBs.