Acute toxicity and quantitative structure-activity relationships of alpha-branched phenylsulfonyl acetates to Daphnia magna.

The acute toxicity (48 h-EC50, microM) of 20 alpha-substituted phenylsulfonyl acetates was measured using Daphnia magna with a static method. On the basis of physicochemical parameters (octanol/water partition coefficient logK(ow) and aqueous solubility logS(w)), the theoretical linear solvation energy relationships (TLSER) and Charge model descriptors, QSARs were calculated for the immobilization of D. magna. For the models with the physicochemical parameters logK(ow) and logS(w), the low squared correlation coefficients indicate that hydrophobicity plays a dominant role on the toxicity and hydrophobicity is not the only factor that influences the activity of the compounds. For the TLSER model and the Charge model, the great squared correlation coefficients suggest that the models have good predictive capability. The higher activity of the compounds can be explained with the disruption of van der Waals interactions between lipid and/or protein compounds within the membrane and the possibility of the compounds to form hydrogen bonds with the receptor molecules. The models may more completely illustrate the toxicity mechanisms.