The growth inhibition (96-h EC50) of two species of green algae, Selenastrurn capricornuturn and Chlorella vulgaris, caused by phenol and 12 chlorophenols (from mono-C1 to penta-C1) was determined according to the Organization for Economic Cooperation and Development guidelines for testing chemicals. The responses of the algae to the chemicals were measured by cell counting, and 96-h EC50 values were correlated with six physicochemical parameters of chlorophenols. The parameters employed in the quantitative structure-activity relationship (QSAR) analyses were n-octanol/water partition coefficient (log Pow), dissociation constant (pK,), Hammett Co constant, index of valence molecular connectivity ( l x"), perimeter of the efficient cross section of molecule (ED) and melting point ( F ) . In the S. capricornuturn assay, the toxicity increased as the number of substituted chlorine atoms increased. In the C. vulgaris assay, although toxicity increased from phenol to dichlorophenol, the toxicities of di-, tri-, tetra-and pentachlorophenol were almost the same. QSAR study shows that log Pow gives the best correlation, even in the C. vulgaris assay, by the use of the square of log Pow. Therefore, the growth inhibition of these algae caused by chlorophenols is mostly influenced by lipophilicity, as is stated frequently in toxicity studies using aquatic animals.
GF‐Scale (GFS) cells, a fibroblastic cell line derived from the scale of goldfish, were used for the determination of the cytotoxicity of chlorophenols (CPs) and the quantitative structure‐activity relationships (QSAR) studies. As the cytotoxicity end point, the amount of neutral red retained by viable cells after exposure to chemicals was quantified. The sequence of cytotoxicity based on the concentration of chemicals that reduced uptake of neutral red by 50% (NR50) was penta‐Cl (PCP) > 2,4,5‐Cl3 > 2,3,4‐Cl3 > 2,3,4,6‐Cl4 > 3,5‐Cl2 > 3,4‐Cl2 > 2,4‐Cl2 > 2,5‐Cl2 > 2,3‐Cl2 > 2,4,6‐Cl3 > 3‐Cl > 4‐Cl > 2,6‐Cl > 2‐Cl > phenol. The in vitro cytotoxicity of these chemicals was found to be significantly correlated to their in vivo acute toxicity to aquatic species, and NR50 values were correlated with six physicochemical parameters of chlorophenols. Log Pow (n‐octanol/water partition coefficient) gave the best correlation in simple linear regression analysis, as is frequently stated in toxicity studies with aquatic animals. Multiparametric linear regression equations yielded improved correlation coefficients and predictive capabilities, including the log Pow and pKa. These results suggest that in vitro fish cytotoxicity assays using the GFS cell lines are useful for ecotoxicity screening of aquatic pollutants.
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