Quantitative structure-activity study of the toxicity of benzonitriles to the ciliate Tetrahymena pyriformis

The toxicities of 34 benzonitriles to Tetrahymena pyriformis have been measured. Structure-activity relationships indicate that for these compounds different mechanisms of toxic action are taking place dependent on the nature of the substituent. Benzonitrile itself, some halogenated and the toluene derivatives model as non-polar narcotics; more polar substituents model well as polar narcotics; whilst the nitro and aldehyde substituted benzonitriles, and compounds that may be metabolised to benzoquinone are shown to exhibit considerable excess toxicity and, thus, the probability is that they are acting by a specific mechanism of action. After the removal of two outliers, QSAR analysis reveals a significant three parameter equation, and confirms the importance of hydrophobicity and descriptors of reactivity for the comprehension and the prediction of the toxicity of the benzonitriles.