Abstract
Using the GUSAR 2013 program, the quantitative structure–antioxidant activity relationship has been studied for 74 phenols, aminophenols, aromatic amines and uracils having lgk7 = 0.01–6.65 (where k7 is the rate constant for the reaction of antioxidants with peroxyl radicals generated upon oxidation). Based on the atomic descriptors (Quantitative Neighborhood of Atoms (QNA) and Multilevel Neighborhoods of Atoms (MNA)) and molecular (topological length, topological volume and lipophilicity) descriptors, we have developed 9 statistically significant QSAR consensus models that demonstrate high accuracy in predicting the lgk7 values for the compounds of training sets and appropriately predict lgk7 for the test samples. Moderate predictive power of these models is demonstrated using metrics of two categories: (1) based on the determination coefficients R2 (R2TSi, R20, Q2(F1), Q2(F2), ) and based on the concordance correlation coefficient (CCC)); or (2) based on the prediction lgk7 errors (root mean square error (RMSEP), mean absolute error (MAE) and standard deviation (S.D.)) The RBF-SCR method has been used for selecting the descriptors. Our theoretical prognosis of the lgk7 for 8-PPDA, a known antioxidant, based on the consensus models well agrees with the experimental value measure in the present work. Thus, the algorithms for calculating the descriptors implemented in the GUSAR 2013 program allow simulating kinetic parameters of the reactions underling the liquid-phase oxidation of hydrocarbons.
Highlights
The antioxidant properties of natural and synthetic substances are in the focus of chemical, biological, and pharmacological studies
Based on the consensus approach implemented in the GUSAR 2013 program, the quantitative relationship between the structure and antioxidant activity of uracil, phenol and aminophenol derivatives of sets TR1–TR3 was modeled
We considered that the QSAR model Mi has a low predictive ability if the following four conditions are simultaneously fulfilled for 95% of the test sets: (1) determination coefficients R2, R20, R2 0, Q2F1, Q2F2 and correlation coefficient (CCC) criterion do not exceed the threshold value equal to 0.6; (2) R2m ≤ 0.5 if ∆R2m ≤ 0.2; (3) MAE value is higher than 15% of the ∆lgk7 interval of the compounds from TRi; (4) the sum MAE + 3·S.D. is larger than 25% of the ∆lgk7 interval of the compounds from
Summary
The antioxidant properties of natural and synthetic substances are in the focus of chemical, biological, and pharmacological studies. Indicative variables were used jointly with quantum-chemically calculated descriptors (energies of the frontier molecular orbitals EHOMO and ELUMO, difference in the heats of formation of phenol and its radical (∆∆HR), bond dissociation enthalpies etc.) [28,29,30,31,32,33,34] All these works are built on fairly narrow sets of similar compounds, e.g., the effect of para-substituents on the antioxidant activity of 10 and 27 phenol derivatives was studied in works [28] and [29], respectively. We have studied a quantitative structure—antioxidant activity relationship in the series of phenols, aminophenols, aromatic amines and uracils with general structural formulas I–V (Figure 1) using the GUSAR 2013 program and constructed the corresponding statistically significant QSAR models for predicting the k7 values. The condition for development of reliable QSAR models is fulfilled [53]
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