QSAR Models For Predicting Plant Cuticle-water Partition Coefficients Of Organic Pollutants

Plant cuticle-water partition coefficients(Kcw)of organic pollutants are crucial to assess their plant accumulation and potential risks.Due to the wide variety of organic pollutants and plants,experimental determination of Kcw is time-consuming and high experimental cost.Up to now,experimental logKcw values are determined for only hundreds of compounds.Therefore,computational models for predicting logKcw values are promising approaches.In this study,a dataset consisting of 279 logKcw values for 125 unique compounds were collected.Based on the dataset,quantitative structure-activity relationship(QSAR)models for predicting logKcw values were developed via multiple linear regression(MLR)analysis.(1)Based on the 279 logKcw values of 125 compounds and Abraham descriptors,a poly-parameter linear free energy relationship(pp-LFER)model was developed,and relative contribution of individual interactions to the overall partition interactions were estimated.The proposed pp-LFER model has good goodness-of-fit(R2adj,tra=0.93,RMSEtra=0.52),robustness(QBOOT2=0.92)and predictability(Qext2=0.94).The developed model can predict logKcw values of diverse compounds with functional groups including-OH,-COOH,-NO2,>C=O,-X(Cl,F,I),-O-,-CH3,-CH2CH3,-NH2,-NH-,>C=C<,-CHO,-S-,-S(O)(O)-,-CN,>N-C(O)-NH2,-O-C(O)-NH-,-C(O)OCH3,>N-NO2,>N-C(O)OCH2CH3,-OCH2COOH.The result of contribution analysis for different interactions to the overall partition interactions indicated that dispersion and hydrophobic interactions(vV)is the most influential interactions(average relative contribution of 56%).The term vV has a positive contribution to the partition of pollutants onto plant cuticles.Hydrogen bond accepting ability(bB)has a negative contribution to compounds partition onto plant cuticles(average relative contribution of 18%).In addition,contribution analysis indicated that,for organic pollutions containing benzene ring(13?31%),double bond(9?17%)or nitrogen-containing heterocycles(9?17%),n/?-electron pairs interactions exhibit obvious positive contributions for the partition.(2)Based on the quantum chemical descriptors,a theoretical linear solvation energy relationship(TLSER)model were developed to predict logKcw of compounds.The proposed TLSER model has good goodness-of-fit(Radj,tra2=0.77,RMSEtra=0.99),robustness(QBOOT2=0.76)and predictability(Qext2=0.71).The developed model can be used to predict logKcw values of polycyclic aromatic hydrocarbons(PAHs),polychlorinated biphenyls(PCBs),pesticides,alkylbenzenes,chlorobenzenes,nitrobenzenes,phenols,alkanes,cycloalkanes,haloalkanes,olefins,alcohols,esters,nitriles,ketones and munitions compounds.The model indicated that partition of compounds between plant cuticles and water is influenced by McGowan molecular volume(Vx),molecular dipole moment(?),most positive hydrogen atom charge(q+)and chemical hardness(?).Vx is the most influential factor for the logKcw values.