Netzeva, T.I.; Aptula, A.O.; Chaudary, S.H.; Duffy, J.C.; Schultz, T.W.; Schüürmann, G.; Cronin, M.T.D. Structure-Activity Relationships for the Toxicity of Substituted Poly-hydroxylated Benzenes to Tetrahymena pyriformis: Influence of Free Radical Formation. QSAR Comb. Sci. 2003, 22, 6, 575–582.

Abstract

The aim of this study was to develop quantitative structure-activity relationships for the toxicity to Tetrahymena pyriformis of 30 substituted poly-hydroxylated benzenes. Physico-chemical descriptors for the expression of free radical formation, associated with the OH moiety on the aromatic ring, were calculated. These included one-electron equilibrium constants that did and did not account for the oxidation of an OH-group, homolytic bond dissociation energy (BDE), electronegativity (EN) and absolute hardness (AH), in addition to the distribution coefficient (log D) as a measure of hydrophobicity. The reactivity descriptors were calculated using the semi-empirical AM1 Hamiltonian in the MOPAC molecular orbital software. Statistically significant two-parameter QSARs for toxicity were obtained by combination of log D with either BDE or AH. The QSARs suggested that toxicity is associated with hydrophobicity and the probability of radical formation.