Using quantum-chemical parameters for predicting anti-radical (HO∙) activity of related structures containing a cinnamoyl fragment II. derivatives of 2’,4’-dihydroxychalcone, flavanone and flavone, containing a hydroxy group in position 7

42 derivatives of 2’,4’-dihydroxychalcone, flavanone and flavone, containing the hydroxy group in position 7 (ring “A”), as well as substituents in the ring “B”, have been studied.

The aim is to study the quantum-chemical parameters of 2’,4’-dihydroxychalcone, flavanone and flavone derivatives containing a hydroxy group in position 7, in order to identify the effect of substituents on Mulliken charges (a.e) in the aromatic core “A”, bond numbers (Nµ), the unsaturation index (IUA) and the electron density of the carbon atoms of the cinnamoyl fragment.

Materials and methods. The listed above parameters have been calculated by the semi-empirical method PM7 (WinMopac 2016 program) on the workstation with an Intel Xeon E5-1620 3.5 GHz processor, 20 GB of RAM.

Results and discussion. The analysis of the values of quantum-chemical parameters, as well as their comparison with the corresponding indicators presented in Report I, revealed a number of important features associated with the influence of the hydroxy group in position 7 (ring “A”) on the studied quantum-chemical parameters of molecules. It has been established that the hydroxy group in the ring “A” does not significantly affect the Mulliken charge and the electron density of the carbon atoms of the propenone unit C-7→C-8→C-9. On atom C-9 (carbonyl carbon), the Mulliken charge always has a positive value, and the electron density is about 3.4670-3.4840 for all three groups of compounds. The transition from 2’,4’-dihydroxychalcone to flavanone and flavone by the formation of the pyrone heterocycle, is accompanied by an increase in the negative charge on C-8, which can be explained by the involvement of the oxygen heteroatom in the transmission of electronic effects. The hydroxy group in the ring “A”, has practically no effect on the charge and electron density of atoms. An analysis of the values of bond numbers and unsaturation indices suggests that atoms C-1 of 2’,4’-dihydroxychalcone and 7-hydroxyflavanone derivatives, are characterized by the lowest Nµ value; the lowest bond numbers are characteristic for atom C-8 derivatives of 7-hydroxyflavone. Consequently, the primary attack of the HO·radical will be directed at C-1 (in chalcones and flavanones) and at C-8 in flavones.

Conclusion. The performed quantum-chemical calculations make it possible to analyze the effect on the main quantum-chemical parameters of the molecule, which can be useful in predicting the biological activity of flavanoid compounds due to their antiradical effect on reactive oxygen intermediate species (ROIs).