Toxicity assessment of organic pollutants: Reliability of bioluminescence inhibition assay and univariate QSAR models using freshly prepared Vibrio fischeri

The toxicity of 14 industrially relevant organic chemicals was determined using freshly grown Vibrio fischeri bioluminescence inhibition assay. The results were compared to lyophilized V. fischeri, 96 h fish, 48 h Daphnia magna and 95 h green algae bioassays. Reliability of octanol–water partition coefficient (K_ow) and first order simple and valence molecular connectivity index (¹Χ,¹Χ^v) based regression models for predicting toxicity to V. fischeri was studied. Correlations were obtained between freshly grown V. fischeri data (Log(EC₅₀)) and Log(K_ow), molecular connectivity indices ((¹Χ,¹Χ^v), energy of the highest occupied (E_HOMO) and lowest unoccupied (E_LUMO) molecular orbitals and their difference (E_LUMO − E_HOMO). A good match was observed between V. fischeri assay conducted with freshly grown and lyophilized culture (r² = 0.90). Good correlations (r² > 0.95) were obtained with all the other bioassays after excluding compounds with Log (K_ow) less than 2.0. Available regression models based on Log (K_ow) and ¹Χ^v yielded lower toxicity values. V. fischeri bioassay showed fairly good correlation with Log (K_ow), (¹Χ and ¹Χ^v (r² > 0.75) but poor correlation with E_HOMO, E_LUMO and (E_LUMO − E_HOMO) in presence of polar compounds. E_HOMO and E_LUMO values are affected by polarity and can be used along with Log (K_ow) and ¹Χ^v for generating better predictive models