A simple assessment of toxicity towards Chlorella vulgaris of organic aromatic compounds in environmental protection

A new approach is introduced for the assessment of toxicity to living organisms from the deposition of different types of organic aromatic compounds in the aquatic environment. Several simple models are introduced for reliable prediction of pIC50, pIC20, pLOEC, and pNOEC towards Chlorella vulgaris (C. vulgaris) of organic aromatic compounds. They need structural parameters as simple descriptors rather than complex descriptors, which are used in the available quantitative structure-activity/toxicity relationship (QSAR/QSTR) models. The largest available reported data of pIC50 for 145 aromatics are used to obtain suitable simple descriptors. A core correlation is introduced for estimating pIC50, which is based on the number of chlorine atoms and molecular weight as well as the contributions of nitro groups and intramolecular hydrogen bonding in phenol derivatives under certain conditions. Its reliability is improved by considering two isomeric structural parameters. Reliable models for pIC20, pLOEC, and pNOEC are also derived and tested using six descriptors. Since the outputs of available QSAR/QSTR models are restricted to phenol and aniline derivatives, the predicted results of the new models are compared with the reported data of one of the best available complex QSAR/QSTR models. Various statistical parameters confirm that the models for pIC50, pIC20, pLOEC and pNOEC show high reliability as well as accuracy, precision, and suitable goodness-of-fit. For example, the predicted results of root mean squared error (RMSE) of pIC50 for 67 and 13 of training-test and external chemical sets of the new/QSTR models are 0.256/0.285 and 0.215/0.376, respectively.