Naslov
PM6 study of free radical scavenging mechanisms of flavonoids: why does O–H bond dissociation enthalpy effectively represent free radical scavenging activity?

Autori
Amić, Dragan ; Stepanić, Višnja ; Lučić, Bono ; Marković, Zoran ; Dimitrić Marković, Jasmina

Izvornik
Journal of molecular modeling (1610-2940) 19 (2013), 6; 2593-2603

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
flavonoids ; radical scavenging ; bond dissociation enthalpy ; hydrogen atom transfer ; single electron transfer followed by proton transfer ; sequential proton loss electron transfer

Sažetak
It is well known that the bond dissociation enthalpy (BDE) of the O–H group is related to the hydrogen atom transfer (HAT) mechanism of free radical scavenging that is preferred in gas-phase and non-polar solvents. The present work shows that the BDE may also be related to radical scavenging processes taking place in polar solvents, i.e., single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET). This is so because the total energy requirements related to the SET-PT [sum of the ionization potential (IP) and proton dissociation enthalpy (PDE)] and the SPLET [sum of the proton affinity (PA) and electron transfer enthalpy (ETE)] are perfectly correlated with the BDE. This could explain why the published data for polyphenolic antioxidant activity measured by various assays are better correlated with the BDE than with other reaction enthalpies involved in radical scavenging mechanisms, i.e., the IP, PDE, PA and ETE. The BDE is fairly well able to rank flavonoids as antioxidants in any medium, but to conclude which radical scavenging mechanism represents the most probable reaction pathway from the thermodynamic point of view, the IP and PA (ETE) should also be considered. This is exemplified in the case of the radical scavenging activity of 25 flavonoids.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

POVEZANOST RADA