The role of intramolecular H-bonds predominant effects in myricetin higher antioxidant activity

Publication date: 1 September 2017 Source:Computational and Theoretical Chemistry, Volume 1115 Author(s): Abolfazl Barzegar Flavonoid antioxidants play essential roles in the prevention of damage caused by free radicals, which is concerned in many chemical and biological processes. The structural electronic properties of myricetin (Myc) and six respective radicals such as total electronic energies, bond dissociation enthalpy magnitudes (BDEs), intramolecular H–bonds strength and charges density distributions have been computed using density functional theory approach with B3P86 level. The important Myc molecular characteristics, the antioxidant activities, electronic structure–activity relationships, OH numbers and positions–activity relationships as well as radical scavenging mechanisms were discussed. The sequential active OH groups for H atom abstraction was predicted as 4′-OH>3′-OH≈5′-OH>3-OH>7-OH>5-OH that concomitant with B-ring>pyrone C-ring>A-ring activity in Myc structure. The vital role of intramolecular H-bonds was comprehensively monitored for the stabilization of B-ring radicals (4′- O , 3′- O , 5′- O ), that lead to the highest activity of 4′-OH, 3′-OH, 5′-OH in B-ring. Also, the electrons delocalization among A, B and C-ring (increasing co-planarity) play second possible role for easy H atom donation. The number of three ortho-phenolic OH groups and radical stabilization by th...

Source: Computational and Theoretical Chemistry - July 5, 2017 Category: Chemistry Source Type: research