Study of the molecular structure and chemical reactivity of pinocembrin by DFT calculations.

Pinocembrin flavonoid (C 15 H 12 O 4 ), 5,7-Dihidroxyflavanone, is one of the major chemical constituents of propolis extracts which is characterized by possessing antioxidant activity. However, the relationship between its structure and antioxidant properties are little known. The principal objective of this work was to study the molecular structure and chemical reactivity (electronic affinity, A ; ionization potential, I ; electronegativity, χ ; hardness, η ; electrophilicity, ω ; Fukui indices) of pinocembrin employing the Density Functional Theory (DFT) method and different model chemistries, which include the PBEPBE, PBE1PBE, MPW1PW91, B3LYP and M05-2X functionals in combination with the 6-31G(d,p) and 6-31+G(d,p) basis set, in search of the most accurate results. This study indicate that different model chemistries were able to reproduce the molecular structure of pinocembrin compared with experimental reference data ( R > 0.99). It is remarkable that M05-2X/6-31G(d,p) afford the best quality to simulate pinocembrin structure. Low values of chemical potential, obtained by different model chemistries, indicate that pinocembrin is capable to donate electrons and participle as an antioxidant compound, while the local reactivity analyzed through the Fukui indices showed that C (4) was the preferred sites for nucleophilic attack, and O (4) and C (8) sites participle in electrophilic and radical attack. [ABSTRACT FROM AUTHOR]