An Approach to Calculate the Toxicity of Simple Organic Molecules on the Basis of QSAR Analysis inHydractinia echinata (Hydrozoa, Cnidaria)

Abstract

We determined the concentration at which organic substances antagonize metamorphosis induction in the hydroid Hydractinia echinata. The substances belong to several classes, such as normal and branched alkanes, alkylbenzenes, polyaromatic hydrocarbons, alkanols, polyols, phenylcarbinols, aliphatic primary amines, diaminoalkanes, aminoalkanols, and substituted aminoethanols. For QSAR analysis we correlated the measured toxicity with the respective logPOW value. Within a substance class the dependence was almost linear, but in different classes the respective slopes were different. In two classes, aliphatic amines and polyalkanols, the toxicity did not increase with increasing logPOW values. This led us to the attempt to calculate parameters for the various structural components of the substances (e.g. the number of C-atoms and the functional groups), which when properly combined result in an estimate of the toxicity of a substance. The results obtained fit well the measured data. The approach was also successfully applied to published toxicity data obtained with other organisms including Tetrahymena pyriformis (ciliate), Daphnia magna (crustacea), and Pimephales promelas (bony fish). On the basis of this approach we made predictions for toxicity values for not yet tested substances with respect to these systems.