DFT studies on role of methoxy group in radical scavenging ability of quebrachitol and viscumitol

Abstract

The structure of quebrachitol and the influence of methoxy group on its radical scavenging ability is investigated by DFT studies. To study its electron donating ability, bond dissociation enthalpy (O-H BDE), frontier molecular orbitals (FMOs), molecular electrostatic potential (MEP) and molecular descriptors of quebrachitol and viscumitol are computed and compared. Charge delocalization and stability of the compounds are analyzed by natural bond orbital (NBO) method. The 4-OH radical of quebrachitol and 3-OH radical of viscumitol possess the least BDE and exhibit weak intramolecular hydrogen bonds which are clearly illustrated by NBO. The results show that quebrachitol, which has one methoxy group, can act as better radical scavenger than viscumitol having two methoxy groups at the same ring. The fundamental vibrational modes and wave numbers of quebrachitol are characterized theoretically based on potential energy distribution.